engineering evaluation/cost analysis rpt (ee/ca), w

•••••••••••••••1

Q3IT CORPORATIONAManhfrnfUx-ITCroup

Project No. 821915May 2001

Draft Report

Engineering Evaluation/Cost Analysis ReportLava Cap Mine Tailings SiteNevada City, California

Contract No. DACA45-98-D-0003Task Order No. 44

Prepared for:U.S. Army Corps of EngineersOmaha DistrictFort Crook Area OfficeOffutt Air Force Base, Nebraska

Prepared by:IT CorporationMonroeville, Pennsylvania

RESPONSIVE TO THE NEEDS OF ENVIRONMENTAL MANAGEMENT

the<figroup May 22, 2001

IT Corporation2790 Mosside BoulevardMonroeville, PA 15146-2792Tel. 412.372.7701Fax. 412.373. 7135

A Member of The IT Group

Project No 821915

SFUND RECORDS CTR117334

Mr. Waleed Shaheen (CEMRO-CD-RR)USAGE, Rapid Response, Ft Crook Area OfficeBuilding 525, Castle HallP O Box 13287OffuttAFB, NE 68113

CONTRACT: DACA45-98-D-0003, TASK ORDER NO 44U.S. ARMY CORPS OF ENGINEERS, RAPID RESPONSE PROGRAMLAVA CAP MINE SUPERFUND SITENEVADA CITY, CALIFORNIA

SUBJECT: DRAFT EE/CA REPORT

Dear Mr Shaheen:

On behalf of Larry Hudson, IT's Rapid Response Project Manager for this task, I am transmittingfour copies of the enclosed Draft Engineering Evaluation/Cost Analysis (EE/CA) for the LavaCap Mine site Please review at your earliest convenience and return any comments you mayhave. As you indicated to me, so as to meet the current schedule, we are requesting commentsfrom reviewers should be received by June 1, 2001. You may call me directly at 412-858-3927.If you would prefer to review this electronically, let me know and I will transmit the text andtables to your office. On behalf of our EE/CA team, we would like to thank the U.S. ArmyCorps of Engineers (USAGE) for the opportunity to assist you

Respectfully submitted,

IT CORPORATION /

James A. Sloss£E/CA Task Manager

JAS:kab ,Enclosures

cc: Dave Setter, USEPA Region IX (2 copies)David Towell, CH2M Hill (1 copy)Dave Bunte, CH2M Hill (1 copy)Larry Hudson, IT Corporation (2 copies)Wah Tak Chan, IT Corporation (1 copy)Paul Ingersoll, IT Corporation (1 copy)Sue Tituskin, IT Corporation (1 copy)Project Files (1 copy)

Steve Ross To: David Seter/R9/USEPA/US@EPA,<[email protected]> [email protected]

cc: [email protected], [email protected], [email protected]/15/2001 02:19 PM subject: Re: RE: Review Comments - Lava Cap EE/CA

Wally, attached are my comments to the Draft EE/CA.

I) Several of the sections make reference to compliance with RCRA andCalifornia Title 22 as ARARs for hazardous waste management. California lawexempts from regulation certain mine wastes as hazardous waste. It may bemore appropriate to provide cost estimates of the response alternatives given1) compliance with California hazardous waste laws and regulations (e.g.disposal cell meeting RCRA standards) and 2) exemption from Californiahazardous waste laws and regulations (e.g. modified disposal cell design).

2) Page 44, and other portions of the draft: DTSC does not consider chemicalpreliminary remediation goals as State ARARs.

3) Page 66: Typo in first paragraph as Alternative 4 should be Alternative 5.

4) Item 16 for Table 3-4a: East Diversion Channel Construction does notappear to be discussed in the text as tasks to be completed under Alternative5.

Thanks for the opportunity to review.

"The energy challenge facing California is real. Every Californian needs totake immediate action to reduce energy consumption. For a list of simple waysyou can reduce demand and cut your energy costs, see our Web-site atwww.dtsc.ca.gov."

>» "Shaheen, Waleed W NWO" <[email protected]> 06/12/20017:19:33 AM »>Review comments by the end of next week (6/22/01) will be fine. We wouldlike to address the comments and revise the final draft EE/CA while it isall still fresh.

Thank you. WallyUSAGE, Rapid Response ProgramCENWO-CD-RR (formerly CD-FC-R)(402) 293-2517-office(402) 291-8177 [email protected] <[email protected]>

-----Original Message-----From: Seter.DavidSepamail.epa.gov

[SMTP:[email protected]]Sent: Friday, June 08, 2001 4:27 PMTo: Shaheen, Waleed W NWOCc: 'Dave Towell'; [email protected]; Re: Review Comments - Lava Cap EE/CA

Wally,

I'm in process of reviewing the comments CH2M Hill has submittedtome--

but to expedite things I can fax them along to you with mycomments.

IS

EE/CA.

Since we won't be doing the public meeting in July, as far as EPA

concerned, we have more lead time for completion of a final draft

I've asked that DTSC submit comments directly to your attention.

Thanks,Dave

David

Seter/R9/USEPA/US@EPA, 'Dave

<[email protected]>

Review Comments -

EE/CA

"Shaheen, Waleed W NWO"

<[email protected]

.army.mi1>

06/08/2001 08:18 AM

To:

Towel1'

cc :

Subject:

Lava Cap

the Draft

weekand

What is the status of review comments from your agency/company on

EE/CA for the LC tailings area? We were looking for them this

need to plan our work for the balance of this month and July.

Thank you. WallyUSAGE, Rapid Response ProgramCENWO-CD-RR (formerly CD-FC-R)(402) 293-2517 office(402) 291-8177 [email protected]

*A UNITED STATES ENVIRONMENTAL PROTECTION AGENCY§ REGION IX

75 Hawthorne StreetSan Francisco, CA 94105

May 23, 2001

Mr. Steve RossDTSC/Region 1Site Mitigation Branch8800 Cal Center DriveSacramento, CA 95826-3200

Re: Lava Cap Mine Superfund SiteDraft EE/CA

Dear Steve,

Enclosed is a copy of the Draft EE/CA prepared by IT for the log dam area of the LavaCap Mine Superfund Site. Please submit your comments directly to Mr. Wally Shaheen of theCorps of Engineers no later than June 8, 2001, and please send a copy of your comments to me soI may include them in EPA's records.

Please contact me if you have any questions or concerns, at 415-744-2212. Thank you.

David A. Seter, P.E.Project ManagerSuperfund Division

enclosure

UNITED STATES ENVIRONMENTAL PROTECTION AGENCYREGION IX


May 23, 2001

Mr. Steve RossDTSC/Region 1Site Mitigation Branch8800 Cal Center DriveSacramento, CA 95826-3200

Re: Lava Cap Mine Superfund SiteDraft EE/CA

Dear Steve,

Enclosed is a copy of the Draft EE/CA prepared by IT for the log dam area of the LavaCap Mine Superfund Site. Please submit your comments directly to Mr. Wally Shaheen of theCorps of Engineers no later than June 8, 2001, and please send a copy of your comments to me soI may include them in EPA's records.

Please contact me if you have any questions or concerns, at 415-744-2212. Thank you.


enclosure

UNITED STATES ENVIRONMENTAL PROTECTION AGENCYREGION IX


June 13, 2001

Mr. Wally Shaheen (CEMRO-CD-RR)USAGE Rapid ResponseBuilding 525, Castle HallP.O. Box 13287OffuttAFB, NE68II3

Re: EPA Comments on EE/CALava Cap Mine Superfund Site

Dear Wally,

EPA has completed its review of the Engineering Evaluation/Cost Analysis prepared byIT Corporation, dated May 2001. Our comments follow. In addition, EPA is forwarding as anattachment the comments of our RI/FS contractor, CH2M Hill.

EPA's specific comments are as follows:

I) /Alternative 2/Sizing of the Diversion Channel: The EE/CA recommends aremedy which includes a diversion channel "sized to accomodate (sp.) a flow of up to500 cfs, which is greater than a 100 year, 24-hour storm and greater than a 6-hour PMPevent". The report does not explain the rationale for selecting the return frequency ofthe design rainfall event. What is the probability of exceedence of the storm eventduring the useful life of the project, and what would be the potential consequences ofsuch an exceedence?

2) Page 9/Please change "eminent potential threat" to "imminent potential threat".

3) Page 19/Please change "Region XI office" to "Region IX office".

4) Page 45/The EE/CA states that implementation of Alternative 2 "would require someimprovement of roads and site facilities". Has the cost of these improvements beenincluded in the estimate, and if so, how much was allocated for this purpose?

5) Page 60/Why is Alternative 3, which involves construction of a central drainagechannel through the tailings pile, considered easier to implement than Alternative 2,which would involve less intrusive work with the tailings themselves?

6) Page 68/Selected Remedy (also Page 39/Detailed Description of Alternative 2): TheEE/CA states that under the recommended alternative the tailings pile "would be graded

to improve and promote incidental runoff... grading the area towards the centraldrainage channel at a minimum slope of 5 percent." This appears to be in error, asFigure 3-1 depicting Alternative 2 does not show a central drainage channel, only theeastern drainage channel. Please correct.

ERA looks forward to working with the Corps and IT to revise the EE/CA. As youknow, it has been necessary to postpone implementation of the non-time-critical removalaction which is the subject of the EE/CA, however, finalizing the document at this time will helpto speed along implementation if and when the removal proceeds. If you have any questions,please call me at 415-744-2212.


Attachment

cc: David Towell, CH2M Hill

MEMORANDUM CH2MHILL

Review of Lava Cap Mine Tailings EE/CAT0: Dave Seter/EPA Region IXCOPIES:

FROM: David Towell/RNODave Bunte/RDDJohn Spitzley/RDDPam Bates/RDD

DATE: june 6f 2001

Per your request, CH2M HILL has reviewed the Draft Report Engineering Evaluation/ CostAnalysis Report, Lava Cap Mine Tailings Site, Nevada City, California (dated May 2001) andprepared by IT Corporation under contract to the U.S. Army Corps of Engineers (USAGE),Omaha District. This memorandum provides the results of our technical review.

General Comments1 . In general, the description of the alternatives developed and their associated costs lack

adequate detail to perform a detailed technical review of the alternatives and theirestimated cost.

2. Except for the lack of detail and some minor inconsistencies, typographic errors,uncertainties regarding costs and applicability of regulations, this report is generallyacceptable.

3. If this document is going to be released to the public, additional explanation should beprovided for the specialized technical terms that occur sporadically throughout the text.Examples include "pug mill," "gabion basket," "baffle spillway,"

4. The references to RCRA may not be applicable for mine tailings. The tailings are ahazardous substance and are regulated under CERCLA as a hazardous substance butmay be exempt from RCRA via the Bevill Amendment. The applicability of RCRArequires clarification.

5. References to the State of California Title 27 should be included in the report. Title 27provides the most recent State of California requirements for disposal of solid wastes.

6. Alternatives 5 and 6 include excavation and disposal of the tailings and the waste rock.It is not clear why the waste rock is included in the material being contemplated forexcavation and disposal. The volume of materials (along with the associated costs ofthese alternatives) to be addressed could be cut in half if waste rock were excluded.

Specific Comments1. Page 1. Executive Summary. 2n<^ paragraph. There appears to be text missing in the

first line of this paragraph.

2. Page 6. Executive Summary. 5"1 bullet. Please define "universal treatment standards

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REVIEW OF LAVA CAP MINE TAILINGS EE/CA

for disposal of arsenic and lead containing waste materials".

3. Page 7. Executive Summary. 1st bullet. The paragraph references "central drainagechannel". The reference should be to the "east channel diversion".

4. Page 8. Executive Summary. 4*h paragraph. The statement that "Construction waterwould be treated as required" should be clarified. Water treatment is included inAlternatives 5 and 6 for leachate obtained from dewatered tailings. The term"construction water" implies water that is used for construction.

5. Page 9. Section 1.0. 2n^ paragraph. The text should be corrected to state that LostLake is 1.25 miles below the mine.

6. Page 9. Section 1.0. 2n^ paragraph, "eminent" should be replace by "imminent."

7. . Section 1.1. 1s* paragraph. The reference to Lava Cap Road in the 4m lineneeds to be changed to read "Banner Ridge - Lava Cap Road."

8. Page 10. Section 1.1. 1st paragraph. At bottom of this page (and many other placesthroughout the document) there is reference to the need for improvements to Lava CapMine Road should heavy truck traffic be expected. Are these road improvement costsincorporated into the estimated alternative costs?

9. Page 13. Section 1.3. 1st paragraph. The last sentence should indicate that thereferenced ecological assessment occurred shortly after the 1997 failure of the logdam.

10. Page 14. Section 1.5. 2n<^ paragraph. The 7"1 line of this paragraph needs to becorrected to state that three quarters of surface water sampling were performed duringthe RI.

11. Section 2.1. Correct typo; reference to USEPA Region XI (this typo also occurselsewhere in the document).

12. Page 20. Section 2.2. Factors present at the site may include "Potential forcontamination of drinking water supplies"

13. Section 2.4 (ARARs): General comment - Notably missing from the ARARs analysis isa discussion on the exemption from regulation of mining waste as hazardous waste[Bevill exclusion found at 40 CFR 261.4(b)(7)]. In Section 3.2.9, the fact that thetailings contain metals in excess of TCLP concentrations is touched upon but the Bevillexemption and how it may impact onsite management and disposal of mining waste isnot discussed. In addition, the mining waste management regulations found in Title 27,Section 22470 should be included as well as the State's mining waste groupclassification found in Section 22480. The requirements for siting, construction,monitoring, and closure of a mining waste disposal unit will be driven by how themining waste is classified (Group A, B, or C).

14. Page 25. Section 2.4.4. 1st paragraph, "remedies" should be replace with "removalaction."

15. Section 2.4.4 - The text indicates that the chemical-specific ARARs presented in Table2-1 are presented for informational purposes and can be used during development ofthe FS. However, it appears that some of the ARARs presented in the table can be

RDD/F:\15I319\IT EECAREVIEW\COMPILEDEECACOMMENTS1.DOC 2


applied to the limited scope of this EE/CA (e.g., TCLP, STLC, and TTLC values). It isdifficult to discern which ARARs apply to the EE/CA and which apply to the site-wideFS. Perhaps the table should modified to identify those ARARs that are related theEE/CA action and those that would apply to the site-wide FS to avoid confusion.

16. Table 2-1: This table does not provide a description of the chemical-specific ARARs orhow each ARAR is applied to the proposed removal actions. Text should be providedto discuss the source of the ARAR and the site-specific application of the requirement.

17. Other comments on Table 2-1 (if the table is not pared down):

• Need to specify if the numerical MCL listed on the table is the federal ormore-stringent State MCL

• Define "Groundwater MCC" and "TCLP Criteria MCC."

• Provide a source for the Basin Plan Objectives (where specifically in the Planthese numerical values are found)

• The latest version of the RWQCB's "A Compilation of Water Quality Goals"should be included and referred to as a source document for this table.

18. Table 2-2: There are several ARARs that are listed as "not ARAR." Several of theseare quite obviously not ARAR (such as the wilderness area, wildlife refuge, coastalzone, etc) and therefore it is suggested that they be removed from the table.

19. Table 2-3: The ARARs listed under "Diversion of Water" and "Dam Construction andRemoval" contain several requirements that are considered "administrative" in natureand should be removed (e.g., "filing and annual fees").

20. Table 2-3: General comment - There are several references to RCRA hazardouswaste regulations and in the ARAR/TBC status column, they are described as being"applicable." However, because these mining wastes are subject to the Bevillexemption, the hazardous waste management requirements would be consideredrelevant and appropriate.

21. Table 2-3: General comment - Some of the citations (those that pertain to the RCRAprogram) include both the federal and the state counterpart. Because California isauthorized to implement the RCRA program, the federal citation is not required.

22. Table 2-3: the row labeled "Air Emissions" should cite the local air district rule forfugitive dust emissions.

23. Page 27, 4th bullet. "Dave" should be replaced with "Dan."

24. Page 27. Section 2.6. The EE/CA has the primary objective of preventing futurereleases of the tailings from the mine site, as was stated on page 1 and page 10 of thedocument. It would be helpful if the presentation of RAOs were modified to identify this(the first bullet and dash in the RAO list) as the primary objective of the EE/CA. Theremaining objectives listed in Section 2.6 will be included as RAOs for the site wideFS.

The additional RAOs must be considered during the development of the EE/CA to theextent that the remedy selected from the EE/CA must be compatible with the site wideremedy, but the EE/CA does not need to specifically meet these RAOs. The role of

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these "secondary" RAOs for this EE/CA should be clarified. This will also help to focusthe evaluation of the alternatives in Sections 3 and 4 on the RAOs that directly apply tothis action.

25. Page 34. Section 3.2; Page 34.1s* paragraph. The risk assessment report does notdiscuss "potential leachate" as the last sentence states.

26. Page 36.1st paragraph. Delete the extra words "over other."

27. Page 38. Section 3.2.10. It is not clear from this section whether institutional controlswere retained or rejected for further consideration.

28. Section 3.29. Include references to STLC and TTLC for characterization of hazardouswastes (substances) in State of California.

29. Section 3.3.1. In general, additional technical detail on all of the alternatives would behelpful.

30. Page 39. Section 3.3.1.2. Have flows from the west side drainages been evaluated todetermine if the existing diversions are adequate to handle them? Are additional detailson the regrading plan and dam face reconstruction available? What is planned in theway of an intake structure for Little Clipper Creek?

31. Page 40. Section 3.3.1.2,1st paragraph. The detailed description of Alternative 2includes "grading the area towards the central drainage channel at a minimum slope of5 percent". Shouldn't the reference to "central drainage channel" should be changed to"east channel diversion?" Also, grading the entire area at 5 percent may not benecessary or beneficial. A uniform 5 percent minimum cross slope would result in a10-foot-high berm on the west side of the valley unless the west perimeter hillslopecontact with the valley is filled. Perhaps a series of northwest to southeast diagonalditches would be more effective and less intrusive. In addition, given the granularnature of the cover material, is likely that precipitation will readily infiltrate.

32. Page 40,1st paragraph. Please explain what "gabion baskets" are.

33. Page 40. Section 3.3.1.3. Alternative 3. See comment above regarding grading.

34. Page 41. Section 3.3.1.4. The text needs to include some explanation of the reasonfor siting the new dam 500 feet downstream (access, geotechnical considerations,channel structure, etc.).

35. Page 41. Section 3.3.1.4. What is the storage volume behind the new dam? What isthe design flow for the spillway?

36. Page 41. Section 3.3.1.4. The text states that under "normal" rainfall conditions, thedam would allow the slow release of water through the dam contained within thetailings up behind the dam. How was "normal" rainfall defined? What does the last partof the sentence mean? How was it determined that the tailings will settle out behindthe dam?

37. Page 41. Section 3.3.1.4. Concentrating the drainage by grading towards thecenterline will promote erosion of the centerline. Suggest that either sheet flow ispromoted or the design include protection of the centerline. The text conflicts withFigure 3-3 which shows drainage directed to the perimeter..

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38. Page 41. Section 3.3.1.5. Why is the waste rock being excavated and disposed? Theexcavation and disposal should focus on the tailings only. This will cut the volume ofmaterials approximately in half.

39. Page 41. Section 3.3.1.5. What is the height of the disposal cell expected to be?

40. Page 41, Section 3.3.1.5. It is not clear why the existing east diversion drainagechannel requires improvements from beyond the proposed tailings disposal cell downto the existing log dam as shown on Figure 3-4. Is this done to address remainingtailings in the abutments to the existing log dam? It would seem more appropriate toremove these tailings in the abutments, construct the diversion channel around thenew disposal cell, then direct the flow to the historic creek channel. Also, it is not clearwhat is being buttressed at the location of the former tailings dam (Is it the oldabutments?).

41. Pages 41 and 42. Sections 3.3.1.5 and 3.3.1.6. The text needs to include a descriptionof the water treatment system that is included in the cost analysis for Alternatives 5and 6.

42. Page 42. Section 3.3.1.6. See prior comments about the need to excavate anddispose of waste rock.

43. Page 42. Section 3.3.1.6. The text discusses the need for "significant improvements"to the access road to the mine. It does not appear that these costs are in the costestimate. Is that correct?

44. Page 42. Section 3.3.1.1. The third sentence states that the tailings would requirestabilization prior to disposal. The fifth sentence states that the "waste material" wouldrequire treatment before disposal. Some additional explanation of the stabilizationprocess assumed for estimating costs should be included. Is the "waste material"mentioned in the 5trt sentence again referring to the tailings?

45. Page 44. Section 3.4.2.1. 1s* paragraph. In addition to direct precipitation on thetailings, run-on to the tailings from western side drainages, adit discharge, andpotential groundwater discharge contribute to leaching of arsenic from the tailings.Little Clipper Creek is dry for about half the year, yet considerable seepage continuesout the base of the log dam. Insufficient data are currently available to support theclaim that diversion of Little Clipper Creek would "significantly reduce" the potential forleaching arsenic.

46. Page 44. Section 3.4.2.1. 1st paragraph. Please clarify the meaning of the lastsentence (this sentence is repeated in the evaluation of Alternatives 3 and 4).

47. Page 44. Section 3.4.2.1. 3rc^ paragraph. This alternative has the same inherentlimitation for channel capacity exceedance that is discussed for Alternative 3 in the 1st

paragraph of Section 3.4.3.1.

48. Page 44. Section 3.4.2.1. 3fd paragraph. The text mentions the potential for leachateand seeps to occur as a result of the limited amount of incidental precipitation falling onthe tailings. As noted above, there is also the potential for run-on from western-sidedrainages, adit discharge, and groundwater discharge to contribute to leachate andseeps.

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49. Page 44. Section 3.4.2.1. 3rd paragraph. The text mentions the potential for leachateand seeps to occur as a result of the limited amount of incidental precipitation falling onthe tailings. As noted above, there is also the potential for run-on from western-sidedrainages, adit discharge, and groundwater discharge to contribute to leachate andseeps.

50. Page 44. Section 3.4.2.1. 3rd paragraph. The text states that the "vast majority of thewatershed drainage area would be diverted away from the tailings." What percentageof the Little Clipper Creek drainage area will be diverted around the tailings pile?

51. Page 44. Section 3.4.2.1 3rd paragraph. The end of this paragraph states that "thereis no way to......know even if the leaching will occur about risk- based standards at all."Given that considerable leaching occurs now, resulting in discharge above standards,even during the time when Little Clipper Creek has been dry for half a year, it seemsvery likely that this would continue after the implementation of Alternative 2.

52. Page 44, Section 3.4.2.1. As discussed in the Section 2 comments, it would be helpfulif the effectiveness evaluation was presented in the context of meeting the primaryRAO and then also discussed the compatibility with and the contribution to meeting thesecondary RAOs.

53. Page 45. Section 3.4.2.2. The l8^ sentence states that Alternative 2 could be easilyimplemented. Based on the structure of the valley and access limitations, it seems asthough the construction of the downstream end of the large eastern diversion channelat the locations shown in Figure 3-1 will not necessarily be easy.

54. Page 45. Section 3.4.2.2. 1s* paragraph. Are the road improvements mentioned inthis paragraph included in the Alternative 2 costs? This comment applies to all of thealternatives.

55. Page 45. Section 3.4.2.2. 2nd paragraph. This paragraph mentions on-site treatmentof wastewater and off-site disposal of any generated wastes. Neither of these activitiesis discussed in the description of Alternative 2 provided earlier in the report.

56. Page 46. Section 3.4.3. Many of the comments provided above for Alternative 2 alsoapply to Alternative 3.

57. Page 47, 2nd paragraph. The last sentence of this paragraph indicates that Alternative3 would be expected to be "less invasive" of the natural environment. Is this intendedas a comparison to Alternative 2 or to other alternatives as well?

58. Section 3.4.3.2. For Alternative 3, suggest that some mention be made of potentialdifficulty associated with constructing the drainage channel over very low strengthtailings and the potential conflict with a long term solution for site.

59. Page 49, Section 3.4.4.1. The effectiveness of this alternative appears to be limited.During a major storm event, the flow from Little Clipper Creek would flow on top of themain body of tailings and potentially cause significant erosion. The tailings would betransported down Little Clipper Creek to the new retention dam. Water would poolbehind the dam and the coarser material would settle. However, the tailings arecomposed of very fine grained material and a portion of the tailings would likely stay insuspension and be carried through the spillway of the dam. This material would thenbe transported further down Little Clipper Creek. This scenario seems to contradict the

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statement that the potential for tailings migration down to Lost Lake would be"effectively eliminated."

60. Page 50. Section 3.4.4.2. Do the cost estimates assume that a "significant amount oflarge rock" will be required from offsite?

61. Page 53. Section 3.4.5.1. It is agreed that Alternative 5 will be very effective; however,treatment of the leachate from the disposal cell would likely be necessary to meet allARARs.

62. Page 54.1s* paragraph. This text should mention the need for leachate treatment.

63. Page 56. Section 3.4.6.2. Was the availability of disposal capacity at commerciallandfills for this volume of material confirmed? What was basis used for thetransportation and disposal costs?

64. Page 59. 2n<^ paragraph. The last two sentences discuss the differences in reducedleaching of arsenic between Alternatives 2 and 3. There should not be any substantivedifference between arsenic leaching under these two alternatives.

65. Page 59. Section 4.1. Alternative 2 also has the advantage of being compatible withfuture remedial actions at the site. It allows for additional work at the log dam locationwith minimal impact on the diversion channel.

66. Page 60. Section 4.2. The end of the 2n" paragraph should mention both Alternatives5 and 6 for the total removal of tailings.

67. Page 61. Section 4.3. "modest" should be deleted from this text. A 35 percentcontingency is fairly typical at this stage and would not generally be referred to asmodest.

68. Section 5. Many of the earlier comments also will need to be incorporated into thissection.

69. Page 63. Section 5; Alternative 2. Correct the reference to "central drainage channel"?

70. Pages 64 and 65. Section 5. Please describe the treatment process included in thecost analysis for Alternatives 5 and 6.

71. Page 65. Last paragraph. Given that the western channel is constructed immediatelyadjacent to the tailings/waste rock piles, it does not appear that there is anysubstantive difference between Alternatives 2 and 3 in protectiveness from overflow.

72. Page 66. 1st paragraph. The reference to Alternative 4 should be changed toAlternative 5. The cost difference between Alternatives 2 and 5 is less than 6 times,not more than 8 times as is stated in the text.

73. Table 2-2, Page 1. It appears that the tailings are located in a 100-year flood plain,(they flooded in 1997)

74. Table 2-3, Page 1. The State of California, Department of Water Resources, hasjurisdiction over all dams that impound 15 acre-feet or more. Dams that impound lessthan 15 acre-feet are not jurisdictional.

75. Table 3-la and Table 3-2a. Suggest that the cost analysis increases the cost of

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reinforced concrete to a minimum $500 per cubic yard. (This estimate may be low forthis remote site.)

76. Table 3-4b. Shouldn't the O&M costs specifically discuss treatment of the leachate,rather than simply using the 2.5% of capital estimate?

77. Cost Tables, General Comment. It would be very helpful to have additional informationon how the costs were developed. This would include a list of the cost assumptionsused, additional detail on how quantities were developed, and the basis for the unitcosts.

78. Cost Tables, General Comment. The discount rate used for the present worthevaluation should be clearly stated. The tables currently only mention a 4% inflationrate. This contradicts the text (Section 3.1.3.4) which states that inflation is generallyignored in estimating present worth costs.

79. Cost Tables, General Comment. Construction oversight at 25 percent of costs ishigher than is typically assumed.

80. Figure 3-4. The construction sequencing mentions construction of a new ClipperCreek Diversion. This should be "Little Clipper Creek."

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ENGINEERING EVALUATION/COST ANALYSIS REPORT

LAVA CAP MINE TAILINGS SITENEVADA CITY, CALIFORNIA

CONTRACT NO. DACA45-98-D-0003TASK ORDER NO. 44

IT PROJECT NO. 821915

PREPARED FOR:U.S. ARMY CORPS OF ENGINEERS

FT. CROOK AREA OFFICEP.O. BOX 13287

OFFUTT AFB, NEBRASKA 68113

AND

U.S. ENVIRONMENTAL PROTECTION AGENCY, REGION IX75 HAWTHORNE STREET

SAN FRANCISCO, CALIFORNIA

PREPARED BY:IT CORPORATION

2790 MOSSIDE BOULEVARDMONROEVILLE, PENNSYLVANIA 15146

MAY 2001

Table of Contents

List of Tables. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . vList of Figures.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . viList of Appendices.................................................................................................................... viiList of Acronyms....... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .viii

Executive Summary... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1Introduction........ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1Objective of the Remedy...................................................................................................!Site History.... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2Basis for USEPA's Action................................................................................................3Development and Screening of Removal Action Alternatives . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .4Conclusions of the EE/CA... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5Recommendation of the EE/CA... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6Conceptual Design.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6

1.0 Introduction.... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 91.1 Site Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 101.2 Site History.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 111.3 Adit Drainage... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 121.4 Faults and Seismicity...... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 131.5 Summary of Site Status and Regulatory Actions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 131.6 Summary of Previous Investigations and Site RI Data............................................ 16

2.0 Removal Action Objectives............................................................................................. 192.1 Basis for Removal Action... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 192.2 Applicability of CERCLA...................................................................................... 192.3 Applicable or Relevant and Appropriate Requirements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 212.4 Identification of Applicable or Relevant and Appropriate Requirements ................22

2.4.1 ARAR Classification Requirements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .232.4.2 To Be Considered Criteria.........................................................................242.4.3 Types of ARARs..... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .242.4.4 Chemical-Specific ARARs and TBC Guidance ... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .25

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Table of Contents (continued).

2.4.5 Location-Specific ARARs and TBC Guidance..........................................252.4.6 Action-Specific ARARs and TBC Guidance .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .26

2.5 Human Health and Ecological Risk Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .262.6 Removal Action Objectives....................................................................................27

3.0 Identification and Analysis of Removal Action Alternatives............................................283.1 Evaluation Criteria.................................................................................................28

3.1.1 Effectiveness Evaluation...........................................................................303.1.2 Implementability Evaluation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .303.1.3 Cost Evaluation.........................................................................................31

3.1.3.1 Capital Cost... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .313.1.3.2 Annual O&M Costs..... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .323.1.3.3 Periodic Costs...........................................................................323.1.3.4 Net Present Worth Costs............................................................323.1.3.5 Sensitivity Analysis... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 333.1.3.6 Estimate Accuracy..................................................................... 33

3.2 General Approaches for Impacted Soil Removal . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .333.2.1 Surface Capping... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 343.2.2 Surface Water Runoff Collection and Treatment....................................... 343.2.3 Source Removal/Excavation...................................................................... 3 53.2.4 Bioremediation (In Situ/Ex Situ).. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 353.2.5 Phytoremediation (In Situ/Ex Situ).... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .363.2.6 Chemical Stabilization (In Situ/Ex Situ)... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .363.2.7 Physical Stabilization (In Situ/Ex Situ)......................................................373.2.8 Chemical Treatment/Soil Washing/Flushing (In Situ/Ex Situ)...................373.2.9 Disposal... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 383.2.10 Institutional Controls to Supplement Engineering Controls .......................38

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3.3 Development of Alternatives.................................................................................. 3 83.3.1 Detailed Description of Alternatives.......................................................... 39

3.3.1.1 Detailed Description of Alternative 1 - No Further Action......... 393.3.1.2 Detailed Description of Alternative 2 - Little Clipper Creek

East Channel Diversion, Regrading, and PhysicalStabilization of Tailings at the Log Dam... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39

3.3.1.3 Detailed Description of Alternative 3 - Little Clipper CreekCentral Channel Diversion, Regrading, and PhysicalStabilization of Tailings at the Log Dam....... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 40

3.3.1.4 Detailed Description of Alternative 4 - Rock Fill RetentionDam Downstream of Original Log Dam Location, Regrading,and Physical Stabilization of Tailings at the Log Dam............... 41

3.3.1.5 Detailed Description of Alternative 5 - Excavation andDisposal of Tailings On Site in Newly Constructed DisposalCells . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .41

3.3.1.6 Detailed Description of Alternative 6 - Excavation andRemoval of Tailings Off Site. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 42

3.4 Analysis of Alternatives......................................................................................... 433.4.1 Detailed Evaluation of Alternative 1 - No Further Action.......................... 43

3.4.1.1 Effectiveness Evaluation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 433.4.1.2 Implementability Evaluation...................................................... 433.4.1.3 Cost Evaluation.........................................................................43

3 4.2 Detailed Evaluation of Alternative 2 - Little Clipper Creek East ChannelDiversion, Regrading, and Physical Stabilization of Tailings at the LogDam.... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .433.4.2.1 Effectiveness Evaluation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 443.4.2.2 Implementability Evaluation......................................................453.4.2.3 Cost Evaluation.........................................................................46

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3.4.3 Detailed Evaluation of Alternative 3 - Little Clipper Creek CentralChannel Diversion, Regrading, and Physical Stabilization of Tailings atthe Log Dam... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 463.4.3.1 Effectiveness Evaluation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .46

3.4.3.2 Implementability Evaluation...................................................... 473.4.3.3 Cost Evaluation.........................................................................48

3.4.4 Detailed Evaluation of Alternative 4 - Rock Fill Retention DamDownstream of Original Log Dam Location, Regrading, and PhysicalStabilization of Tailings at the Log Dam ... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .493.4.4.1 Effectiveness Evaluation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 493.4.4.2 Implementability Evaluation...................................................... 503.4.4.3 Cost Evaluation.........................................................................51

3.4.5 Detailed Evaluation of Alternative 5 - Excavation and Disposal ofTailings On Site in Newly Constructed Disposal Cells . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .523.4.5.1 Effectiveness Evaluation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 523.4.5.2 Implementability Evaluation...................................................... 533.4.5.3 Cost Evaluation......................................................................... 54

3.4.6 Detailed Evaluation of Alternative 6 - Excavation and Removal ofTailings Off Site.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 543.4.6.1 Effectiveness Evaluation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 543.4.6.2 Implementability Evaluation......................................................553.4.6.3 Cost Evaluation......................................................................... 57

4.0 Comparative Analysis of Alternatives . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .584.1 Comparative Effectiveness Evaluation...................................................................584.2 Comparative Implementability Evaluation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 604.3 Comparative Cost Evaluation.................................................................................61

5.0 Conclusions and Recommendations.................................................................................625.1 Recommendation................................................................................................... 67

6.0 Conceptual Design .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .68

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List of Tables

Table Title

2-1 Chemical-Specific ARARs and TBC Guidance2-2 Location-Specific ARARs2-3 Potential Action-Specific ARARs and TBCs3-la Alternative 2 - Engineering Cost Estimate3-lb Alternative 2 - Present Worth Analysis3-2a Alternative 3 - Engineering Cost Estimate3-2b Alternative 3 - Present Worth Analysis3-3 a Alternative 4 - Engineering Cost Estimate3-3b Alternative 4 - Present Worth Analysis3-4a Alternative 5 - Engineering Cost Estimate3-4b Alternative 5 - Present Worth Analysis3-5a Alternative 6 - Engineering Cost Estimate3-5b Alternative 6 - Present Worth Analysis4-1 Summary of Alternative Screening

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List of Figures,

Figure Title

1 -1 Site Location Map1-2 Site Plan3-1 Alternative 2 - Little Clipper Creek Eastern Diversion3-2 Alternative 3 - Little Clipper Creek Central Diversion3-3 Alternative 4 - New Downstream Dam3-4 Alternative 5 - On-Site RCRA Cell3-5 Alternative 6 - Removal and Off-Site Disposal

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List of Appendices,

Appendix Title

A California Department of Fish and Game LetterB Action Memorandum for 1997 Removal Action at Lava Cap Mine Site

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List ofAcronyms_

Acronym

ARARCAOCERCLACFRcfsCOPCDISCEE/CAFSgpmHHRAITmg/kgNCPNPDESNPLO&MPROPMPRAORCRARJRMERWQCBSARATBCTCLPug/LUSAGEuseUSEPA

Title

applicable or relevant and appropriate requirementCleanup and Abatement OrderComprehensive Environmental Response, Compensation, and Liability ActCode of Federal Regulationscubic foot (feet) per secondconstituent(s) of potential concernDepartment of Toxic Substances ControlEngineering Evaluation/Cost AnalysisFeasibility Studygallon(s) per minuteHuman Health Risk AssessmentIT Corporationmilligram(s) per kilogramNational Contingency PlanNational Pollutant Discharge Elimination SystemNational Priorities Listoperation and maintenancepreliminary remediation goalprobable maximum precipitationremoval action objectiveResource Conservation and Recovery ActRemedial Investigationreasonable maximum exposureRegional Water Quality Control BoardSuperfund Amendment and Reauthorization Actto be consideredToxicity Characteristic Leaching Proceduremicrogram(s) per literU.S. Army Corps of EngineersUnited States CodeU.S. Environmental Protection Agency

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Executive Summary

IntroductionThis document has been prepared to document the Engineering Evaluation/Cost Analysis(EE/CA) performed for the Lava Cap Mine tailings site, located just outside Nevada City,Nevada County, California. The Rapid Response Program of the U.S. Army Corps of Engineers(USAGE) has been tasked by the U.S. Environmental Protection Agency (USEPA), Region IX toprepare this EE/CA in accordance with the requirements for performing a non-time criticalremoval action under the Comprehensive Environmental Response, Compensation, and LiabilityAct (CERCLA). This EE/CA was performed by IT Corporation (IT) on behalf of the USAGE asper the scope of services negotiated under Contract No. DACA45-98-D-0003, Task OrderNo. 44, dated March 26, 2001. This scope of services required development of the EE/CA inaccordance with the USEPA's Office of Emergency and Remedial Response GuidanceDocument, "A Guidance on Conducting Non-Time Critical Removal Actions Under CERCLA"USEPA, Publication No. EPA/540/R-93/057, August 1993, and the evaluation in detail ofpotential remedies for the mitigation of certain risks associated with the mine tailings present atthe Lava Cap Mine site. This action is considered a non-time critical removal action for thepurposes of risk reduction. Based on this evaluation and public comments, the USEPARegion IX will prepare an action memorandum to identify and document the selected responseaction.

Objective of the RemedyThe primary objective of the remedy proposed under this as a non-time critical removal action isto reduce the potential for ecological and human health risks by stabilizing a large depository ofresidual mine tailings that have a high potential to catastrophically migrate downstream to LittleClipper Creek. This action will not necessarily constitute the final action for the site, as asitewide remedial investigation/feasibility study (RI/FS) is in progress and other remedies maybe proposed to reduce the nature of certain risks presented by the site. The remedies developedin the EE/CA to a limited extent may address the chemical-specific risks that may be presentedby the tailings. Moreover, the remedies are intended to address the potential physical hazardassociated with a potential second failure of the tailings retention dam (e.g., catastrophicmigration of the tailings pile downstream) and the added ecological impact that would impose onLost Lake and the drainages leading to Lost Lake.

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Site HistoryCH2M Hill reports the following in a prepublication version of the site RI report.

Historically gold and silver mining activities were initiated at the Lava Cap Mine (formerlyknown as the Central Mine) in 1861. The Banner Mine began operation in 1860. The BannerMine was located approximately 1.5 miles north of the Lava Cap Mine. These two mines werelater operated by the Lava Cap Gold Mining Corporation starting in 1934 and at that time, theCentral Mine became known as the Lava Cap Mine. Various groups intermittently operated theCentral and Banner Mines between 1860 and 1943.

The initial operating period at the mines was from 1860 to 1918. Relatively small-scale miningoperations occurred during that period. Approximately 20,000 tons of ore were mined from theBanner Mine/Central Mine between 1865 and 1890. In the early years, the Central Mine wasmined primarily for silver. During this period, amalgamation was used to process the ore. Thisprocess uses mercury to recover the silver and gold from the ore. Due to high sulfides, thisprocess was not as effective on the Central Mine ore.

The Banner and Central Mines were inactive from 1918 until 1934, when mining activitiesresumed under the Lava Cap Gold Mining Corporation. Prior to the resumption of mining, aflotation plant was built to process the ore. At some point after 1934, when the mines werereopened, the Banner and Lava Cap Mines were connected underground by means of a5,000-foot drift. Ore from the Banner portion of the mine was transported to the Central shaftand transported to the surface, where it was processed in the Lava Cap mill.

After operations resumed in 1934, Lava Cap Mine was one of the largest gold mines operating inCalifornia. The ore production ranged from approximately 300 to 400 tons per day during thisperiod. The primary mining method was cut and fill. In this method, the open stope formed bymining was filled with waste rock after the ore was removed. This provided a more stablemethod than leaving the stope open under weak rock condition. Operation of the mine ceased in1943 due to World War II and limits imposed on the production of non-strategic materials.

Attempts to reopen the mine in 1978 included application for a dewatering permit and resulted inCalifornia Regional Water Quality Control Board (RWQCB) inspection of the site. Samplingand inspection revealed environmental impacts as a result of the erosion of tailings and leachingof arsenic. Regulatory involvement continued which included working with the mine owners to

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implement control measures at the site. After the catastrophic failure of the log dam in 1997, thesite was evaluated and placed on the National Priorities List (NPL).

Basis for USEPA's ActionThe USEPA Region IX has requested the interagency assistance of the USAGE to assesspossible removal action alternatives for the Lava Cap Mine site. Former activities conducted atthe site as noted above resulted in the disposal of a large mass of mine tailings behind a tailingsretention dam at the site. In January 1997, heavy rains caused major flood conditions at the site.The conditions produced by this rain event caused the log dam to fail and released an estimated10,000 cubic yards of mine tailings downstream.

A preliminary draft of the human health risk assessment prepared for the site as part of the RI/FSprocess indicated potential risks result from the concentrations of arsenic and lead in the minearea. Impacts have the potential to continue as a result of migration through leaching intosurface water and groundwater.

The California Department of Fish and Game also indicated in a letter that the presence oftailings in downstream areas has significantly altered the stream ecology through inundation andapparent chemical toxicity.

The California Department of Toxic Substances Control (DTSC) issued an information sheet inJune 1997 warning of potential hazards from contact with downstream sediment that haveaccumulated below the mine in Lost Lake. The issuance of this information sheet was based onMarch and April 1997 sampling results that indicated the presence of arsenic in Lost Lake waterat concentrations up to 28.4 micrograms per liter (jig/L) and in shoreline soils at concentrationsup to 1,130 milligrams per kilogram (mg/kg). In October 1997, the USEPA Region IXEmergency Response Office determined that conditions associated with the tailings release fromthe Lava Cap Mine met the National Contingency Plan (NCP) Section 300.415(b)(2) criteria fora removal action. The primary concern was the potential for additional releases of tailings fromthe unstabilized tailings pile. This concern was based on the high arsenic concentrations and themobility of the extremely fine-grain tailings, which are easily suspended and transported insurface water. A removal action was implemented in the fall of 1997, which included theinstallation of peripheral drainage conduits to route Little Clipper Creek around the mine tailingsand covering of the lower part of the tailings area with heavier waste rock to prevent continued

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erosion. Although this action stabilized and improved the site, it was not considered adequate toprevent more migration of tailings should a repeat of the 1997 rainfall conditions occur.

During October and November 1997, 4,000 cubic yards of tailings were removed from justupstream of the damaged log dam and stockpiled on the waste rock pile immediately to the northof the tailings pile. The stockpiled tailings were placed on a liner and covered with a liner, thencovered with a clay cap and waste rock to help protect the liner and cap. The oversteepenedslopes of the tailings pile immediately behind the dam were graded, and the entire tailings pilewas covered with waste rock. Stream diversions of Little Clipper Creek and other drainageswere also constructed around the waste rock and tailings piles. In February 1998, USEPAconducted additional work at the site to stabilize another smaller tailings release and furtherimprove drainage. In the summer of 1998, the emergency response action was completed. Allwork related to the action took place on the Lava Cap Mine property, at or above the log dam.

In 1998, USEPA evaluated the Lava Cap Mine site to determine potential risks to human healthand the environment posed by the site and to determine if it warranted listing on the NPL as aSuperfund site. Based on this evaluation, USEPA formally listed the Lava Cap Mine site on theNPL in February 1999, allowing Superfund funding to be spent on investigation and cleanup ofthe site.

Development and Screening of Removal Action AlternativesThis EE/CA screens appropriate technologies for mitigation of metals contamination in tailingsand sediments. These technologies include:

• Surface Capping• Surface Water Runoff Collection and Treatment• Source Removal/Excavation• Bioremediation (In Situ/Ex Situ)• Phytoremediation (In Situ/Ex Situ)• Chemical Stabilization (In Situ/Ex Situ)• Physical Stabilization (In Situ/Ex Situ)• Chemical Treatment/Soil Washing/Flushing (In Situ/Ex Situ)• Disposal• Institutional Controls to Supplement Engineering Controls.

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The CERCLA evaluation criteria of effectiveness, implementability, and cost are used toevaluate and screen these technologies, leading to development of complete removal actionalternatives which address site impacts. Alternatives are then developed in consideration ofapplicable or relevant and appropriate requirements (ARAR) for the site.

Based on this evaluation, six removal alternatives are developed. These are:

• Alternative 1 - No Further Action

• Alternative 2 - Little Clipper Creek East Channel Diversion, Regrading, andPhysical Stabilization of Tailings at the Log Dam

• Alternative 3 - Little Clipper Creek Central Channel Diversion, Regrading, andPhysical Stabilization of Tailings at the Log Dam

• Alternative 4 - Rock Fill Retention Dam Downstream of Original Log DamLocation, Regrading, and Physical Stabilization of Tailings at the Log Dam

• Alternative 5 - Excavation and Disposal of Tailings On Site in NewlyConstructed Disposal Cells

• Alternative 6 - Excavation and Removal of Tailings Off Site

Each alternative was screened individually against the CERCLA criteria of cost,implementability, and effectiveness.

A second analysis was performed comparatively screening these alternatives relative to eachother, again considering the criteria of effectiveness, implementability, and cost.

Based on this comparative evaluation of the proposed alternatives, a recommendation was madefor a removal action alternative to be implemented at the site.

Conclusions of the EE/CABased on site history and current status under the NCP, regulatory actions to date, the potentialhuman health and environmental risks reported, and an evaluation of possible actions that couldbe taken to reduce potential site risks, this EE/CA concludes:

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• The Lava Cap Mine site has a predicted potential human health risk above CERCLAstandards, sufficient to warrant USEPA Region XI to implement an appropriateremoval action.

• The presence of the tailings in the Lava Cap Mine drainage basin has demonstrateddetrimental environmental and ecological impacts on the stream channel.

• The presence of unsecured tailings at the site remains an ecological risk todownstream drainage areas. The movement of these tailings could occur againshould extended heavy rains impact the area again.

• Additional physical stabilization of the tailings and water diversion around the site isexpected to provide a benefit in reducing potential human health and ecological riskand would be a likely component of any final site remedy.

• Off-site management of tailings would be prohibitively expensive due tocharacteristics that would likely classify these materials as Resource Conservationand Recovery Act (RCRA) hazardous waste due to the presence of arsenic and lead.The waste would require pretreatment to reduce toxicity or treatment at the receivingfacility to meet the universal treatment standards for disposal of arsenic and leadcontaining waste materials.

• Additional site-specific engineering and geotechnical information is required before arecommendation for a final permanent remedy for the site can be made with therequired degree of certainty.

Recommendation of the EE/CABased on the conclusions of the EE/CA, an analysis of the cost and benefits of each alternative,consideration of site-specific ARARs, and consideration of the potential technical uncertaintyassociated with each alternative, the recommendation of this EE/CA is to implementAlternative 2 as a non-time critical removal action. This would involve the construction of aconcrete-lined peripheral east diversion drainage channel for the purpose of completelyintercepting and diverting Little Clipper Creek drainage from the watershed area above the sitearound the tailings repository. Removal of the remaining log dam features, anchoring the basearea, along with additional physical stabilization and grading of the tailings would eliminate anyfurther potential for migration downstream.

Conceptual DesignFollowing approval to proceed, all the regulatory and permitting considerations will beidentified. The removal action contractor selected by the USAGE will develop all theappropriate plans and submittals to comply with the substantive requirements of any permits.

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The recommended remedy includes:

• The installation of a drainage channel to completely intercept/divert Little ClipperCreek and run-on drainage away from the far northern and eastern limits of thetailings area. Little Clipper Creek and other captured drainage will be divertedaround the tailings area to the eastern side through an approximately 10-foot-wide by3-feet-deep reinforced concrete-lined trapezoidal drainage ditch. The existingdrainage piping will be removed. Other ancillary drainages approaching the site fromthe east will also be captured by the diversion ditch. The ditch will be sized toaccommodate a flow of up to 500 cfs, which is greater than a 100-year, 24-hour stormand greater than a 6-hour PMP event. The remnants of the existing log dam would beremoved and the lower tailings area graded to prevent erosion and physically stabilizethe area. This is estimated to involve approximately 18,000 cubic yards of grading.Areas that are regraded and any deposits of excavated tailings would be covered witha geotextile fabric overlain by an 18-inch-thick layer of coarse waste rock to furtherstabilize them. The former dam face area would be butressed with grouted riprap orgabion baskets and a baffle spillway will be installed at the outlet of the channel. Theentire tailings pile surface area would be graded to improve and promote incidentalrunoff (with minimal erosion), grading the area towards the central drainage channelat a minimum slope of 5 percent. Prior to implementation of the remedy, appropriatedetailed engineering would be completed including geotechnical testing and plans forconstruction prepared including a work plan, health and safety plan, erosion andsedimentation control plan, construction quality assurance plan, environmentalprotection plan, etc. for agency approval.

As part of developing the removal action work plan, a more extensive engineering survey of thearea would be required and additional geotechnical information obtained. From this survey,detailed delineation drawings of the routing of the diversion channel, cuts, grades, constructionfeatures, areas to be excavated, areas to be stabilized, restoration requirements, etc. would beprepared. Within the overall work plan would be the standard required documentation for civilconstruction/removal work of this nature such as:

• Construction work plan

• Sedimentation and erosion control plan• Storm water management plan• Revegetation plan• Project quality assurance/quality control plan• Environmental protection plan

• Traffic control and transportation plan

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• Construction water and waste management plan• Permit requirements (substantive)• Sampling and monitoring plan

• Health and safety plan.

In conjunction with the preparation of the appropriate plans, site preparation will begin onceauthorization to proceed has been established. Setup will require location of a base camp typearea for the location/storage of equipment, personnel, treatment operations, etc. Some measuresmay be developed as the removal action proceeds, such as the most appropriate placement ofcover soil and revegetation to be used in a particular area. Flexibility in the work plans will benecessary in order to be responsive to anticipated changing conditions.

The major effort for this project will be in planning and logistics. The narrow and steep one laneroad will limit heavy truck traffic moving in and out of the site. Transportation logistics andconstruction sequencing will be critical to maintain productivity. Schedule will be critical asconstruction would need to be completed before the possibility of any early heavy rainfall.

It is anticipated that heavy equipment such as trackhoe excavators, backhoes, and bulldozers willbe used for the majority of the removal work. Articulated off-road haul trucks may be neededfor some of the tailings excavation activity. Some dewatering and subsequent treatment may berequired. The methodology for management of construction water will be detailed in the variouswork plans.

Materials that are dry when excavated will be placed directly into appropriately sized trucks andtransported for placement. Materials that are saturated with free liquids will be appropriatelydewatered. Construction water would be treated as required. The release of untreated water tothe streambed during excavation will be minimized to the extent possible by dewatering theexcavation area, diversion around the excavation, or other means. Silt fencing in the streamchannel and other sedimentation control measures will be used to prevent downstream pollution.These measures will be detailed in the sedimentation and erosion control plan.

Work sequencing and planning will also anticipate the possibility of catastrophic weather eventsand minimize the amount of exposed area that could wash out to the extent practical, but not atthe expense of hindering the rate of removal.

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1.0 Introduction

This document has been prepared to document the Engineering Evaluation/Cost Analysis(EE/CA) performed for the Lava Cap Mine tailings site, located just southeast of Nevada City,Nevada County, California and due east of Grass Valley, California. Figure 1-1 provides alocation map for the site.

Early in 1997, heavy rains caused the failure of a tailing retention dam at the base of the minesite. A large deposit of tailings (approximately 10,000 cubic yards) washed downstream as fardown as Lost Lake, approximately 2 to 3 miles below the site. Estimates indicate approximately150,000 cubic yards of tailings and waste rock remains behind the failed log dam structure thatwas holding back the tailings. A remedial investigation/feasibility study (RI/FS) is beingprepared for the site. The RI/FS will address sitewide issues including the former mine itself, theimpacts on Lost Lake from the mine's former operations, and continuing mine drainage.However, due to the eminent potential threat posed by the unsecured tailings on the downstreamecology and ecology of Lost Lake, the U.S. Environmental Protection Agency (USEPA),Region IX office has tasked the Rapid Response Program of the U.S. Army Corps of Engineers(USAGE) to prepare this EE/CA. The purpose of the EE/CA is to develop and screen possibleremedies to prevent future migration of the tailings and to support a request for funding so thatan accelerated non-time critical removal action can be implemented in advance of anyrecommendations from the sitewide FS.

This EE/CA has been prepared in accordance with the requirements of the ComprehensiveEnvironmental Response, Compensation, and Liability Act (CERCLA). IT Corporation (IT) hasprepared this document on behalf of the USAGE per the scope of services negotiated underContract No. DACA45-98-D-0003, Task Order No. 44, dated March 26, 2001. The format isconsistent with the requirements for preparing an EE/CA identified in the USEPA's Office ofSolid Waste and Emergency Response Guidance Document, "Outline of EE/CA Guidance,"USEPA, Superfund Branch, March 30, 1988, and as updated in USEPA's Office of Emergencyand Remedial Response Guidance Document, "Guidance on Conducting Non-Time CriticalRemoval Actions Under CERCLA," USEPA, Publication EPA/540/R-93/057, August 1993.These documents detail the methodology that should be used to develop and evaluate potentialremedies and estimate the costs for comparison of remedies so that the implementation fundingcan be secured.

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The remedies developed in this EE/CA report were developed to address the primaryrequirements needed to prevent further erosion and migration of the tailings and to a limitedextent the chemical-specific risks that may be presented by the tailings. The remedies areintended to address primarily the potential physical hazard associated with a potential secondfailure of the dam (e.g., catastrophic failure of the tailings pile and inundation downstream), andthe resulting ecological impact that would be imposed on Lost Lake and the drainages leading toLost Lake should such a migration occur. There is also a potential chemical toxicity risk presentdue to the leachability of arsenic as rainwater and runoff percolates through tailings. Chemicalrisks will be addressed under the sitewide FS and may require additional measures to beimplemented.

This action is considered a non-time critical removal action for the purposes of risk reduction.However, the potential for tailings migration is dependent on the frequency and duration ofprecipitation. Thus, it is the desire of USEPA to implement control measures before the heaviestpart of the next California rainy season, which tends to be the months of December, January, andFebruary. Based on this EE/CA and public comments, the USEPA will develop an actionmemorandum to confirm the selected response action, leading to the implementation of theremedy by USAGE.

Portions of the following narrative and the site data presented in this report have been extracted,summarized, or excerpted in their entirety from sections of the draft RI report provided inadvance of final issue by CH2M Hill. This assistance is here acknowledged and is appreciated.

1.1 Site DescriptionThe Lava Cap Mine site is located just southeast of the outskirts of Nevada City, California. Asite map showing the local drainage basins, roads, and topography is provided in Figure I-2.The Lava Cap Mine site is accessed using the narrow Lava Cap Mine Road, just off of Idaho-Maryland Road and Lava Cap Road. The Lava Cap Mine proper is on the southern slope ofBanner Ridge at an elevation of approximately 2,840 feet. The access road (Lava Cap MineRoad) transverses the ridge dropping down into the mine area. It is initially moderate in gradeand reasonably well developed as it descends due south. The road then narrows considerably toone lane and is less improved as it descends steeply southwest across Banner Ridge. At the baseof the ridge, the road then loops back around decreasing in grade and heading northeast for ashort distance. This leads down into the developed portion of the mine area. The upper part ofthe road in particular would require some improvements should heavy truck traffic be expected

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as a result of any remedy. The upper ridge road is steeply sloped with no side guardrail or otherbarrier.

Field investigations were conducted at Lava Cap Mine to characterize the mine tailings and toassess potential impacts on surface water and groundwater. Field investigations were conductedbetween October 1999 and June 2000 by the Northern California Offices of USEPA'senvironmental consultant, CH2M Hill, Inc. Based on that investigation, final RI/FS reports arein progress that is intended to address sitewide issues. These sitewide areas include the formermine, mine area, mine adit drainage, Lost Lake, tailings deposition areas, impacts on the areadowngradient of Lost Lake, sitewide surface water, and groundwater.

This EE/CA is focused only on mitigating the potential risks posed by the mine tailings locatedbehind the failed dam structure. References to other areas are provided to demonstrate thepotential risk posed by the current state of the tailings and to identify considerations that shouldbe included in developing a remedy. To the extent practical, any remedy proposed as part of aremoval action is intended to be consistent with the types of expected recommendations underthe FS so that the maximum cost benefit can be achieved.

1.2 Site HistoryCH2M Hill reports historically gold and silver mining activities were initiated at the Lava CapMine (formerly known as the Central Mine) in 1861. The Banner Mine began operation in 1860.The Banner Mine was located approximately 1.5 miles north of the Lava Cap Mine. These twomines were later operated by the Lava Cap Gold Mining Corporation starting in 1934 and at thattime, the Central Mine became known as the Lava Cap Mine. Various groups intermittentlyoperated the Central and Banner Mines between 1860 and 1943.

The initial operating period at the mines was from 1860 to 1918. Relatively small-scale miningoperations occurred during that period. Approximately 20,000 tons of ore were mined from theBanner Mine/Central Mine between 1865 and 1890. In the early years, the Central Mine wasmined primarily for silver. During this period, amalgamation was used to process the ore. Thisprocess uses mercury to recover the silver and gold from the ore. Due to high sulfides, thisprocess was not as effective on the Central Mine ore.

The Banner and Central Mines were inactive from 1918 until 1934, when mining activitiesresumed under the Lava Cap Gold Mining Corporation. Prior to the resumption of mining, a

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flotation plant was built to process the ore. At some point after 1934, when the mines werereopened, the Banner and Lava Cap Mines were connected underground by means of a5,000-foot drift. Ore from the Banner portion of the mine was transported to the Central shaftand transported to the surface, where it was processed in the Lava Cap mill.

After operations resumed in 1934, Lava Cap Mine was one of the largest gold mines operating inCalifornia. The ore production ranged from approximately 300 to 400 tons per day during thisperiod. The primary mining method was cut and fill. In this method, the open stope formed bymining was filled with waste rock after the ore was removed. This provided a more stablemethod than leaving the stope open under weak rock condition. Operation of the mine ceased in1943 due to World War II and limits imposed on the production of non-strategic materials.

Tailings from ore processing were deposited in the ravine on the Lava Cap Mine property. A logdam, approximately 30 feet high, was built to hold the tailings in place where the ravinesteepened and narrowed. The initial date of construction of the log dam is not known; however,it is believed to have been built shortly after mining operations resumed in 1934. The waste rockand overburden were deposited in two piles between the mineshaft and the tailings pond abovethe log dam.

The upper portion of the formerly active mining area now contains the leftover deposits of thecoarse waste rock. This material, as noted above, was left over from the removal of rock thatwas necessary to expose gold-bearing ore. Unlike the tailings, the waste rock was not finelycrushed or processed. This material graduates to the finer tailing size material, in the largesettling area/tailings pile in advance of the log dam. It is believed the waste rock material wouldbe suitable to physically stabilize or cover, as needed, the tailings pile area below.

At the upper part of the mine property are four occupied residences and numerous former minebuildings. Two of the residences are located a distance away from the former mining operations.A third is within 200 yards of the waste rock and tailings piles and the fourth is within 200 feetof the waste rock pile. The elevation drops from Elevation 2870 to Elevation 2710 at the base ofthe log dam, over a distance of some 1,400 feet.

1.3 Adit DrainageDuring the period the Lava Cap Mine was active, access to the mine was possibly an adit thatconnected to a horizontal tunnel bisecting the Central Mine shaft. At some point after the mine

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ceased operations, the adit caved in and was no longer usable for mine access. The discharge ofgroundwater into the mine during the mining operation was reported to have been about35 gallons per minute (gpm). Currently, water discharges continuously from the mine near thecaved-in adit in the waste rock pile area. In a 1984 study, the caved-in adit discharge wasmeasured at rates ranging from 130 gpm in early April 1984 to 47 gpm in August 1984. Inanother study conducted in this same general timeframe, the adit flow reportedly declined toabout 20 gpm by the end of the dry season (September through October). Drainage from themine exits the adit and is intercepted. This drainage is then routed via the western diversionchannel directly to Little Clipper Creek below the remaining log dam. The flow from the adit iscontaminated with elevated levels of arsenic that have been leached naturally from the remainingore body. An ecological assessment of the Little Clipper Creek below the log dam reportedlifeless conditions, most likely a result of elevated levels of arsenic.

1.4 Faults and SeismicityThere are no active faults present in the vicinity of Lava Cap Mine, but the site is located in thenorthern Foothills Fault System. Ancient fractures, joints, and inactive faults are common in thisregion. For design purposes, the site lies in a seismic zone classification of Seismic Zone 4. Themain walls of the Lava Cap Mine workings have reportedly been weakened by fracturing. Thereare two possibly active faults located in the area, one 4 miles east and one 4 miles west of theLava Cap Mine site. To the east, there is the northeast trending Cement Flill fault that may havehad Late Cenozoic movement of greater than 5 feet vertical. To the west, there is a 1.5 milelong, north-trending Greenhorn Creek lineament (with no observed displacement noted) near themajor Pre-Cenozoic northern Melones fault. There are no earthquake epicenters reported in theLava Cap Mine area. However, seismicity data within a 30-mile radius indicate that moderateearthquakes were reported in 1867, 1888, and 1909. In the Foothills Fault System, calculationsfor the Cement Hills fault indicate the maximum earthquake magnitude would be 5.5, with amaximum surface displacement of 4 inches. Similarly, the Greenhorn Creek lineament couldresult in a maximum earthquake magnitude of 5.6, with a maximum surface displacement of6 inches. The active Little Grass Valley fault zone 40 miles north of Lava Cap Mine is capableof generating the maximum credible earthquake for the area, resulting in a magnitude of 6 to 6.5and a 0.02 to 0.1 ground acceleration at Lava Cap Mine.

1.5 Summary of Site Status and Regulatory ActionsIn February 1978, Lava Cap Mine (owned at the time by Keystone Copper Corporation)submitted a National Pollutant Discharge Elimination System (NPDES) permit application to the

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California Regional Water Quality Control Board (RWQCB). Keystone Copper Company wasseeking to discharge 63 million gallons of mine water to Little Clipper Creek as part of a projectto dewater the mine workings (in the likelihood of reopening the mine). In response to thispermit application, the RWQCB conducted a site inspection in May 1978 and requestedadditional information. The RWQCB did not issue a NPDES permit. During this site inspection,a mine discharge water sample had an arsenic concentration of 660 micrograms per liter (ug/L).

The upper area immediately north of the mine area is drained by Little Clipper Creek. Thisdrainage formally flowed through the center of the tailings deposition area/settling pond andseeped through or over top of the tailings dam. The Lava Cap Mine property is located entirelywithin the Little Clipper Creek drainage basin. Little Clipper Creek is the dominant surfacewater drainage leading south away from the mine. The upper reaches of Little Clipper Creekabove the mine are seasonally dry (ephemeral) and become perennial (year-round flow) belowthe log dam at the mine where Little Clipper Creek is fed by mine discharge. During the RI, fourquarters of water sampling were performed. The upstream reaches of Little Clipper Creek weredry during October/November 1999 and flowing during the California rainy season (January andMay 2000, when sampling was performed). Rainfall and mine drainage percolate through theLava Cap Mine waste rock/tailings pile prior to flowing into Little Clipper Creek. Streamdiversions constructed around the tailings pile in 1997 restrict upgradient Little Clipper Creekflow to the far eastern edge of the waste rock/tailings pile area, then into a culvert that dischargesLittle Clipper Creek flow back into the primary channel immediately south of the log dam. Adiversion was also constructed to divert mine discharge from the adit into a culvert that carriesthe discharge around the waste rock/tailings pile and releases it to flow into Little Clipper Creekbelow the log dam. Little Clipper Creek flows downstream from the Lava Cap Mine log dam forapproximately 1 mile to the confluence with Clipper Creek in the deposition area above LostLake. The combined Little Clipper Creek and Clipper Creek flow continues downstream inClipper Creek through the deposition area and into Lost Lake. Deposition of tailings-impactedsediment in the Clipper Creek delta has separated Lost Lake into a northern and southern lobe.

The removal, management, or mitigation of tailings below the breached log dam at the mine siteare not parts of this removal action. These descriptions which include areas below the log damare provided for information purposes and also to document the impact the release of tailingshave had on the environment or may have in the event further releases of tailings occur.

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The total area of Lost Lake is now about 5 acres (approximately 3.6 acres in the northern lobeand 1.3 acres in the southern lobe, depending on the season). Lost Lake is contained by the LostLake Dam which is approximately 45 to 50 feet high with a concrete spillway. There is constantseepage beneath the Lost Lake Dam into the Clipper Creek channel below the dam. In addition,during most of the year, there is at least some flow over the spillway on the dam. Clipper Creekcontinues for less than a quarter of a mile below Lost Lake before it enters Little GreenhornCreek. Little Greenhorn Creek eventually (after approximately 2 miles) joins Greenhorn Creek,which flows into Rollins Reservoir. Water from Rollins Reservoir discharges into the BearRiver, which flows into Lake Combie approximately 11 miles downstream of Rollins Reservoir.

During a major winter storm in January 1997, the upper half of the log dam collapsed, releasingover 10,000 cubic yards of tailings into the lower portion of Little Clipper Creek. In May 1997,staff from the Department of Toxic Substances Control (DTSC), California Department of Fishand Game, and Nevada County Department of Environmental Health inspected the mine anddowngradient areas. Extensive deposits of tailings were observed in Little Clipper Creek and inClipper Creek below the confluence with Little Clipper Creek, and in Lost Lake. Tailings werealso observed in wetland areas contiguous with these water bodies, in some cases, reportedlycovering the vegetation. A summary letter of the findings of this site assessment was providedback to DTSC by California Department of Fish and Game. A copy of this letter is provided inAppendix A.

DTSC issued an information sheet in June 1997 warning of potential hazards from contact withLost Lake sediments. The issuance of this information sheet was based on March andApril 1997 sampling results that indicated the presence of arsenic in Lost Lake water atconcentrations up to 28.4 u.g/L and in shoreline soils at concentrations up to 1,130 milligrams perkilogram (mg/kg). In October 1997, the USEPA Region IX Emergency Response Officedetermined that conditions associated with the tailings release from the Lava Cap Mine met theNational Contingency Plan (NCP) Section 300.415(b)(2) criteria for a removal action. Theprimary concern was the potential for additional releases of tailings from the unstabilized tailingspile. This concern was based on the high arsenic concentrations and the mobility of theextremely fine-grain tailings, which are easily suspended and transported in surface water. Acopy of the Action Memorandum prepared for this removal action is provided in Appendix B.

During October and November 1997, 4,000 cubic yards of tailings were removed from justupstream of the damaged log dam and stockpiled on the waste rock pile immediately to the north

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of the tailings pile. The stockpiled tailings were placed on a liner and covered with a liner, thencovered with a clay cap and waste rock to help protect the liner and cap. The oversteepenedslopes of the tailings pile immediately behind the dam were graded, and the entire tailings pilewas covered with waste rock. Stream diversions of Little Clipper Creek and other drainageswere also constructed around the waste rock and tailings piles. In February 1998, USEPAconducted additional work at the site to stabilize another smaller tailings release and furtherimprove drainage. In the summer of 1998, the emergency response action was completed. Allwork related to the action took place on the Lava Cap Mine property, at or above the log dam.

In 1998, USEPA evaluated the Lava Cap Mine site to approximate potential risks to humanhealth and the environment posed by the site and to determine if it warranted listing on theNational Priorities List (NPL) as a Superfund site. Based on this evaluation, USEPA formallylisted the Lava Cap Mine site on the NPL in February 1999, allowing Superfund funding to bespent on investigation and cleanup of the site.

1.6 Summary of Previous Investigations and Site Rl DataIn response to property owners' complaints of high volumes of sediments in Little ClipperCreek, the RWQCB and the California Department of Fish and Game collected water samples inSeptember 1979. Analytical results show arsenic as high as 1,860 ug/L in Little Clipper Creekbelow the tailings dam. Because of these results, the RWQCB issued a Cleanup and AbatementOrder (CAO) to Keystone Copper Company for the Lava Cap Mine site in October 1979. InMay and June 1982, the RWQCB collected water samples at Lava Cap Mine (the exact samplelocations are unknown). The arsenic concentration near the property boundary was 26 ug/L inMay 1982. The June 1982 results showed arsenic as high as 540 ug/L in the mine tailings area(USEPA, 1994a). Franco-Nevada Mining Corporation attempted to re-open the mine in 1984.Franco-Nevada contracted with Hydrosearch, Inc., to collect upstream, mine area, anddownstream surface water samples in April, May, and June 1984. Arsenic was not detected inthe upstream samples; however, reported concentrations in the mine discharge ranged from 490to 660 |ng/L. These concentrations decreased with downstream distance. In 1985 and 1990, thesite owner collected surface water samples from unspecified locations for arsenic analysis.Arsenic was present in surface water samples at concentrations ranging from 22 to 630 ug/L. InJanuary 1989, the mine owner had the waste rock and mine tailings analyzed for arsenic andlead. Both were detected in the waste rock at concentrations of 2,200 mg/kg and 4,100 mg/kg,respectively. They also were detected in mine tailings at concentrations of 1,100 mg/kg and50 mg/kg, respectively.

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As part of a preliminary site inspection, USEPA conducted a field sampling event at the LavaCap Mine in May 1994. Sediment samples from on-site wetland areas had arsenic and leadpresent at concentrations up to 7,070 mg/kg and 1,140 mg/kg, respectively. These wetlands werewiped out during the 1997 storm event and USEPA's subsequent removal action. Sedimentsamples collected upgradient of the site had arsenic and lead concentrations up to 20 mg/kg and16.9 mg/kg, respectively. Soil samples from Lava Cap Mine waste rock and tailings had arsenicand lead at concentrations up to 1,900 mg/kg and 206 mg/kg, respectively. Soil samplescollected upgradient of the site had arsenic and lead concentrations up to 373 mg/kg and60.9 mg/kg, respectively.

After the log dam failure, DTSC sampled surface water, sediment, and surface soil periodicallybetween 1997 and 1999. Arsenic concentrations in Little Clipper Creek surface water werefairly steady during this time period, but concentrations in Lost Lake fluctuated considerablybetween sampling events. Samples from a small pond at the confluence of Little Clipper Creekand Clipper Creek had arsenic concentrations ranging from 706 to 2,070 ^ig/L. Arsenicconcentrations in soil samples collected around Lost Lake decreased with increasing distanceaway from the water's edge.

The mine discharge from the adit was sampled on 10 dates covering 11 months during theUSEPA RI. Arsenic concentrations detected ranged from 199 to 668 u.g/L. This range isconsistent with mine discharge sample results presented previously for the historicalinvestigations. The historic samples of mine discharge ranged from 34 to 660 ng/L. One of thewater samples collected from about 50 feet below the log dam in 1979 reportedly containedarsenic at 1,860 ng/L. This arsenic concentration is much higher than anything detected in LittleClipper Creek below the log dam during the RI. The peak concentration during the RI was532 ng/L. Historic arsenic concentrations measured in Little Clipper Creek between the mineand Lost Lake during periodic sampling events from 1984 through 1999 ranged from less than5 jig/L to 130 ng/L. These concentrations are slightly lower than those detected during the RI,which ranged from 19 u.g/L to 285 ng/L. In Lost Lake, samples collected during the RIcontained arsenic ranging from 5.8 ng/L to 70.6 |ag/L. This range is consistent with most of thesamples that had been collected by DTSC. However, in July and August 1997 (the first summerafter the log dam failure), DTSC measured arsenic concentrations in Lost Lake ranging from574 ng/L to 849 ug/L.

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All previous samples of the mine tailings and waste rock contained high concentrations ofarsenic, ranging from 669 to 1,180 mg/kg and 1,670 to 3,190 mg/kg, respectively. The samplesof waste rock/tailings collected during the RI contained arsenic in a similar range, with anaverage of 1,340 mg/kg and a maximum of 2,070 mg/kg. The highest surface soil concentrationdetected historically, 15,400 mg/kg, was from the Cyanide Building. Samples collected from theCyanide Building during the RI were also very high in arsenic, ranging from 1,620 to31,200 mg/kg.

In 1997, DTSC collected a number of samples around the perimeter of Lost Lake, starting nearthe water's edge and, in some cases, stepping out more than 100 feet from the lake. The highestconcentrations were found within 15 feet of the lake and ranged up to 1,130 mg/kg. The USEPARI samples from these same areas averaged over 400 mg/kg, with a peak of 818 mg/kg. Higherelevation samples from around Lost Lake had much lower concentrations in the historic and RIdata, averaging 10.5 and 12.8 mg/kg, respectively. DTSC collected sediment samples fromLittle Clipper Creek below the mine and Lost Lake. Arsenic concentrations in these samplesranged from 391 to 552 mg/kg. The USEPA RI samples in these areas were similar, but slightlyhigher averaging 655 mg/kg, with a peak of 1,150 mg/kg.

The documentation of sampling results in contained in the CH2M Hill sitewide RI/FS report.

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2.0 Removal Action Objectives

This section presents the basis for conducting a removal action at the site and the regulatoryauthority which allows USEPA to act in order to protect human health and the environment. Therequirements applicable to a potential action are discussed and a summary of potential site risksis presented. The removal action objectives (RAO) based on the potential site risk are thenpresented.

2.1 Basis for Removal ActionThe ownership of the site is private. As previously described, site owners attempted to resumeoperations at the mine which initiated a RWQCB site inspection. The initial log dam failureinitiated a removal action to secure the site. The potential risks confirmed at the site haveresulted in placing the site on the NPL. As an NPL site, the USEPA Region XI office canexercise CERCLA cleanup authority at the site to limit or mitigate human health andenvironmental risks.

2.2 Applicability of CERCLAAny required mitigation will be performed under USEPA Region IX authority as a CERCLAresponse action. This EE/CA provides and demonstrates the cost justification to secureauthorization for funding expenditure.

Paragraph (b)(2) of Section 300.415 of the NCP lists the following factors that should beconsidered when determining the appropriateness of a removal action within the context of anEE/CA:

(i) Actual or potential exposure to nearby populations, animals, or food chain fromhazardous substances, pollutants, or contaminants;

(ii) Actual or potential contamination of drinking water supplies or sensitiveecosystems;

(iii) Hazardous substances or pollutants or contaminants in drums, barrels, tanks, orother bulk storage containers that may pose a threat of release;

(iv) High levels of hazardous substances, pollutants, or contaminants in soils largely ator near the surface that may migrate;

(v) Weather conditions that may cause hazardous substances or pollutants orcontaminants to migrate or be released;

(vi) Threat of fire or explosion;

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(vii) The availability of other appropriate federal or state response mechanisms torespond to the release;

(viii) Other situations or factors that may pose threats to public health or welfare of theenvironment.

A site may have only one or a combination of these criteria present to require a removal action.Factors present at this site include:

• The presence of tailings upstream containing potentially leachable constituents ofpotential concern (COPC) at concentrations that could pose a potential human healthor ecological risk to downstream receptors.

• The threat of spreading contamination downstream which could cause ecologicalimpacts and impacts on surface water through excessive sedimentation, streamchannel inundation, oxygen depletion, increased erosivity, and stream channeltoxicity. These conditions could potentially occur should extreme weather conditionsprevail for an extended period, yielding significant or sustained rainfall.

• The potential physical hazard presented by a large mass of unsecured tailings. Underthe current configuration, the tailings pile retains back water and could potentiallyslide in mass or move catastrophically.

• The potential threat of spreading contamination into underlying soils andgroundwater.

CERCLA Section 300.415(2) establishes USEPA authority such that "At any release, regardlessof whether the site is included on the National priorities List (NPL), where the lead agencymakes the determination, based on the factors in paragraph (b)(2) of this section, that there is athreat to public health or welfare of the United States or the environment, the lead agency maytake any appropriate removal action to abate, prevent, minimize, stabilize, mitigate, or eliminatethe release or the threat of release."

In determining appropriate removal actions, CERCLA Section 300.415(5)(e) states "Thefollowing removal actions are, as a general rule, appropriate in the types of situations shown;however, this list is not exhaustive and is not intended to prevent the lead agency from takingany other actions deemed necessary under CERCLA, CWA Section 311, or other appropriatefederal or state enforcement or response authorities, and the list does not create a duty on the leadagency to take action at any particular time:

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(1) Fences, warning signs, or other security or site control precautions -- where humansor animals have access to the release;

(2) Drainage controls, for example, run-off or run-on diversion ~ where needed toreduce migration of hazardous substances or pollutants or contaminants off-site or toprevent precipitation or run-off from other sources, for example, flooding, fromentering the release area from other areas;

(3) Stabilization of berms, dikes, or impoundments or drainage or closing of lagoons ~where needed to maintain the integrity of the structures;

(4) Capping of contaminated soils or sludges ~ where needed to reduce migration ofhazardous substances or pollutants or contaminants into soil, ground or surfacewater, or air;

(5) Using chemicals and other materials to retard the spread of the release or to mitigateits effects — where the use of such chemicals will reduce the spread of the release;

(6) Excavation, consolidation, or removal of highly contaminated soils from drainage orother areas — where such actions will reduce the spread of, or direct contact with, thecontamination;

(7) Removal of drums, barrels, tanks, or other bulk containers that contain or maycontain hazardous substances or pollutants or contaminants ~ where it will reducethe likelihood of spillage; leakage; exposure to humans, animals, or food chain; orfire or explosion;

(8) Containment, treatment, disposal, or incineration of hazardous materials ~ whereneeded to reduce the likelihood of human, animal, or food chain exposure; or

(9) Provision of alternative water supply ~ where necessary immediately to reduceexposure to contaminated household water and continuing until such time as localauthorities can satisfy the need for a permanent remedy."

These are examples of types of actions that may be appropriate, depending on site-specificconditions or the presence of specific types of chemical hazards, and not all these hazards arepresent at the Lava Cap Mine site.

2.3 Applicable or Relevant and Appropriate RequirementsA primary concern in the development of alternatives is protection of human health and theenvironment. Section 300.415 (j) of NCP requires that primary consideration be given toremoval alternatives that attain or exceed applicable or relevant and appropriate requirements(ARAR) to the extent practicable. The purpose of the Section 300.415 requirement is to makeCERCLA actions consistent with other pertinent federal and state environmental requirements.After the risk assessment (Section 2.5) and preliminary screening of possible technologies(Section 3.2), identification of ARARs was the next step in preparing this EE/CA. The

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requirements in Section 300.415 of CERCLA have been followed in the preparation of thisEE/C A, in development of ARARs, and potential remedies for the site.

2.4 Identification of Applicable or Relevant and Appropriate RequirementsThe assessment of ARARs is an integral part of the remediation process mandated underSection 121 (d) of CERCLA, as amended by Superfund Amendment and Reauthorization Act(SARA). ARARs are used to develop remedial action objectives, determine the appropriateextent of site cleanup, and govern implementation and operation of the selected remedial action.Specifically, the preamble of CERCLA states, the purpose of the law is "to provide for liability,compensation, cleanup, and emergency response for hazardous substances released into theenvironment and the cleanup of inactive hazardous waste disposal sites." Remedial actions that"clean up" hazardous substances at CERLCA sites must comply with state and federalstandards and criteria that are legally applicable to the substance, pollutant, or contaminant; orthat are relevant and appropriate under the circumstances [42 United States Code(U.S.C.) 9621(d)(2)(A)].

Section 300.430(f)(l)(i) of the NCP provides the criteria for selecting a removal alternative. Oneof these criteria states that "Overall protection of human health and the environment andcompliance with ARARs (unless a specific ARAR is waived) are threshold requirements thateach alternative must meet in order to be eligible for selection." An alternative that does notmeet an ARAR under federal environmental or state environmental or facility siting laws may beselected under the following circumstances [Section 300.430(f)(l)(ii)(C)]:

• "The alternative is an interim measure and will become part of a total remedial actionthat will attain the applicable or relevant and appropriate federal or state requirement;

• Compliance with the requirement will result in greater risk to human health and theenvironment than other alternatives;

• Compliance with the requirement is technically impracticable from an engineeringperspective,

• The alternative will attain a standard of performance that is equivalent to that requiredunder the otherwise applicable standard, requirements, or limitation through use ofanother method or approach;

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• With respect to a state requirement, the state has not consistently applied, ordemonstrated the intention to consistently apply, the promulgated requirement insimilar circumstances at other remedial actions within the state; or

• For Fund-financed response actions only, an alternative that attains the ARAR willnot provide a balance between the need for protection of human health and theenvironment at the site and the availability of Fund monies to response to other sitesthat may present a threat to human health and the environment."

Section 300.415 (j) of CERCLA requires the selection of an alternative that will attain ARARs tothe extent practicable. Fund-financed removal actions under CERCLA Section 104 and removalactions pursuant to CERCLA Section 106 shall, to the extent practicable considering theexigencies of the situation, attain ARARs under federal environmental, state environmental, orfacility siting laws. Waivers described in Section 300.430(f)(l)(ii)(C) may be used for removalactions. Other federal and state advisories, criteria, or guidance may, as appropriate, beconsidered in formulating the removal action [see Section 300.400(g)(3)]. In determiningwhether compliance with ARARs is practicable, the lead agency may consider appropriatefactors, including:

(1) The urgency of the situation.(2) The scope of the removal action to be conducted.

2.4.1 ARAR Classification RequirementsAccording to NCP regulations [40 Code of Federal Regulations (CFR) 300.400(g)], arequirement may be either "applicable" or "relevant and appropriate" to a removal action, but notboth. These terms are defined below:

Applicable requirements are "those cleanup standards, standards of control, and othersubstantive requirements, criteria, or limitations promulgated under federalenvironmental, state environmental, or facility siting laws that specifically address ahazardous substance, pollutant, contaminant, remedial action, location, or othercircumstance found at a CERCLA site" (40 CFR 300.5).Relevant and appropriate requirements are "those cleanup standards, standards ofcontrol, and other substantive requirements, criteria, or limitations promulgated underfederal environmental, state environmental, or facility siting laws that, while not'applicable' to a hazardous substance, pollutant, contaminant, remedial action,location, or other circumstance at a CERCLA site, address problems or situationssufficiently similar to those encountered at the CERCLA site that their use is wellsuited to the particular site" (40 CFR 300.5).

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Once a federal or state law has been classified as applicable or relevant and appropriate, itsrequirements must be distinguished between substantive and administrative. "Substantive"requirements are "those requirements that pertain directly to actions or conditions in theenvironment." "Administrative" requirements are "those mechanisms that facilitate theimplementation of the substantive requirements of a statue or regulation." Compliance withadministrative requirements is not mandated for on-site actions (USEPA, 1988). For example,CERCLA specifically exempts on-site actions from federal, state, and local permittingrequirements [42 U.S.C. 9621(e)(l)]. Furthermore, only those state requirements that are morestringent than federal requirements are ARAR [40 CFR 300.5], "More stringent" would alsoinclude those state laws or programs that have no federal counterpart as "they add to the Federallaw requirements that are specific to the environmental conditions in the State" (USEPA, 1988).State requirements, however, must be adopted by formal means (i.e., promulgated) and applieduniversally through the state (i.e., not just to Superfund sites, but to all circumstances addressedin the requirement) [42 U.S.C. 9621(d)(2)(C)(iii)(I)].

2.4.2 To Be Considered CriteriaIn addition, the NCP identifies a third category of guidance, termed "information to-be-considered" (TBC). The TBC category "consist of advisories, criteria, or guidance that weredeveloped by EPA, other federal agencies, or states that may be useful in developing CERCLAremedies" [40 CFR 300.400(g)(3)]. Because these are not promulgated requirements, TBCs donot have the status of ARARs. However, these guidelines may be used when they are necessaryto ensure protection of public health and the environment. If ARARs do not address a particularcircumstance at a CERCLA site, then TBCs can be used to establish remedial guidelines ortargets.

2.4.3 Types of ARARsCERCLA remedial actions may trigger several different types of requirements or ARARs.USEPA provides guidance on three categories of ARARs specific to the pollutant, location, oraction, as discussed below:

• Chemical-specific requirements set health- or risk-based concentration limits orranges for specific substances in various environmental media. If a given chemicalhas more than one such requirement, the more stringent ARAR should be met.Because some media have no promulgated chemical-specific ARARs or haverelatively few chemicals covered by such pre-established requirements, USEPA'sARAR guidance stipulates that it may frequently be necessary to turn to chemical-


specific advisory levels, such as carcinogenic potency factors or reference doses, toestablish cleanup levels.

• Location-specific requirements set restrictions on activities according tocharacteristics of the site or its immediate environs (e.g., regulations pertaining todevelopment in a 100-year floodplain). These requirements may apply if theCERCLA site is located in such a restricted area.

• Action-specific requirements set controls or restrictions on specific activities relatedto the management of hazardous substances (e.g., Resource Conservation andRecovery Act [RCRA] standards for design and operation of hazardous wastemanagement facilities). These requirements are not chemical-specific, but specific togiven removal actions; they may specify acceptable methods that meet technology-based performance standards.

2.4.4 Chemical-Specific ARARs and TBC GuidanceThe action in this EE/CA is considered a non-time critical removal action for the purpose of riskreduction. The objective of the remedies is to minimize future migration of the mine tailingsfrom the site. The remedies developed address to a limited extent the chemical-specific risks andphysical hazards associated with a potential second failure of the dam (e.g., catastrophicmigration of the tailings pile downstream), and the additional ecological impact, that would beimposed on Lost Lake and the drainages leading to Lost Lake.

The removal action will minimize the future migration of chemical contaminates from the site byimplementing control measures, but does not specifically address off-site migration of minetailings that have already occurred from the site. Chemical-specific ARARs related to thesitewide and off-site remediation will be addressed in the FS. Therefore, the potential chemical-specific ARARs and TBC guidance included in Table 2-1 are presented more for informationalpurposes and can be used in the future for the development of the FS.

2.4.5 Location-Specific ARARs and TBC GuidanceRemedial action alternatives may be restricted or precluded by federal, state, or facility lawsbased on its location within a site or its immediate environment. Location-specific ARARs aredesigned to protect the local area from potentially damaging removal actions. For example,altering habitat of an endangered species to construct a treatment facility may jeopardize thesurvivability of the species. The converse is also true; location-specific ARARs also protectremoval alternatives from the environment. For example, locating a treatment facility within afloodplain without proper engineering precautions may result in structural damage during aflood.

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Table 2-2 identifies the federal and state laws that contain promulgated standards, requirements,criteria, or limitations that will be considered as potential ARARs for this EE/CA.

2.4.6 Action-Specific ARARs and TBC GuidanceAction-specific ARARs are promulgated state or federal laws that set controls or restrictions onactivities related to the management of hazardous materials. Later, within Section 3.0, removalaction alternatives for this EE/CA are developed. Each of the active removal alternatives will becontrolled or restricted by action-specific ARARs and TBC guidance. Table 2-3 provides a listof potential action-specific ARARs and TBC guidance.

2.5 Human Health and Ecological Risk SummaryThe authority for USEPA to initiate an action under the CERCLA program is contingent on apotential or proven threat to human health or the environment. A removal action is justified dueto the following potential or proven threat to human health and the environment (Lava CapHuman Health Risk Assessment, 2001; California Department of Fish and Game, 1997):

• Current and future cancer risks are estimated to be 5 x 10"3, for mine workerspotentially exposed to surface soils and sediments in the waste rock/tailings pile areasand in and around the mine buildings, from ingestion, dermal contact, and inhalationroutes of exposure (Exposure Unit 1). Risks are primarily from elevated arsenicconcentrations. This cancer risk estimate is above USEPA's target cancer risk rangeof 1 x 10"6 to 1 x 10"4. The proposed action; however, is only directed at materials inthe waste rock/tailings pile area, not the mine buildings, and arsenic levels in thesource area are lowest in the waste rock/tailings pile area and highest near theCyanide Building. To adjust for this, the arsenic reasonable maximum exposure(RME) concentration of 1.3 x 104 mg/kg for Exposure Unit 1 is divided by theaverage surface soil waste rock/tailings pile area arsenic concentration of1.34E3 mg/kg to obtain a scaling factor of 9.7-fold. This scaling factor is used toadjust the estimated cancer risk from 5 x 10"3 to 5 x 10"4. This revised arsenic cancerrisk is still above USEPA's target cancer risk range of 1 x 10"6 to 1 x 10"4. Asproposed physical stabilization activities include placement of waste rock on therelocated tailings, direct contact exposure to fine-grained tailings will be reduced.

• Surface water and groundwater cancer risks are estimated to range up to 1.7 x 10"4

and 1.1 x 10'3, respectively, based on results of the Human Health Risk Assessment(HHRA). These cancer risk estimates are above USEPA's target cancer risk range of1 x 10"6 to 1 x 10"4. As some, but not all, of these risks result from surface waterinfiltration through the tailings pile, diversion of surface water around the piles isexpected to reduce these estimated surface water and groundwater cancer risks.

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• Degraded and impacted fish and wildlife resources remain at risk from continuederosion and discharge of tailing material from the mine site to Little Clipper Creek.

• Continued input of upstream material (tailings) in Lost Lake will physically limit ordestroy many of the existing resource values, including spawning and nesting sitesand foraging and escarpment areas.

• Resources downstream of Lost Lake also remain at risk from continued input ofupstream materials (tailings) due to the physical limitations of the drainage and thelake to hold and stabilize eroded material.

This summary is presented based on the following references:

• California Department of Fish and Game, 1997, letter from John I. Hiscox, AssociateFishery Biologist to Dave V. Ziarkowski, Hazardous Substance Scientist, CaliforniaDepartment of Environmental Protection (CEPA), Department of Toxic SubstanceControl (DTSC), Sacramento, May 8 (provided as Appendix A).

• Baseline Human Health Risk Assessment, 2001, Lava Cap Mine Site, prepared byCH2M Hill, preliminary issue advance copy.

2.6 Removal Action ObjectivesBased on data presented in the site investigation report and a visual assessment of the site, thesite-specific RAOs for this EE/CA are:

• Mitigate future ecological risks by controlling the release of additional mine tailingsat the dam to Little Clipper Creek including:

Further releases of tailing material to downstream areas.Concentrations of dissolved and suspended tailing contaminants in downstream

surface water.Concentrations of dissolved tailing contaminants in leachate derived from surface

water run-on to the tailings pile.• To the extent practicable, mitigate or prevent additional migration of contaminants

that would result in an excess lifetime cumulative cancer risk greater than 10"4 to 10"6,or noncancer hazard greater than 1.0.

• Comply with ARARs to the extent practicable.• During the implementation of the removal action, to the extent practicable, the

remedy must protect any sensitive areas where they may be present including.Rare and endangered plants and animalsArcheological resources, features, or artifactsWetlands, special, or unique habitatsHistorically significant features or landmarks.

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3.0 Identification and Analysis of Removal ActionAlternatives__________________________

Section 2.0 presents the rational for developing and evaluating removal action alternatives. Theevaluation criteria presented below are those identified within USEPA's guidance and areconsistent with objectives of the NCP. As required by the NCP, protection of human health andthe environment remain overriding considerations.

3.1 Evaluation CriteriaThe goal of the non-time critical removal action process is to select remedies that protect humanhealth and the environment, maintain protection over time, and minimize untreated waste. Astrong statutory preference exists for remedies that will result in a permanent and significantdecrease in toxicity, mobility, or volume and provide long-term protection as identified inSection 121 of CERCLA, as amended. The primary requirements for the selected remedy arethat it be protective of human health and the environment and comply with ARARs. Thealternative screening should focus on meeting these criteria. The alternatives developed to meetthese goals are then compared based on:

• Effectiveness• Implementability• Cost.

To the extent practicable, any non-time critical removal action alternative implemented based onan EE/CA or focused FS should be an integral component of the anticipated final remedy or itshould be the permanent remedy in its entirety. In the case where data gaps exist, EE/CAguidance directs environmental practitioners to select technologies based on good engineeringpractice, experience, regulatory review, known site-specific conditions and limitations, and costeconomy.

For this EE/CA, the screening of alternatives is based on their potential to eliminate, reduce,and/or control risks posed by potential exposure pathways. The NCP [40 CFR 300.430(e)(7)(i)]cites the general evaluation criteria of effectiveness, implementability, and cost. These criteriaare to be considered in the evaluation of alternatives. The types of specific considerations withineach of these general evaluation criteria are listed below:

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• Effectiveness:- Protectiveness of human health and the environment- Protective of workers during implementation- Complies with ARARs- Ability to achieve removal objectives- Level of treatment/containment expected

No residual effect concerns.

• ImplementabilityTechnical feasibility

- Construction and operational considerations- Demonstrated performance/useful life

Adaptable to environmental conditionsContributes to response action performance

- Can be implemented in a reasonable timeframe- Availability

Equipment- Personnel and services- Outside laboratory testing capacity- Off-site treatment and disposal capacity

Post-removal/mitigation site control- Administrative feasibility

Easements or right-of-ways required- Impact on adjoining property- Ability to impose institutional controls- Likelihood of obtaining a exemption from statutory limits (if needed).

• Cost:- Capital cost of equipment- Capital cost of installation

Operations and maintenance (O&M) costPresent worth cost.

An expanded discussion of each of these screening criteria is presented below.


3.1.1 Effectiveness EvaluationThe effectiveness screening evaluation assesses the alternatives' ability to meet RAOs to provideprotection of human health and the environment now and in the future. Measures ofeffectiveness include: 1) reduction of contaminant toxicity, mobility, or volume throughtreatment; 2) long-term protection of human health and the environment; and 3) short-termprotection of human health and the environment during the removal action. These evaluationcriteria are defined in the NCP under 40 CFR 300.430(e)(7)(i).

3.1.2 Implementability EvaluationThe implementability evaluation is the measure of 1) technical feasibility; 2) administrativefeasibility to construct, operate, and maintain a removal action alternative; and 3) availability ofservices and materials. The implementability criterion provides a way to evaluate the potentialof an alternative to be adapted to site-specific conditions. These evaluation criteria are defined inthe NCP under 40 CFR 300(e)(7)(ii).

Technical feasibility is evaluated using the following criteria:

• Constructability• Reliability (e.g., demonstrated performance and operation)• Maintenance• Timeliness/schedule of implementation.

Administrative feasibility is evaluated using the following criterion:

• Ability to obtain permitting, licensing, or regulatory approval.

The availability of services and materials is evaluated using the following criteria:

• Availability of on-property/off-site treatment, storage, and disposal facilities andcapacity

• Availability of equipment

• Availability of design, operating, and support personnel.


3.1.3 Cost EvaluationThe cost evaluation involves developing the level of engineering detail and preparing asufficiently accurate cost estimate for each alternative so that a relative and appropriate costcomparison can be made between competing alternatives. The cost estimates are based onactual expected project expenses modified by site-specific information, cost curves, generic unitcosts, vendor information, conventional cost estimating guides, and commercial removal anddisposal costs. A net present worth of each alternative is to be developed so that each alternativecan be compared on an equivalent basis. For alternatives where the implementation may extendbeyond the first year, a reasonable discount rate is assumed for purposes of calculating netpresent worth.

The accuracy of cost estimates prepared for FS level evaluations are intended to have anaccuracy range of +50 percent to -30 percent as required by standard practice under USEPAguidance. Final costs will ultimately depend on actual labor and material costs, actual siteconditions, productivity, competitive market conditions, final scope, final schedule, finalengineering design, and other variables. Costs for this EE/CA were developed in accordancewith guidance provided in USEPA's cost estimating guidance manuals, "Remedial ActionCosting Manual" (September 1985) and "A Guide to Developing and Documenting CostEstimates During the Feasibility Study" (July 2000).

The NCP states the types of costs to be assessed [(40 CFR 300(e)(7)(iii)] include capital, annualO&M, and periodic costs. The following definitions are consistent with USEPA guidance andthe intent of the NCP.

3.1.3.1 Capital CostCapital costs are those expenditures that are required to construct a remedial action. They areexclusive of costs required to operate or maintain the action through its lifetime. Capital costsconsist primarily of expenditures initially incurred to build or install a remedial action. In theinstance of a removal action, these would include the cost of constructing facilities, engineeringor other professional/technical services, purchasing of equipment, construction labor, materials,security, sampling, worker protection, monitoring waste management, transportation, anddisposal. Capital also includes contractor markups, overhead, profit, and mobilization/demobilization. Capital costs would also include the cost to obtain any permits. CERCLAactions are exempt from actually obtaining any permits, but must comply with the substantiverequirements of any permits such as NPDES for any treated water discharge requirements.

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Temporary treatment permits may be required for treatment of any hazardous wastewater orwaste. Air monitoring for dust or other hazardous air pollutants may be an expectation forassuring worker and community protection, to the extent the requirement for monitoring may becodified in state or federal. Also, substantive permitting requirements for permanent on-sitedisposal of certain treated or untreated waste materials might apply.

3.1.3.2 Annual O&M CostsO&M costs are those post-construction costs necessary to ensure or verify the continuedeffectiveness of an action. These costs are estimated on an annual basis.

Annual O&M costs include all labor, equipment, and material costs, including contractormarkups such as overhead and profit, associated with activities such as ongoing monitoring,operating and maintaining any equipment, containment or treatment systems, and ongoingdisposal associated with these operations. Annual O&M costs also include expenditures forengineering/professional/technical services as necessary to support O&M activities. Thisremoval action may have associated long-term O&M once the implementation of the remedy iscompleted. This might include inspection and maintenance of structures, cleaning andmaintenance on diversion channels or water courses, etc., depending on the final remedyselected.

3.1.3.3 Periodic CostsPeriodic costs are those costs that occur only once very few years (e.g., 5-year reviews,equipment replacement, etc.), or expenditures that occur only once during the entire O&M periodor remedial timeframe (e.g., site closeout, remedy failure, replacement). These costs may beeither capital or O&M costs, but because of their periodic nature, it is often more practical toconsider them separately from other capital or O&M costs in the estimating process. This ismainly because the net present worth of these costs would have to be calculated differently sincethe periodic frequency is a timeframe other than annually. This removal action is not expected tohave associated periodic costs once the removal action is completed.

3.1.3.4 Net Present Worth CostsAfter calculating all the associated costs as listed above, for comparison purposes each cost isconverted into a net present worth cost, so that costs for each alternative can be compared on anequivalent basis. The net present worth is calculated using the standard engineering economicanalysis formulas that convert future dollars to present dollars assuming a uniform discount rate

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or interest rate. USEPA recognizes that the discount rate (cost of money) will vary over time.To determine an appropriate discount rate to be used in the calculation, USEPA recommends thata reasonable rate be selected based on good engineering judgement that reflects the likelyexpected economic conditions over the life of the alternative. For alternatives that include long-term remediation or perpetual care, the standard assumption of a 30-year life is to be used.Inflation is generally ignored in the calculation.

3.1.3.5 Sensitivity AnalysisIn the context of certain remedial activities, a sensitivity analysis is sometimes helpful todetermine how significant certain assumptions are relative to the outcome of a cost estimate.Examples of parameters that could widely vary the final cost include: estimated duration of thealternative, percentage of hazardous/versus not hazardous waste material, duration of the workday or work week, transportation distances, volumes of materials to be treated or handled, etc. Asensitivity analysis is not always required, but sometimes is valuable when competingalternatives are closely matched in the total net present worth cost and are essentially equivalentin other critical areas such as protection of human health and the environment. A spreadsheet isa good presentation format for a sensitivity analysis. Graphs and comparison charts comparingthe results may also be effective.

3.1.3.6 Estimate AccuracyThe required accuracy for an EE/CA cost estimate is +50 percent to -30 percent. This isequivalent to a study grade or preliminary design level estimate, although most estimates andestimators strive to be more accurate in this process as these estimates usually provide theeventual basis for project funding. The accuracy of estimates is greatly improved when moresite-specific information is available, thus minimizing design assumptions that have to be made.

3.2 General Approaches for Impacted Soil RemovalThe following technology types would be generally used to address soils impacted with metalscontamination and would be potentially applicable to the Lava Cap Mine site:

• Surface Capping• Surface Water Runoff Collection and Treatment• Source Removal/Excavation

• Bioremediation (In Situ/Ex Situ)• Phytoremediation (In Situ/Ex Situ)

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• Chemical Stabilization (In Situ/Ex Situ)• Physical Stabilization (In Situ/Ex Situ)• Chemical Treatment/Soil Washing/Flushing (In Situ/Ex Situ)

• Disposal• Institutional Controls to Supplement Engineering Controls.

The applicability of these possible remedy components is evaluated below based on current siteknowledge and site ARARs. The contaminated areas at the Lava Cap Mine site were not everdefined as waste management units. The residual tailings wastes have been characterized andreported to contain elevated levels of arsenic and other metals. The risk assessment reportindicates the tailings and potential leachate contain elevated levels of metals which do constitutea potential human health and environmental risk should they be allowed to remain in theirpresent condition.

3.2.1 Surface CappingIt would be technically possible to cap all the residual tailings in place. However, the nature ofthe local drainage would likely require complete excavation and installation of an underliner toprevent lateral infiltration and seeps. In some locations, tailings deposits are possibly as much as20 to 30 feet thick, varying based on the depth of the original channel profile. As a minimum, acap might be installed over the main tailings area. However, without an underliner, lateralinfiltration from Little Clipper Creek could still occur. Excavation, relocation, placement, andpermanent disposal of tailings on site within an engineered/capped cell would need to conform tocurrent federal and California solid/hazardous waste regulations.

3.2.2 Surface Water Runoff Collection and TreatmentCollection of surface water runoff that may be impacting tailings would be appropriate. LittleClipper Creek has been routed to the east of the tailings, but some drainage also continues toimpact the surface of the tailings. The current diversion of Little Clipper Creek is not believed tobe adequate to accommodate another rainfall incident similar to the 1997 storm. Fullyintercepting Little Clipper Creek by installing barrier walls and diversions at the uppermost partof the mine site and routing through an adequately sized diversion would minimize the potentialfor other future erosion, catastrophic migration of tailings, and leaching of constituents from thetailings into surface water. Little Clipper Creek would have to be diverted in such a way that theentire volume of flow would be intercepted/collected and discharged below the existing log dam.

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Surface drainage on the tailings pile itself could also be enhanced to promote directed runoff,with sufficiently reduced velocity to avoid erosion and transport.

3.2.3 Source Removal/ExcavationSource removal makes technical sense for eliminating the potential risk posed by residualtailings either migrating or impacting surface water through contaminant leaching. Either partialor total excavation would be expected to be beneficial. Partial excavation, contouring, andgrading would prevent excessive retention of water and improve runoff flow, minimizing erosionand leaching. Total excavation combined with either removal or capping in an engineered cellwould likely provide the most permanent remedy. However, such a remedy is likely to be costlybecause of the large volume of tailings remaining at the site Excavation or removal of materialcould be accomplished with standard equipment such as backhoes and trackhoes (for deep areas).Standard bulldozers or other blade equipment could be used for grading and sloping to improverunoff.

3.2.4 Bioremediation (In Situ/Ex Situ)Certain metals can be effectively bioremediated through two mechanisms. Under certainconditions, strong highly reducing bacteria can reduce the oxidation states of certain metals suchas chromium to lower oxidation states that are potentially less toxic. Assuming conditions toreverse the reduction reaction are not favorable, a benefit in toxicity can be realized. Thisprocess involves culturing naturally-occurring bacteria, typical of those found in swamp areas,then flooding the media to be reduced for a period of time so that the bacteria will complete thereduction of resident metals. However, this type of bioremediation would have very limitedapplication at this site. The reduced trivalent form of arsenic is more toxic than the higherpentavalent state. Since arsenic is the most prevalent contaminant, this technology is not likelyto be effective. Therefore, this technology is dismissed from further consideration.

Another type of soils bioremediation is a leaching-based process. Various bacteria producenatural surfactants that enhance the removal of metals from soil. The bacteria are cultured andthen used to extract the metals from the tailings. Through the course of a number of cycles, theconcentration of contaminants is reduced. In application, this approach is similar to the heap-type leaching arrangements that are used to chemically extract metals. Piles would be placedover a lined or contained area so that solutions containing the metals could be collected.Solutions with bacteria and appropriate nutrients would then be circulated down through thecontaminated media. This type of treatment may require a long treatment period to achieve

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adequate reductions in concentrations. The cost for treatment, maintenance, and management ofresidual contaminated liquids is expected to be high. There appears to be no cost advantage forthis approach over other approach versus other treatment options such as stabilization, andwithout significant pilot testing, it is uncertain how effective this approach would be under site-specific conditions. Thus, this technology is dismissed from further consideration.

3.2.5 Phytoremediation (In Situ/Ex Situ)Phytoremediation involves planting certain types of plant species in waste materials thatpreferentially uptake and concentrate metals in their biomass. Subsequent harvesting of thebiomass and concentration and/or disposal renders the impacted media lower in metalsconcentration and not subject to potential regulation. The technology can be implemented in situunder some site conditions, such as in marshes, bogs, or along banks where vegetation can bereadily and thickly established. However, the wide area of distribution and varying thickness ofdeposits would make it nearly impossible to implement effectively. In some areas, the roots ofplants would not extend the full depth. Also, the tailings area currently does not support anysignificant establishments of higher level vegetation. This could be the result of soil propertiesor chemical toxicity in the interstitial pore water.

If phytoremediation were to be implemented at the site, the tailings would need to be excavatedand taken to an open area where they could be spread in lifts of suitable thickness forestablishing selected plant species. The tailings may require amending with nutrients and otherongoing care. The process may require several years and the biomass harvested from the plantsmay require management as a hazardous waste if concentration of metals within plant tissue wassignificant. This technology option is expected to be extremely costly and take a long time toimplement relative to other technology options that will provide an immediate benefit. Sincethere is no practical, technical, or cost advantage, this technology option is dismissed fromfurther consideration.

3.2.6 Chemical Stabilization (In Situ/Ex Situ)Metals contamination in a matrix of soil or sand such as that found in the Lava Cap Mine tailingscan be effectively isolated from the environment through stabilization. This process uses limeand/or other pozzolonic materials such as fly ash, cement, silicates, etc., to chemically bindinorganic constituents in a matrix that will eliminate leaching. This approach could beimplemented both in situ and ex situ. However, due to the irregularities in the depth of thetailings, the best way to implement this approach would be to excavate the tailings, stabilize

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them ex situ using equipment such as a pug mill, then transporting them to a permanent storagecell. The chemistry is the same performed either in situ or ex situ and would require pilot testingto confirm a suitable stabilization mix for reducing the teachability of the arsenic.

3.2.7 Physical Stabilization (In Situ/Ex Situ)Physical stabilization involves using natural or engineering controls to physically stabilizestream or river banks, sediments, or other features of a waterway. Natural stabilization involvesestablishing heavy vegetation to prevent erosion and washout. The application of naturalstabilization technology would be most appropriate along banks and in shallow water wherewater tolerant/loving plants could become established. If implemented at the Lava Cap Minesite, it would require the tailings be excavated or prepared in such a way that vegetation could beestablished that would retain the tailings and prevent erosion. Alternatively, man-madeengineering controls can perform the same function. Physical stabilization can be accomplishedby installing/anchoring geotextile fabrics, placing riprap or other heavy cover, using certainsurface/soil cements, or other geotechnical engineering soil stabilization/anchoring approaches.

Some physical stabilization was performed during the 1997 removal action. Riprap and wasterock was used in some locations to cover the tailings to prevent further migration and erosion.

3.2.8 Chemical Treatment/Soil Washing/Flushing (In Situ/Ex Situ)Contaminants such as metals can be chemically extracted from contaminated media. Theprocess typically involves some type of flushing or recirculating the washing solution, whichthen dissolves or absorbs the constituents of concern. It would be nearly impossible to performthis type of treatment at the Lava Cap Mine site in situ. In situ treatment requires being able tomaintain hydraulic control and recover all of the washing solution after it is applied. The natureof the underlying drainage would prevent control and capture of any washing solutions. Tailingscould be excavated and moved to a site where the flushing process could be more rigorouslycontrolled and the waste fluids collected for treatment. In essence, this is how gold wasextracted from the tailing by a leaching process. This process would require a considerableamount of time to complete and would not be expected to be more economical compared to othertreatment technologies such as stabilization. Also, the management of the residual extractionwastes would be a concern as they are likely to be sufficiently concentrated to constitute ahazardous waste. Therefore, based on technical considerations, waste management, andanticipated high cost, this technology process option is dismissed.

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3.2.9 DisposalSampling results from the tailings indicate they could be a characteristically hazardous waste bythe Toxicity Characteristic Leaching Procedure (TCLP) method. These materials do containmetals which may pose a risk depending on how they are managed. The available disposaloptions must consider that potential, but would not be impacted by the more stringent provisionsof RCRA for management of hazardous waste. Possible disposal options include: on-sitedisposal in an engineered cell, transportation to an approved off-site facility that may reprocessand reclaim any residual value in the waste material, or off-site disposal at an approved facilitybased on waste classification.

3.2.10 Institutional Controls to Supplement Engineering ControlsInstitutional controls include such actions as the recording of restrictive deed covenants,enforcement of access restrictions, installing restrictive fencing, providing alternative watersupplies, installing point of use water treatment systems, performing ongoing monitoring todetermine the level of controls or use restrictions, land acquisition, resident relocation, or otherinstitutional actions to protect human health.

Institutional controls may prevent inappropriate land usage or disturbance of areas that have beenengineered to prevent erosion. However, as a stand-alone remedy, institutional controls withoutengineering measures will not prevent erosion or leaching of contaminants associated with thetailings.

3.3 Development of AlternativesIn developing alternatives, the scope of this EE/CA is limited to just the tailings area. Althoughthere are additional risks associated with the overall site, such as flow from the adit, tailings inLost Lake, various seeps, and impacted groundwater, the remedies developed and presented areonly to improve the stability and reduce the potential risk associated with the migration of thetailings below the dam to Little Clipper Creek. These alternatives represent approaches forachieving the greatest short-term cost benefit in terms of environmental and human health riskreduction and are developed anticipating additional measures for the site may be implementedunder the pending FS. Based on the site requirements, RAOs for the site, the baseline riskassessment, site-specific ARARs, and the technology screening presented in Section 4.2, thefollowing alternatives are proposed for removal/mitigation of the tailings located at the Lava CapMine site:

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• Alternative 1 - No Further Action• Alternative 2 - Little Clipper Creek East Channel Diversion, Regrading, and

Physical Stabilization of Tailings at the Log Dam• Alternative 3 - Little Clipper Creek Central Channel Diversion, Regrading, and

Physical Stabilization of Tailings at the Log Dam• Alternative 4 - Rock Fill Retention Dam Downstream of Original Log Dam

Location, Regrading, and Physical Stabilization of Tailings at the Log Dam• Alternative 5 - Excavation and Disposal of Tailings On Site in Newly

Constructed Disposal Cells• Alternative 6 - Excavation and Removal of Tailings Off Site

3.3.1 Detailed Description of AlternativesThe following sections provide detailed descriptions of the above alternatives for the site. Thesedescriptions detail the basic assumptions relative to the costing of each alternative. A detailedcost breakdown for each alternative is provided in Tables 3-la/b through 3-5a/b.

3.3.1.1 Detailed Description of Alternative 1 - No Further ActionThe No Further Action alternative means no additional action will be taken, which includesmonitoring, maintenance, or perpetual care. It is developed as a baseline to compare otheralternatives and has no associated cost or level of effort.

3.3.1.2 Detailed Description of Alternative 2 - Little Clipper Creek East ChannelDiversion, Regrading, and Physical Stabilization of Tailings at the LogDam

Alternative 2 involves the installation of a drainage channel to completely intercept/divert LittleClipper Creek and run-on drainage away from the far northern and eastern limits of the tailingsarea. Little Clipper Creek and other captured drainage will be diverted around the tailings areato the eastern side through an approximately 10-foot-wide by 3-feet-deep reinforced concrete-lined trapezoidal drainage ditch. The existing drainage piping will be removed. Other ancillarydrainages approaching the site from the east will also be captured by the diversion ditch. Theditch will be sized to accommodate a flow of up to 500 cubic feet per second (cfs), which isgreater than a 100-year, 24-hour storm and greater than a 6-hour probable maximumprecipitation (PMP) event. The remnants of the existing log dam would be removed and thelower tailings area graded to prevent erosion and physically stabilize the area. This is estimatedto involve approximately 18,000 cubic yards of grading. Areas that are regraded and anydeposits of excavated tailings would be covered with a geotextile fabric overlain by an 18-inch-

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thick layer of coarse waste rock to further stabilize them. The former dam face area would bebutressed with grouted riprap or gabion baskets and a baffle spillway will be installed at theoutlet of the channel. The entire tailings pile surface area would be graded to improve andpromote incidental runoff (with minimal erosion), grading the area towards the central drainagechannel at a minimum slope of 5 percent. Prior to implementation of the remedy, appropriatedetailed engineering would be completed including geotechnical testing and plans forconstruction prepared including a work plan, health and safety plan, erosion and sedimentationcontrol plan, construction quality assurance plan, environmental protection plan, etc. for agencyapproval. A plan for this alternative is provided in Figure 3-1.

3.3.1.3 Detailed Description of Alternative 3 - Little Clipper Creek Central ChannelDiversion, Regrading, and Physical Stabilization of Tailings at the LogDam

Alternative 3 involves the installation of a drainage channel to completely intercept/divert LittleClipper Creek and run-on drainage away from the far northern and eastern limits of the tailingsarea. Little Clipper Creek and other captured drainage will be diverted through a constructedtrapezoidal concrete-lined drainage channel centrally down through the tailings area. Thedrainage channel would be approximately 10-feet-wide by 3-feet-deep reinforced concrete-linedtrapezoidal drainage ditch. The existing drainage piping for diverting Little Clipper Creek wouldbe left as is. The newly constructed central drainage ditch will be sized to accommodate a flowof up to 500 cfs, which is greater than a 100-year, 24-hour storm and greater than a 6-hour PMPevent. The remnants of the existing log dam would be removed and the lower tailings areagraded to prevent erosion and physically stabilize the area. This is estimated to involveapproximately 18,000 cubic yards of grading. Areas that are regraded and any deposits ofexcavated tailings would be covered with a geotextile fabric overlain by an 18-inch-thick layer ofcoarse waste rock to further stabilize them. The former dam face area would be butressed withgrouted riprap or gabion baskets and a baffle spillway will be installed at the outlet of thechannel. The entire tailings pile surface area would then final graded to improve and promoteincidental runoff (with minimal erosion), grading the area towards the central drainage channel ata minimum slope of 5 percent. Prior to implementation of the remedy, appropriate detailedengineering would be completed including geotechnical testing and plans for constructionprepared including a work plan, health and safety plan, erosion and sedimentation control plan,construction quality assurance plan, environmental protection plan, etc. for agency approval. Aplan for this alternative is provided in Figure 3-2.


3.3.1.4 Detailed Description of Alternative 4 - Rock Fill Retention DamDownstream of Original Log Dam Location, Regrading, and PhysicalStabilization of Tailings at the Log Dam

Alternative 4 involves the construction of a new rock core dam with a central spillwayapproximately 500 feet downstream of the existing log dam and Little Clipper Creek invertElevation 2665 mean sea level. The existing drainage piping diverting Little Clipper Creek willremain as is. The remnants of the existing log dam would be removed and the lower tailings areagraded to prevent erosion and physically stabilize the area. This is estimated to involveapproximately 18,000 cubic yards of grading. Areas that are regraded and any deposits ofexcavated tailings would be covered with a geotextile fabric overlain by an 18-inch-thick layer ofcoarse waste rock to further stabilize them. The former dam face area would be butressed withgrouted riprap or gabion baskets. The entire tailings pile surface area would be graded toimprove and promote incidental runoff (with minimal erosion), by grading the area from theperimeter towards the centerline at a minimum slope of 5 percent. The new rock core tailingsretention dam would be designed to be "leaky," meaning under normal rainfall conditions, thedam would allow the slow release of water through the dam contained within the tailings upbehind the dam. Under extreme weather conditions when excessive overland runoff occurs, flowwould discharge through the principal spillway that would be sufficiently anchored to preventexcessive erosion or failure of the retention dam. Prior to implementation of the remedy,appropriate detailed engineering would be completed including geotechnical testing and plansfor construction prepared including a work plan, health and safety plan, erosion andsedimentation control plan, construction quality assurance plan, environmental protection plan,etc. for agency approval. A plan for this alternative is provided in Figure 3-3.

3.3.1.5 Detailed Description of Alternative 5 - Excavation and Disposal of TailingsOn Site in Newly Constructed Disposal Cells

Alternative 5 involves systematic excavation and relocation of all tailings into a constructedlined landfill/impoundment on site. This would involve the excavation of up to approximately150,000 cubic yards of tailings and waste rock. The landfill/impoundment would involve avalley fill design at the upper portion of the site in the vicinity of the existing tailings repositoryfrom the previous removal action and the adit drainage, occupying an area of approximately2.5 acres The area would be appropriately prepared and an underliner installed to meetapplicable requirements. The unit would likely have to be designed to meet RCRA Subtitle Crequirements, as the presence of metals in the tailings such as arsenic would likely leach from thewaste tailings above TCLP limits for hazardous waste classification. Following placement, theformerly impacted areas would be graded and restored to match the natural surroundings and

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topography, while minimizing the potential for erosion and downstream sedimentation. Areaswith an extreme potential for erosion would be anchored, covered, or reinforced as appropriatewith geotextile fabric, riprap, etc. The existing east diversion drainage channel would requireimprovement to handle a 500 cfs storm event similar to the channel proposed in Alternative 2.The remnants of the existing log dam would be removed and placed in the landfill. The formerdam face area would be butressed if needed for additional stabilization with riprap or gabionbaskets. Prior to implementation of the remedy, appropriate detailed engineering would becompleted including geotechnical testing and plans for construction prepared including a workplan, health and safety plan, erosion and sedimentation control plan, construction qualityassurance plan, environmental protection plan, etc. for agency approval. A plan for thisalternative is provided in Figure 3-4.

3.3.1.6 Detailed Description of Alternative 6 - Excavation and Removal of TailingsOff Site

Alternative 6 involves the systematic excavation and relocation of the tailings to an off-sitedisposal facility. This would involve the excavation of up to approximately 150,000 cubic yardsof tailings and waste rock and transportation to an appropriate landfill off site. It is assumed thatthe waste rock would be disposed of as nonhazardous and the tailings would require stabilizationprior to disposal at a hazardous waste facility. This alternative would likely require significantimprovements to the access road to accommodate the high level of truck traffic. The wastematerial would require treatment either by the disposal facility or on site before ultimate disposalin order to meet Universal Treatment Standards for land disposal of arsenic-containing waste.Following excavation and removal of the tailings, the formerly impacted areas would be gradedand restored to match the natural surroundings and topography, while minimizing the potentialfor erosion and downstream sedimentation. Areas with an extreme potential for erosion wouldbe anchored, covered, or reinforced as appropriate with geotextile fabric, riprap, etc. Theexisting drainage piping diverting Little Clipper Creek will remain as is. The remnants of theexisting log dam would be removed. The former dam face area would be butressed if needed foradditional stabilization with riprap or gabion baskets. Prior to implementation of the remedy,appropriate detailed engineering would be completed and plans for construction preparedincluding a work plan, health and safety plan, erosion and sedimentation control plan,construction quality assurance plan, environmental protection plan, etc. for agency approval. Aplan for this alternative is provided in Figure 3-5.

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3.4 Analysis of Alternatives

3.4.1 Detailed Evaluation of Alternative 1 - No Further ActionThe "No Further Action" alternative involves taking no further action at the site, eitheradministrative or response actions; performing no additional monitoring; and conducting noadditional short-term or long-term assessment or investigation.

3.4.1.1 Effectiveness EvaluationThe "No Further Action" alternative would not be effective in preventing further environmentaldegradation such as the mobilization of tailings downstream or leaching of metals from residualtailings. No Further Action would not eliminate the potential human health impacts that wereidentified, would not prevent further impacts on surface water or groundwater, and would notprevent environmental uptake by fish or other organisms. No Further Action could result incontinued and possibly catastrophic migration of the tailings down into Little Clipper Creek andLost Lake.

3.4.1.2 Implementability EvaluationThe "No Further Action" alternative would not require any implementation. All current activityat the site would be terminated. No additional monitoring or sampling would be performed. Noadditional cost would be expended. The natural processes of weathering, dispersion, dilution,transport, assimilation, retardation, etc., would be allowed to proceed unabated, unaided, anduncontrolled. There would be no limits on the implementability of this alternative. However, itwould not meet the requirements under the NCP.

3.4.1.3 Cost EvaluationThere is no cost associated with the "No Further Action" alternative because no removal actions,institutional controls, or further monitoring is proposed.

3.4.2 Detailed Evaluation of Alternative 2 - Little Clipper Creek East ChannelDiversion, Regrading, and Physical Stabilization of Tailings at the Log Dam

This alternative involves construction of a concrete-lined east side diversion channel to replacethe current diversion ditch and reroute Little Clipper Creek completely away from the tailingspile and to collect and divert as much surface runoff as possible. Grading and physicalstabilization of tailings in the lower part of the tailings area and physical stabilization of the logdam area are also included in the scope. The goal of this alternative is to divert as much water

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away from the tailings as possible and physically stabilize the surface of the tailings pile toprevent erosion from incidental precipitation.

3.4.2.1 Effectiveness EvaluationAlternative 2 would provide a significant advantage in protecting the environment and reducinghuman health risk. By diverting runoff away from the tailings, the potential for leaching arsenicand the potential for tailings migration would be significantly reduced. Some arsenic maycontinue to be leached as a result of incidental precipitation on the tailings pile and subsequentinfiltration and flow through the tailings pile. Sloping and contouring of the surface wouldimprove runoff flow and limit infiltration volume during high yield rain events. The amount ofarsenic that might continue to be leached or the impact it may have on the environment isunknown. However, relative to other contributions such as certain seeps and adit drainage, thiscontribution would be expected to be small until those flows are controlled or treated.

There is expected to be no significant difficulties presented to workers during implementation ofthe remedy. The most significant chemical hazard would be presented as a result of dustevolution and repeated contact with the tailings. These hazards would be mitigated byengineering controls and personal protection as determined to be necessary by the project'sCertified Industrial Hygienist/safety officer. There would be typical safety hazards associatedwith construction activity and operation of heavy equipment, which are not expected to beoverriding or any more significant with this remedy compared to the other activity remedies.

The remedy is expected to comply with ARARs with the exception that chemical preliminaryremediation goals (PRG) for the site might not be met and some additional measures to furtherevaluate/reduce risk may need to be deferred and implemented under the sitewide FS. Thislimitation is due to the potential for leachate and seeps to occur as a result of the limited amountof incidental precipitation falling on the immediate area of the tailings. The vast majority of thewatershed area drainage would be diverted away from the tailings by the new Little ClipperCreek diversion channel. However, some human health risk may remain above site PRGs andsome downstream ecological impacts may still occur as a result of a limited amount of arsenicleaching from the tailings. At this time, there is no way to quantify the significance of thispotential contribution to overall site risk or to know even if the leaching will occur above risk-based standards at all. However, this remedy would be considered a prudent measure to takeunder a removal action because of the significant site improvement and significant reduction in

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potential ecological and chemical risk that is expected as a result of physical stabilization of thetailings and diverting all of Little Clipper Creek.

3.4.2.2 Implementability EvaluationAlternative 2 could be easily implemented. The resources and materials necessary are available.The remedy is technically feasible and all the engineering concepts of water diversion andphysical stabilization are well demonstrated. There are no overriding construction considerationsassociated with implementation. Implementation would require some improvement of roads andsite facilities to bring equipment into the area. The timing of the action would need to coincidewith appropriate weather conditions as heavy rainfall could make implementation of the remedydifficult or cause delays until conditions improve. It is expected that the remedy will beimplemented prior to the heaviest part of the next rainy season.

The remedy could be implemented within a reasonable timeframe estimated at about 2 to3 months. The necessary equipment, materials, personnel, and services are readily available.Outside testing services for both chemical analysis and geotechnical support would be readilyavailable within the Sacramento area. Treatment capacity for wastewater (on site) and off-sitedisposal capacity for any generated wastes would also be readily available.

Obtaining any easements or right-of-ways is not expected to be an overriding concern, althoughsome access agreements may be required. The remedy is not expected to impact adjoiningproperty adversely. Once implemented, it is expected to enhance adjoining and downstreamproperties by enhancing the environment and decreasing risk.

Periodic inspection may be required to ensure that any erosion is repaired. Some long-termmaintenance may be required to remove sedimentation from the diversion channel and makerepairs should the concrete diversion structure begin to show deterioration.

The remedy would accommodate a range of changing environmental conditions, which is thereason an open channel design is proposed rather than an enclosed pipe. The proposedengineering controls are expected to sustain a 6-hour PMP event, which exceeds the1997 rainfall event that led to the earlier failure of the log dam. The remedy would contribute tothe response action performance and could be implemented within a reasonable timeframe. Theremedy is expected to be administratively feasible and favorable and acceptable to the localcommunity.

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3.4.2.3 Cost EvaluationA detailed cost breakdown for estimated capital, operating, maintenance, and net present worthcosts for Alternative 2 is presented in Tables 3-la and 3-lb. The estimated capital cost for thisalternative is $1,119,000 and the estimated annual O&M cost is $28,000. The calculated netpresent worth cost is $1,603,000.

The costs are based on IT's experience on other projects, cost data from standard constructionestimating publications, and actual quotes for certain services. The estimate is a FS level costestimate having an accuracy of plus 50 percent minus 30 percent.

3.4.3 Detailed Evaluation of Alternative 3 - Little Clipper Creek Central ChannelDiversion, Regrading, and Physical Stabilization of Tailings at the Log Dam

This alternative involves construction of a concrete-lined diversion channel to reroute LittleClipper Creek down through the central part of the tailings area. Grading to improve runoffflow, physical stabilization in the lower part of the tailings area where needed, and physicalstabilization in the log dam area are also included in this alternative. The goal of this alternativeis to transport Little Clipper Creek watershed drainage over the tailings without allowingsignificant infiltration to occur. This is accomplished by the installation of a lined centraldiversion channel and physical stabilization of the surface of the tailings pile to prevent erosionfrom incidental precipitation.

3.4.3.1 Effectiveness EvaluationAlternative 3 is expected to provide an advantage in protecting the environment and reducinghuman health risk. Little Clipper Creek watershed drainage is prevented from impacting thetailings by routing through a central drainage channel running down through the tailings area.By keeping runoff away from the tailings, the potential for leaching arsenic and the potential fortailings migration would be reduced. There is an inherent limitation in this alternative in that ifthe channel capacity is exceeded, the excess will overflow and could infiltrate or erode thetailings. Potentially significant erosion would be expected as a channel overflow would occur asa result of catastrophic flooding conditions and the water velocity in the channel would be atmaximum.

Some arsenic may continue to be leached as a result of incidental precipitation on the tailingspile and subsequent infiltration and flow through the tailings pile. Sloping and contouring of thesurface would improve runoff flow and limit infiltration volume during high yield rain events.

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The amount of arsenic that might continue to be leached or the impact it may have on theenvironment is unknown. However, relative to other contributions such as certain seeps and aditdrainage, this contribution would be expected to be small until those flows are controlled ortreated.

There is expected to be no significant difficulties presented to workers during implementation ofthe remedy. The most significant chemical hazard would be presented as a result of dustevolution and repeated contact with the tailings. These hazards would be mitigated byengineering controls and personal protection as determined to be necessary by the project'sCertified Industrial Hygienist/safety officer. There would be typical safety hazards associatedwith construction activity and operation of heavy equipment, which are not expected to beoverriding or any more significant with this remedy compared to the other activity remedies.This remedy would be expected to be less invasive of the natural environment as it minimizes theamount of disturbance in areas beyond the tailings pile.

The remedy is expected to comply with ARARs with the exception that chemical PRGs for thesite might not be met and some additional measures to further evaluate/reduce risk may need tobe deferred and implemented under the sitewide FS. This limitation is due to the potential forleachate and seeps to occur as a result of the limited amount of incidental precipitation falling onthe immediate area of the tailings. The vast majority of the Little Clipper Creek watershed areadrainage would be collected and flow over the tailings pile by the new Little Clipper Creekdiversion channel. However, some human health risk may remain above site PRGs and somedownstream ecological impacts may still occur as a result of a limited amount of arsenic leachingfrom the tailings. At this time, there is no way to quantify the significance of this potentialcontribution to overall site risk or to know even if the leaching will occur above risk-basedstandards at all. However, this remedy would be considered an appropriate measure to takeunder a removal action because of the significant site improvement and significant reduction inpotential ecological and chemical risk that is expected as a result of physical stabilization of thetailings and intercepting Little Clipper Creek.

3.4.3.2 Implementability EvaluationAlternative 3 could be easily implemented. The resources and materials necessary are available.The remedy is technically feasible and all the engineering concepts of water diversion andphysical stabilization are well demonstrated. There are no overriding construction considerationsassociated with implementation. Implementation will require some improvement of roads and

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site facilities to bring equipment into the area. The timing of the action would need to coincidewith appropriate weather conditions as heavy rainfall could make implementation of the remedydifficult or cause delays until conditions improve. It is expected that the remedy will beimplemented prior to the heaviest part of the next rainy season.

The remedy could be implemented within a reasonable timeframe estimated at about 2 to3 months. The necessary equipment, materials, personnel, and services are readily available.Outside testing services for both chemical analysis and geotechnical support would be readilyavailable within the Sacramento area. Treatment capacity for wastewater (on site) and off-sitedisposal capacity for any generated wastes would also be readily available.

Obtaining any easements or right-of-ways is not expected to be an overriding concern, althoughsome access agreements may be required. The remedy is not expected to impact adjoiningproperty adversely. Once implemented, it is expected to enhance adjoining and downstreamproperties by enhancing the environment and decreasing risk.

Periodic inspection may be required to ensure that any erosion is repaired. Some long-termmaintenance may be required to remove sedimentation from the diversion channel and makerepairs should the concrete diversion structure begin to show deterioration.

The remedy would accommodate a range of changing environmental conditions, which is thereason an open channel design is proposed rather than an enclosed pipe. The proposedengineering controls are expected to sustain a 6-hour PMP event, which exceeds the1997 rainfall event that led to the earlier failure of the log dam. The remedy would contribute tothe response action performance and could be implemented within a reasonable timeframe. Theremedy is expected to be administratively feasible and favorable and acceptable to the localcommunity.

3.4.3.3 Cost EvaluationA detailed cost breakdown for estimated capital, operating, maintenance, and net present worthcosts for Alternative 3 is presented in Tables 3-2a and 3-2b. The estimated capital cost for thisalternative is $1,124,000 and the estimated annual O&M cost is $28,100. The calculated netpresent worth cost is $1,611,000.

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The costs are based on IT's experience on other projects, cost data from standard constructionestimating publications, and actual quotes for certain services. The estimate is a feasibility gradelevel cost estimate having an accuracy of plus 50 percent minus 30 percent.

3.4.4 Detailed Evaluation of Alternative 4 - Rock Fill Retention Dam Downstreamof Original Log Dam Location, Regrading, and Physical Stabilization ofTailings at the Log Dam

This alternative involves construction of a new "leaky" rock fill dam approximately 500 feetdownstream of the existing log dam, creating a secondary sediment/tailings trap. Grading toimprove runoff flow, physical stabilization in the lower part of the tailings area where needed,and physical stabilization in the log dam area are also included in the scope. The goal of thisalternative is to capture any tailings that migrate from the mine tailings area, before they reachLost Lake. The remedy would have a limited benefit in reducing potential teachability as thecurrent drainage patterns would not be significantly altered.

3.4.4.1 Effectiveness EvaluationAlternative 4 would provide a limited advantage in protecting the environment and reducinghuman health risk. The potential for leaching arsenic and the potential for tailings migrationwould not be reduced below the current levels as no significant changes in drainage patternswould be a result of implementation. The potential for tailings migration down to Lost Lakewould be effectively eliminated. Some arsenic may continue to be leached as a result ofincidental precipitation on the tailings pile and the unaltered drainage from Little Clipper Creek,which at times flows over the top of the tailings. The current levels of infiltration and flowthrough the tailings would be changed only slightly as a result of sloping and contouring of thesurface for stabilizing the lower log dam area.

The amount of arsenic that might continue to be leached or the impact it may have on theenvironment is unknown. Relative to other contributions such as certain seeps and adit drainage,this contribution is small compared to the contribution coming from those flows.

There is expected to be no significant difficulties presented to workers during implementation ofthe remedy. The most significant chemical hazard would be presented as a result of dustevolution and repeated contact with the tailings. These hazards would be mitigated byengineering controls and personal protection as determined to be necessary by the project'sCertified Industrial Hygienist/safety officer. There would be typical safety hazards associated

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with construction activity and operation of heavy equipment, which are not expected to beoverriding or any more significant with this remedy compared to the other activity remedies.

The remedy is expected to comply with ARARs with the exception that chemical PRGs for thesite might not be met and some additional measures to further evaluate/reduce risk may need tobe deferred and implemented under the sitewide FS. This limitation is due to the potential forleachate and seeps to occur as a result of the current routes of site drainage and incidentalprecipitation falling on the immediate area of the tailings. Although some Little Clipper Creekwatershed area drainage would be diverted away from the tailings by the existing Little ClipperCreek diversion channel, some of that flow is not currently diverted and runs on or through thetailings.

Some human health risk may remain above site PRGs and some downstream ecological impactsmay still occur as a result of continued arsenic leaching from the tailings. At this time, there isno way to quantify the significance of this potential contribution to overall site risk or to knoweven if the leaching will occur above risk based standards at all.

3.4.4.2 Implementability EvaluationAlternative 4 could be implemented with some difficulty. The biggest limitation would beaccessibility. To get equipment down to the location of the new dam, either a new peripheralroad would need to be cut or a temporary roadway down the stream channel would need to beconstructed. The limited access and limited amount of space at the working face of the new damarea would make this construction activity more difficult. The resources and materials necessaryare available, although some importation of large rock may be necessary if waste rock is notadequate in size or available on site in sufficient in quantity for construction of the dam.

The remedy is technically feasible and all the engineering concepts of water dam constructionand physical stabilization are well demonstrated. There are no overriding constructionconsiderations associated with implementation, although the new dam will be subject to stringentState requirements for dam construction, safety, and ongoing inspection. Implementation mayrequire some improvement of roads and site facilities to bring equipment into the area. Should asignificant amount of large rock be required from off site, this will necessitate more significantaccess road improvements on the upper site entrance road to accommodate the higher level oftruck traffic.

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The timing of the action would need to coincide with appropriate weather conditions as heavyrainfall could make implementation of the remedy difficult or cause delays until conditionsimprove. It is expected that the remedy will be implemented prior to the heaviest part of the nextrainy season.

The remedy could be implemented within a reasonable timeframe estimated at about 2 to3 months. Any early rainy weather would make construction difficult or would requiretemporary diversion of Little Clipper Creek. The necessary equipment, materials, personnel, andservices are readily available. Outside testing services for both chemical analysis andgeotechnical support would be readily available within the Sacramento area. Treatment capacityfor wastewater (on site) and off-site disposal capacity for any generated wastes would also bereadily available.

Obtaining any easements or right-of-ways is not expected to be an overriding concern, althoughsome access agreements may be required. Depending on the exact final location, theconstruction of a new dam downstream may require the purchase of adjacent land or the takingof it by eminent domain. The remedy could impact adjoining property adversely as the new damwould create a downstream sedimentation basis which could back up some water during therainy season. Once implemented, it is expected to enhance downstream properties by decreasingpotential environmental risk.

Periodic inspection will be required to ensure that any deterioration of the dam structure isidentified early and repaired. Some long-term maintenance may be required to removesedimentation from the upstream retention/settling basin and to make repairs should erosion ordeterioration occur.

The remedy would accommodate a range of changing environmental conditions. The remedywould contribute to the response action performance and could be implemented within areasonable timeframe. The remedy is expected to be administratively feasible, but may not be asfavorable and acceptable to the local community.

3.4.4.3 Cost EvaluationA detailed cost breakdown for estimated capital, operating, maintenance, and net present worthcosts for Alternative 4 is presented in Tables 3-3a and 3-3b. The estimated capital cost for this

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alternative is $1,241,000 and the estimated annual O&M cost is $31,000. The calculated netpresent worth cost is $1,778,000.


3.4.5 Detailed Evaluation of Alternative 5 - Excavation and Disposal of TailingsOn Site in Newly Constructed Disposal Cells

This alternative involves construction of an on-site RCRA landfill that would permanentlyisolate the tailings from the environment. Such a landfill would comprise 2.5 acres at the upperportion of the site. The subgrade area would be prepared and a double-lined landfill would beconstructed. Tailings and waste rock would be systematically excavated and placed in theengineered disposal cells as the landfill is built out. Once all the tailings and waste rock hadbeen moved and placed, the disposal area would then be covered with an impermeable cover. Aleachate collection system would dewater the landfill. The quantity of water collected would beexpected to taper off within 1 to 3 years so that a minimal amount of leachate treatment (if anylong term) would be required. Disturbed areas would be restored and naturally vegetated. Thesynthetic cover would be covered with soil and vegetated to prevent erosion. The tailings wouldnot be treated and would be classified as a hazardous waste. As a result, the landfill would haveto meet RCRA Subtitle C requirements.

3.4.5.1 Effectiveness EvaluationAlternative 5 would provide a significant advantage in protecting the environment and reducinghuman health risk. By containing all the tailings, the potential for leaching arsenic and thepotential for tailings migration would be completely eliminated. Some arsenic may continue tobe confirmed in Little Clipper Creek as a result of natural leaching from native soils, certainseeps caused by the former mine, and the adit drainage. However, the potential risks associatedwith the former tailings would be completely eliminated. Sloping and contouring of the surfaceafter excavation would improve runoff flow and limit erosion until natural restoration effortsbecame established.

There is expected to be no significant difficulties presented to workers during implementation ofthe remedy. The most significant chemical hazard would be presented as a result of dustevolution and repeated contact with the tailings. These hazards would be mitigated by

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engineering controls and personal protection as determined to be necessary by the project'sCertified Industrial Hygienist/safety officer. There would be typical safety hazards associatedwith construction activity and operation of heavy equipment, which are not expected to beoverriding or any more significant with this remedy compared to the other activity remedies.

The remedy is expected to comply fully with ARARs and eliminate all risks associated with thepresence of the tailings pile. Little Clipper Creek drainage would be restored to route closer tothe natural flow path prior to the operation of the mine. This remedy would be a highly effectiveaction to take under a removal action because of the significant site improvement and completereduction in potential ecological and chemical risk that would be achieved.

3.4.5.2 Implementability EvaluationAlternative 5 could be implemented, but with some difficulty. The construction of such alandfill and the relocation of all the tailings and waste rock would be a significant engineeringundertaking. However, the level of effort would not be an overriding consideration. Theresources and materials necessary are available. The remedy is technically feasible and all theengineering concepts of excavation, landfill construction, site restoration, leachate collection,etc. are well demonstrated. Implementation may require some improvement of roads and sitefacilities to bring equipment into the area. The timing of the action would be less impacted bythe weather although heavy rainfall for an extended period could make implementation of theremedy more difficult or cause delays until conditions improve. It is expected that the remedywill be implemented prior to the heaviest part of the next rainy season.

The remedy could be implemented within a reasonable timeframe estimated at about 3 to4 months. Off-road articulated trucks may be necessary in order to achieve adequate productionrates. The necessary equipment, materials, personnel, and services are readily available. Outsidetesting services for both chemical analysis and geotechnical support would be readily availablewithin the Sacramento area. Treatment capacity for wastewater (on site) and off-site disposalcapacity for any generated wastes would also be readily available.

Obtaining any easements or right-of-ways is not expected to be an overriding concern, althoughsome access agreements may be required. The remedy is not expected to impact adjoiningproperty adversely. Once implemented, it is expected to enhance adjoining and downstreamproperties by significantly enhancing the environment and decreasing human health andecological risk.

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Periodic inspection may be required to ensure that any erosion is repaired. Some long-termmaintenance may be required to maintain the leachate collection and treatment system. Mowingto keep growth down on the surface cover would also be required in perpetuity.

The remedy would accommodate a range of changing environmental conditions. It would not besignificantly impacted by wide fluctuations in rainfall as the cover soil would be properly slopedand stabilized to prevent erosion. The permanent cap would prevent infiltration.

The remedy would contribute to the response action performance and could be implementedwithin a reasonable timeframe. The remedy is expected to be administratively feasible andfavorable and acceptable to the local community.

3.4.5.3 Cost EvaluationA detailed cost breakdown for estimated capital, operating, maintenance, and net present worthcosts for Alternative 5 is presented in Tables 3-4a and 3-4b. The estimated capital cost for thisalternative is $6,322,000 and the estimated annual O&M cost is $158,000. The calculated netpresent worth cost is $9,056,000.


3.4.6 Detailed Evaluation of Alternative 6 - Excavation and Removal of TailingsOff Site

This alternative involves complete excavation and removal of all tailings and waste rock off site.This material would require disposal at a facility permitted to accept hazardous waste as a resultof arsenic leachability. The material would require pretreatment by the receiving facility toachieve universal treatment standard prior to disposal in a landfill.

3.4.6.1 Effectiveness EvaluationAlternative 6 would provide the greatest advantage in protecting the environment and reducinghuman health risk because all contamination and the physical presence of the tailings areeliminated. By completely removing all the tailings and waste rock, the potential for leachingarsenic and the potential for tailings migration would be completely eliminated. Some arsenicmay continue to be confirmed in Little Clipper Creek as a result of natural leaching from native

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soils, certain seeps caused by the former mine, and the adit drainage. However, the potentialrisks associated with the former tailings above would be completely eliminated from the siteforever. Once natural vegetation had been established to assure erosion would not occur, therewould be no ongoing maintenance, inspection, or operation of any type of treatment system.Sloping and contouring of the surface after excavation would improve runoff flow and limiterosion until natural restoration efforts became established.

There is expected to be no significant difficulties presented to workers during implementation ofthe remedy. The most significant chemical hazard would be presented as a result of dustevolution and repeated contact with the tailings. These hazards would be mitigated byengineering controls and personal protection as determined to be necessary by the project'sCertified Industrial Hygienist/safety officer. There would be typical safety hazards associatedwith construction activity and operation of heavy equipment, which are not expected to beoverriding or any more significant with this remedy compared to the other activity remedies.

The remedy is expected to comply fully with ARARs and eliminate all risks associated with thepresence of the tailings pile. Risks would remain associated with residuals in the soil and othermedia. Little Clipper Creek drainage would be restored to route closer to the natural flow pathprior to the operation of the mine. This remedy would be the most effective action to take undera removal action because of the significant site improvement and complete reduction in potentialecological and chemical risk that would be achieved.

3.4.6.2 Implementability EvaluationAlternative 6 could be implemented with some difficulty. The remedy would be a majorexcavation involving up to 150,000 cubic yards of material. The largest limitation onimplementing this alternative would be the high level of truck traffic over the entrance/exit roadfor transporting loads off site to a suitable disposal facility. Assuming 20-ton loads are possible,11,250 round trips would be required for transport of the waste material. This traffic load wouldrequire significant improvements in the access road to the site. Currently, the road is one laneallowing for traffic in one direction at a time.

The excavation and disposal of all the tailings and waste rock would be a significant engineeringundertaking due to the large volume of material to be handled. However, the level of effortwould not be an overriding consideration. The resources and materials necessary are available.The remedy is technically feasible and all the environmental engineering concepts of excavation,

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off-site treatment to meet universal treatment standards, and secure waste disposal are welldemonstrated. Implementation will require some significant improvement of roads and sitefacilities to bring equipment into the area.

The timing of the action would be less impacted by the weather although heavy rainfall for anextended period could make implementation of the remedy more difficult or cause delays untilconditions improve. Also, weather conditions would have to be considered in constructionsequencing so that the remaining tailings at any time were not destabilized and made moresusceptible to erosion. It is expected that the remedy would be implemented prior to the heaviestpart of the next rainy season, which would require a production rate of 2,500 tons per day if theproject were completed in a 90-day timeframe. This would reflect a very high rate ofproductivity which may not be feasible given site the site access road limitations.

The necessary equipment, materials, personnel, and services are readily available. Outsidetesting services for both chemical analysis and geotechnical support would be readily availablewithin the Sacramento area. Treatment capacity for wastewater (on site) and off-site disposalcapacity for any generated wastes would also be readily available.

Obtaining any easements or right-of-ways is not expected to be an overriding concern, althoughsome access agreements may be required. The remedy is not expected to impact adjoiningproperty adversely. The excessive truck traffic would be a nuisance to residents and adjacentproperty owners. However, once implemented, it is expected to enhance adjoining anddownstream properties by significantly enhancing the environment and decreasing human healthand ecological risk.

Periodic inspection may be required until natural vegetation became reestablished after theexcavation. The remedy would accommodate a range of changing environmental conditions.Once completed, environmental conditions would have no impact other than causing the area toreturn to a more natural state. Residual contamination may still be present associated with othermedia such as the underlying soils.

The remedy would contribute to the response action performance and could be implementedgiven the potential production limitations due to the site access road. The remedy is expected tobe administratively feasible and favorable and acceptable to the local community.

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3.4.6.3 Cost EvaluationA detailed cost breakdown for estimated capital, operating, maintenance, and net present worthcosts for Alternative 6 is presented in Tables 3-5a and 3-5b. The estimated capital cost for thisalternative is $38,871,000 and the estimated annual O&M cost is $0. The calculated net presentworth cost is $38,871,000.

The costs are based on IT's experience on other projects, cost data from standard constructionestimating publications, and actual quotes for certain services. The estimate is a feasibility gradelevel cost estimate having an accuracy of plus 50 percent minus 30.

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4.0 Comparative Analysis of Alternatives______________•%

This section discusses the advantages and disadvantages of each alternative and compares therelative merits of alternatives to each other. The criteria for the comparison are the same as thosedescribed in Section 3.0. The alternatives evaluated in this section are:

• Alternative 1 - No Further Action• Alternative 2 - Little Clipper Creek East Channel Diversion, Regrading, and

Physical Stabilization of Tailings at the Log Dam

• Alternative 3 - Little Clipper Creek Central Channel Diversion, Regrading, andPhysical Stabilization of Tailings at the Log Dam

• Alternative 4 - Rock Fill Retention Dam Downstream of Original Log DamLocation, Regrading, and Physical Stabilization of Tailings at the Log Dam

• Alternative 5 - Excavation and Disposal of Tailings On Site in NewlyConstructed Disposal Cells

• Alternative 6 - Excavation and Removal of Tailings Off Site

Table 4-1 provides a comparative screening summary for Alternatives 1 through 6.

4.1 Comparative Effectiveness EvaluationThe "No Further Action" alternative (Alternative 1) would not be effective in preventing furtherdegradation to the environment. Without mitigation or control, the tailings will continue to posea potential human health and ecological risk.

The remaining alternatives (Alternatives 2, 3, 4, 5 and 6) provide a range of improved protectionof human health and the environment over current site conditions. Alternative 6 involving off-site disposal would be most effective, providing for total removal of the tailings and totalremoval of all associated human health and ecological risks. It complies fully with ARARs,achieves RAOs for the mine tailings pile, and constitutes a permanent long-term remedy with noassociated long-term maintenance for the tailings. Residual contamination associated with othermedia such as the underlying soils would remain and be addressed by the FS. Alternative 5involving on-site disposal of all tailings in a constructed landfill would provide a similarreduction in human health and ecological risk provided leachate collection and landfillmaintenance are maintained in perpetuity. Because the residuals (tailings) remain on site, theremedy would present some (albeit very limited) on-site risk due to the generation of the leachatewhich would have to be properly managed and treated. The potential risk from the tailings

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would remain contained and controlled as long as the landfill cover is continually maintained andremains in place. Thus, Alternative 5 would be slightly less desirable than Alternative 6 in termsof long-term effectiveness and permanence of the remedy. Alternatively, Alternative 6 doespresent a long-term liability due to hazardous waste transport and disposal at an off-site location.These two alternatives provide the greatest reduction in potential on-site risk, with Alternative 6being the most protective.

Alternatives 2 and 3 involving both improved physical stabilization of the tailings, grading, andwater diversion would provide some reduction in chemical risk and a total reduction in the risksassociated with tailings migration. Neither would completely meet all ARARs or correctiveaction objectives. However, this removal action does not have to provide a permanent remedy atthis time, as the primary objective is to control the potential for catastrophic migration of thetailings. A permanent remedy will be provided in the FS. Other potential site risks will beevaluated and remedied as appropriate under the sitewide RI/FS. Under both alternatives, theprimary goal of preventing tailings migration would be achieved through engineering controlsand improvements. In addition to preventing tailings migration, Alternative 2 provides thegreatest potential to reduce leaching of arsenic from the tailings by diverting Little Clipper Creekcompletely away from the tailings pile. Under Alternatives, which proposes the centraldrainage channel for Little Clipper Creek, there is a potential for more infiltration into thetailings to occur.

Under Alternative 4 which involves the construction of a new sediment and tailings retentiondam downstream, the risks associated with tailings migration are controlled. However, thisalternative will provide little reduction in the leaching potential from the tailings relative tocurrent site conditions; thus, it provides the least reduction in potential chemical risk of all theactive remedial alternatives.

Ranking the alternatives in terms of overall effectiveness, Alternative 6 would be the mostprotective, followed by Alternative 5, Alternative 2, Alternative 3, and Alternative 4.Alternative 1, the No Action alternative, would neither control the migration of tailings norreduce any potential chemical risk associated with leaching from the tailings. Thus, it would bethe least acceptable.

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4.2 Comparative Implementabilfty EvaluationThe "No Further Action" alternative would be the easiest option to implement. However, the"No Further Action" alternative would not be protective of human health or the environment.

Of the remaining alternatives (Alternatives 2, 3, 4, 5, and 6), Alternatives 2 and 3 involvingconstruction of either a peripheral or central diversion channel would be the easiest toimplement. The materials, technology, and resources are available for all the alternatives. Thesetwo alternatives would involve the least amount of resources and effort and would have theshortest construction duration. Of the two, the central channel option under Alternative 3 wouldlikely be slightly easier to implement compared to the peripheral channel. The peripheralchannel would require more clearing and grubbing through currently undisturbed areas andpossibly excavation into bedrock, whereas the central channel construction proposed underAlternative 2 would be installed through the tailings pile which would be a relativelystraightforward excavation.

Installation of a new downstream dam as proposed under Alternative 4 would be more difficultto construct than either of the diversion channels proposed under Alternatives 2 or 3.Alternative 4 would be easier to build than the new landfill proposed under Alternative 5 andwould involve much less excavation than total removal of tailings as proposed underAlternative 6.

Alternative 5 would be the more difficult to implement compared to Alternative 6 involving totalexcavation and off-site disposal because Alternative 5 involves both total excavation of allmaterials and construction of a RCRA landfill cell. Alternative 6 would only require thelogistical coordination of off-site trucking to allow for the total excavation of all materials.Under Alternative 6, once the materials were excavated, they could be directly loaded intowaiting trucks and there would be no rehandling, regrading, or engineered placement ofmaterials as would be required for the landfill construction under Alternative 5. However,Alternative 6 may not be able to be completed in the timeframe required due to access roadconditions for trucks hauling and off-site disposal.

Ranking the alternatives in order of implementability, Alternative 1, the No Action alternative,would rank easiest to implement (but would not be acceptable). Alternative 3 involving thecentral drainage channel would rank second and Alternative 2 involving the construction of aperipheral diversion channel would rank next. Alternative 4 involving the construction of a new

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dam downstream would follow Alternative 3. Alternative 6 involving complete removal and off-site disposal of all tailings and waste rock would be the second most difficult action toimplement. Alternative 5 involving the construction of an on-site landfill for disposal of alltailings and waste rock is expected to be the most difficult alternative to implement.

4.3 Comparative Cost EvaluationThe "No Further Action" alternative has no associated cost.

The estimated costs for the active remedial alternatives (Alternatives 2, 3, 4, 5, and 6) arepresented in Tables 3-la/b through 3-5a/b. The total net present worth costs for thesealternatives range from $1,603,000 to $38,870,000. Alternative 2 involving the construction ofthe east diversion channel is expected to have the lowest associated net present worth cost andAlternative 6 involving complete excavation with total off-site disposal is expected to have thehighest associated net present worth cost. Alternatives 2, 3, and 4 are approximately the same incost within the comparative level of the estimate performed at this degree of estimate accuracy.

All the active remedial alternatives would have some form of ongoing associated maintenanceexcept for Alternative 6. Alternatives 2 and 3 would require periodic inspection, maintenance,and cleaning of the diversion channel to assure that it maintains proper operating capacity.Under Alternative 4, the new dam would require periodic inspection. Should the sedimentationbasin created by the dam become impacted with tailings, then some periodic cleanout maybecome necessary. Under Alternative 5, there would be some perpetual care required for thelandfill including operation of the leachate collection and treatment system, periodicmaintenance of site drainage structures, and maintenance of the soil cover over the landfill.Alternative 6 has no associated long-term O&M cost as all waste material is removed anddisposed off site. Following site restoration, no long-term care would be required.

The greatest uncertainty factors associated with the cost estimates include:

• Limited availability of engineering and geotechnical data to develop the preliminarydesign and to base engineering assumptions.

• The ability of the access road to sustain heavy equipment traffic and the degree ofimprovements that may be necessary to facilitate heavy use.

• Early seasonal inclement weather could limit or prevent the construction of theremedy.

These uncertainties are covered by a rather modest contingency of 35 percent in the cost buildup.

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5.0 Conclusions and Recommendations____________

This report screened a number of technologies for mitigation of mine tailings found at the LavaCap Mine site, Nevada City, California. These included:

• Surface Capping• Surface Water Runoff Collection and Treatment• Source Removal/Excavation

• Bioremediation (In Situ/Ex Situ)• Phytoremediation (In Situ/Ex Situ)

• Chemical Stabilization (In Situ/Ex Situ)• Physical Stabilization (In Situ/Ex Situ)• Chemical Treatment/Soil Washing/Flushing (In Situ/Ex Situ)

• Disposal• Institutional Controls to Supplement Engineering Controls.

Following the technology screen, six alternatives were developed for detailed evaluation. Thealternatives developed and evaluated for this site include:

• Alternative 1 - No Further Action - The No Further Action alternative means noadditional action will be taken, which includes monitoring, maintenance, or perpetualcare. It is developed as a baseline to compare other alternatives and has no associatedcost or level of effort.

• Alternative 2 - Little Clipper Creek East Channel Diversion, Regrading, andPhysical Stabilization of Tailings at the Log Dam - Alternative 2 involves theinstallation of a drainage channel to completely intercept/divert Little Clipper Creekand run-on drainage away from the far northern and eastern limits of the tailings area.Little Clipper Creek and other captured drainage will be diverted around the tailingsarea to the eastern side through an approximately 10-foot-wide by 3-feet-deepreinforced concrete-lined trapezoidal drainage ditch. The existing drainage pipingwill be removed. Other ancillary drainages approaching the site from the east willalso be captured by the diversion ditch. The ditch will be sized to accommodate aflow of up to 500 cfs, which is greater than a 100-year, 24-hour storm and greaterthan a 6-hour PMP event. The remnants of the existing log dam would be removedand the lower tailings area graded to prevent erosion and physically stabilize the area.This is estimated to involve approximately 18,000 cubic yards of grading. Areas thatare regraded and any deposits of excavated tailings would be covered with ageotextile fabric overlain by an 18-inch-thick layer of coarse waste rock to further

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stabilize them. The former dam face area would be butressed with grouted riprap orgabion baskets and a baffle spillway will be installed at the outlet of the channel. Theentire tailings pile surface area would be graded to improve and promote incidentalrunoff (with minimal erosion), grading the area towards the central drainage channelat a minimum slope of 5 percent. Prior to implementation of the remedy, appropriatedetailed engineering would be completed including geotechnical testing and plans forconstruction prepared including a work plan, health and safety plan, erosion andsedimentation control plan, construction quality assurance plan, environmentalprotection plan, etc. for agency approval.

Alternative 3 - Little Clipper Creek Central Channel Diversion, Regrading, andPhysical Stabilization of Tailings at the Log Dam - Alternative 3 involves theinstallation of a drainage channel to completely intercept/divert Little Clipper Creekand run-on drainage away from the far northern and eastern limits of the tailings area.Little Clipper Creek and other captured drainage will be diverted through aconstructed trapezoidal concrete-lined drainage channel centrally down through thetailings area. The drainage channel would be approximately 10-feet-wide by 3-feet-deep reinforced concrete-lined trapezoidal drainage ditch. The existing drainagepiping for diverting Little Clipper Creek would be left as is. The newly constructedcentral drainage ditch will be sized to accommodate a flow of up to 500 cfs, which isgreater than a 100-year, 24-hour storm and greater than a 6-hour PMP event. Theremnants of the existing log dam would be removed and the lower tailings areagraded to prevent erosion and physically stabilize the area. This is estimated toinvolve approximately 18,000 cubic yards of grading. Areas that are regraded andany deposits of excavated tailings would be covered with a geotextile fabric overlainby an 18-inch-thick layer of coarse waste rock to further stabilize them. The formerdam face area would be butressed with grouted riprap or gabion baskets and a bafflespillway will be installed at the outlet of the channel. The entire tailings pile surfacearea would then final graded to improve and promote incidental runoff (with minimalerosion), grading the area towards the central drainage channel at a minimum slope of5 percent. Prior to implementation of the remedy, appropriate detailed engineeringwould be completed including geotechnical testing and plans for constructionprepared including a work plan, health and safety plan, erosion and sedimentationcontrol plan, construction quality assurance plan, environmental protection plan, etc.for agency approval.

Alternative 4 - Rock Fill Retention Dam Downstream of Original Log DamLocation, Regrading, and Physical Stabilization of Tailings at the Log Dam -Alternative 4 involves the construction of a new rock core dam with a centralspillway approximately 500 feet downstream of the existing log dam and LittleClipper Creek invert Elevation 2665 mean sea level. The existing drainage pipingdiverting Little Clipper Creek will remain as is. The remnants of the existing log damwould be removed and the lower tailings area graded to prevent erosion andphysically stabilize the area. This is estimated to involve approximately 18,000 cubicyards of grading. Areas that are regraded and any deposits of excavated tailingswould be covered with a geotextile fabric overlain by an 18-inch-thick layer of coarse

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waste rock to further stabilize them. The former dam face area would be butressedwith grouted riprap or gabion baskets. The entire tailings pile surface area would begraded to improve and promote incidental runoff (with minimal erosion), by gradingthe area from the perimeter towards the centerline at a minimum slope of 5 percent.The new rock core tailings retention dam would be designed to be "leaky," meaningunder normal rainfall conditions, the dam would allow the slow release of waterthrough the dam contained within the tailings up behind the dam. Under extremeweather conditions when excessive overland runoff occurs, flow would dischargethrough the principal spillway that would be sufficiently anchored to preventexcessive erosion or failure of the retention dam. Prior to implementation of theremedy, appropriate detailed engineering would be completed including geotechnicaltesting and plans for construction prepared including a work plan, health and safetyplan, erosion and sedimentation control plan, construction quality assurance plan,environmental protection plan, etc. for agency approval.

Alternative 5 - Excavation and Disposal of Tailings On Site in NewlyConstructed Disposal Cells - Alternative 5 involves systematic excavation andrelocation of all tailings into a constructed lined landfill/impoundment on site. Thiswould involve the excavation of up to approximately 150,000 cubic yards of tailingsand waste rock. The landfill/impoundment would involve a valley fill design at theupper portion of the site in the vicinity of the existing tailings repository from theprevious removal action and the adit drainage, occupying an area of approximately2.5 acres. The area would be appropriately prepared and an underliner installed tomeet applicable requirements. The unit would likely have to be designed to meetRCRA Subtitle C requirements, as the presence of metals in the tailings such asarsenic would likely leach from the waste tailings above TCLP limits for hazardouswaste classification. Following placement, the formerly impacted areas would begraded and restored to match the natural surroundings and topography, whileminimizing the potential for erosion and downstream sedimentation. Areas with anextreme potential for erosion would be anchored, covered, or reinforced asappropriate with geotextile fabric, riprap, etc. The existing east diversion drainagechannel would require improvement to handle a 500 cfs storm event similar to thechannel proposed in Alternative 2. The remnants of the existing log dam would beremoved and placed in the landfill. The former dam face area would be butressed ifneeded for additional stabilization with riprap or gabion baskets. Prior toimplementation of the remedy, appropriate detailed engineering would be completedincluding geotechnical testing and plans for construction prepared including a workplan, health and safety plan, erosion and sedimentation control plan, constructionquality assurance plan, environmental protection plan, etc. for agency approval.Alternative 6 - Excavation and Removal of Tailings Off Site - Alternative 6involves the systematic excavation and relocation of the tailings to an off-site disposalfacility. This would involve the excavation of up to approximately 150,000 cubicyards of tailings and waste rock and transportation to an appropriate landfill off site.It is assumed that the waste rock would be disposed of as nonhazardous and thetailings would require stabilization prior to disposal at a hazardous waste facility.

PT/05/22/01 (!:17PMyWP/821915/LavaCapEE-CAReport 64

This alternative would likely require significant improvements to the access road toaccommodate the high level of truck traffic. The waste material would requiretreatment either by the disposal facility or on site before ultimate disposal in order tomeet Universal Treatment Standards for land disposal of arsenic-containing waste.Following excavation and removal of the tailings, the formerly impacted areas wouldbe graded and restored to match the natural surroundings and topography, whileminimizing the potential for erosion and downstream sedimentation. Areas with anextreme potential for erosion would be anchored, covered, or reinforced asappropriate with geotextile fabric, riprap, etc. The existing drainage piping divertingLittle Clipper Creek will remain as is. The remnants of the existing log dam wouldbe removed. The former dam face area would be butressed if needed for additionalstabilization with riprap or gabion baskets. Prior to implementation of the remedy,appropriate detailed engineering would be completed and plans for constructionprepared including a work plan, health and safety plan, erosion and sedimentationcontrol plan, construction quality assurance plan, environmental protection plan, etc.for agency approval.

Alternative 1, the No Further Action alternative, was evaluated for baseline comparisonpurposes, but is dismissed from further consideration due to failure to meet ARARs. It wouldnot protect human health and would not alleviate the stress imposed on the environment.

Of the remaining alternatives (Alternatives 2, 3, 4, 5, and 6), Alternative 4 only provides forphysical stabilization/retention of the tailings, but does not reduce potential chemical toxicity asa result of arsenic leaching below current baseline site conditions. Whereas, Alternatives 2, 3, 5,and 6 do provide for both physical stabilization/retention (or removal) of tailings and to varyingdegrees, reducing the potential chemical toxicity below current baseline site conditions. Thus,these alternatives would be preferable over Alternative 4 on the basis of protection of humanhealth and the environment. The cost of Alternative 4 is similar to Alternatives 2 and 3. Also,the constructability of Alternative 4 is expected to be more difficult compared to Alternatives 2and 3. Thus, Alternative 4 is dismissed on this basis.

Of the remaining alternatives (Alternatives 2, 3, 5, and 6), Alternatives 2 and 3 are similar interms of cost. Alternative 2 would be more favored in that it is expected to be more protectiveby diverting all runoff to the maximum extent practical away from the tailings pile. There is aninherent risk in constructing the center channel under Alternative 3 that erosion could occur, thechannel could leak, overflow, etc. If the channel were constructed peripherally as proposedunder Alternative 2, any overflow would be to the outside of the tailings and would be less likelyto cause environmental impacts. On this basis, Alternative 2 is retained over Alternative 3.

PT/05/22/01 (ll7PM)/WP/8219l5/LavaCapEE-CA Report 65

Of the remaining alternatives (Alternatives 2, 5, and 6), there is a significant difference in termsof cost. Option 6 is the most costly at more than 50 times the cost of Alternative 2. However,Alternative 6 is the most protective to human health and the environment. Alternative 4 is alsohighly protective of human health and the environment, but is more than 8 times the cost ofAlternative 2 and this evaluation does not need to provide the final remedy. Thus, on the basis ofcost, Alternative 6 is dismissed over Alternative 5 as the additional incremental protectionafforded by off-site disposal versus on-site disposal does not merit the tremendous difference incost.

Of the remaining alternatives (Alternatives 2 and 5), Alternative 5 provides complete isolation ofthe tailings, completely eliminates the potential for leaching, and may eliminate some of theseeps. Alternative 2 provides physical stabilization of the tailings, reduces the potential forleaching, and would constitute a part of the remedy proposed under Alternative 5. Alternative 5would require a similar channel as proposed under Alternative 2 to divert rainwater around thelandfill and the tailings during construction and after the landfill is capped.

Alternative 5 would likely constitute a final permanent remedy for the tailings portion of themine site. However, it is not the only possible permanent remedy. These are currently beingevaluated by CH2M Hill in the context of a sitewide FS. Since the FS is in progress and a rangeof remedies including on-site disposal of the tailings are being evaluated for permanentmitigation of the site, it may be premature to implement a permanent remedy without allowingfurther evaluation to be performed under the FS. Further, there is a higher degree of costuncertainty associated with Alternative 5 due to a lack of site engineering and geotechnicalinformation. Since Alternative 2 does meet the primary goal of physically stabilizing the tailingsand it would reduce potential chemical toxicity by reducing leaching through the tailings, itseems to be a favored measure to be taken at this time. The drainage improvements proposedunder Alternative 2 could be incorporated into the permanent remedy for the site. Thus, from anengineering and economic perspective, the expenditure would not be wasted uponimplementation of a final remedy. Whereas, the uncertainty associated with any remedy beyondphysical stabilization and runoff control/diversion of sitewide drainage makes implementation ofAlternative 5 questionable from both an engineering and economic perspective at this time.Further evaluation that is ongoing may indicate complete containment of the tailings in an on-sitelandfill is a necessity. However, this action as a non-time critical removal action does not appearto be justifiable at this time without additional assessment and site investigation. Thus,


Alternative 2 would be preferable over Alternative 5 as a final recommendation of thisassessment.

Based on the evaluations performed, this EE/CA concludes:

• The Lava Cap Mine site has a predicted potential human health risk above CERCLAstandards, sufficient to warrant USEPA Region XI to implement an appropriateremoval action.

• The presence of the tailings in the Lava Cap Mine drainage basin has demonstrateddetrimental environmental and ecological impacts on the stream channel.

• The presence of unsecured tailings at the site remains an ecological risk todownstream drainage areas. The movement of these tailings could occur againshould extended heavy rains impact the area again.

• Additional physical stabilization of the tailings and water diversion around the site isexpected to provide a benefit in reducing potential human health and ecological riskand would be a likely component of any final site remedy.

• Off-site management of tailings would be prohibitively expensive due tocharacteristics that would likely classify these materials as RCRA hazardous wastedue to the presence of arsenic and lead. The waste would require pretreatment toreduce toxicity or treatment at the receiving facility to meet the universal treatmentstandards for disposal of arsenic and lead containing waste materials.

• Additional site-specific engineering and geotechnical information is required before arecommendation for a final permanent remedy for the site can be made with therequired degree of certainty.

5.1 RecommendationBased on these conclusions, an analysis of the cost and benefits of each alternative, considerationof site-specific ARARs, and consideration of the potential technical uncertainty associated witheach alternative, the recommendation of this EE/CA is to implement Alternative 2 as a non-timecritical removal action. This would involve the construction of a concrete-lined peripheral eastdiversion drainage channel for the purpose of completely intercepting and diverting LittleClipper Creek drainage from the watershed area above the site around the tailings repositoryarea. Removal of the remaining log dam features, anchoring the base area, along with additionalphysical stabilization and grading of the tailings would eliminate any further potential formigration downstream.

PT/05/22/OI (1:17 PM)AVP/821915/Lava Cap EE-CA Report 67

6.0 Conceptual Design

Following approval to proceed, all the regulatory and permitting considerations will beidentified. The removal action contractor selected by the USAGE will develop all theappropriate plans and submittals to comply with the substantive requirements of any permits.

The selected remedy includes:

• The installation of a drainage channel to completely intercept/divert Little ClipperCreek and run-on drainage away from the far northern and eastern limits of thetailings area. Little Clipper Creek and other captured drainage will be divertedaround the tailings area to the eastern side through an approximately 10-foot-wide by3-feet-deep reinforced concrete-lined trapezoidal drainage ditch. The existingdrainage piping will be removed. Other ancillary drainages approaching the site fromthe east will also be captured by the diversion ditch. The ditch will be sized toaccommodate a flow of up to 500 cfs, which is greater than a 100-year, 24-hour stormand greater than a 6-hour PMP event. The remnants of the existing log dam would beremoved and the lower tailings area graded to prevent erosion and physically stabilizethe area. This is estimated to involve approximately 18,000 cubic yards of grading.Areas that are regraded and any deposits of excavated tailings would be covered witha geotextile fabric overlain by an 18-inch-thick layer of coarse waste rock to furtherstabilize them. The former dam face area would be butressed with grouted riprap orgabion baskets and a baffle spillway will be installed at the outlet of the channel. The ~>entire tailings pile surface area would be graded to improve and_promote itrunoff (with minimal erosion), grading the area towards theccentral^gfamage channelat a minimum slope of 5 percent. Prior to implementation of the remedy, appropriatedetailed engineering would be completed including geotechnical testing and plans forconstruction prepared including a work plan, health and safety plan, erosion andsedimentation control plan, construction quality assurance plan, environmentalprotection plan, etc. for agency approval.

As part of developing the removal action work plan, a more extensive engineering survey of thearea would be required and additional geotechnical information obtained. From this survey,detailed delineation drawings of the routing of the diversion channel, cuts, grades, constructionfeatures, areas to be excavated, areas to be stabilized, restoration requirements, etc. would beprepared. Within the overall work plan would be the standard documentation for civilconstruction/removal work of this nature such as:

• Construction work plan

• Sedimentation and erosion control plan

PT/05/22/01 (!:17PMywP/8219]5/LavaCapEE-CAReport 68

• Storm water management plan• Revegetation plan• Project quality assurance/quality control plan

• Environmental protection plan• Traffic control and transportation plan• Construction water and waste management plan• Permit requirements (substantive)

• Sampling and monitoring plan

• Health and safety plan.

In conjunction with the preparation of the appropriate plans, site preparation will begin onceauthorization to proceed has been established. Setup will require location of a base camp typearea for the location/storage of equipment, personnel, treatment operations, etc. Some measuresmay be developed as the removal action proceeds, such as the most appropriate placement ofcover soil and revegetation to be used in a particular area. Flexibility in the work plans will benecessary in order to be responsive to anticipated changing conditions.

The major effort for this project will be in planning and logistics. The narrow and steep one laneroad will limit heavy truck traffic moving in and out of the site. Transportation logistics andconstruction sequencing will be critical to maintain productivity. Schedule will be critical asconstruction would need to be completed before the possibility of any early heavy rainfall.

It is anticipated that heavy equipment such as trackhoe excavators, backhoes, and bulldozers willbe used for the majority of the removal work. Articulated off-road haul trucks may be neededfor some of the tailings excavation activity. Some dewatering and subsequent treatment may berequired. The methodology for management of construction water will be detailed in the variouswork plans.

Materials that are dry when excavated will be placed directly into appropriately sized trucks andtransported for placement. Materials that are saturated with free liquids will be appropriatelydewatered. Construction water would be treated as required. The release of untreated water tothe streambed during excavation will be minimized to the extent possible by dewatering theexcavation area, diversion around the excavation, or other means. Silt fencing in the stream

PT/05/22/01 (]:17PMy\VP/8219]5/LavaCapEE-CAReport 69

channel and other sedimentation control measures will be used to prevent downstream pollution.These measures will be detailed in the sedimentation and erosion control plan.

Work sequencing and planning will also anticipate the possibility of catastrophic weather eventsand minimize the amount of exposed area that could wash out to the extent practical, but not atthe expense of hindering the rate of removal.

PT/05/22/01 (l:I7PMywP/821915/LavaCapEE-CAReport 70

Table 2-1Chemical-Specific ARARs and TBC Guidance

Constituent

AluminumAntimonyArsenicBariumBerylliumCadmiumChromium (III)Chromium (IV)Total ChromiumCobaltCopperCyanideIronLeadManganeseMercuryNickelSeleniumSilverSulfateThalliumVanadiumZinc

Federal Potential ARARs

State1 or SDWA [USEPAMaximum Contaminant

Levels (MCL)]

Primary

0.006 mg/L0.01 mg/L2.0 mg/L

0.006 mg/L0.005 mg/L

0.1 mg/L

0.002 mg/L

0.002 mg/L

0.05 mg/L

0.002 mg/L

Secondary3

0.05 to 0.2 mg/L

1.0 mg/L

0.3 mg/L

0.05 mg/L

0.1 mg/L250 mg/L

5.0 mg/L

RCRA

Ground-waterMCC

0.05 mg/L1.0 mg/L

0.01 mg/L

0.05 mg/L

0.05 mg/L

0.002 mg/L

0.01 mg/L0.05 mg/L

TCLPCriteria

MCC

5.0 mg/L100 mg/L

1.0 mg/L

5.0 mg/L

5.0 mg/L

0.2 mg/L

1.0 mg/L5.0 mg/L

CWA Ambient WaterQuality Criteria for

Protection of Fresh-water Aquatic Life

Acute

360 ug/L

3.7 ug/L550 ug/L15 ug/L

17 ug/L22 ug/L

65 ug/L

2.1 ug/L1,400 mg/L

20 ug/L3.4 ug/L

110 ug/L

Chronic4

190 ug/L

1.0 ug/L180 mg/L10 ug/L

11 ug/L5.2 ug/L

2.5 ug/L

0.012 ug/L160 ug/L5 ug/L

100 ug/L

State Potential ARARs

Criteria forIdentification as aHazardous Waste

Soluble(STLC)

15 mg/L5.0 mg/L100 mg/L0.75 mg/L1.0 mg/L5 mg/L

5.0 mg/L

80 mg/L25 mg/L

5.0 mg/L

0.2 mg/L20 mg/L1.0 mg/L5.0 mg/L

24 mg/L250 mg/L

Total(TTLC)

500 mg/kg500 mg/kg1 0 mg/kg75 mg/kg100 mg/kg2.5 g/kg

500 mg/kg

8.0 g/kg2.5 g/kg

1.0 g/kg

20 mg/kg2.0 g/kg

100 mg/kg500 mg/kg

2.4 g/kg5.0 g/kg

RWQCB2

Basic PlanObjectives

Maximum

0.01 mg/L0.1 mg/L

0.22 ug/L

0.0056 mg/L0.01 mg/L0.3 mg/L0.01 mg/L0.05 mg/L

0.016 mg/L

TBCsDept. of Health

Services DrinkingWater Supply Action

Levels

Primary

5.0 mg/L

Totaland

Other

5.0 mg/L5.0 mg/L200 ug/L

200 ug/L

SDWAMCL

(MCLG)

0.006 mg/L

2.0 mg/L0.004 mg/L0.005 mg/L

0.1 mg/L

1.3 mg/L0.2 mg/L

0.002 mg/L

0.05 mg/L

0.0005 mg/L

Prop. 65Safe UseNumbers

Maximum

1.0 ug/L

0.05 ug/L

1 California Health and Safety Code requires the Department of Health Services to adopt maximum contaminant levels for certain chemicals.2 Regional Water Quality Control Board.3 For water that is to be used for drinking, the MCLs set under the Safe Drinking Water Act (SDWA) are generally the applicable or relevant and appropriate standard. A standard

for drinking water more stringent than an MCL may be needed in special circumstances, such as where multiple contaminants in groundwater or multiple pathways of exposurepresent extraordinary risks. In setting a level more stringent than the MCL, a site-specific determination should be made by considering MCLGs. Prior consultation with USEPAheadquarters is encouraged in such cases.

4 Federal Ambient Water Quality Criteria, more stringent than an SDWA MCL, may be found relevant and appropriate when there are environmental factors that are beingconsidered a site, such as protection of aquatic organisms.

Sources: USEPA Superfund Public Health Evaluation Manual. ERA 540/1-86/060 (OSWER Directive 9285.4-1) October 1986; USEPA Quality Criteria for Water 1986. EPA 440/5-86-001, May 1986 (S1 Federal Register 43665); and CDHS, Sanitary Engineering Branch, Drinking Water Action Levels Recommended by the Department of Health Services,January 1987.

PT/05/22/01 (l:26PMyWP/821915/Ttble 2-1

Table 2-2Location-Specific ARARs

Location Requirement/Prerequisite Citation Comment ApplicabilityWithin 61 meters(200 feet) of a faultdisplaced in Holocenetime

All treatment, storage, and disposal ofhazardous wastes are prohibited within200 feet of a Holocene fault.

40 CFR 264.18(a)

22 CCF 66264.18(a)

If wastes at the site were determined to be hazardous underRCRA or Title 22 CCR and must be managed as a hazardouswaste, these requirements would apply. There are no activefaults present in the vicinity of Lava Cap Mine, but the site islocated in the northern Foothills Fault System. Ancientfractures, joints, and inactive faults are common in this region.There are two possible active faults located in the area, one4 miles east and one 4 miles west of the Lava Cap Mine site.To the east, there is the northern trending Cement Hill fault thatmay have had Late Cenozoic movement of greater than 5 feetvertical. To the west, there is a 1.5 mile-long-north-trendingGreenhorn Creek lineament (with no observed displacementnoted) near the major Pre-Cenozoic northern Meloines faults.Although no known active fault is located with 200 feet of LavaCap Mine site, the presence of inactive faults in the regionshould be considered in the design of a landfill. Therefore,these requirements would not apply, but may be relevant andappropriate.___________________________

Potential ARARif wastegeneratedduring removalactivities isstored on siteand ishazardous

Within 100-yearfloodplain

Treatment, storage, and disposal forhazardous wastes must be constructed toavoid washouts if located in a 100-yearfloodplain._________________

40CFR264.18(b) This requirement applies to the management of hazardouswaste in 100-year floodplain. The Lava Cap Mine site is notlocated in a 100-year floodplain and, therefore, theserequirements are not applicable.

Not an ARAR

Land treatment and disposal units forhazardous wastes may not be located in a100-year floodplain.____________

22 CCR 66264.18(b)

The Lava Cap Mine site is not located in a floodplain and,therefore, these requirements are not applicable.

Within floodplain Relates to actions that will occur in afloodplain, i.e., lowlands, and relatively flatareas adjoining inland and coastal watersand other flood-prone area. Actions mustbe taken to avoid adverse effects, minimizepotential harm, restore and preserve naturaland beneficial values.

Executive Order 11988,Protection of Floodplains(40 CFR 6, Appendix A)

Not an ARAR

This requirement applies to the placement of hazardous wasteliquids. Hazardous waste liquids are not planned to be placedon the site.

Within salt domeformation, undergroundmine, or cave___

If a RCRA hazardous waste, placement ofnoncontainerized or bulk liquid hazardouswaste is prohibited.____________

40CFR264.18(c)

22 CCR 66264.18(c)

Not an ARAR

Identify possible losses to significant scientific, prehistorical, orarchaeological data. If any sites are found, they must berecorded and data preserved.

Within area whereaction may causeirreparable harm, loss,or destruction ofsignificant artifacts

Alteration of terrain threatens significantscientific, prehistorical, historical, orarchaeological data. Action must be takento recover and preserve artifacts applicableto federal projects on public land only.Provides for the preservation of historicaland archaeological data._________

National Archaeological andHistorical Preservation Act,(16 U.S.C. Section 469);36 CFR Part 65

Potential ARAR

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Location Reg u i rement/Prereq u Isite CitationProperty at Lava Cap Mine is not proposed for listing as aNational Historic Landmark, although it may be eligible forlisting.

Comment ApplicabilityHistoric project ownedor controlled by federalagency.

If property is included in or is eligible for theNational Register of Historic Places, actionsmust be taken to preserve historicproperties and to minimize harm to NationalHistoric Landmarks.

National Historic PreservationAct Section 106(16U.S.C.470 ef sec/.); 36 CFR Part800

'otential ARAR

Enacted to take into account the effects ofremedial activities on any historic propertiesincluded in or eligible for inclusion on theNational Register of Historic Places. Theseproperties may include districts, sites,buildings, structures, and objects that aresignificant in American history, architecture,archaeology, engineering, and culture.

Need to Identify if there are any cultural resources at the site bycompleting a Cultural Resource Survey. Determine if site isincluded in the National Register or if it is eligible for NationalRegister. Identify the possible effects of the proposed remedialactivities on any cultural resources.

Critical habitat uponwhich endangeredspecies or threatenedspecies depend

Requires action to conserve endangeredspecies or threatened species, includingconsultation with Department of the Interior,Fish and Wildlife Service.

Endangered Species Act of1973;(16U.S.C. 1531 efseqr.); 50 CFR Part 402

Need to identify any threatened or endangered species orcritical habitat that would be affected by a proposed remedialaction.

Potential ARAR

Requires the protection of non-gamespecies and threatened and endangeredplants and animals. Also, provides for theprotection, enhancement, and restoration offish and wildlife habitat and related waterquality, including review of the potentialimpact of development activities and landuse changes on that habitat.________

California EnvironmentalProtection ProgramPRC Section 21190

Need to identify any threatened or endangered species thatwould be affected by a proposed remedial action.

Potential ARAR

Wetlands Wetlands are defined by Executive Order11990 Section 7. Requires action tominimize the destruction, loss, ordegradation of wetlands. Actions to prohibitdischarge of dredged or fill material intowetlands without permit.

Executive Order 11990,Protection of Wetlands(40 CFR 6, Appendix A)

Clean Water Act Section 404;40 CFR, Parts 230, 231

Porter-Cologne Water QualityControl Act, Water CodeSection 13000

There are wetlands downstream of Lava Cap Mine that may beaffected.

Potential ARAR

Wilderness area Areas federally owned and designated aswilderness areas must be administered insuch a manner as will leave it unimpairedas wilderness and to preserve its wildernesscharacter.

Wilderness Act(16U.S.C1131 efseg.);50 CFR 35.1 efseq.

Lava Cap Mine site is not within or adjacent to any federallydesignated wilderness area.

Not an ARAR

The Lava Cap Mine site is not designated as part of theNational Wildlife Refuge System.

Wildlife refuge If an area is designated as part of NationalWildlife Refuge System, only actionsallowed under the provisions of 16 U.S.C.Section 668 dd(c) may be undertaken inareas that are part of the National WildlifeRefuge System._____________

16 U.S.C. 668 ddefseq.;50 CFR Part 27

Not an ARAR

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LocationArea affecting stream orriver

Within coastal zone

Within area affectingnational wild, scenic, orrecreational river

Oceans or waters of theUnited States

Sole-source aquifer

Requirement/PrerequisiteDirection, channeling, or other activity thatmodifies a stream or river and affects fish orwildlife will require actions to protect fish orwildlife.

Diversions, channeling, or any other activitythat affects a stream or watercourse iscontrolled. The Department of Fish andGame has primary responsibility for theprotection of California's fish and wildliferesources.

Applies to activities affecting the coastalzone including lands thereunder andadjacent shorelands.Applies to activities affecting the coastalzone including land thereunder andadjacent shorelands.

Activities that affect or may affect any of therivers specified in Section 1276(a). Avoidtaking or assisting in action that will havedirect adverse effect on scenic river.

Applies to oceans and waters of the UnitedStates, and actions to dispose of dredgeand fill material into ocean waters isprohibited without a permit.

Protection of aquifer through federalassistance funding. Applies to aquifers thatare sole or principal drinking water sourcesand if contaminated would present asignificant hazard to public health. Prohibitsinspection of waste.

CitationFish and WildlifeCoordination Act(16U.S.C.C.,661 etseq.)40CFR6.302

California Fish and GameCode

Coastal Zone ManagementAct(16U.S.C. Section 1451et seq.)California Coastal Act of1976 (Public Resource Code,Div 20 Sections 30,000 etseq.)Scenic River Act[16U.S.C. 1271 erseqr.,Section 7(a)];40CFR6.302(c)California Wild and ScenicRiversClean Water Act(Section 404); 40 CFR 125,Subpart M; Marine ProtectionResources and SanctuaryAct, Section 103SDWA 42 USC Section 300h,40 CFR Section 146.4

CommentThe Fish and Wildlife Coordination Act requires consultationwith the Department of Fish and Wildlife prior to any action thatwould alter a body of water of the United States. Thisrequirement could be applicable to any action that would resultin modification of any stream or river.The Fish and Game Code empowers the Department of Fishand Game (DFG) to protect and enhance fish and wildlifepopulations of this state. DPG is directly authorized to abatepetroleum products in state waters and regulate all diversion,channeling, or other activities in streams and watercourses.The state requirements would be applicable to any actionresulting in the modification of state watercourses.The site is an inland area with no direct access to coastalareas.

The site is an inland area with no direct access to coastalareas.

No national wild or scenic rivers are located on the Lava CapMine site or will be impacted by proposed remediation.

Would be applicable to any remedial action involving dredgingor sediment removed.

No sole-source aquifer is located at the Lava Cap Mine site.

ApplicabilityARAR

Not an ARAR

Not an ARAR

Not an ARAR

Potential ARAR

Not an ARAR

ARAR = Applicable or Relevant and Appropriate RequirementCCR = California Code of RegulationsCFR = Code of Federal RegulationsRCRA = Resource Conservation and Recovery ActTBC = To Be Considered

PT/05/22/01 (1:28 PM)/WP/8219l5/T«ble 2-2

Table 2-3Potential Action-Specific ARARs and TBCs

ActionSampling andAnalysis

Storm WaterDischarges toSurface Water

Diversion ofWater

DamConstruction andRemoval

Law/RegulationRCRA Hazardous Waste; 40 CFR 26122 CCR 66261; 40 CFR 136, App. A,(SW-846 sampling methods)Storm Water Discharge40 CFR 122.2623 CSR 2235.2

Evidence of Water Rights23 CCR 303

Engineering Plans and Specifications23 CCR 304

Construction and Supervision23 CCR 305 and 31223 CCR 119

Application for Construction23 CCR 310 and 311Filing and Annual Fees23 CCR 314 and 31 5

Small Dams Review Board23 CCR 320-325

Requirement of Law/RegulationSpecific requirements for identifying hazardous wastes.Establishes analytical requirements for testing and evaluatingsolid, hazardous, and water wastes.Provides for the use of best management practices to controlstorm water, erosion control, and sediment transport.

Provides requirements to demonstrate evidence of waterrights prior to construction or enlargement of a dam or thediversion of water.Requires that plans and specifications submitted to thedepartment must be prepared by, or under the direction of, aCivil Engineer who is registered pursuant to California law, orbe prepared by such other person as may be permittedunder the provisions of said code.Requires that work of construction, enlargement, repairs,alterations, or removal of a dam or reservoir shall be underthe responsible charge of a Civil Engineer who is registeredpursuant to California law, or of such other person as may bepermitted under provisions of the Business and ProfessionsCode to assume responsible charge of such work.Provides the requirements to be included in the applicationfor the construction and removal of a dam.Provides for filing and annual fees associated with theconstruction, enlargement, repair, alteration, or removal ofdams.Provides for a review process for owners of small dams orproposed small dams in regards to any decisions related totechnical standards, study requests, engineeringrequirements, or other technical matters

ARAR/TBC StatusARAR Applicable for identifying hazardous waste.

ARAR Applicable to the use of best manaqementpractices to control storm water, erosion, andsediment during excavation activities and theplacement of excavated material on site.Substantive surface control measures need to beimplemented as appropriate although a state permit,per se, will not be obtained.ARAR Applicable to the construction of a new rockdam and the diversion of surface water at the site.

ARAR Applicable to the desiqn and construction ofa new rock dam downstream and removal of logdam.

ARAR Applicable to the construction of a new rockdam downstream and removal of log dam.

ARAR Applicable to the construction of a new rockdam downstream and removal of log dam.ARAR Applicable to the construction of a new rockdam downstream and removal of log dam.

ARAR Applicable to dams less than 25 feet in heiqhtwith reservoir storage less than 2,000 acre-feet.

PT/05/22/01 (2:22PMyWP/821915/T.ble 2-3


ActionGeneralRemediation

Disposal On Site

Law/RegulationRCRA Hazardous Waste Generation40 CFR 26222 CCR 66262

RCRA General Facility Standards40 CFR 264. 1Q), SubpartA

Closure Performance Standard and Post-Closure Maintenance of Mining Units27 CCR 22510

Reclamation plan for Mining Sites14 CCR 3502

Mining Unit Siting and ConstructionStandards27 CCR 22490Design and Operating Requirement forLandfill40 CFR 264.30122 CCR 66264.301Action Leak Rate40 CFR 264.30222 CCR 66264.302

Construction Quality Assurance Program40 CFR 264. 1940 CFR 264.30322 CCR 66264. 1922 CCR 66264.303

Requirement of Law/RegulationEstablishes standards for generators of hazardous waste formanifesting, pre-transporting, and recordkeeping andreporting requirements.

Provides the requirements which apply to remediationwaste management sites. Instead of the requirements ofSubparts B, C and D of 40 CFR 264, the owners oroperators of the remediation waste management site mustmeet the requirements of 40 CFR 264.1(j) (1) - (12).Provides the closure and post-closure maintenancerequirements for Mining Units. These requirements are toestablish waste containment, precipitation and drainagecontrols to minimize the threat to water quality.Provides elements (i.e., environmental setting of the site,future public exposure, design final land slopes, backfilling,settlement of fill, etc.) to be included in a reclamation planfor mining sites.Provides site criteria and construction standards for newmining units.

Provides the design and operating requirements for alandfill. The design requires the installation of a linersystem and leakage collection and removal system.

Provides for Department approval of an action leakage ratefor landfill units. The action leakage rate is the maximumdesign flow rate that the leak detection system (LDS) canremove without the fluid pressure head on the bottom linerexceeding 1 foot (30.5 cm) at any given portion of the liner.A construction quality assurance (CQA) program is requiredfor all surface impoundment, waste pile, and landfill unitsthat are required to comply with 264.221 (c) and (d),264.251 (c) and (d), and 264.301 (c) and (d). The programmust ensure that the constructed unit meets or exceeds alldesign criteria. The program must be developed andimplemented under the direction of a CQA officer who is aregistered professional engineer.

ARAR/TBC StatusARAR Applicable to the substantive requirements ifhazardous waste is generated and managed on site.Because the recordkeeping and reportingrequirements outlined in this section areadministrative, not substantive, they would not beapplicable to on-site management of generatedwaste. However, if wastes are transported off site, themanifesting, pre-transporting, and recordkeeping andreporting requirements would be applicable.ARAR Applicable to the requirements if excavatedmaterial are classified as hazardous waste andplaced and/or disposed of on site.

ARAR Relevant and appropriate to the remediationof the Lava Cap Mining site.

ARAR Relevant and appropriate to the remediationof the Lava Cap Mining site.

ARAR Relevant and appropriate for general designcriteria for containment structures and storm waterdrainage control.ARAR Applicable design requirements if excavatedmaterial is classified as hazardous waste anddisposed of on site in a landfill.

ARAR Applicable to the design of an on-sitehazardous waste landfill.

ARAR Applicable to the design of an on-sitehazardous waste landfill.

PT/05/22/01 (2:22PM>WP/821915/T.ble 2-3


ActionDisposal On Site(continued)

Off-Site Disposalof HazardousWaste

Packaging,Labeling, andStorage

Transportation

AirEmissions

Law/RegulationResponse Action40 CFR 264.30422 CCR 66264. 304

RCRA Land Disposal Restrictions40 CFR 268, Subparts A, B, C, D, and E22 CCR 66268

RCRA Land Disposal Restrictions40 CFR 268, Subparts A through E22 CCR 66268

RCRA Hazardous Waste Generation40 CFR 262 Subparts A through D

DOT Hazardous Materials TransportationRegulations49 CFR 171-173 and 177-180RCRA Hazardous Waste Transportation40 CFR 263, Subparts A, B, and C22 CCR 66263RCRA Hazardous Waste Generation40 CFR 262.20(f)22 CCR 66262

Fugitive Dust Emissions

Requirement of Law/RegulationThe owner or operator of landfill units subject to 264.301 (e)or (d) shall have an approved response action plan beforereceipt of waste. The response action plan shall set forththe actions to be taken if the action leakage rate has beenexceeded.Identifies hazardous wastes that are restricted from landdisposal and defines those limited circumstances underwhich an otherwise restricted waste may continue to be landdisposed. These treatment standards are to a great extentconcentration-based. However, certain wastes are requiredto be treated by a specific technology prior to land disposal.Identifies hazardous wastes that are restricted from landdisposal and defines those limited circumstances underwhich an otherwise restricted waste may continue to beland disposed.Specifies requirements for hazardous waste packaging,labeling, manifesting, recordkeeping, and accumulationtime.

Establishes classification, packaging, and labelingrequirements for shipments of hazardous materials.

Specifies requirements for hazardous waste manifestcompliance, recordkeeping, and hazardous wastedischarges during hazardous waste transport.This section excludes from the requirements of Subpart B(The Manifest) transport of hazardous wastes on a public orprivate right-of-way within or along the border of contiguousproperty under control of the same person.This requirement restricts persons from causing or allowingfugitive particulate matter to go beyond the premise wheresuch matter originates.

ARAR/TBC StatusARAR Applicable to the design of an on-sitehazardous waste landfill.

ARAR Applicable to the placement of hazardouswaste on site in a landfill.

ARAR Applicable if excavated materials areclassified as hazardous waste and are disposed ofoff site in a landfill.

ARAR Applicable to the substantive requirementsfor the on-site accumulation of hazardous waste andto the manifesting and recordkeeping requirements iftransported off site.ARAR Applicable if hazardous materials aredisposed of off site.

ARAR Applicable if hazardous waste is transportedoff site.

ARAR Applicable if hazardous waste is transportedon site.

ARAR Applicable to fugitive dust emissions duringexcavation and land disturbance activities.

ARAR = Applicable or relevant and appropriate requirementCFR = Code of Federal RegulationsCCR = California Code of RegulationsUSEPA = U.S. Environmental Protection AgencyRCRA = Resource Conservation and Recovery ActTBC = To be considered

PT/05/22/01 (2:22PM)AVP/821915/Table 2-3

Table 3-1 aEngineering Cost Estimate

Alternative 2

Item1.0

2.02.12.2

3.0

4.04.14.24.34.44.5

5.0

6.06.16.2

7.0

8.0

9.0

10.0

11.0

DescriptionEstimatedQuantity Unit

UnitPrice

Mobilization/Demobilization @ 10% of Items 2 - 6

Log Dam RemovalRemovalChipping

Removal of Tailings

Channel ConstructionCutFillConcreteBaffle SpillwayOutlet Apron

Fill

Cover TailingsGeotextileScreened Waste Rock

7501

18,000

875600

13,525225450

19,500

24,20012,100

CYLS

CY

CYCYSFCYSY

CY

SYCY

$6.40$8,700.00

$9.20

$8.90$1.75$5.00

$400.00$106.50

$1.75

$1.15$8.50

Subtotal

Contingency @ 35% Subtotal

Engineering and Permitting @ 10% of Subtotal & Contingency

Construction Oversite @ 25% of Subtotal & Contigency

TOTAL-:. : . ...:: : : - :---::- :: : : :.:: : : • : : : : ::: •'•• : •:. ::: .... . :,..:. ... : : : : : : :: :: :: :

TotalPrice$55,829.25

$4,800.00$8,700.00

$165,600.00

$7,787.50$1 ,050.00

$67,625.00$90,000.00$47,925.00

$34,125.00

$27,830.00$102,850.00

$614,121 .75

$214,942.61

$82,906.44

$207,266.09

$1,119,236.89

PT/5/22/01 (2:48 PMyWP/82191SrTables 3-1 through 3-5 Page 1 of 1

Table 3-1 bPresent Worth Analysis

Alternative 2

DescriptionTotal Capital Cost

Annual Operation and Maintenance (O&M) Costs ( 2.5% of the Capital Cost )

Present Worth of O&M Cost ( 30- Year Term, 4.0% Inflation Rate )

CostPrice

$1,119,236.89

$27,980.92

$483,902.07

PT/5/22/01 (2:48 PMyWP/821915ATables 3-1 through 3-5 Page 1 of 1

Table 3-2aEngineering Cost Estimate

Alternative 3

Item1.0

2.02.12.2

3.0

4.04.14.24.34.44.5

5.0

6.06.16.2

7.0

8.0

9.0

10.0

11.0

DescriptionMobilization/Demobilization @ 10% of Items 2 - 6


Removal of Tailings

Channel ConstructionCutFillConcreteBaffle SpillwayOutlet Apron

Fill

Cover TailingsGeotextileScreened Waste Rock

EstimatedQuantity

7501

18,000

1,000600

15,700225360

19,600

24,20012,100

Unit

CYLS

CY

CYCYSFCYSY

CY

SYCY

UnitPrice

$6.40$8,700.00

$9.20

$8.90$1.75$5.00

$400.00$106.50

$1.75

$1.15$8.50

Subtotal . : . : . . : . ; . , : : : . : : - • - - . - - - . - - - - -




TOTAL: -• ••••• : : : :: : : : : . •••• ••••••••• ••••••• . : : : :::.:..:.. .:, , • : - • - : : : : •.,,,••:;•


$4,800.00$8,700.00

$165,600.00

$8,900.00$1,050.00

$78,500.00$90,000.00$38,340.00

$34,300.00

$27,830.00$102,850.00

$616,957.00

$215,934.95

$83,289.20

$208,222.99

$1-124,404.13

PT/5/22/01 (2:48 PMyWP/821915/Tables 3-1 through 3-5 Page 1 of 1

Table 3-2bPresent Worth Analysis

Alternative 3




Total Present VV6rth{<3apital

CostPrice

$1,124,404.13

$28,110.10

$486,136.13

PT/5/22/01 (2:48 PM)/WP/821915/Tables 3-1 through 3-5 Page 1 of 1


Alternative 4

Item1.0

2.02.12.2

3.0

4.04.14.2

5.05.15.25.3

6.0

7.0

8.0

9.0

10.0

11.0

12.0

13,0

DescriptionEstimatedQuantity Unit

UnitPrice

Mobilization/Demobilization @ 10% of Items 2 - 8


Removal of Tailings

Cover TailingsGeotextileWaste Rock

Principal SpillwayAntiseep Collars6' diameter CMP Barrel (100 ft)10' diameter CMP Riser (10 ft)

Rock Dam Construction

Outlet Protection

Inlet Protection

7501

18,000

3,1301,500

211

12,000

470

470

CYLS

CY

SYCY

EALSLS

CY

SY

SY

$6.40$8,700.00

$10.95

$1.15$8.50

$1 ,000.00$15,500.00$12,500.00

$20.00

$106.50

$106.50

Subtotal




TOTAL:.::.... ,• ••'••• ; .:.::.: •.:,.:.;:::;:;;;;.::•: ^d- •: :: •-^•^•;:;:. • . : . •:. :: ::• :..::::::.::..:..:: : :,:;;::, : . ..•:-.. :::,::: .: : ::,. ;:.: .


$4,800.00$8,700.00

$197,100.00

$3,599.50$12.750.00

$2,000.00$15,500.00$12,500.00

$240,000.00

$50,055.00

$50,055.00

$656,765,45

$229,867.91

$132,995.00

$221 ,658.34

$1,241,286,70


Total Capital Cost

Annual Operation and f

Present Worth of O&M


Alternative 4

Description

Maintenance (O&M) Costs ( 2.5% of the Capital Cost )

Cost ( 30- Year Term, 4.0% Inflation Rate )

Siljf̂ l:;;̂

CostPrice

$1 ,241 ,286.70

$31,032.17

$536,670.30

PT/5/22/01 (2:48 PMyWP/82191J/Tables3-l through 3-3 Page 1 of 1


Alternative 5

Item1.0

2.02.12.2

3.03.13.2

4.04.14.2

5.0

6.0

7.07.17.27.3

8.08.18.28.3

DescriptionMobilization/Demobilization

Removal of Waste Rock and TailingsWaste RockTailings

UnderdrainGravelGeotextile

Secondary LinerClay60 mil Liner

Leak Detection

Primary Liner

Leachate CollectionGeocomposite12" Waste RockLeachate Collect Piping, Pump, and Tank

Waste Rock and Tailings PlacementWaste RockTailingsWater Treatment

EstimatedQuantity

1

30,00050,000

4,10012,100

12,30012,100

12,100

12,100

12,1004,100

1

51,800100,000

1

UnitLS

CYCY

CYSY

CYSY

SY

SY

SYCYLS

CYCYLS

UnitPrice

$40,000.00

$6.40$9.60

$26.40$1.15

$20.00$3.91

$5.35

$3.91

$5.35$8.50

$50,000.00

$6.50$11.35

$20,000.00


$192,000.00$480,000.00

$108,240.00$13,915.00

$246,000.00$47,311.00

$64,735.00

$47,311.00

$64,735.00$34,850.00$50,000.00

$336,700.00$1,135,000.00

$20,000.00

9.0

10.0

Intermediate Cover

Synthetic Cover

4,100

12,100

CY

SY

$6.50

$3.91

$26,650.00

$47,311.00

PT/5/22/01 (2:55 PM)/WP/821915/Tables3-l through 3-5 Page 1 of 2


Alternative 5

Item11.0

12.0

13.0

14.0

15.0

16.016.116.216.316.516.5

17.017.117.2

18.0

DescriptionDrainage Layer

Protective Cover (12" Waste Rock)

Topsoil

Fine Grading

Vegetative Cover (Cell Only)

East Diversion Channel ConstructionCutFillConcreteBaffle SpillwayOutlet Apron


EstimatedQuantity

12,100

6,150

2,050

5.0

2.5

875600

13,525225450

7501

[ UnitSY

CY

CY

ACRE

ACRE

CYCYSFCYSY

CYLS

UnitPrice

$5.35

$7.00

$21.40

$900.00

$2,515.00

$8.90$1.75$5.00

$400.00$106.50

$6.40$8,700.00

Subtotal . . :: : ;,;;: ; ; ; ; ; ; ; ; ; ; ; ; ; .;.;;; .;.. .. .. ;; • ; . ; . :. . : . : - ••••••:, ";.::::.::::;;::.:::;:;;;:: :::::; : ;::: :/, . ' . :


$43,050.00

$43,870.00

$4,500.00

$6,287.50

$7,787.50$1,050.00

$67,625.00$90,000.00$47,925.00

$4,800.00$8,700.00

$3,345,088.00

19.0

20.0

21.0

22,0




TOTAL.;:. ;;; ; . . •., •..^.•..../;:::^;:;;.:;.^:;:^^^^

$1,170,780.80

$677,380.32

$1,128,967.20

$6,322,216.32

PT/5/22/01 (2:5J PM)AVP/821915/Tables 3-1 through 3-5 Page 2 of 2


Alternative 5




CostPrice

$6,322,216.32

$158,055.41

$2,733,410.23

PT/5/22/01 (2:48 PMyWP/821915nables 3-1 through 3-5 Page 1 of 1


Alternative 6

Item1.0

2.02.12.2

3.03.13.23.3

4.04.14.24.3

5.0

6.0

7,0

8.0

9.0

10.0

DescriptionMobilization/Demobilization


Waste Rock RemovalRemovalTransportationDisposal

Removal of TailingsRemovalTransportationStabilization/Disposal

Water Treatment

Fine Grade/Site Restoration

EstimatedQuantity

1

7501

60,00060,00060,000

100,000100,000100,000

1

26,620

UnitLS

CYLS

CYCYCY

CYCYCY

LS

SY

UnitPrice

$40,000.00

$6.40$8,700.00

$6.40$40.00$25.00

$9.60$60.00

$112.50

$20,000.00

$0.58

Subtotal


Engineering and Permitting @ 2.5% of Subtotal & Contingency


11.0' TOTAL : : . " " : : . . - - . ! . : : - ' : \ . : . " . . [ . . . . . \ . \ l [ [ \ ' \ . . . . .^..... . . : : ' • : ' : : : : . . . . . . .


$4,800.00$8,700.00

$384,000.00$2,400,000.00$1,500,000.00

$960,000.00$6,000,000.00

$1 1 ,250,000.00

$20,000.00

$15,439.60

$22,552,939,60

$7,904,028.86

$762,174.21

$7,621,742.12

$38,570,884,79

PT/5/22/01 (2:48 PMyWP/82191 J/Tables 3-1 through 3-5 Page 1 of 1


Alternative 6


Annual Operation and Maintenance (O&M) Costs


CostPrice

$38,870,884.79

$0.00

$0.00


Table 4-1Summary of Attemative Screening

AlternativeAlternative 1 - NoAction

Alternative 2 - LittleClipper Creek EastChannel Diversion,Regrading, andPhysical Stabilizationof Tailings at the LogDam

Alternative 3 - LittleClipper Creek CentralChannel Diversion,Regrading, andPhysical Stabilizationof Tailings at the LogDam

Alternative 4 - RockFill Retention DamDownstream ofOriginal Log DamLocation, Regrading,and PhysicalStabilization ofTailings at the LogDam

EffectivenessWould not meetARARs. Would notachieve primaryRAOs.Would achieve theprimary RAO ofstabilizing tailings.Would reduceleaching from thetailings, but may nottotally eliminatechemical risk.

Would achieve theprimary RAO ofstabilizing tailings.Would reduceleaching from thetailings, but may nottotally eliminatechemical risk. Someconcern from thecentral channel routingwhich could overflowunder adverseconditions(e.g., pluggingcombined withflooding).Achieves the primaryRAO of stabilizing thetailings. Does notreduce the potentialchemical risk belowcurrent site levels.

ImplementabilrtyEasiest alternative toimplement. Requiresno resources,materials, or services.Alternative would beimplementable. Allmaterials and servicesare available. Thenarrow accessroadway would be aconsideration for theimplementation of allalternatives requiringcoordination of themovement of heavyequipment and trucktraffic.Alternative would beimplementable. Allmaterials and servicesare available. Thenarrow accessroadway would be aconsideration for theimplementation of allalternatives requiringcoordination of themovement of heavyequipment and trucktraffic.

Alternative would beimplementable. Allmaterials and servicesare available. Thenarrow accessroadway would be aconsideration for theimplementation of allalternatives requiringcoordination of themovement of heavyequipment and trucktraffic.

CostNo associated costNo long-termmaintenance.

Total net presentworth costapproximately$1,603,000. Somelong-term O&Mrequired for periodicmaintenance of thecanal.

Total net presentworth costapproximately$1,610,000. Somelong-term O&Mrequired for periodicmaintenance of thecanal.

Total net presentworth costapproximately$1,778,000. Somelong-term O&Mrequired for periodicinspection andmaintenance of thedam and cleaning ofsediments in theretention basin.

CommentsWould not beacceptable.

Prevents furthermigration of tailingsand reduces some ofthe chemical risk.Drainageimprovements anddiversion would likelybe a component ofany permanent siteremedy. Providesgreatest value forimproving conditionsat the site at this time.Prevents furthermigration of tailingsand reduces some ofthe chemical risk.

Only preventsmigration of tailings,does not reducechemical risk.

PT/05/22/01(1:18 PM)AVP/8 2191 Stable 4-1

Table 4-1Summary of AKernative Screening

AlternativeAlternative 5 -Excavation andDisposal of TailingsOn Site in NewlyConstructed DisposalCells

Alternative 6 -Excavation andRemoval of TailingsOff Site

EffectivenessAchieves the primaryRAO of stabilizing thetailings and providesfor a completereduction of potentialchemical risk.

Achieves the primaryRAO of stabilizing thetailings and providesfor a completereduction of potentialchemical risk. Mosteffective alternativeand most protective ofhuman health and theenvironment.

ImplementabilityAlternative would beimplementable. Allmaterials and servicesare available. Thenarrow accessroadway would be aconsideration for theimplementation of allalternatives requiringcoordination of themovement of heavyequipment and trucktraffic. This alternativerequires a morethorough siteevaluation to locateand design the landfillbefore construction.Alternative would beimplementable. Allmaterials and servicesare available. Thenarrow accessroadway would be amajor considerationfor this remedy,requiring extensivecoordination of themovement of heavyequipment and trucktraffic to assureadequate productivity.

CostTotal net presentworth costapproximately$6,322,000. Somelong-term O&Mrequired for periodicmaintenance of thelandfill cover and forongoing operation ofthe leachate collectionand treatment system.

Total net presentworth costapproximately$38,870,000. Nolong-term O&M oncesite restorationmeasures are secure.Most expensivealternative toimplement.

CommentsMay or may not be thebest permanentremedy for the site.Recommend deferringto the FS as furtherevaluation for the bestoverall permanent siteremedy is beingdeveloped.

Most protectiveremedy, but also mostexpensive.

PT/05/22/01 (1 18PM)AVP/821915/Table4-l

FIGURES

EXISTINGGRADE

/ { / m

6" THICK CONC W/WWF REINF.

NEW LITTLE CLIPPERAPPROXIMATE CREEK .DIVERSION W/..,...._ _

ROCK <5c TAILfNGSj, T /^,.BAFFLE SPILLWAY

,(SEE csCHANNEL DETAIL)? CHANNEL DETAIL

SCALE: 1" = 5'-0

^

EXISTING LITTLE CUPPERCREEK DIVERSION \\(TO BE^ REMOVED) v

AREA TO BE REGRADED0 PROMOTE DRAINAGE

1;8,000 CD; YDS.)

EXISTIG WESTERNI DIVERSION EXISTING,LOG DAM

(TO ^E REMOYEO)

S C A L E

RGURE 3-1U.S. ARMY CORPS OF ENGINEERS

RAPID RESPONSEOMAHA DISTRICT

ALTERNATIVE 2LITTLE CUPPER CREEK EASTERN DIVERSION

LAVA CAP MINE EE/CA REPORTNEVADA COUNTY. NEVADA CITY. CA.

DRAWN BY STRITMATTER 5/14/01 • APPROVED BY

TOPOGRAPHIC MAP BASED ON ELECTRONIC FILEOBTAINED FROM CH2M HILL FEB. 8. 2001.

EXISTINGGRADE

6" FREEBOARD

^ \i('"_N221'gpOO \'S

KIMATE LIMITS -OF f-1 *WASH filOCK & TAILINGS ,?

I i \ $> <^ S /v--.,

Nf220950'0,

oQ.

;SF?i X

• N22MOOO ;

SI

/

AREA TO BE REGRADEb0 PROMOTE DRAINAGE

V8.000 CU. YDS.) 1tw

EXISTING WESTERNDIVERSION

.̂ f

\

REFERENCE:————————


%

$ i \!> <> -;

-EXISTING TAILINGS-f PILE

/•^

\ '• -2830•- -"'•-. _

^o^'ZZZ...../ / '\

.-•'

f-

>'"\/^EXISTING LITTLE,CUPPER

CREEK. DIVERSION A(T0 BE-CLOSED N PLACE)

-NEW LITTLE CLIPPER CREEKCENTRAL DIVERSION W/BAFFLE/ SPILLWAY(SEE CHANNEL DERAIL)

EXISTING LOG DAM{TO BE REMOVED)

:-^w /"\

60 ..........

,37

DATE BY CHK'D APRVD

6" THICK CONC W/WWF REINF.

CHANNEL DETAILSCALE: 1" = 5'-0"

S C A L E

200 400 FEET

FIGURE 3-2

DESCRIPTION/ISSUE

IT CORPORATION

DESIGNED BY

U.S. ARMY CORPS OF ENGINEERSRAPID RESPONSEOMAHA DISTRICTALTERNATIVE 3

LITTLE CLIPPER CREEK CENTRAL DIVERSIONLAVA CAP MINE EE/CA REPORT

NEVADA COUNTY, NEVADA CITY. CA.PJI

SCALE:

r-200'

5/M/01

DRAWN BY STRITUATTER S/14/01 APPROVED BY

CHECKED BY

DRAWING NO.

821815-B2

XISTING TAILINGS

APPROXIMATE BMITS OFROGK & TAILINGS• 10'0 CMP PRINCIPAL

SPILLWAY RISER

DOWNSTREAM DAM DETAILSCALE: 1" = 20'-0"EXISTING LITTLE CLIPPER!

CREEK DIVERSION V

AREA TO BE REGRADEDPROMOTE DRAINAGE

18,000 CU. YDS.)

EXlSTINlG WESTERN| DIVERSION EXISTING.LOG DAM

REMOVEp)

S C A L E

NEW DOWNSTREAM! DAMPRIMARY SPILLWAYEE DAM DETAIL} i FIGURE 3-3

U.S. ARMY CORPS OF ENGINEERSRAPID RESPONSEOMAHA DISTRICT

ALTERNATIVE 4NEW DOWNSTREAM DAM



.-TEMPORARYX /STOCKPILE

AREA; /NEW RCRA CELLSEE NOTES <Sc DETAIL...

:iMATE LIMITS,OF r—NEW LITTLE CLIPPERli!OCK & TAILfNGS DIVERSION W/'/BAFFLE/SPILLWAY

•. v..,..,v .-•-— EXISTING LITTLE,CLIPPER

- C R E E K : DIVERSION V-(TO BE> REMOVED) N

TEMPORARYSTOCKPILEAREA

EXISTING WESTERNDIVERSION EXISTING LOG DAM

(TO SE REMOVED

;x '--^ /-.. '"•, "V. "2?1.&

TOPOGRAPHIC MAP BASED ONOBTAINED FROM CH2M HILL F

ELECTRONIC FILEB. 8. 2001.

/1'-0" GRADED WASTE ROCK

- - - - -TAILINGS- - - - -

o:UJ

XX0'-6" TOPSOIL£__ \±S \X Vj' W V/ \

1'-6" COVER' ' V V— .̂.-jx-

WASJE_ROCK-___AND__!

xT-0" GRADED WASTE ROCK/

•3'-0 CLAYLINER-

O Y-O" UNDERDRAIN) O

CELL DETAILNTS

NOTES/CONSTRUCTION SEQUENCES:

1. CONSTRUCT NEW CLIPPER CREEK DIVERSION

2. REMOVE AND TEMPORARILY STOCKPILE WASTEROCK AND TAILINGS AT LOCATIONS SHOWN.

3. CONSTRUCT RCRA LINER WITHIN CELL.

4. FILL RCRA CELL WITH WASTE ROCK AND TAILINGS.

5. CAP RCRA CELL.

6. REGRADE/RESTORE EFFECTIVE AREAS.

7. REMOVE EXISTING LOG DAM.

DATE BY CHK'D APRVC DESCRIPTION/ISSUE

GEOCOMPOSITEDRAINAGE LAYER

40 MIL TEXTURED HOPESYNTHETIC COVER

GEOCOMPOSITELEACHATE COLLECTION60 MIL HOPEPRIMARY LINER

GEOCOMPOSITELEAK DETECTION

60 MIL HDPESECONDARY LINER

GEOTEXTILE

S C A L E

200 400 FEET

FIGURE 3-4

ITCORPOMTKMDESIGNED Ol

U.S. ARMY CORPS OF ENGINEERSRAPID RESPONSEOMAHA DISTRICT

ALTERNATIVE 5ON-SITE RCRA CELL

LAVA CAP MINE EE/CA REPORTNEVADA COUNTY. NEVADA CITY, CA.

PJI

SCALE:

r-zoo1

5/14/01 CHECKED BY

DRAWN BY STRITMATTER 5/14/01 APPROVED BY

DRAWING NO.

821B1S-B4SHEET NO. REVISION NO

EXISTING TAILINGS PILE(TO BE REMOVED AND

ISPOSED OF OFFSITE)

AREA TO BR REGfcADEDTO PROMOTE DRAINAGE

: N221'flPOO X*U:X ; : ' / \LIMITS OFv-A& TAILINGS \

REMOVED AND \OFFSITE) \

AF^ROXJI/ 'WASTE R

EXISTING LITTLE CUPPERCREEK DIVERSION

EXISTING WESTERNDIVERSION EXISTING LOG DAM

(TO BE REMOVED)1

S C A L E

FIGURE 3-5U.S. ARMY CORPS OF ENGINEERS

RAPID RESPONSEOMAHA DISTRICT

ALTERNATIVE 6REMOVAL AND OFF-SITE DISPOSAL


.. \ \ \ \%

DRAWN BY STRITUATTER 5/14/01 APPROVED BV

TOPOGRAPHIC MAP BASED ONOBTAINED FROM CH2M HILL F

ELECTRONIC FILEB. 8. 2001.

APPENDIX A

CALIFORNIA DEPARTMENT OF FISH AND GAME LETTER

DEPARTMENT OF FISH AND GAME

WO, CA

V. tiarkovaki May g, 199?Hatardouc Substance ScientistCKPA; Dept. of Toxic Substance Control10151 Croydon ¥ay. Suita 3Sacraneato, CA. 95827-2106

Mr. Siarkovski:

On May 7, 1997 we net on-site with Ms.Caran Gozzi. NevadaCounty Department of Invironme&tal Health* to inspect the Lava CapMine cite, little Clipper Creek drainage and Loat take (HevadaCounty). The purpose of the inspection waa to qualitatively assessfiah and wildlife resource* damaged or at*risk fron a catastrophicdischarge of tailings fron the Lava Cap Mine cite into LittleClipper Creek in January, 1997, during large storm events.Preliminary analysis of eroded sedinents by your office havesuggested high levels of Arsenic in fche estimated 20,000 tons oferoded Material. ;tittle Clipper Creek, tributary to Clipper Creek, henceGreenhorn Creek are perennial streaam |of interest to the Hepartaento£ Fish and Cane (DIG) for their fish and wildlife resource values.The subject drainages Maintain a variety of fiah and wildliferesources including riparian, wetland habitat, neadow wetlandhabitat, aquatic spawning and rearing jhabitats, and upland habitatsassociated with the atrean corridors* Species of interest in theinpacted area include rainbow trout, resident nacroinvertebrates,foothill yellow-legged frogs (Ca.lif. iSpecies-of•Special-Concern),western pond turtle (Calif. Species-of-Special-Concern), as well asell resident reptiles, anphibiana.! firth, birda and suusnals.Recreational angling does occur in the area, particularly alongpublic-access corridors In the lower .reaches of the drainage.

My obaervationa, constants and reconnendations regarding thisevent site ere as follows: iI1. Eroded Material discharged into the Little Clipper Creekdrainage fron the Lava Cap Mine site have aignificantly inpactedand degraded downstream fiah and wildlife resource values.2. Degraded and inpacted fish and wildlife resources ranain at-riskfron continued erosion and discharge i of tailing naterial frost themine cite. i •:3* Existing deposits of discharged nine naterial in Little ClipperCreek consists of extensive deposits of perched and wetted naterialwith the consistency of fine talc. Tht nafarial plumes easily with

flow and appear* to remain in suspension for prolonged periods.Such Material ia hazardous to mo* t aquatic species utilicing gilla.4. Qualitative evaluation* indicate that Little Clipper Creek baa•ssentially loat its assemblage ; of macro invertebrate population*,with no estblished species being found ia the stream above itsconfluence with Clipper Greek. Above j:hat confluence, Clipper Craekitself maintains a viable assemblage Qf aquatic macroinvertebrates.Qualitative Observation* indicate- ; populations of Caddi,* KB .JCaddisfly larvae), Placaetera so. (S^onefly larvae),so ft, (Mayfly larvae), Cojeoptara ap. (Aquatic beetles). Diptara BP..(Midges and grubs), and Bae^otark ao -• ( Backawimmers and Skippers).Igg mmssee and Adult aana boyjU* fgop thill Yellow-legged Frogs)were also observed' in this reacfe of I stream. It is likely that anequivalent assemblage of species .existed in areas of Little ClipperCreek prior to existing conditions, i5. Lost Lake consists of an aging 5 io 6 acre impoundment locateddownstream of the confluence of tittlle Clipper and Clipper Creeks.The lake Maintains a variety of well-established marsh and riparianwetland habitats around its banks!. Villows, alders, sedges, rushes,cattails, cottonwooda and horsetailj are prevalent in the area.Specific obaervations of fish and wildlife on the survey dateincluded nesting Blackbirds, nesting Redtail Hawks, Oreat Blue

Vesjtern Pond Turtles, Bullfrogs,Sunfish. Green Sunfish, and

Heron* Mallard ducks, Mergansers,Treefrogs, Laragemouth Bass, Bluaquatic Garter Snakes. Numerous pther birds were also present butnot identified. DFG oonsidera complex!habitats such as Lost Lake animportant resource for fish and wildlife.6. Loat Lake currently exhibits impacjts from the upstream eroaionof material from the Lava Cap Mine. i Extensive bars and alluvialfans have developed within the lake and immediately upstream of themouth of Clipper Creek. Marsh areAs show signs of extensivedeposition of the subject material kith many plants completelycovered by the material. Although th^re is no evidence of directfish and wildlife loss at this e^te. DFG is concerned thatcontinued input of upstream material will physically limit ordestroy many of the existing resource Valuta at this site. Spawningend nesting sites as well as foraging and escapement areas arebeing directly impacted by the; ongoing transport of upstreamsediments into the lake. j i' ! '

7. Although downstream transport!of 4ine material past Lo»t Lakeinto Greenhorn Creek is likely : to be tempered by toe holdingcapacity of the lake itself, DFG is concerned with the physicallimitations of the drainage and i the j lake to hold and stabilizeeroded material. Downstream resdurceJE remain at risk from thisevent. i ;

i !DFG recognises the problem^ end coat* associated with any

cleanup and remediation plan for this jsite and effected drainages.From a fish and wildlife perspective.! resources already loat areonly a fraction of the potential resource idamage if action is not

taken prior to the 1997/98 wintejr season. DPC recommends that allimmediate efforts be directed to mine site stabilisation end waterpassage to minimize any future movement of Material fro* the site.In-streae and in-lake cleanup are likely to result in more resourcedamage than they would Mitigate,. Flushing flows down the LittleClipper Creek drainage with United dredging to remove depositedmaterial immediately upstream of Last Lake may be a long-termapproaob to shorten the time of recovery on the drainage. This vorkit only appropriate once the siinle site has been stabilized.

As indicated at our meeting. DFO will co-operate with youraganey in helping to procure a fish sample from Lost Lake fortissue analysis. Cost restrictions Cor lab analysis will requirefunding.

Should you require further information on this issue, pleesvcontact me at P.O. Bex 704. Nevada City Ca. 95959: phone (916) 265-0805.

Sincerely.

rphn I, HiscoxAssociate fishery BiologistDepartment of Fish and Game

CC: Ms. Caren Oozzi; Nevada County Inviron. HealthMr. Jim Ickman:. CVRVQCfiHr. Jeff Finn: ore VMLt. Ken HiU«on; DFO VLP

APPENDIX B

ACTION MEMORANDUM FOR 1997 REMOVAL ACTION ATLAVA CAP MINE SITE

UNITED STATES ENVIRONMENTAL PROTECTION AGENCYREGION DC

79 Hawthorne StratiSan Franclaco, CA 94105

MEMORANDUM

DATE: 3 Oct 1997

SUBJECT: Request for a Approval of a Removal Action at Lava Cap Mine Site.Nevad

^^^EmSFfSScyT^sponsc Office

TO: Keith Takata, Director, Superfui^d Division

THRU: Terry Brubaker, Chief, Emergency Response Office

ACTION MEMORANDUM

PURPOSE

The purpose of this Action Memo is to request and document approval of the prop*removal action described herein for the Lava Cap Mine Site, Nevada City, CA.

H. SITE CONDITIONS AND BACKGROUNDSite Status: Non-NPL

Category of Removal: Time*Critical

CERCLIS ID: CA983618893

Site ID: 3Y

A. Site Description

1. Removal site evaluation•o-

The removal site evaluation has consisted of the review of reports and analytical datapreviously generated by State agencies, and an environmental consultant Discussions were heldwith another EPA on-scene coordinator and omen familiar with site conditions and past eventsonsfte. On 17 Sept 1997, EPA toured the Lava Cap Mine site with officials from the CaliforniaEnvironmental Protection Agency's Department of Toxic Substances Control ("DTSC") and theNevada County Department of Environmental Health (TNCDEFT).

High concentrations of arsenic (greater than 16,000 mg/kg) have been found in surfacesoils at and near the she. For reference, EPA has in the past utilized a preliromary remediationgoal (PRO) of 22 mg/kg for arsenic b situations where direct contact 'with residents presented aprimary risk. Based on the existence of high concentrations of arsenic onsite, the documentedreleases of arsenic oflsite, and the history of past site operations and associated problems at LavaCap Mine, we believe that an immediate threat to human health and the environment exists at theLava Cap Mine site.

Arsenic is a "hazardous substance" as that term is defined under Section 101(14) ofCERCLA. The U.S. Department of Health and Humaiji Services, the International Agency forResearch on Cancer, the U.S. EPA, and Ac National Toxicology Program have all classifiedarsenic as a known human carcinogen. Arsenic poses £ancer and non-cancer risks to people inthe concentrations found onaite. The exposure pathways are from ingestion, inhalation, anddermal exposure to arsenic-contaminated soils and sediments;

Environmental threats result from the continued oflsite migration of arsenic-contaminatedwater, soils, and sediments. The California Department; of Fish and Game ("Fish & Game") hasfound these releases have killed most aquatic life downstream of Lava Cap Mine in Little Clipperand Clipper Creeks. These releases resulted in elevated; arsenic levels 1.5 miles downstream inLost Lake's water and sediments due to deposition of Lava Cap Mine's waste. Local residentshave been observed taking fish from Lost Lake, indicating a potential direct ingestion pathwayfrom expected elevated levels of arsenic m the biota of Lost Lake. Should the releases continuedownstream past Lost Lake, they pose a threat to Rollins Reservoir, a lake used for publicdrinking water supply 3 miles downstream.

2. Physical location

The site occupies approximately 33 acres in a semi-rural area at 14501 Lava Cap MineRd., Nevada City, CA 959S9. The area is an abandoned gold mine with several ore processingbuildings and mining wastes onsite bordered by forests and residential areas. There are tworesidences onsite.

3. Site characteristics

Gold mining and ore processing operations ceased in 1943. Operations resulted in twopiles of mining waste at the site: a waste rock pile and a mill tailings pile. This waste has beenonsite for about 50 years. The waste hi the mill tailings £ile is of primary concern because of itshigh arsenic concentrations and the fact that this extremely fine-grained material is easilysuspended in water and carried oflsite. The mill tailings pile had been contained behind a 40-foottall log dam until failures in 1979 and 1997 caused major releases of these highly-contaminatedsediments downstream and oflsite. The dimensions of the mill tailings pile behind the dam in1979 were estimated by the State to be 300ft x 300ft x 60ft high (200,000 cubic yards). Thecatastrophic dam collapse on January 1,1997, released over 10,000 cubic yards downstreamduring a major winter storm. A nearby resident reported hearing a loud noise similar to an

explosion after dark on that day. In addition to immediately releasing arsenic-contaminated milltailings, this dam collapse resulted in die remaining tailings left behmd with no structure ofsufficiant integrity to adequately hold them in place. Currently, the angle<of-repose of the tailingspile is steep and unstable. Significant additional erosion and the subsequent release of largeamounts of arsenic-contaminated soils and sediments vfttl certainly occur with additional majorstorms. Hie fine particle size of the anenio-contaminated mill tailings enhances migrationbecause they are easily suspended in water, and subject to dispersal by wind.

i4. Release or threatened release into (heienvironment of a hazardous substance,

or pollutant or contaminaif

Arsenic is a hazardous substance pursuant to CERCLA. Numerous samples collected bythe State of California have documented high concentrations of arsenic in water, soils, andsediments both onsite and offsite. These concentrations' in soils arc as high as 16,000 rag/kgarsenic which greatly exceed the PRO of 22 mg/kg. Arsenic released at these concentrationsposes an immediate threat to human health and the environment

5. NPLstatns

The site is not on the NPL.

B, Other Actions to Pate

1. Previous actions

California's Central Valley Regional Water Quality Control Board ("CVRWQCB")found serious violations of their laws and regulations in! 1̂ 79 at Lava Cap Mine. These findingsresulted in the Board issuing a Cleanup and Abatement (Order to Keystone Copper Corp., RuthFlax, and Tracy Hudgins directing mem to take the fbU6wing actions:

i1. Remove the sediment from the stream and control the discharge by addingsettling basins; . '

2. Divert surface runoff around the mine waste f£ll and around or over the millwaste fill deposit hi order to control the discharge of arsenic and sediment ladenwaters to Little Clipper Creek; and i

3. Obtain an evaluation of the mill waste dam structure; by a professional engineeror engineering geologist, since the structural integrity of the mfll waste dam wasin doubt. !

This Order resulted in Lava Cap Mine constructing three small settling basins below thedam and some flow diversions around the tailings. No improvements were made to the dam.

Following complaints from nearby residents that silt was being released from Lava CapMine, a Board biologist inspected the Little Clipper Greek downstream of Lava Cap Mine andobserved that wconditions...are not suitable for stream life." Various points along a one-milesection of Little Clipper Creek downstream of the dam were observed and found to contain "no4ive stream organisms." The stream bed was found to be smothered by a fine silt from die LavaCap Mine she.

i ;

In 1994, Bechtel Environmental, working under an EPA contract, conducted a siteinspection at Lava Cap Mine. Their findings echoed those of me State inspectors before them,BechteTs samples found arsenic concentrations as high, as 7,070 mg/kg arsenic in onsitesediments. In 1997, Fish and Game re-inspected the slte-Agjam, eroded material was found inLittle Clipper Creek downstream of the Lava Cap Min$. F&O concluded that "degraded andimpacted fish and wildlife resources remain at-risk from continued erosion and discharge oftailing material from Ac mine site." The stream was biologically dead below Lava Cap Mine,and tailings had migrated to Lost Lake and seriously impacted wildlife there. Several timesduring 1997. DTSC has conducted sampling onsite and, ofudte at Lava Cap Mine to determinethe locations and concentrations of arsenic contaminatkm.

! !

Following the dam collapse on January 1,1997J Steveh Elder, the she property owner,constructed a drainage ditch upstream of the mfll tailings which partially diverted surface awayaround the tailings.

2. Current actions

No current actions to respond to the threats at Lava Cap Mine are underway.

C. State and Local Authorities'! Roles I

1. State and local actions to date: I

As previously discussed, State agencies have conducted extensive sampling andinspections of the Lava Cap Mine since the issuance of,a cleanup and abatement order in 1979.This order was not complied with. No other effective response actions have been taken by privateparties or public agencies at the she. \

2. Potential for continued State/local re iponse

Neither the State of California nor Nevada Comity have adequate resources to respondonsite. !

ITL THREATS TO PUBLIC HEALTH OR WELFARE OR THE ENVIRONMENT,AND STATUTORY AND REGULATORY AUTHORITIES

5

A. Threat! to friiblic HeaMi nr WfUarg

1. Actual or potential exposure to hazardous substances or pollutants orcontaminants by nearby populations or the food chain

High concentrations of arsenic have been rele iscd to surface waters onsite and offsite.Arsenic poses a threat of exposure through ingestion, skin absorption, or inhalation by peoplenearby. In 1994, an estimated 1,776 people lived wit lin one mile of the site, and 24,091 livedwithin four miles of the she. j

Arsenic has been released downstream as far as Lost Lake where it threatens the fisheryand other aquatic resources between the dam and the Lake.

2. Actual or potential contamination «f drinking water supplies

Arsenic released from the she poses a threat tcj ground water resources in the vicinity.Should arsenic continue to migrate downstream past tost Lake, the public water supply atRollins Lake will be threatened. This could occur if LJwt Lake overflows due to flooding or if itadam is breached. I ;

i : .

3. Hazardous substances or pollutants or contaminants In drums, barrels,tanks, or other bulk storage containers, that may pjose a threat of release

N/A |

4. High levels of hazardous substances 4»r pollutants or contaminants in soils ator near the surface, that may migrate ' '• • .

iThe migration of high concentrations of arsenij from soils and sediments on the surface

at Lava Cap Mine has been well documented. This migration is expected to continue based onthe unstable and deteriorating conditions onsite. • ]i

5. Weather conditions that may cause hhzardons substances or pollutants orcontaminants to migrate or be released >«• | '

Severe storms, typical during the rainy season ita Northern California, may causeadditional massive releases of the mill tailings currently in or near the collapsed dam onsite.These weather conditions caused the catastrophic structural failure of the dam on January 1,1997. ! l

6. Threat of fire or explosion

N/A.

B. Threats to the Environment

1. Actual or potential exposure to hazardous substances or pollutants orcontaminants by nearby animals or the food chain j

Arsenic released on she and ofisfte has expose^ the aquatic ecosystem downstream ofLava Cap Mine so profoundly that Fish and Game has ifound seriously degraded wildlifeconditions. This condition contrasts with more typical stream aquatic wildlife conditionsobserved in Little Clipper Creek upstream of Lava Cap; Mind Mill tailings were also observed inLost Lake, where negative wildlife impacts can be reasonably expected.

2. Actual or potential contamination of pensitive ecosystems:

Fish and Game is very concerned that sensitive ecosystems bom onsite and downstreamare being seriously contaminated by releases of arsenic from Lava Cap Mine. The ecosystemcontains two California Species-of-Special-Interest foothill yellow-legged frog, and westernpond turtle. In addition, aH resident reptiles, amphibians, fish; birds, and mammals arethreatened.

|3. Hazardous substances or pollutants or contaminants in drums, barrels;

tanks, or other bulk storage containers, that may pose a threat of release.

N/A

4. High levels of hazardous substances o r pollutants or contaminants in soilslargely at or near the surface, that may migrate

As previously described, the unstable condition s in the mill tailings area pose the threat ofcontinued releases of high concentration arsenic.

5. Weather conditions that may cause hi izardous substances or pollutants orcontaminants to migrate or be released

As previously described, severe weather may <a use additional, possibly catastrophicreleases of arsenic from Lava Cap Mine.

6. Threat of fire or explosion

TV. ENDANGERMENT DETERMINATION ;

Actual or threatened releases of hazardous substances from this site, if not addressed byimplementing the response action selected in this Action Memorandum, may present animminent and substantial endangennent to public health, or welfare, or the environment.

7 I '

V. PROPOSED ACTIONS AND ESTIMATED COSTS

A. Propnted Action! j

1. Proposed action description j

The proposed action is designed to prevent the continued off-site migration of arsenic-contaminated mill tailings from the Site by the followi ig actions:

1. Surface water flows iipstream of the Med mm taihngs will be div«tedupstream of the mill tailings pile dam to substa Jtially reduce the water flowthrough the contaminated areas. These diversk as will be designed andconstructed to accommodate flows comparablejto those occurring during the1996-1997 rainy season; and !

2. The mill tailings (approximately 80,000-100,000 cubic yards) remainingin the vicinity of the failed dam will be stabilized by moving them to an areawhere an engineered surface pile can be constructed adequate to prevent furtheroff-site migration. This pile wfll be constructed with a cover to minimize surfacewater erosion and infiltration, and built to ensure that the pile will remain stablefor 10 years. i

i2. Contribution to remedial performance

. | ;The Irmg-ferm ^leanyp plan for the site: :

There is presently no long-term plan for this

Threats that will require gmfHtJOTl prior to the ftprt pf 8 lopg-tarpfiT- ----- ——— 1——_ -—— TJ—— —— -p - _ - _ - _ _ _ , _ _ _ _ _ _

The threat of additional offeite migration of arsenic wfll be addressed prior to die start ofa long-term cleanup. !

. The etent to OVft^ ^^ go-to ensure that threats

The proposed removal action should substantially reduce the threat of additional offsitemigration of arsenic by stabilizing the current mill tailings. We cannot predict at this time theextent to which it will be effective, particularly its effectiveness following major storms, or formore than one rainy season. Additional response actions may be required. More comprehensiveresponse actions addressing ofisite contamination are not being proposed at this time.

Conistenc With th lon-tern

Though no long-term action is expected to be required at this time, nothing in thisproposal should adversely affect any long-term remedial action.

8i

3. Description of alternative technologiesi •:

No alternative technologies are proposed at thiji time.

4. EE/CA

N/Ai

5. Applicable or relevant and appropriate requirements (ARARs)! ;

Section 300.415(1) of the NCP provides that re noval actions must attain ARARs to theextent practicable, considering the exigencies of the sit nation.

Section 300.5 of the NCP defines ^TT1ic^?lf' cleanup standards, standardsof control, and other substantive environmental protect ion requirements, criteria or limitationspromulgated under Federal environmental or State env ironmental or facility siting laws thatspecifically address a hazardous substance, pollutant, contaminant, remedial action, location orother circumstances at a CERCLA site. i i

• l i

Section 300.5 of the NCP definat relevant and yppmpjriafe requirements as cleanupstandards, standards of control and other substantive n^quirenieQts. criteria, or limitationspromulgated under Federal environmental or State envjronmental or facility siting laws that,while not "applicable** to a hazardous substance, pollutant, or contaminant, remedial action,location, or other circumstances at a CERCLA site, address problems or situations sufficientlysimilar to those encountered at the CERCLA site and ajre well-suited to the particular site.

i •Because CERCLA on-site response actions do not require permitting, only substantive

requirements are considered as possible ARARs. Administrative requirements such as approvalof, or consultation with administrative bodies, issuance1 of permits, documentation, reporting,record keeping, and enforcement are not ARARs for fhj: CERCLA sctions confined to the she.

Only those State standards that are identified by a State in a timely manner and are morestringent than Federal retirements may be applicable of relevant and appropriate.

The following ARARs have been identified for {the proposed response action. All can beattained* • i

ARARs: Potential Federal ARARs are the RCRA Land Disposal Restrictions(LDRs) 40 CFR 268.40 Subpart D implemented through Title 22 Section 66268.40; theCERCLA Off-Site Disposal Rule Oswer Directive 93473-8FS; and the U.S. Department ofTransportation of Hazardous Materials Regulations 49 CFR Part 171, 172 and 173.

!

State ARARs; None identified at mis time; subfcgencies of the California EPA, includingthe RWQCB and DISC, as well as the Department of Fish & Game, will be requested to identifypotential state and local ARARs for consideration. ,

6. Project schedule

The proposed removal action is planned to confluence in October 1997. Every effort willbe made to complete the removal action by the end ̂ ti—^u— «- -«~id working during theheaviest part of the rainy season,

Ctt»tm

See Appendix B attached.

VL EXPECTED CHANGE IN THE SITUATlOfJ SHOULD ACTION BE DELAYEDOR NOT TAKEN i

. jIf the removal action should be delayed or not tjdcen, arsenic will continue to pose the

immediate threat of exposure to people and the environment in the vicinity of the site. Arsenicmay continue to migrate making future response cfibrtsj more technically difficult and expensive.

OUTSTANDING POLICY ISSUES

None.

Vm. ENFORCEMENT

Sec Appendix A attached.

IX. RECOMMENDATION

This decision document represents the selected removal action for the Lava Cap Mineate, in Nevada City, CA, developed in accordance with; Comprehensive EnvironmentalResponse, Compensation and Liability Act ("CERCLA") as amended, 42 U.S.C. §9601 et seq.,and the National Contingency Plan ("NCP"), 40 CF.R. 'Part 300. This decision is based on theadministrative record for the site. . i

Conditions at the site meet the NCP section 300,415(bX2) criteria for a removal It isrecommended that you approve the proposed removal action. The total project ceiling ifapproved will be $973,692. Of this, an estimated S708J300 conies from the Regional removalallowance.

')O -Approval Signature Date

Disapproval Signature Date

engineering evaluation/cost analysis rpt (ee/ca), w

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