PROPOSED PLAN FOROPERABLE UNIT 5

A R K A N S A S V A L L E Y S M E L T E R A N DCOLORADO

Z I N C - L E A D M I L L Colorado 1o f P u b l i c L _and EnvironmentU.S. Environmental Protection AgencyRegion VmJuly 2000

Operable Unit 5California Gulch Super fund SiteLeadville, ColoradoE

EPA Announces ItsThe U.S. Environmental Protection Agency (EPA), in cooperationwith the Colorado Department ofPublic Heal th and Environment(CDPHE), announces its preferred alternative1 to address thetai l ing, f l u e dust, and non-residential area soils sources of metalcontamination located within Operable Unit (OU) 5 of theCalifornia Gulch Super fund Site (Cali fornia Gulch Site) inLeadville, Colorado. These areas contribute to metalscontamination that pose a risk to human health and theenvironment.OU5 is defined as the smelter, slag, and mill sites for whichASARCO Incorporated (Asarco) is \he Potentially Responsible

Preferred Alternat iveParty (PRP). This Proposed Plan addresses the portion of OUSthat involves tailing, f l u e dust, and non-residential area soils at theArkansas Valley (AV) Smelter and the Colorado Zinc-Lead(CZL) Mill sites.The preferred cleanup alternative consists of excavating andplacing f l u e dust in a ful ly-encapsulated, lined, on-site repository.The tailing and non-residential area soils would be consolidatedand covered with a vegetated soil cover. This Proposed Plan alsosummarizes the other cleanup alternatives that were consideredfor the OUS AV/CZL sites.

MARK Y O U R C A L E N D A R : O P P O R T U N I T I E S F O R P U B L I C I N V O L V E M E N TPublic Meeting:

August 1,2000,7:00 p.m.National Mining Hall of Fame and Museum(10th Street Entrance), Leadville, Colorado

Public Comment Period:July 27-August 28,2000

Send Writ t en Comments to:Rebecca Thomas (8EPR-SR)EPA Remedial Project Manager999 18th Street, Suite 500Denver, Colorado 80202-2466Thomas.Rebecca@epa.gov

Information Repositories:The Proposed Plan and other documentsin the Administrative Record are availableat the following locations:Lake County Public LibraryH I S Harrison AvenueLeadville, CO 80461

Colorado Mountain College LibraryLearning Resource CenterLeadville.CO 80461EPA S u p e r f u n d Records Center. 999 18th Street5th Floor, North TerraceDenver, CO 80202(303)312-6473

CDPHE S u p e r f u n d Records Center4300 Cherry Creek Drive SouthBuilding 2,2*1 FloorDenver, CO 80246______(303)692-3331______Key Contacts;Rebecca ThomasEPA Remedial Project Manager (RPM)(303)312-6552T o l l - f i e e (800) 227-8917 x 6552

Russell AlienCDPHE State Project O f f i c e r(303)692-3382Toll-free (888) 569-1831 x 3382

Marion GalantCDPHE Community RelationsManagerToll-free (888) 569-1831 x 3304

'Words shown in bold italics ire defined in the glossary it the end of the document

P U B L I C I N V O L V E M E N T P R O C E S SEPA is issuing this Proposed Plan as part of its publicparticipation responsibilities under Section 300.430(0(2) of theNational Oil and Hazardous Substance Pollution Contingency«xn(NCP).The EPA and CDPHE encourage residents and other interestedparties to read and comment on this Proposed Plan. Detailedinformation is contained in the Remedial Investigation (RI), andthe Focused Feasibility Study (FFS) for OUS AV/CZL sites.These documents describe the OUS AV/CZL sites contaminationand the cleanup alternatives considered. This information andother documents in the Administrative Record are available at thelocations listed on the f irst page of this document TheAdministrative Record contains all of the information that theEPA will use to make its final remedy (cleanup) selection.After considering Stat e and community comments, the EPA willmake its f inal cleanup decision. The EPA may modi fy thepreferred alternative or select another alternative presented in thisProposed Plan.The EPA and CDPHE encourage citizens to review and commenton all identi f i ed alternatives, and provide any new information forthe EPA to consider. Oral or written comments may be submittedduring the public meeting, or written comments may be sent to theEPA Remedial Project Manager (RPM), Rebecca Thomas,postmarked or e-mailed no later than August 28,2000.Upon timely request, the EPA may extend the public commentperiod. Such requests should be made in writing to Ms. Thomasat the address shown on Page 1, postmarked no later than August28,2000.Once the public comments are received, the EPA, in consultationwith the State , will make its final decision on the cleanupalternative. The EPA will then publish a Record of Decision(ROD), a document that describes the selection of the finalcleanup plan and responds to the State and community comments.The EPA expects to issue this ROD fo l l owing the public commentperiod.

S I T E B A C K G R O U N DThe California Gulch Site is located in Lake County, Colorado, inthe Upper Arkansas River Basin, approximately 100 milessouthwest of Denver (see Figure 1). The Site encompassesapproximately 16.5 square miles and includes the towns ofLeadville and Stringtown, a portion of the Leadville HistoricMining District, and the portion of the Arkansas River from itsconfluence with California Gulch downstream to the Lake ForkCreek confluence.

Beginning in about 1860, the Leadville area was used extensivelyfor mining, miiii^g^ and smelting operations. As mines weredeveloped, waste rock was excavated along with the ore anddumped near the mine entrances. Ore was crushed and separatedinto metal l i c concentrates at mills and the tailing were generallyslurried into impoundments. The metallic concentrates were thentransported to smelters for further processing. Slag and otherwaste products were produced from the smelters.The AV/CZL sites are located approximately 1.5 miles southwestof Leadville on the north bank of California Gulch (Figure 2).The combined area of the AV Smelter and CZL Mill sites isapproximately 70 acres. All of the AV/CZL site lies above theadjacent 500-year f l ood plain of lower California Gulch, which isincluded in OUS. The OU5 AV/CZLsites are located within theI n d u s t r i a l / M i n i n g a n dBusiness/Highway zoning districtsestablished by Lake County, but thesites are not currently being used forindustrial or mining operations. Thesurrounding properties are also zonedfor Indus tr ia l /Mining uses, and theproperty adjacent to the southernboundary is currently used forindustrial operations. Stringtown, located immediately south ofCali fornia Gulch within unincorporated Lake County, is thenearest residential area.The AV Smelter was the longest operating smelter in theLeadville area, processing lead ore and reprocessing slag toproduce lead, silver, and other metals. The plant was built in1879 and was in operation until 1961. By approximately 1900,the AV Smelter was the only surviving lead smelter operating inthe Leadville district A wide variety of ores were processed overthe period of operation. The principal materials produced by thesmelter were lead bullion, copper matte, slag, and f l u e dustThe CZL Mill operated from 1926 to 1930 processing ores with acustom f loata t ion process to produce zinc, lead, gold, silver, andsome copper concentrations. In 1935, the mill was remodeled andcontinued to use the f l oa ta t ion process until operations ceased in1938. Ores processed by the mill were received from several localmines and waste dumps. The primary byproduct of mill operationwas tailing, which was discharged below the mill and presumablyinto the Cjy. Tail ing ImpoundmentThe majority of smelter and mill structures have been demolishedalthough some buildings and foundations are still present today.The smelter-related materials remaining at the AV Smelter siteconsist primarily of demolition debris - brick, concrete, metal, tile,wood and glass • and residual mine waste and smelter materialsincluding slag, coke/charcoal, limestone, ore, matte, tailing, andf l u e dust At the f in,. Mill site, the concrete foundations of themill structures remain, and debris associated with the main milland smaller deposits of tailing, ore and/or waste rock, and possiblyore concentrate are also present

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2000 2000 FEETFigure 2

O U 5 A V / C Z L S I T ECalifornia Gulch Super fund SiteUadvf f l e , Colorado

In 1983, EPA placed the California Gulch Site on the NationalPriorities List (NPL), because of concerns about the impact ofmine drainage on surface waters in the Cali fornia Gulch and theimpact of heavy metals loading to the Arkansas River.Subsequent investigations revealed the presence of heavy metalsin soils and waste piles in and around residential and commercialareas of Leadville. Several RIs have been performed to collect datanecessary to id en t i fy the nature and extent of contamination. ASite-wide Screening Feasibi l i ty Study (SFS) was undertaken as ajoint e f f o r t between the PRPs and EPA. The SFS was completedin September 1993. It developed remedial action objectives(RAG) and identi f ied an appropriate range of remedialalternatives appl i cab l e to the various sources that were to beconsidered during the FFS. Before completing the SFS, EPAprovided notice and copies of the draf t SFS to the public andaccepted comments on the draf t report

In 1994, Asarco entered into a Consent Decree (CD) with theUnited States , the Sta t e of Colorado, and other PRPs at theCalifornia Gulch Site. Pursuant to the terms and conditions of theCD, Asarco completed a FFS for OUS for the AV/CZL sites. Thi sstudy evaluated and screened remedial alternatives retained in theSFS for tailing, f l u e dust, and non-residential area soils. The FFSalso revisited the remedial technologies and process optionsretained in the SFS to reassemble the alternatives based on thespec i f i c conditions at the AV/CZL site. Two previous versions ofthe OUS FFS, which were submitted to EPA on behalf of Asarco,evaluated all of the OU5 site including the Elgin Smelter,Grant/Union Smelter, WestemZinc Smelter, and Arkansas Val l eySouth H i l l s i d e Slag Pile, which are collectively called the"EGWA" sites. EPA and Asarco agreed to revise the FFS for onlythe AV/CZL sites and the associated non-residential area soils.These sites are the subject of this Proposed Plan.The Leadville area has been classified as a National HistoricLandmark. As part of the CD, cultural resource surveys werecompleted for OUS. Both the AV Smelter and the CZL Mill sites,identi f ied as sites 5LK892 and 5LK845 respectively, have beenidenti f ied as eligible for nomination to the National Register ofHistoric Places and as contributing features to the LeadvilleHistoric Mining District

S C O P E A N D ROLE O F T H E A C T I O NOUS is one of 12 OUs identi f ied for the California Gulch Site.OUs 1 to 11 are identi f ied as source areas. OU12 will addressSite-wide surface water and groundwater quality.This action, referred to as OUS AZ/CZL, will be the final actionfor the AV Smelter and CZL Mill sites in OUS. The remainingportions of OUS (the "EGWA" sites) will be addressed separately.

S U M M A R Y O F S I T E R I S K SEPA performed human health and ecological risk assessments atthe California Gulch Site to evaluate potential hazards fromexposure to contaminated site media. Contaminated media at theOUS AV/CZL sites are tailing, f l u e dust, and non-residential areasoils. The primary contaminants of concern at OUS AV/CZLinclude arsenic, cadmium^ lead, and zinc.Human Health RiskAssessments: The baseline human health riskassessments for the California Gulch Site considered the risks toworkers and recreational visitors from ingestion of soil and dustat the AV and CZL sites. For soils and dust, lead and arsenic arethe primary contaminants of concern based on their potential tocause adverse health e f f e c t s .Action levels were developed for lead and arsenic in soils underresidential, commercial, and recreational land use scenarios.These action levels can be compared to soil concentrations todetermine if a potential risk exists. Action levels are compared toaverage contaminant concentrations over an exposure area. Theaction levels in soil for a residential exposure scenario are 3,500milligrams per kilograms (mg/kg) for lead and 120 to 340 rag/kgfor arsenic. The action levels in soil for an industrial workerexposure scenario are 6,100 to 7,700 mg/kg for lead and 610 to690 mg/kg for arsenic. The action levels in soil for a recreationalexposure scenario are 16,000 mg/kg for lead and 1,400 to 3,200mg/kg for arsenic.At the AV Smelter site, the arsenic and lead action levels forindustrial workers were exceeded in several surface samples. Theaction levels for recreational exposure were also exceeded incertain areas. The highest metal concentrations were measured inf l u e dust and other residual mine waste and smelter materials inthe main smelter area. • At the cy\. Mil l , the industrial workeraction level for arsenic (610 m g / k g ) was not exceeded in grabsamples, but it was exceeded in a composite sample of tailing.The industrial worker action level for lead was routinely exceededin near surface source materials (0 to 2 inches) at the rzi. Millsite.Ecological Risk Assessments: The ecological risk assessments(ERA) for the California Gulch Site evaluated potential risk toterrestrial and aquatic receptors (i.e., plants, animals, and f i s h )from exposure to surface water and soil contaminated by minewastes.The ERAs concluded that sources within the OUS AV/CZL sitepresent po t ent ia l ly unacceptable risks to terrestrial ecologicalreceptors (e.g., p lant s and wi ld l i f e) . The f o l l ow ing exposurepathways were identi f ied as potent ial ly unacceptable risk:

* Direct contact with sources contaminated with arsenic,lead, cadmium, and zinc by w i l d l i f e ;

• Plant and soil fauna (invertebrates and soil bacterianecessary for healthy soil) directly exposed to sourcescontaminated with arsenic, cadmium copper, lead,silver, and zinc;• Wildlife ingesting sediments and surface watercontaminated by zinc, cadmium, and lead; and• Aquatic life exposed to surface water and sedimentcontaminated with arsenic, barium, cadmium, copper,iron, and lead.

The risk characterization indicated potential ly unacceptable risksto the mountain bluebird, the least chipmunk, and bald eaglethrough direct contact of certain sources within OU5 AV/CZL.

S U M M A R Y O F A L T E R N A T I V E SEPA considered a wide range of cleanup options in the SFS.However, the FFS re-evaluated and screened the remedialtechnologies and process options from the SFS for tailing andnon-residential area soils (which included f l u e dust) to account forthe site-specific conditions at the OU5 AV/CZL site. Some of thecleanup options were eliminated during preliminary screeningbecause they would not e f f e c t i v e l y address contamination, couldnot be implemented, or would have had excessive costs comparedto other protective alternatives. The cleanup options were furtherevaluated and screened. Fol lowing screening, f ive alternativeswere retained in the FFS for further evaluation. These alternativesare discussed below.It is the lead agency's current judgment that the PreferredAlternative ident i f i ed in this Proposed Plan is necessary to protectpublic health or welfare or the environment from actual orthreatened releases of contaminants into the environment.ALTERNATIVE 1: No Action. No remediation would takeplace under this alternative. This alternative is presented as abaseline condition for comparison of Alternatives 2 through 5.Capital CostTime to ImplementAnnual Operation and Maintenance Cost30-year Present Worth Cost

$0Immediate

$0$0

ALTERNATIVE 2: Containment In Place (Soil Cover). Underthis alternative, the tailing, f l u e dust, non-residential area soils,and non-salvageable smelter demolition debris would be coveredwith an 18-inch thick, vegetated soil cover. Limited gradingwould occur to allow construction of the cover and to controlsurface water runof f . All smelter structures within the remediatedarea of the AV Smelter site would be demolished to grade exceptthe easternmost of the two ore bins, the base of two smoke stacks,and the concrete (Dewey) arch. Any salvageable demolition

debris, such as metal, would be relocated to a designated locationin the southwest portion of the AV Smelter site (known as thejunk yard). A Mitigation Plan would be prepared to addressdesignated historical structures that may be adversely a f f e c t e d . Atthe CZL Mill site, non-residential area soils would be removedfrom the mill foundations, which will remain in place.Institutional controls such as deed notices or deed restrictions toprovide notification that a barrier is in place, and/or zoningrestrictions to maintain the industrial zoning currently in place forOU5 would be implemented. County and/or City zoningordinances would be modified to create of a zoning "overlaydistrict" to provide a screening process to id en t i fy propertieswhere special precautions or requirements may be necessary. Oneoccupied residence has been identi f ied within the site. Anyexisting land use will be eligible for the Lake County CommunityHeal th Program. Land use and p l a n / p r o p o s a l s for future land useat each site would be monitored and evaluated as pan of the f iveyear review process.Capital CostTime to ImplementAnnual Operation and Maintenance Cost30-year Present Worth Cost

$3,230,0002 years

$14,000$3,600.000

ALTERNATIVE 3: Consol idation/Containment (Flue DustRepository and Soil Cover) (preferred alternative). Thisalternative includes excavating and depositing f l u e dust into anon-site, lined, f u l l y encapsulated repository. This repository wouldlikely be located at the hill slope, west of the former baghousestructure and would be lined with a geomembrane liner. Allsmelter structures within the remediated area of the AV Smeltersite would be demolished to grade except the easternmost of thetwo ore bins, the base of two smoke stacks, and the concrete(Dewey) arch. Any salvageable demolition debris, such as metal,would be relocated to a designated location in the southwestjunkyard area. A Mitigation Plan would be prepared to addressdesignated historical structures that may be adversely a f f e c t e d .Tailing, non-residential area soils, and non-salvageable materialswould be consolidated near the former blast furnace and baghouseat the AV site and at the base of the slope near the mill foundationat the CZL site. An 18-inch thick vegetated soil cover would beplaced over both the f l u e dust repository and consolidatedtailing/non-residential area soils. Demolition of the structures andsalvage of debris and institutional controls would be implementedas described in Alternative 2.Capital CostTime to ImplementAnnual Operation and Maintenance Cost30-year Present Worth Cost_______

$2,815,0002 years

$19,000$3.250.000

ALTERNATIVE 4: Consolidation/Containment (Flue DustRepository and G C L / S o i l Cover). Alternative 4 would includeall the components of Alternative 3 plus a geosynthetic clay liner(GCL) beneath the soil cover layers for the consolidated tailing,non-residential area soils, and non-salvageable materials.Capital CostTime to ImplementAnnual Operation and Maintenance Cost30-year Present Worth Cost________

$3,900,0003 years

$19,000$4.300,000

ALTERNATIVE S: Consolidation/Containment (Soil Cover)& E x c a v a t i o n / O f f s i t e Disposal This alternative includes thef o l l owing components: (1) excavating and disposing f l u e dust atan o f f s i t e hazardous waste treatment, storage, and disposalfa c i l i ty; (2) excavating and disposing of tailing within theCalifornia Gulch Sit e at the Apache Tail ing Impoundment (OUT);and (3) consolidating and covering non-residential area soils witha soil cover at the AV/CZL site. Demolition of the structures andsalvage of debris would be implemented as described inAlternative 2; non-salvageable debris would be contained underthe soil cover installed for the non-residential area soils. AMitigationPlan would be prepared to address designated historicalstructures that may be adversely a f f e c t e d . Institutional controlswould be implemented as described in Alternative 2.Capital CostTime to ImplementAnnual Operation and Maintenance Cost30-year Present Worth Cost

$15,000,0002 years

$14,000$15,400,000

3. Long-term ef fec t ivenes s and permanence refers to the abilityof a remedy to provide reliable protection of human health and theenvironment over tune.4. Reduction of toxicitv. mobility, or volume through treatmentrefers to the preference for a remedy that reduces health hazards,the movement of contaminants, or the quantity of contaminants atthe site through treatment5. Short-term e f f ec t ivenes s addresses the period of time needed tocomplete the remedy and any adverse e f f e c t s to human health andthe environment that may be caused during the construction andimplementation of the remedy.6. Implementabi l i tv refers to the technical and administrativef eas ib i l i ty of the remedy, including the availability of materialsand services needed to carry out the remedy and coordination ofFederal, State , and local governments to work together to clean upthe site.7. Cost evaluates the estimated capital and operation andmaintenance costs of each alternative in comparison to other,equally protective measures.8. S t a t e acceptance indicates whether the Stat e agrees with,opposes, or has no comment on the preferred alternative.9. Community acceptance includes determining whichcomponents of the alternatives interested persons in thecommunity support, have reservations about, or oppose. (Thisassessment will not be completed until public comments on theProposed Plan are received.).____________.

C R I T E R I A T O E V A L U A T E C L E A N U PO P T I O N S

The above alternatives were evaluated in detail using the ninecriteria identi f ied in the NCP. The criteria are summarized below.The first two cleanup evaluation criteria, overall protection ofhuman health and the environment, and compliance withApplicable or Relevant and Appropriate Requirements (ARAR),are threshold criteria that must be met by the selected remedialaction. The remaining criteria are used to help select the preferredremedy.

NCP Evaluation Criteria1. Overall protection of human health and the environmentaddresses whether or not a remedy provides adequate protectionand describes how risks posed through each pathway areeliminated, reduced, or controlled.2. Compliance with ARARs addresses whether or not a remedywill meet all Federal and State environmental laws and/or providegrounds for a waiver._________________

C O M P A R I S O N O F A L T E R N A T I V E STabl e 1 provides a comparison of the remedial action alternativesbased on seven of the nine NCP criteria. The communityacceptance criteria evaluation will not be completed untilcomments on this Proposed Plan are received. Evaluation of theoverall protection of human health and the environment is basedprimarily on the predicted ability of the alternatives to achieve thef o l l owing RAOs defined for tailing, f l u e dust, and non-residentialarea soils in the FFS. EPA has included protection of humanhealth since a residential use has been identi f ied at the AV site.The f o l l ow ing RAOs were def ined for tailing:

• Control airborne transport of tailing particles.• Control erosion of tailing into local water courses.• Control leaching and migration of metals from tailinginto surface water.• Control leaching and migration of metals from tailinginto groundwater.

T A B L E 1 IC O M P A R I S O N O F A L T E R N A T I V E S F O R T H E O U 5 A V / C Z L S I T E - N C P C R I T E R I A | |

Overall Protection ofH u m a n H e a l t h and theEnvironment

Compliance withARARsLong-TenuEf f e c t iv ene s s andPermanence

Reduction of T o z i c i t y ,Mobil i ty , or Volumethrough TreatmentShort-TermE f f e c t i v e n e s s

[ m p l e m e n t a b i l i t y

Cost

Alternative 1No Action

RAOs would not be met.

Does not comply withARARs.Magnitude of risk due todirect contact would notbe reduced.

Does not includetreatment

No disturbance to thecommunity. Note f f e c t i v e in reducingshort-term risk to theenvironment.

Not an issue.

SO

Alternative 2Containment In Place (Soil

Cover)

All RAOs would be achieved.Soil cover would reducein f i l t ra t i on by about 72%.

Complies with all ARARs.

Soil cover e f f e c t i v e inminimizing the potent ial fordirect contact, migration ofmetals, and airborne transportof source materials.Institutional Controls helpensure permanence of soilcover.

Does not include treatment.

Good short-term effectiveness.Minimal risk to communityand workers. Engineeringcontrols would be used toreduce the short-term risk tothe community and workersfrom dust emissions andexposure of contaminants.

Technically implementable.Administratively feas ible butdependent on current owner toallow remedy and to restrictfuture kind use on the coveredarea.$3,600,000

A l t e r n a t i v e sConsolidation/Containment

( F l u e Dust Repository and SoilCover)

All RAOs would be achieved.Soil cover would reduceinf i l tra t ion by about 81%. Fluedust repository would reducein f i l t ra t ion by 99.99%.Complies with all ARARs.

Soil cover e f f e c t i v e inminj in i^ ing t^e potential fordirect contact, migration ofmetals, and airborne transport ofsource materials. Repositorye f f e c t i v e in eliminating f l u e dustas a metal source. InstitutionalControls help ensure permanenceof soil cover and repository.Does not include treatment

Good short-term effectiveness.Minimal risk to community andworkers. Engineering controlswould be used to reduce theshort-term risk to the communityand workers from dust emissionsand exposure of contaminants.

Technically implementable.Administratively f ea s i b l e but .dependent on current owner toallow remedy and to restrictfuture land use on the coveredarea.$3,250,000

Alternative 4Consolidation/Containment( F l u e Dust Repository and

GCL/Sol l Cover)All RAOs would be achieved.Soil cover would reduceinf i l t ra t i on by about 97%. F l u edust repository would reducein f i l t ra t ion by 99.99%.Complies with all ARARs.

Same as Alternative 3. Additionof geosynthetic clay liner (GCL)in soil cover would furtherreduce infil tration.

Does not include treatment

Good short-term effectiveness.Engineering controls would beused to reduce the short-termrisk to the community andworkers from dust emissions andexposure of contaminants. Roadtraffic would increase over theshort-term.

Technically unplementable.Administratively f ea s ib l e butdependent on current owner toallow remedy and to restrictfu ture land use on the coveredarea.$4,300.000

Alternative SConsol idation/Containment

(Soil Cover) &E x c a v a U a n / O f f s U e Disposal

All RAOs would be achieved.Soil cover would reducein f i l t ra t ion by about 93%.

Complies with all ARARs.

Soil cover e f f e c t i v e inminimizing the potential fordirect contact, migration ofmetals, and airborne transportof source materials. Of l s i l edisposal eliminates f l u e dust asa metal source. InstitutionalControls help ensurepermanence of soil covers.Does not include treatment.

Low short-term e f f e c t ivene s sbecause of high risk tocommunity and workers due too f f s i t e disposal truck traffic andincreased excavation activities.Engineering controls would beused to reduce the risk fromdust emissions and exposure tocontaminants.Moderately d i f f i c u l t toimplement May needtreatment variance forstabilizing f l u e dust, whichcould delay remedy. Requiresschedule coordination.$15,400,000

The f o l l ow ing RAOs were defined for f l u e dust• Control airborne transport of flue'dust particles.• Control erosion of f l u e dust and deposition into localwatercourses.• Control release and migration of metals from f l u e dustinto surface water.• Control leaching and migration of metals from f l u e dustinto groundwater.• Control fffntstminnticm exposure tn humans, animals and

aquatic l i f e .The f o l l owing RAOs were defined for non-residential area soils:

• Control airborne transport of non-residential area soilparticles.• Control erosion of non-residential area soils anddeposition into local water courses.• Control leaching and migration of metals from non-residential area soils into surface water.• Control leaching and migration of metals from non-residential area soils into groundwater.• Control contamination exposure to animals, and aquaticl i f e .

The f o l l ow ing RAO was def ined for residential area soils:• Prevent direct exposure of the populat ion to elevatedconcentrations of contaminants in the surficial soil.

To comply with the requirements of the NCP, a No ActionAlternative was established as the first option in order to comparethe benefit s and costs of the remaining four alternatives. Asshown in Table 1, Alternatives 2 through 5 would comply withRAOs and provide overall protection of human health and theenvironment by covering or removing the source materials toprevent direct contact, control erosion and airborne transport, andminimize the potential for metals transport to groundwater andsurface water.Alternatives 2,3, and 4 provide essentially an equal level of long-term protection with respect to preventing direct contact, metalstransport to surface water, and preventing airborne transport bycovering the source materials present at the site. Alternative 5provides a s l ight ly higher level of long-term protection becausef l u e dust and tailing would be removed from the site.Alternatives 2, 3,4 and 5 would comply with all ARARs.Alternatives 3 and 4 provide a higher level of long-term protectionover Alternative 2 because the materials would be consolidatedand covered and the f l u e dust would be contained in a f u l l y -encapsulated repository, substantially reducing the potential forrelease of metals and providing a high sa f e ty margin for protectionof groundwater. Alternatives 3 and 4 would also provideadvantages due to the reduction of the cover area by consolidatingmaterials. Addition of a GCL to the cover system in Alternative

4 for tailing and non-residential area soils would not be expectedto provide a significant increase in protection of the environmentRemoval of f l u e dUst and tailing in Alternative 5 would eliminatethe potential for risk or metals transport from these materials.The short-term ef fec t ivenes s , based on disturbance duringimplementation, would be good for Alternatives 2, 3, and 4because the risks to workers and the community would be lowduring structure demolition and consolidation activities.Alternative 5 would provide low short-term ef fec t ivenes s toworkers and the community because of the increased risks duringexcavation and truck transportation of f l u e dust and tailingmaterial. Approximate ly 450 semi-truck trips would be needed totransport the f l u e dust from the site.No treatment processes are being considered to reduce toxitity,mobility, or volume of source material that will remain on site.Alternatives 2, 3, and 4 could be readily implemented usingstandard construction methods. Administratively, each of thesealternatives would require the cooperation of the- currentlandowner to allow institutional controls to be placed on thecovered areas. Alternatives 3 and 4 might have better cooperationfrom the current landowner than Alternative 2 since the coveredareas for Alternatives 3 and 4 are less than Alternative 2, thus,opening up the majority of the site for unrestricted industrial use.Alternative 5 would be moderately d i f f i c u l t to implement,primarily due to problems with the disposal fa c i l i ty being able totreat the f l u e dust to meet RCRA land disposal restrictionrequirements. If treatment is not possible, then a treatmentvariance would be required, which could take between one to twoyears to obtain.The estimated present worth costs range from zero for No Action(Alternative 1) to $15,400,000 for Alternative 5. The estimatedpresent worth cost of Alternative 3 is less than Alternatives 2,4,and 5. The estimated present worth cost of Alternative 5 is over4'/i times more than Alternative 3. The estimated cost forimplementing institutional controls for Alternatives 2 through 5is approximately $50,000. Thi s cost does not impact thecomparative analysis for the alternatives.CDPHE has reviewed and provided comments on the pertinentOU5 AV/CZL documents.

S U M M A R Y O F T H E P R E F E R R E DA L T E R N A T I V E

Alternative 3 (Consolidation/Containment [Flue Dust Repositoryand Soil Cover]) was selected as the preferred alternative based onthe f o l l owing reasons:/As required, Alternative 3 meets the threshold cleanupevaluation criteria (overall protection of human health and theenvironment, and compliance with ARARs).

/Alternat ive 3 provides very good long-term ef fec t ivenes s andpermanence./Alternat ive 3 eliminates direct contact with and airbornetransport of f l u e dust, tailing, and non-residential area soilsparticles and minimizes both the erosion of f l u e dust, tailing, andnon-residential area soils and deposition into local water sources./Alternat ive 3 controls leaching and migration of metals fromf l u e dust/Alternat ive 3 controls the risks (defined by the risk assessment)including direct contact with contaminated sources by w i l d l i f e andplant s and soil fauna./Alternat ive 3 is readily implementable. The remediationtechnologies selected for this alternative have been successfullyemployed at other Super fund sites./Alternat ive 3 is the least costly of the remedial alternatives.Based on this reasoning, the EPA proposes Alternative 3 as thepreferred alternative for the AV/CZL sites in OU5.

A C R O N Y M SARAR A p p l i c a b l e or Relevant and Appropr ia t e RequirementsAsarco ASARCO IncorporatedAV Arkansas V a l l e yCD Consent DecreeCDPHE Colorado Department of Public Heal th and

EnvironmentCZL Colorado Zinc-LeadE G W A Elgin Smelter, Grant/Union Smelter, Western Zinc

Smelter, and Arkansas Val l ey South H i l l s i d e Slag Pilesites

EPA U. S. Environmental Protection AgencyERA Ecological Risk AssessmentFFS Focused Feasibi l i ty StudyGCL Geosysnthetic Clay Linerm g / k g Milligrams per kilogramNCP National Oil and Hazardous Substance Pollution

Contingency PlanNPL National Priorities ListOU Operable UnitPR? Potentially Responsible PartyRAO Remedial Action ObjectiveRI Remedial InvestigationROD Record of DecisionRPM Remedial Project ManagerSFS Site-Wide Screening Feasibi l i ty S t u d y

G L O S S A R YAdministrative Record: The body of documents EPA uses toform the basis for selection of a response.Alternative: An option for reducing site risk by cleaning up orotherwise limiting exposure to contamination.A p p l i c a b l e or Relevant and A p p r o p r i a t e Requirements:Federal and state requirements for cleanup, control, andenvironmental protection that a selected remedy for a site willmeetBaseline Human Heal th Risk Assessment: A CERCLA studyconducted at the same time as the RI that determines andevaluates risk that site contamination poses to human health in theabsence of remedial action.Capi ta l Costs: Expenses related to the labor, equipment andmaterial costs of construction.Consent Decree: A legal agreement between EPA and one ormore potent ial ly responsible parties that spec i f i e s the obligationsto perform and pay for response actions.Focused Feas ib i l i ty Study: The FFS identi f ie s and evaluates themost appropriate technical approaches to address contaminationproblems at a Super fund site.Inst i tut ional Controls: Legal restrictions applied to source areasto control or prevent present and future use, and may consist ofland use controls (zoning and restrictions) or communityawareness programs.Loading: Mass concentration of contaminants in the surfacewater or groundwater, which results from surface water andgroundwater contact with contaminated media.National OU and Hazardous Substance Pol lut ion ContingencyPlan: The EPA's regulations governing all cleanups under theSuper fund program.National Priorities List: EPA's list of the most seriousuncontrolled or abandoned hazardous waste sites ident i f i ed forpossible long-term remedial response.Non-residential Area Soi l s : Soil s impacted by past smelting andmining activities that are located in areas currently zonedagricul tural/ fore s t , recreational, highway/business, retail core,commercial, and industrial mining.Operable Unit: A distinct portion of a Super fund site or adistinct action at a Super fund site. An operable unit may beestablished based on a particular type of contamination,contaminated media (e.g., soils, water), source of contamination,and/or some physical boundary or restraint

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Operation and Maintenance Cost: The cost and time frame ofoperating labor, maintenance, materials, energy, disposal, andadministrative activities of the remedy.Potential ly Responsible Party: Those identi f ied by EPA aspotential ly liable under CERCLA for cleanup costs.Preferred Alternative: Out of all the alternatives considered, thepreferred alternative is the alternative that is proposed by EPA toremediate the site.30-Year Present Worth Cost: An analysis of the current valueof all costs. Also known as Net Present Worth, the Present WorthCost is calculated based on a 30-year time period and apredetermined interest rate.Proposed Plan: A document requesting public input on aproposed remedial alternative.Record of Decision: A document which is a consolidated sourceof information about the site, the remedy selection process, and theselected remedy for a cleanup under CERCLA.Remedial Action Objectives: Medium-specific (e.g.,groundwater, tailing) goals for protecting human health and theenvironmentRemedial Investigation: A study conducted to id en t i fy the types,amounts, and locations of contamination at a site. It alsoevaluates possible risk to public health and the environment fromexposure to contamination.Residential Area Soi l s : Soi l s in a residential area of the Site thatmay have been impacted by past smelting and mining activities.Residential areas include residential properties, yards, parks,vacant lots, alleys, schools, and day care centers.Tailing: Deposited waste material from milling operations ofmined ores.

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