miller, inc. environmental services

& MILLER, INC.Environmental Services

April 15, 1994

United States EnvironmentalProtection Agency

Region IIEmergency & Remedial Response DivisionNew York/Superfund BranchWestern New York SectionRoom 73726 Federal PlazaNew York, New York 10278Attention: Thomas Taccone

Olean Well Field Site Projection Coordinator

Re: Response to USEPA Proposed Revisions to Draft Olean Well Field SupplementalRemedial Investigation Report (Project No. AY0167.001)

Dear Mr. Taccone:

At the request of Libby Ford, the Olean Cooperating Industries SRI/FS Coordinator, thisletter has been prepared as a response to the USEPA letter dated March 30, 1994 providingcomments on the proposed revisions to the draft Supplemental Remedial Investigation (SRI)Report submitted by letter dated February 11, 1994.

We respectfully submit the following response to comments:

1. See the attached proposed revision of Sections 6.3.2 and 6.3.3.

4. The tables identified by EPA will be moved from Volume IIA of the report to anAppendix. Geraghty & Miller will coordinate with Ebasco to inform them of thetable numbering revisions needed on their tables.

7. Two figures (upper aquifer and lower aquifer) depicting groundwater analyticalresults will be prepared. The data set will consist of data generated during theSRI and the site monitoring program (October 1989 to January 1994). Thegroundwater data will summarize the analytical results at each groundwatersampling location listing individually the concentrations of TCE, 1,2-DCE, 1,1,1-TCA, PCE, and total VOCs (excluding acetone and methylene chloride). Eachlocation will identify the minimum and maximum concentrations detected and thesampling date. Where the minimum concentration is at or below quantitationlimits, the figure will identify these as not-detected (ND).

30224 Madison Avenue Extension • Albany. New York 12203 • (518) 452-7826 • FAX (518) 452-4398

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GERAGHTY & MILLER. INC.

8. Upper and lower aquifer potentiometric surface maps will be prepared using theFebruary 13, 1993 and February 27, 1993 water-level data as requested. Thebase map will not be expanded to additional Weston Mills wells beyond thecurrent limits of the base map. The following will be added to the end of Section5.9 paragraph 1:

"Water-level measurements were also collected from existing monitoringwells in the vicinity of Haskell Creek. Although several of these wells arebeyond the limits of the base map, the water-level elevation data fromthese wells were evaluated in the preparation of the potentiometricsurface maps."

9. The effect of the McGraw-Edison air stripper on ground water will be discussedin the SFS.

12. While the exact radius of influence of the municipal wells is not known,interpolation of groundwater elevation data in the vicinity of the municipalsindicates that there is capture of groundwater upgradient of these wells."Effectual" will be deleted from page 9, paragraph 4. Page 58, paragraph 3, (2),will be changed to "the capture of groundwater by the three municipal wells".We understand that EPA is reconsidering its request for groundwater modeling.

14. An organic vapor analyzer is an FID. An HNu (manufactured by Photovac) isa PID. Both of these air monitoring devices were used by Ebasco to screen soilsamples when their portable GC was not available (see Tables 3 and 4). Page 13,paragraph 4 will be revised as follows:

"Ebasco did not use a portable GC during the drilling of soil borings SB-01 through SB-08, SB-13 through SB-18, and SB-20 through SB-29 ascalled for in the approved Field Operations Plan (Section 3.3.2). Instead,they performed an alternative field screening for VOCs on soil samplescollected from these borings. The procedure for this screening consistedof directly monitoring soil samples upon opening of the split-spoonsampler using an organic vapor analyzer (OVA) or an HNu. Use of anOVA or HNu does not allow identification or quantitation of individualVOCs as the specified portable GC would have.

19. Page 28, paragraph 4, last sentence will be revised as follows:

"This determination was made with EPA approval after full discussionwith the CIs, Geraghty & Miller, Inc., and Ebasco."

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22. Page 30, paragraph 2, last sentence will be revised as follows:

"Although no targeted VOCs were detected at soil gas points McG SG-37,McG SG-43, McG SG-48, and McG SG-66, the EPA determined that soilborings should be drilled at these locations to evaluate the potential forcontamination around the building. Aerial photographs taken of this areain 1955 and 1960 indicated a darkened area in this general location.

26. Page 33, paragraph 4, fourth sentence will be deleted as requested.,

29. Page 36, paragraph 5. The following will be inserted after the first sentence ofthis paragraph:

"The two soil gas samples were collected in areas that had high soil gasresults in 1991. Results from the two soil gas samples collected in 1993confirmed that a contaminant source in the soil could be reliably locatedduring a subsequent soil gas survey."

40. If groundwater data generated after January 1994 indicates that SRI or SFS reportconclusions should be modified, a supplemental letter report could be issued.

42. Page 70, paragraph 3. The following will be added after the last sentence:

"Based upon Figure 38, VOCs detected in Monitoring Well CW-18A maybe from a source in the vicinity of McGraw-Edison or areas furtherupgradient."

44. See the attached proposed revision of Section 6.3.




48. We continue to believe that this paragraph reflects the most reasonableinterpretation of the data, thus it will be retained in the report.

49. For the reasons we stated at our April 5 meeting, we will retain this factuallycorrect statement.

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51. Neither Monitoring Well SW-8 nor the private well at S&S Car Cleaner are partof the quarterly site monitoring program and therefore should not be discussed inSection 6.3. The following will be inserted in Section 5.7, paragraph 1, after thefirst sentence.

"Monitoring Well SW-8 could not be sampled as called for in theworkplan due to damage to the well. The private well at S&S CarCleaner was sampled as an alternate. The depth of this well is 54 feetbelow ground surface and it is presumed to be screened in the loweraquifer."

52. The range of VOCs in groundwater samples (from open boreholes and monitoringwells) are presented in Tables 63, 66, 108, and 109 (CI sites) and Tables 113-117, 121-125, and 128 (non-CI sites). This data is discussed in Sections 5.5 and5.6 respectively. It is inappropriate to make comparisons between the datagenerated from turbid samples from an open borehole, and the data generatedfrom properly constructed monitoring wells. The Final report will crossreference to these results in it's discussion of soil sampling results in Sections 5.3and 5.4.

53. Page 78, paragraph 3, line 4, "is limited" will be changed to "is probablylimited" as requested. The discussions of the soil gas survey will remain in thereport as requested.

56. We will respond to this comment once EPA provides feedback to the CIs aspromised at our April 5 meeting with EPA.

57. We will respond to this comment once EPA provides feedback to the CIs aspromised at our April 5 meeting with EPA.

58. Figure 2: As discussed at our April 5 meeting, EPA should request that Ebascoindicate the location of background borings SB-29 and SB-30 on this Figure. Wewill then revise the figure on the AutoCAD system.

59. As you requested, a figure depicting the soil analytical results generated duringthe SRI will be prepared. The soil data will summarize the analytical results ateach soil sampling location listing individually the three highest VOCconcentrations found at that location (excluding acetone and methylene chloride)and the total VOC concentration (excluding acetone and methylene chloride).Each sampling location will indicate the concentration and date.

61. See response to comment 8.

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65. Figure 39: As requested, the location of the depressions will be interpolated fromadjacent water-level elevations and the depression contour will be labeled with aground water elevation.

If you have any questions or comments regarding these proposed revisions, please contactus.

Sincerely,

GERAGHTY & MILLER, INC.

William J. GraySenior Scientist/Project Manager

WJG/TLSay0167.001oleanadmin:taccone2.1tr

cc: Olean SRI/FS Distribution List w/enclosure

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well locations were very similar (79 ug/L). TCE concentrations in 18M have been belowconcentrations in 37/38M since September 1992.

In addition to TCE, a trace level of 1,1,1-trichloroethane (1,1,1-TCA) was consistentlydetected in 18M, and trace levels of 1,1,1-TCA and 1,1-cis dichloroethylene (cis 1,2-DCE) wereconsistently detected in 37/38M, see Figures 65, 66, and 67. The magnitude of/these tracelevels have decreased over the pumping period. As the data summary in/Table P44 indicates,1,1,1-TCA concentrations were on the order of 3 to 6 ug/L in 18M,%pd 3\to 7.9\ug/L in37/38M, before and shortly after the start of continuous pumping; the March 1993\lX, 1-TCAresults for both well locations are on the order of 1 ug/L< likewise, the cis 1,2-DCEconcentrations in 37/38M have gradually decreased over time t^ôughout the pumping periodfrom earlier levels of 7.5 to 9.4 ug/L to the March 1993 levels of(the order of 1 to 2 ug/L.These trace concentrations are well below the federal MCLs fbr 1,1,^-TCA and cis 1,2-DCEof 200 ug/L and 70 ug/L, respectively.

Overall, total VOC concentrations inWroufidwaterJiifluent to Municipal Wells 18M and37/38M have been reduced by 75% and S2%^ respectively since the wells went back into fulltime service in February 1990^

6.3 MOMTORINaWE^LiS IN^HE LOWER AQUIFER

The quarterly monitoring program that has been instituted since October 1989 includesMonitorina^WeiisÂlcas D-2, AVX-5D, MEC-A2, CW-4, CW-9, CW-9A, CW-10, CW-10ACW-lând^tTWr 18.\Figures 68 through 77 are graphs of VOC concentrations detected overtime iihxeach <>fth£se vyells. Each graph shows both the total VOC concentrations (top line) andthe relative concerimitions of individual compounds. Results from the 1984 RI samples orsamples collected within the 1984 to 1985 time frame are also shown where available.

q Q oGERAGHTYcf MILLER. INC. ^

The discussion below addresses VOC concentration trends in individual monitoring wellswithin different geographical parts of the monitored area, followed by an overview ofgroundwater quality within the general area.

6.3.1 Eastern Area

The most dramatic decrease in VOC concentration has occurred/Mi Monitoring WellMEC-A2 and nearby Monitoring Well CW-18 at the eastern end of the\j*wmtored aiea . In1984, Well MEC-A2 exhibited a TCE concentration of 310 ug/L; five years later mJ3fecember1989, 170 ug/L of TCE was detected. A steady decrease in TGE concentration in MEC-A2 hascontinued from December 1989 through the present. The most refeent quarterly result forJanuary 1994 indicated a TCE concentration of 1.9 ug/L, which is below the MCL (5 ug/L) forthis compound, see Figure 68. Total VOC concentrations in Monitoring Well MEC-A2 havedecreased from 79 ug/L in March 1990 to 1.9/ng/Lin January 1994 (approximately 97%) sincethe start of continuous pumping of the mutficipalwellsin^ebruary 1990.

Monitoring Well CW-18 is located approximately 400 feet southwest and downgradientof MEC-A2. TCE concentrations of 350 and\44/ug/L were detected in the 1984 RI samplescollected from this well. Eive yearsWer, in October 1989 through March 1990, concentrationsof 3 to 9 ug/L were detected .\Inthe quarterly samples subsequently collected from CW-18 fromJune 1990 through January 1994^TGE and other targeted VOCs have consistently not beendetected, see Figure 69. \ /

6.3.2

WellAVX^D has a unique configuration in the groundwater quality data base in that itis the only wettin which TCE is not the predominant constituent (Figure 70). Cis 1,2-DCE wasdetected at the highest concentrations (up to 11,000 ug/L), while 1,1,1-TCA and1,1-dichloroethane are also major components (frequently above 1,000 ug/L). Other VOCs suchas 1,1-dichloroethylene (hundreds of ug/L) and vinyl chloride (up to 220 ug/L) were alsoconsistently detected above MCLs. TCE concentrations in this well have ranged from 95 to

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1,500 ug/L. Groundwater samples collected from CW-10A, a well completed in the upperportion of the lower aquifer approximately 800 feet to the southwest, had similar constituentsat much lower concentrations.

As shown on Figure 70, VOC concentrations in Monitoring Well AVX-5D were very lowwhen first sampled in 1985. Since the start of quarterly monitoring in October 19819, the VOCconcentrations have shown an overall increase. The increase in VOC concentrations in WellAVX-5D since October 1989 may be due to the startup of the municipaX^lTmirnpihg whichhas resulted in the lowering of water levels in the lower aquifer beneath the till layej^and thushas resulted in an increased flux/leakage from the till layer into/me)bwer aquifer. Also, duringthis same time frame, the pumping rate of the AVX produaiorKjmlJ^ower aquifer) decreasedfrom 200 gpm in 1984 to 105 gpm in 1988, to approximately 50 gpm in 1990, which remains

the current pumping rate (Huber 1993). The decreases in the XVX/production well pumpinghave decreased the hydraulic gradient in the vicinity of this well and reduced its influence ongroundwater flow. As discussed in Section 5^3.1, eTfevated concentrations of VOCs weredetected in the soil at AVX-SB06, the apparent souraeraiea^ Based on the VOC concentrationsdetected in a groundwater grab sample from this son boring the potential exists for a dense non-aqueous phase liquid (DNAPL)-at this site. However, since this sample was visibly turbid,therefore the results of the/VOC analysis represent some combination of VOC concentrationsin both soil as water. /ConHnjied traclang of groundwater quality data subsequent to sourcecontrol at this site will generate aatJhWnich can be used to more fully evaluate the potential for

DNAPL conditions. \ /

/The/fourMTionttoring wells in the northern area downgradient of AVX-5D have allexhibited an overall decreasing trend in TCE concentrations. In the Monitoring Well CW-9\. \/ /cluster, located approximately 400 feet south of AVX-5D, this decrease is most marked in CW-

\7^9A completed™ the upper part of the lower aquifer (Figure 71). TCE concentrations of 600to 630 ug/L were measured in the CW-9A 1984 RI samples and five years later in October1989, TCE concentrations were measured at 400 ug/L. TCE concentrations have decreasedfrom October 1989 through January 1994. The most recent quarterly result (January 1994)indicates a TCE concentration of 38 ug/L in CW-9A. Total VOC concentrations in Monitoring

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Well CW-9A have decreased from 140 ug/L in March 1990 to 38 ug/L in January 1994(approximately 73%) since the start of continuous pumping of the municipal wells inFebruary 1990.

In CW-9, the deeper well in the cluster, TCE concentrations of 110 to 230 ug/L weredetected in the 1984 RI samples (Figure 72). Five years later, in October/198 ,̂ this wellexhibited a comparable TCE concentration of 220 ug/L. The quarterly momtoring\esults fromOctober 1989 through January 1994 indicate a degree of fluctuation, in TGEyctwcentrauon. Themost recent quarterly result (January 1994) indicated a TCE concentration of 220 ugf^tn CW-9.Total VOC concentrations in Monitoring well CW-9 have increased from 150 ug/L in March1990 to 220 ug/L in January 1994 (approximately 46%) sjrice ti^sta^t of continuous pumpingof the municipal wells in February 1990.

In the Monitoring Well CW-10 clustep^v^pcated approximately 800 feet southwest ofAVX-5D, Well CW-10A, which is compfetedun the^npper part of the lower aquifer, hashistorically exhibited relatively low TCE confeentranons^ere the start of monitoring (Figure 73).TCE concentrations of 10 to 19 ug/L were dettectdd in the CW-10A 1984 RI samples and fiveyears later in October 1989, thi$-well exhibited^ cemiparable concentration of 11 ug/L. Duringthe most recent quarterly/monitoring data for CW-10A (June 1993), indicates the TCE

/ /~~concentration was non^detec^aW

Concentrations of cis-X2-I)CE found in MW-10A are higher than those of TCE, but aredecreasing/The ci^J ,2-DCE concentrations of 65 to 80 ug/L were detected in 1984 and rangedfrom 28/to 47~ug/L in the period from October 1989 to March 1991. The most recent quarterlyresult\JuneN^93) was significantly lower, at 1.8 ug/L. Total VOC concentrations inMonitoringxWell (ZW-10A have decreased from 37 ug/L in March 1990 to 1.8 ug/L in June1993 (approximately 95%) since the start of continuous pumping of the municipal wells inFebruary 1990. Monitoring Well CW-10A has not been sampled since June 1993.

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In CW-10, the deeper well in this cluster, TCE concentrations of 230 to 250 ug/L weredetected in the 1984 RI samples (Figure 74). Five years later in October 1989, a somewhatelevated concentration of 340 ug/L was detected; however, this result was followed by arelatively steep and steady decrease in concentration in subsequent monitoring periods. Thisdecrease in concentration has been maintained through January 1994. The most recent quarterlyresult (January 1994) indicated a TCE concentration of 15 ug/L in CW-)fr/Total VOCconcentrations in Monitoring Well CW-10 have decreased from 180 ug/L in March 1990 to 15ug/L in January 1994 (approximately 92%) since the start of continuous p^mping^of themunicipal wells in February 1990.

6.3.3 Western Area

The Alcas D-2 well has exhibited some degree of fluctua'tkm, blit neither a clear overallincreasing nor decreasing trend in TCE concentration (Figure 75). In 1984, this well exhibiteda TCE concentration of 2,150 to 4,140 ug^L. tothe quarterly monitoring from October 1989through January 1994, individual results have range^ftpm 1,300 to 7,000 ug/L. The mostrecent TCE result (January 1994) was 4,700

As discussed in Sortion 5.3.p., Monitoring Well Alcas D-2 is proximate to an area ofcontaminated soil and ^foun^water (IrTthe upper/shallow aquifer) identified during the SRI in1993. The highest conceiHrationXof^COi in soil on this property were detected in the upper two

feet of Soil Borings AL-SBOXamKAL-SBOS. These borings are approximately 23 feet apart,wrings (AL-SB01, AL-SB02, AL-SB03, AL-SB05, and AL-SB06) had TCE

tere three orders of magnitude less than the concentrations detected at AL-Sroundwater flow from the vicinity of Monitoring Well Alcas D-2 (Figure

Sture zone of Municipal Well 18M. However, since this sample was visiblythe results of the VOC analysis represent some combination of VOC

concentrations in both soil and water. Continued tracking of groundwater quality datasubsequent to source control at this site will generate data which can be used to more fullyevaluate the potential for DNAPL conditions.

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Monitoring Well CW-13 is completed in the lower part of the lower aquiferapproximately 350 feet south of Alcas D-2. Well CW-13 has exhibited TCE concentrations twoorders of magnitude lower than those detected in Alcas D-2 (Figure 76). A TCE concentrationof 49 ug/L was detected in CW-13 in the 1984 RI samples. Five years later in October 1989,a TCE concentration of 100 ug/L was detected. Subsequent quarterly results through March1991 indicated a steady gradual decrease in TCE concentration to 18 ug/L, untiLJuim>1991 when81 ug/L was measured. The June 1991 increase in TCE concentration m/CW-KJ appears tocorrelate with an increase, in June 1991, at Alcas D-2, but on a mucn\s/maHer scale. TCEconcentrations in Monitoring Well CW-13 have decreased steadily since June 199X^̂ 116 mostrecent quarterly result (January 1994) indicated a TCE concentration of 14 ug/L in CW-13.

The Alcas D-2 well also exhibited concentrations of\is-l,2<DCE (up to 200 ug/L) thatexceed the federal MCL of 70 ug/L. Only trace levels of cis-K2-DCE (up to 5.8 ug/L) havebeen detected in Monitoring Well CW-13. Totat^OC concentrations have increased from 3,200ug/L in March 1990 to 4,700 ug/L in January J994 (approximately 47%) in Monitoring WellAlcas D-2, and decreased from 86 ug/A in^Mareh^J^O to 14 ug/L in January 1994

(approximately 84%) in Monitoring Well CW-13 since the start of continuous pumping of themunicipal wells in February

6.3.4 Southern-Cent

Monitoring Well CWH* looted just north of the Allegheny River, well completed in thelower aqurfefthaHias exhibited an overall increase in TCE concentration over the period ofrecord/(Figufe^). Trace TCE concentrations of 4.5 and 5 ug/L were detected in this wellduring\the 1̂ 84 91 sampling. A comparable trace TCE concentration of 6.9 ug/L was alsodetected nve year,* later in December 1989. After the start of continuous production wellpumping in February 1990, Well CW-4 exhibited a steady gradual increase in TCE concentrationwith a peak concentration of 74 ug/L in June 1991. Groundwater containing higher TCE

concentrations than were previously detected in this area appears to have moved into and perhapsthrough the CW-4 area, as a result of the municipal wells pumping. TCE concentrations in CW-4 have been decreasing to the lower pre-pumping levels since December 1991. The most recent

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quarterly result (January 1994) indicated a TCE concentration of 7.5 ug/L.

6.3.5 Overview

In general, lower aquifer groundwater quality in the study area measured between1984/1985 and June 1993 has improved, as indicated by the individual well discussions above.In 1984/1985 TCE concentrations in the hundreds of ug/L were exhibkea by She 18M and37/38M municipal wells and by several of the upgradient monitoring weJK^n contrast, theJanuary 1994 results indicated that TCE concentrations in the municipal wells ancKm/many ofthese monitoring wells has declined to tens of ug/L. With the exceptions of the Alcas D-2 andAVX-5D wells, the TCE concentrations in the entire Depembe^X^ database for the wellswithin the study area ranged from not detected to 80 ug/LXThe most recent quarterly results(January 1994) indicate that TCE concentrations in both the municipal wells and monitoringwells (with the exception of Alcas D-2, A^X 5D, and CW^) have maintained TCEconcentrations of tens of ug/L. A similarôra5arison~ieannot be made for the Non-CI sitesbecause few monitoring wells have been ins^leoâncHnomiored on, or downgradient of theseproperties.

With respect to the/wells near the CI facilities, TCE has decreased to relatively lowconcentrations in ME(>A2,<^na hasshown increases in Alcas D-2 and AVX-5D. However,TCE concentrations in MunicipaiêljXoM and Monitoring Well CW-13 directly east/southeast

of Alcas D-2 have historically;and/continue to be two orders of magnitude lower than those inAlcas D-2./^fCE^CQncentrations have decreased in three monitoring wells (CW-9A, CW-10A,and CW^lOVtfirectly downgradient and cross-gradient of AVX-5D, and TCE has decreased tonon-detectabk concentrations in Monitoring Well CW-18 located downgradient of MEC-A2.

TCE concentration/in Monitoring Well CW-9 have slightly increased.

In general, the data indicate that the influence of the continuous municipal well pumpingsince February 1990 has been either to initiate decreases in TCE concentration in monitoringwells in the lower aquifer (e.g. CW-10), or to accelerate or sustain decreases in TCEconcentrations in monitoring wells in the lower aquifer that appeared to show an independent

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decrease between 1984 and 1989 prior to pumping (e.g. CW-9A, CW-10A, MEC-A2, CW-18).

The AVX-5D and Alcas D-2 wells continue to exhibit relatively elevated concentrationsof other VOCs which exceed federal MCLs besides TCE (1,2-DCE in both wells and 1,1,1-TCA, 1,1-DCE and vinyl chloride in AVX-5D). However, these relatively elevatedconcentrations appear to be confined to the proximity of the wells as evidencpa byahe lack ofconcentrations exceeding standards in adjacent downgradient lower aquifer monitoring wells.The municipal wells have continued to show only trace concentrations of oth£r VQC constituents(1,1,1-TCA and cis 1,2-DCE) and even the trace levels appear to have decreased/"

A summary comparison of the quarterly groundwater sartjpnng\esults for January 1994and the 1984 sampling for the RI/FS is presented in Table

6.4 MONITORING WELLS IN THE UpERAQUIFER

The quarterly monitoring program that has beeiKijmituted since October 1989 includesthree monitoring wells completed in the upper, aquMer, CW-4A, CW-18A and CW-15A. VOCconcentrations detected over timeJn each of tnfese^wells are shown on Figures 78, 79, and 80.

All three of these weHskave demonstrated an improvement in groundwater quality overthe monitoring period. ^Monitonng^Well CW-4A exhibited TCE concentrations of 350 to

400 ug/L in the 1984 RI samples/Figure 78). Since March 1990 there has been a progressive

decrease irKTCEconcentration from 270 ug/L to the most recent quarterly result for TCE in

January'1994^(8^2 ug/L). Total VOC concentrations have decreased from 278 ug/L in March1990ts8.2 dg/L/in January 1994 (approximately 97%) in Monitoring Well CW-4A since thestart of continuouXpumping of the municipal wells in February 1990.

Monitoring Well CW-18A exhibited 3,300 to 7,800 ug/L TCE concentration in the 1984RI samples (Figure 79). Five years later, in October 1989, a TCE concentration of 950 ug/L

was detected, and since that time, TCE concentrations have continued to decrease (460 ug/L inJanuary 1994). Total VOC concentrations have decreased from 1,175 ug/L in March 1990 to

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460 ug/L in January 1994 (approximately 61%) in Monitoring Well CW-18A since the start ofcontinuous pumping of the municipal wells in February 1990.

Monitoring Well CW-15A exhibited TCE concentrations of 160 to 190 ug/L in the 1984RI samples (Figure 80). Comparable TCE concentrations were detected five years later in theperiod from October 1989 to December 1991. Quarterly results from December 1991 throughJanuary 1994 indicate a steady decrease in TCE concentrations to 23 ug/L/in JuneN.993. Total

/ s\ \VOC concentrations have decreased from 229 ug/L in March 1990 to 2/N4g/L MI JanuArv 1994(approximately 88%) in Monitoring Well CW-15A since the start of continuous pumping of themunicipal wells in February 1990.

Groundwater samples collected from open boreholes during the SRI indicatedconcentrations of TCE ranging from 0.5 ug/L to 110,000 ug/L xi thenipper aquifer across theOlean Well Field. TCE concentrations detectecHft^groundwater grab samples corresponded wellwith the concentrations detected in soil sample&at those-4ocations. This scenario was fairlyconsistent with regard to the other target^! coinpo<mdy(l,2-DCE, PCE, 1,1,1-TCA, andtoluene).

A review of VOC concentrations in upper aquifer groundwater samples collected duringthe January 1994 quVOC concentrations detFebruary 1990. In general,has been seensince\1984.

rly s^rQpling mdipate decreases in the range of 61% to 97% from thesinc.ethe' start of continuous pumping of the municipal wells in\ovpfail improvement of groundwater quality in the uppe~ aquifer

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