0

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Organic Chemicals Division

W.R. Groce &Co. Poisson Avenue

GRACE No5huo, N.H. 03061

(603) 888-2320

December 18, 1980

Mr. Paul Dadak Permits Branch U.S. Environmental Protection Agency J.F. Kennedy Federal Building Boston. Mass. 02202

Dear Mr. Dadak:

Enclosed please find a copy of the revised proposal for a two-to­three month pumping test at the Assabet municipal wells in Acton. Mass. This proposal was prepared by our consultants, Camp Dresser &McKee Inc. (CDM).

As you know, w. R. Grace has applied to the EPA for an NPDES permit, which is necessary to conduct the proposed test. The permit application was transmitted to you with my cover letter, dated August 18, 1980. The enclosed revised proposal contains additional detail regarding water quality sampling schedules and other items, and should include all items necessary for processing the NPDES permit application. We therefore request your expeditious review of this proposal and approval of the NPDES permit application.

Please contact CDM's Jeffrey E. Diercks or Robert A. Weimar, or myself, if you have any questions regarding the proposal.

Donald K. Slade Project Engineer

DKS/sdEncl. cc: Mr. Herbert M. Luz, W. R. Grace &Co.

Mr. Allan R. Campbell, W. R. Grace &Co. . Mr. Gilbert T. Joly, Massachusetts DEQE ~ f.: Mr. William Slagle, Massachusetts Division of w&ter Pollution Control ~ ML .Lawrence H.· -Goldman, Enforcement Division, U.S. b~~ 'ED Protection Agency ~~\.;~I \f Mr. Robert A. Weimar, CDM Mr. Jeffrey E. Diercks, CDM DEC 29 19!)

Ef~FJP.GJ.1 E i~ f DIViSION

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CAMP DRESSER & Mc KEE INC. lnduslnal Engoneenng Dovosoon

etlVWOM'II!fllal etlglfleflfS. 5Cif!IIIISI$,•. plallflflts. & m-~nt COttsuhants One Cenler Plaza

Boslon. Massacnusells 02108 617 742-5151

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December 15, 1980

Mr. Gilbert T. Joly, P.E. Regional Environmental Engineer Massachusetts Department of Environmental

Quality EngineeringCentral Regional Office 75 Grove Street Worcester, MA 01605

DEQE Order Paragraph No. 6 Assabet Wells Pumping Test Response to DEQE's 9/4/80 letter

Dear Mr. Joly:

On behalf of our client, W.R. Grace &Company, Camp Dresser &McKee Inc. (COM) is hereby responding to your letter dated September 4, 1980 regard­ing conduct of a long-term (two-to-three month) pumping test at the Acton Water District's Assabet Municipal Wells. COM's original proposal for this test was outlined in a letter dated August 1.3, 1980 and was made in compliance with Paragraph No. 6 of the July 14, 1980 DEQE Order to W.R. Grace &Co. The following comments and recommendations refer to each of the nine items listed in your correspondence; in addition, we have attemp­ted to clarify the context and purpose of the proposed program.

Context and Purpose of Proposed Program

The proposed pumping test is an integral part of the overall waste cleanupeffort being conducted by W.R. Grace &Co. in response to the DEQE Order and the recently negotiated Final Decree between the U.S. Environmental Protection Agency and W.R. Grace &Co. The overall goals of the cleanupeffort are to cease all waste discharges to the environment; assess all existing contamination problems; establish and undertake appropriate remedial actions to accelerate contaminant removal from the aquifer, and, if possible, restore the aquifer potability; and to prevent any future contamination problems. These goals are to be accomplished in two basic phases:

(1) a general waste site closure program, as mandated by the DEQE Order, Paragraph No. 5; and,

(2) an aquifer restoration program, as mandated by the DEQE Order, Paragraph No. 7.

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CAMP DRESSER & McKEE INC. lncluslroal Eng1nee11ng 01~111011

Mr. Gilbert T. Jol.v. . . December 15. 1980 -2­

The general waste site closure program is intended to identify the potential waste sources to the groundwater system and develop methods to prevent ·~ future contamination. The aquifer restoration programts proposed to identify existing groundwater contaminant phnes and · develop methods to accelerate their removal.

The purpose of the proposed pumping test, discussed in our August 13 proposal, are as follows:

- (Prf.ary purpose) To determine the feasibility of producingpotable water from Assabet Well No. 1, while using Assabet Well No. 2 and Grace Well No. 3 as "interceptor wells" to intercept known contaminants from the primary and emergencylagoon areas.

- To determine the maximum feasible yield from Assabet Well No. 1.

- To obtain adequate hydrogeological and geochemical data to develop accurate analytical/numerical models to evaluate aquifer restoration proposals during the eventual AquiferRestoration Program.

Therefore, it is clear that the pumping test program is interrelated with the Aquifer Restoration Program (Item No. 7 of the DEQE Order) and the General Waste Site Closure Program (Item No. 5 of the DEQE Order). For this reason, we have attempted, where possible, to coordinate the necess­ary tasks from all phases of the clean-up effort. F~r example, all well installations at the site will be conducted as part of the sampling and analysis program to be performed during the general waste site closure program so that the field work is conducted in an integrated, efficient manner. In addition, the information on aquifer characteristics and con­taminant plume movement obtained from the pumping test will be a basis for our investigations of aquifer restoration alternatives.

Along with the major program purposes stated above, a number of subordinate goals will be addressed by the pumping test program. These include evalu­ating the feasibility of using simple aeration treatment on the contaminated groundwater, evaluating the effectiveness of a "distant early warning"monitoring well system around Assabet Well No. 1, estimating the time nec­essary for cleaning of Assabet Well No. 2, and a number of other items also of relevance to the Aquifer Restoration Program (DEQE Order, Paragraph No. 7).

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CAMP DRESSER & McKEE INC. lndustual Eng~r•ung D•vt110n

Mr. Gilbert T. JolyDecember 15, 1980_·.. ~ -~ .. -3­

Response to DEQE Comments

Responses to the nine items in the September 4 letter follow. (A copyof the letter ts included as Appendix A.) To provide a logical order to this discussion, the nine items have been rearranged in the followingorder: Item No. 9, then Nos. 3, 2, 4, 6, 7, 58, 1, SA, and 8.

Item No. 9 -- Number and Location of New Monitoring Wells. We have reviewed the discussions on new well locations offered by various commen­tators, and we offer the following comnents on !n.~ revisions to our proposal.

The monitoring well array proposed in our August 13 letter was intended primarily to serve as a "distant early warning" system for any contaminants which might reach Assabet Well No. 1. The wells will be used both for mon­itoring the test and as an integral part of long-term operation of Assabet Well No. 1. The wefls were not primarily fntended to specifically locate--other contaminant sourees:-i) thougnsome t nformaHon-regarding genera1 source direction may be obtained. Use of a more extensive monitoring well arraywould be required to pinpoint other sources but that was not the intent of our proposal.

We have, however, reviewed our proposal in light of an apparent desire for a greater amount of contaminant location data from different points in the aquifer, and have incorporated some possible suggestions into this revised proposal. The revised plan is shown on Figure 1. Final well locations will, of course, also depend on actual surface conditions encountered in the field.

The monitoring wells will be similar to the existing BarCad wells. Theywill be drilled to bedrock or refusal. In general, the wells will each include three or four BarCad samplers, the exact locations of which will be determined in the field. Ahydraulic piezometer (i.e., a standard water level monitoring wells) will be located in the upper part of the aquifer system, and a pneumatic piezometer (a device constructed of nylontubin9 and using air pressure relationships to obtain water level measure­ments) w111 be located about ten feet from the bottom of the hole. We are presently investigating the possibility of using the BarCads themselves to obtain water level readings. If this is feasible, it would eliminate the need for any pneumatic piezometers.

Discussion regarding additional well installation at the Assabet River is contained in the following section.

••••

----

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LEGEND

0 EXISTitiG PRODUCTION WELL 0 ....., "~,.:{;r-1.. '~

ABOVE GROUND TEMPORARY I I DISCHARGE PIPE 8WfiG·I ...,. r·' : UNDERGROUND TEMPORARY 0 I

--• DISCHARGE PIPE I 11 I..OUSTIIIAL

® PROPOSED BARCAD MOMlORING WELLS f) ACTON I lANIWilL Af·Ta Al·l8 PROPOSED STANOoQRD MONITORING WELLS 0 I ,..DUIT'"AL ~

assaan I ..All.. I S&ltD .J Ioat·Taa..D l)L (r ••., ·-·· GIIAY!L

"" ... 0 ,. ,.., 1

ASSABET I AND 2 ) ,-­PUMP TO ASSABET RIVER (', '

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W.R. GRACE COMPANY • ORGANIC CHEMICALS DIV ISION

ACTON, MASSACHUSETTS

0 PROPOSED EXTENDED-DURATION 0 7!0 !tOn 1000

PUMPING TEST FACILITIES SCAlf .. FIEf

s:"tr.no:",.o:'UitC'D Jqpn

Oll0:>3ll 3ALLYliJ.SDUH<IY 3:>YliO"ll"H

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CAMP DRESSER & McKEE INC. lndustr,.l Engon1e11ng OovosoonMr. Gilbert T. Joly

December 15, 1980 -s-

Item No. 3 -- Additional Wells at the Assabet River. Two additional moni­toring wells, one on each side of the Assabet River, were suggested "to better define the hydraulic connection between the Assabet River and the two supply wells". It is our opinion that installation of two monitoring wells 1.-ediately adjacent to the river is not necessary to understand the relationship between the river and the aquifer. If the intent of these wells were to quantify the amount of river infiltration fnduced during the test, they would provide insufficient data for this purpose as knowledge of the river bed permeability would also be necessary. Hence, we can only assume that the wells were intended to demonstrate induced infiltration in a qualitative manner by comparing groundwater and river levels. However, the existence of induced infiltration has already been well documented by both the GZD and COM reports; the GZD report provided estimates of induced infiltration based on streamflow depletion curves, and the COM report pro­vided estimates of induced infiltration based on mass-balance considerations. We. therefore, do not believe these proposed wells would significantly add to our understanding of the hydrologic system.

Additional monitoring wells at the Assabet River, however, may provide sig­nificant data on the quality of induced infiltration to the aquifer. al ­though this purpose is not the primary focus of the proposed test. Because of your apparent desire to maximize groundwater quality data, we have in­cluded these wells in our program as located on Figure 1 (attached). These wells would be drilled such that they penetrated the aquifer at both shallow and deep depths.

Item No. 2 -- Proposed Sampling Schedule. A detailed proposed sampling schedule 1s presented 1n Table 1. It can be seen that the proposed program includes a limited number of weekly samples. a set of samples taken every four weeks from BarCad wells near the Assabet production wells, and an initial round of sampling from a majority of the wells in the area tributary to the Assabet wells.

Several criteria were used to establish the schedule shown in Table 1. Weekly samples are to be taken only from points where a more substantial data base is needed to evaluate certain procedures. Specifically. weekly samples will be taken to determine the potability of the Assabet wells, the effectiveness of the Grace cooling water return as an aeration treat­ment technique, and the effect of the municipal well water discharge upon the river water quality. Also, samples are to be taken weekly from two of the proposed wells near the municipal production wells and to examine the usefulness of this monitoring well array as a "distant early warning" sys­tem for long-term use by the Acton Water District. The two wells chosen would be those with the highest concentrations. Other wells in the imme­diate vicinity of Assabet Well Nos. 1 and 2 will be sampled every four weeks.

• •

11111 Tm

Production llt11s

Extsttng Sttndlrd Test !!t11s

btsting llrCad !It11 I

Exhttng Other !!tlh

PropoHd larC.d Wells

Proposed Sttndlrd Test !!t11s

SURFACE WATER Location

Cooltng wttr dhcllargt

Sinttng Pond Turtle Pond ...s.nt Pond

Assabtt 1 Aulllltl &race 3

Al .. Al·£ A2·£---1..-.2 IIIIA· .....,:t --1-CIII ...,-ow-.:s-ow 73-:t 73-4 73-5 73-6 73·7 73·8 77·1 77·2 77·3 Tll-1·78 Tll·2·78 71·1 78·3 M·78 A5-78 M-78 A7·78 A8·78 t-78 Ill ll2 ll3... 81 12 83 14 15 16 17 18 19 110

suttng Rtnk tl•plast

Two lltghest•concentration wel h in ring around Assabtt 1

Other thrH wells in ringarour.d Asnbtt 1

Other tllrH llrCad 1111 h

Assabtt River .,nttortng wells

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0

AsSibtt Rtver, upstrt1111of dtscll~rge

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Asllbtt Rt ver. clownstre111 0 of dhdla,.

llot.. :

0 • Saplt u•en for organic cont111inants.

TAILE 1

PIIOPOS£0 SNIPLIIIIi SCMDIUl£

bery F.nll lllitial loulld llot to M ..... Only S!!pled

0 0 0

0 (2 ltvth)

l See llott 2

l Sat llott 2

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Set Note 1•0 ~5 levels)0 • ltvthl

0 (Z levtls) 0 Z other levels)0 (2 levels) 0 2 other levels)

X Set Note 1 0 (3 ltvtlsl

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I • Sa~~ple tlttn for inorganic par-ters (pH, nitrate, chloride, tottl dissolved soltds). 1 • llot to bt Slllpltd u it h outstdt area expected to bt tributary to Assabtt welh. 2 • llot to bt Slllpltd as nearby well wtll bt Slllpltd instead.

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CAMP DRESSER & McKEE INC. lndUIII181 Eng111eerong OtvosoonMr. Gilbert T. Joly

December 15, 1980 --7­

An initial round will be taken of most wells in the area tributary to the Assabet wells. Wells outside this tributary area will not be tested; although we recognize the value of a comprehensive, general sampling round, data obtained from these wells would not have an impact on the pumping test itself, and some of these wells will probably be sampled in conjunction with other work to be performed at the W.R. Grace plant. Certain wells within the tributar,y area were not selected due to the nearby presence of another well which ~s included tn the sampling round.

The initial sampling round from Assabet Municiapl Wells Nos. 1 and 2, and from Grace Well No. 3, would include tests for all 129 EPA Priority Pollu­tants. Other samples taken during the initial round would be analyzed by gas chromatography/mass spectrometry (GC/MS) for volatile organics. Sub­sequent rounds may be analyzed by a volatile organics scan using GC in order to reduce cost. Additional information regarding laboratory selec­tion, detection limits, etc., is presented in our response to Item No. 8.

As shown in Table 1, we also propose to take several samples for selected inorganic parameters, including pH, nitrates, chlorides and total dissolved solids. Samples for these analyses will be taken every four weeks from the production wells, several test wells, and several surface waters as listed on Table 1. The purpose of this testing is to determine whether these parameters, which are expected to be significantly different in the groundwaters from the surface water, can be used to assess surface water/groundwater interactions in the aquifer.

It should be noted that the proposed sampling program may be expected to undergo revision as the test proceeds. Results of analyses of the early sampling rounds may affect choice of sampling locations in later rounds.

Item No. 4 -- Water Level Honitoring Schedule. A detailed schedule of proposed water level readings is presented in Table 2. It can be seen that the aquifer was divided into several segments for the purpose of establishing monitoring frequencies.

The observation wells nearest to the two municipal production wells will be the most affected during the first few days of the test. We have pro­posed that those wells within 300-feet of Assabet Wells Nos. 1 and 2 be monitored frequently during the first three days of the test, then daily thereafter. In addition, water levels in Grace Well No. 3, Turtle Pond, and the Assabet River and its nearby wells would be recorded daily, as shown in Table 2.

TMU Zr ·: NOPOSED IIATDI LEY£l IOCITDIIIIIG I'IOGitAM

Monltorl!!l '-x Stt llo. IIIII 11111 llo. or Surface At Stlrt IIIII llot Description lilttr .._ Dttb lillkb Elld of Test DII1X Monitored

1. llttlltll 300 flit Asubtt 1 l of Asubtt llllls Asubtt z l

A1·• l A1·E l M·E I 16-1 I 17·1 I

Proposed ftve new lartld l 1111h tn rtng 11'0111111 Assalltt 1 l:r'" and 10111r ltvt s

lrltl 3 I Assabtt ltver -.nttort111 •11• I

Turtle Pond I Assabtt ltver I

z. llttlltn aqutfer IIIlA·1 •trtbuttry to UIIA·2 I Assabtt llllls UIIA·3 •I UIIA·S

IlliG·1-ow •111'-2·011 I 73·3 I 73·4 I 73·5 I 73-6 X

{) 73-7 I 73·8 X.._; 77·1 •77·2 X 77·3 •Tll·l-78 l Tll-2·78 X 78·1 78·3 A4·78 A5-78 A6-78 A7·78 AB·78 9·78

•••••••• " 54 •• 11 82 •••84 85 X 89 I

Proposed thrtt new larCad wells (upper and 1-r 1tvtls) "'skrat Pond •Stnking Pond •Pond in IllS pit X

3. Outside arta G2 X tributary to &3 I Asubtt llllh

83 X 88 I 810 X

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1. Proposed new larC.d wells -ld be rtad both at the •ll point near tht weter table and at 1 pntuMtic pitZOIItttr nar tht botto. of the wel 1.

2. Consideration is bting gtven to tht possibility of obttining water level rtldings fr0111 installed lartad devic:n.

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CAMP DRESSER &McKEE INC. lncluslf,.l EnglnMiong DovollQnMr. Gilbert T. Joly

December 15, 1980 -9­

Wells within the area tributary to the Assabet wells would also be moni­tored during the test. Groundwater levels are not expected to changequickly in this area -- average daily fluctuations are likely to be less than one-half inch. Hence, there is no need for daily monitoring. Weeklymonitoring will be more than sufficient to provide the data needed to observe the behavior of the groundwater system.

Wells outside the area tributary to the municipal productions wells do not need to be monitored for this test. Nevertheless. we recognize the desire for a complete set of readings on all wells in the area, and we propose this be done at the beginning and end of the test.

We see no need for several rounds of static readings before the test begins. Presumably the reason that this was suggested was to establish the natural groundwater fluctuations occurring at the start of the test. If this is desired, however, readings taken during the test at outlying areas {i.e •• beyond the area of influence of the wells) will suffice. Further, Grace Well No. 3 should not be shut down prior to the start of the test. Rather, it should be operated at a constant rate for a periodof time before the test begins so that the initial round of water level readings reflects an established, near-equilibrium cone of influence around Grace Well No. 3. The only changes in the groundwater systemoccurring during the test will thus be caused by pumping the municipalwells and by natural conditions.

Item No. 6 -- Measurement of River Levels. Continuous monitoring of the river levels, such as would be provided by a recording gauge, is not necessary for this test. Such readings would be necessary in a detailed assessment of the interrelationships between the river and the groundwater system, but this analysis is outside the scope of the present study as discussed above under Item No. 3. Therefore, we are proposing to install a staff gauge in the river; the staff gauge will be read once per day as will nearby wells.

Item No. 7 -- Grace Wells Operation. The simultaneous operation of all Grace production wells had been considered at one point as an aid in accelerating the flushing of the aquifer. Only Grace Well No. 3, however, has shown significant contamination and is advantageously located to inter­cept part of the known contaminant plume from the W.R. Grace &Co. plantsites. We are therefore proposing that only Grace Well No. 3 be operatedduring the test. The term "Grace wells" referred to in page 4, paragraph3 of our August 13 letter was an error.

~AMP DRESSER & McKEE INC. lndustual EngtnHIIflll Oro1110n

Mr. Gilbert T. JolyDecember 15, 1980

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Item No. 58 -- Rain Gauge Readings. The actual amount of precipitation recharge reaching the aquifer is dependent upon two factors: precipita­tion and evapotranspiration. Evapotranspiration levels can only be estimated, not directly measured. Hence, the UIOUnt of precipitationrecharge also can only be an estimate. Measurement of precipitationinvolving multiple and/or overly-sophisticated gauges is therefore far too refined for this test. We are proposing to set up near the Assabet wells one rain gauge, equivalent or superior to the WeatherMeasure Corp.Model No. P567 "fence-post gauge", which would be read daily.

Item No. 1 - - Coordination with Acton Water District and Item No. SA - ­Access to Information. Because of the litigation potential between the ACton Water District and W.R. Grace &Co., COM has been instructed that questions of informational exchange with the District shall be addressed in the first instance by the attorney.

Item No. 8 -- Analytical Concerns. We are not at the present time propos­ing specific laboratories or quality control procedures to be used in the long-term pumping test. We agree with the recommendation in the GZD report that, prior to a major sampling round, "Specifications for the chemical testing should be issued and proposals solicited. An audit should be conducted on the selected testing facility by those experiencedin Quality Assurance and Quality Control protocol and expert in the field of organic chemistry.'' We propose to prepare such specifications and select a laboratory in cooperation with representatives of other interested parties. This work would begin immediately upon approval of the pumping test plan proposed herein.

SUIIIIIAry

We expect that the foregoing comments form a satisfactory response to your concerns about our proposal. We therefore request DEQE approval of performance of the long-term pumping test as outlined in our August 13 letter and supplemented herein.

We recognize, however, that further discussion may be necessary followingreview of this letter by the various interested parties. Please contact our Project Manager, Mr. Robert A. Weimar, if you have any questions or desire additional information.

Very truly yours,

Division

JTO/m

CAMP DRESSER & McKEE INC. ~ne~uauoa~ £ne-ono OtvtiiOII

Mr. Gilbert T. JolyDecember 15, 1980 -11­

cc: Mr. Thomas Mcloughlin, Deputy Commissioner for RegionalServices. Massachusetts DEQE

Mr. Willard Pope. General Counsel, Mass. DEQE Mr. Herbert M. Luz. Vice President. Manufacturing.Organic Chemicals Division. W.R. Grace l Compa~

Mr. Peter A. Fine, Foley, Hoag l Eliot Mr. Donald K. Slade, Project Engineer. W.R. Grace l CompanyActon water District Acton Board of Selectmen

JED,RAW

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APPENDIX A DEQE September 4, 1980 Letter