-·--·--- ­~.I. Palmer, Vice President • ~Inn Division

W. R. Groce & Co. S5 Hoyden Avenue lexington, Mau. 02173

(617) 861-6600

January 18, 1982

Mr. John R. Moebes, Chief Pennits Branch U.S. Environmental Protection AgencyJohn F. Kennedy Federal BuildingBoston, r~assachusetts 02203

W.R. Grace &Co. - Acton Aquifer Restoration ProgramProposed Pumping Test . NPDES Discharge Penni~ No . MA0027421

Dear Mr. Moebes:

At the Januar,y 6, 1982, public hearing on the proposed draft NPDES pennit, a number of concerns were expressed on the effects of the proposed discharge to the Assabet River and its downstream users. Although this contemplateddischarge, in our opinion, incorporates safeguards to adequately protect pub11 c hea 1 th and the environment, ~1e ·have neverthe1 ess deve1oped a revised test scheme which we believe addresses the principal concerns, while preserving the basic purposes of the test {i .-e., to obtain sound engineering data for aquifer restoration).

The principal changes developed in conjunction with our consultant, COM, are as follows:

1 Improved Discharge Quality. The original proposal contemplated discharging the combined output bf Assabet No. 1, a clean well having water at essentially potable levels, and Assabet No. 2 containing substantially higher contamination. We now propose to recycle Assabet No. 2 back to Sinking Pond {as is currentlydone with Grace Well No. 3) and to discharge only water from Assabet No. 1 to the river. This will result in an 80 percentreduction in the contaminant level as well as a 50 percent reduction in the discharged volume. The additional step of . aeration of the No. 1 well discharge will .be retained as an additional safeguard.

1 Quicker Analysis. To insure prompt analysis, W.R. Grace proposes to purchase a Gas Chromatograph (an analytical instrument of the type used by EPA) to be installed and operated at the Acton site • . Daily samples will be taken and results made available within a few hours to monitor the discharge quality.

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GRACE Mr. John R. Moebes, Chief January 18, 1982 page Two ·

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• Pre-discharge f·1onitorin~. In order to obtain advanced water qu&lity data prior to a scharge, we propose to install an array of monitoring wells surrounding Assabet No. 1~ . These wells will sample an effective groundwater reservoir of approximately three to five weeks' capacity, thus giving this amount of advance notice on changes in water qualityprior to discharge.

,,: We would propose to carr,y out a one or two day trial prior t~ beginning the pumping test proper, in which the water from Assabet No. 1 would be discharged (sprayed) over the ground. This would permit a··-check of ·the overall operationbefore initiating actual discharge to the river.

We will be happy to provide any additional details that you may require.Yourss;a-J .

Nigel I. Palmer Vice President, Technical Services Polyfibron Division ·

NIP:sm cc: Mr. Stephen J. Silva, EPA

U.S. Environmental Protection AgencyRegion 1 - Permits Branch J.F.K. Federal Building, Room 2109 Boston, Massachusetts 02203 ... Attn: Veronica Harrington

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' · . W.R. GRACE ·u · )PROPOSED SINKING POND AQUIF UMPJNG TEST

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Item Original Proposal Revised Proposal===­BASIC OPERATION r

• ~le11 No. 1 Pumpage 500,000 gpd to Assabet River flo Change 1

• Well No. 2 Pumpage 500,000 gpd to Assabet River None to River,500,000 gpd to Sinking Pond.

• W.R. Grace No. 3 Pumpage 500,000 gpd (appr~x~) to Sinking Pond No Change• Discharge Treatment Spray Aeration I ·, · No Change q• Pilot Testing Activated-carbon and Aeration Tower· No Change

IMPACT TO ENVIRONt-tENT . . I

t Expected Concentrations iri Approx. 30 ppb (1, · l~dichloroethylene) . ·Approx. 5 ppb. (l,dichlor6et~Y.!~~!) ..Discharge Water 5 ppb other, before aeration; reduction 5 ppb others. before aeratlOn,

. . of 50 to 90 percent expected. reduc~ions of 50 to 90 percentexpected.

'!. . * It Maximum Concentrations ip .Approx. 0.7 ppb, 1,1-dichloroethylene, Approx. 0.05 ppb, 1,1-dichloro­Assabet River at Acton2 0~1 ppb others, before aeration. ethylene, 0.05 ppb others, . I

.. .. .. before aeration. ilMONITORING AND REPORTING . ·. :. ·.,·

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., ,• Daily Monitoring None Assabet 1 discharge. Results available within a few hours.

• Weekly r~onitorirag Assabet Wells Nos. 1 and 2, W.R. GraceNo. 3, · · - . ~ i - - -- -·- -- --·--------- --Assabet River (3 points - 1 upstrea.,•~ No changedownstream)Cooling Water Discharge.. . . . .. . . .

·serecte(f'iquf re'rmim"ftort rlg--;iells • Monthly Selected aquifer monitoring wells No Change

NOTES: - ··· - - ----- ----·- ·- - · .. . ­1. Maximum expected levels, based on 1979 analyses.2. Average summer flow assumed.

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lfotJrE 62 W.R. GRACE . COMPANY • ORGANIC CtiE..IICALS DIVISION

· ACTON, t.t ASSACH~SETTS

ORIGINAL . f0 .. .000 PROPOSED EXTENDED-DURATION0 P!4 !4ft

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