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· GeoT ~ --1-rans

Specialists in Solving Ground-Water Problems

Ms. Barbara Newman Region I us Environmental Protection Agency HRS-CAN2 JFK Federal Building Boston, MA 02203

Dear Ms. Newman:

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February B, 1988

This letter describes the objectives and scope of a series of on-site pumping tests whidl have been proposed for the W .R. Grace property. These tests, as indicated in the Work Plan whidl had been prepared by Hydro Groop and previously been submitted to EPA (Gedl'rans, 1987, Chapter 6 and Appendix E), will provide useful information regarding design of an on-site groundwater r:eor:Nery and treatment system. The proposed work is based on investigations and analyses done by W.R. Grace's c:x:flsultants (GeoEnvironmental Consultants, Hydro Groop, and Gedl'rans). The following sections summarize the objectives and .scope of the proposed pumping tests.

Obiectiye.

The proposed pilot study hydraulic testing is planned to provide informatial necessary to design an on-site qroondwater oollec:ticn and tJ:eatment system which will CXI'ltral. the off-site movement of oootaminated grcAlJldwater and permanently remove CXIltaminants from the groundwater beneath the W.R. Grace property. In order to design an effective hydraulic containment and oc:ntaminant removal system, it is necessary to do preliminary hydraulic testing of both the unocnsalidated avert>urden and the underlying bedrock and gather data for on-site treatment system design. The results of the preliminary hydraulic testing will be used to evaluate hydraulic characteristics of both the overburden and beclrock, identify and evaluate effective capture zones for the pumping wells, and design the final recovery well and performance monitoring system.

pescription of the Work.

The initial pilot test plans include installation of four test recovery wells cx:nsisting of two bedrock wells and two overburden well&. The bedrock wells will be six inches in diameter with stainless steel screens that extend fifty feet into the bedrock. Bentonite seals will separate the bedrock from the avetburden. '!be avem\m!en wells will be eight inch by 16 inch diameter gravel packed wells, screened for ten feet above the bedrock surface. The wells will be installed in a cluster arrange nt at two locations.

1740 Massachusetts Avenue, Boxborough, Ma chuaetts 01719 USA (617} 264-0550

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Ms. Barbara Newman 2 February 16, 1988

one well cluster will be located near existing wells, Gl4S and Gl4D. This locat.ial was selected because it is :in close proximity to the western edge of the sa.rt:h drainage ditch, which is the principal on-site contamination source area and the area with the hiqhest levels of groundwater contamination. The pilot testing will be used to evaluate the potential to remove a large percentage of the cart:amination relatively quickly. The second well cluster will be located between existing wells, G3S, G3D, and G3DB, and the main cryavac buil.ding. · 'Ihls is the area where ocntaminated groondwater is currently flowing off-site. The pilot testing will be used to design a system to effectively control the off-site movement of contaminated groundwater.

A five-day constant rate pumping test is planned for each of the four wells. An electric submersible pump will be set in each well for the duration of the pumping test. Pumping and recovery water levels in the pumping and selected observation wells will be measured and recorded using pressure transducers, data loggers, and manual measurements. It is anticipated that multi-channel data loggers will be used to provide continuous water level measw:ements at approximately twenty cbservatim wells. The specific wells to be maU.t:m:ed for eadl of the four tests will be determined subsequently, but it is anticipated that the following wells will be maU.t:m:ed during one or more of the tests:

GlS, GlD G3S, G3D, GJDB G4S, G4D G7S, G7D GlOS, GlOD, GlODB GllS, GllD Gl2S, Gl2D Gl3S, Gl3D Gl4S, Gl4D Gl5S, Gl5D Gl6S, Gl6D Gl7S, Gl7D Gl8S, Gl8D Gl9S, Gl9D G20S, G20M, G20D G21S, G21D G22S, G22D G23S, G23D G24S, G24D G25S, G25D G27S, G27D G31S, G31D GOlS, GOlD, GOlOB

~pumpJng water lsvel measurements will be mad to id8'1tity non-pumping Wlrter l8vel. trends. During pu ping, water 1 lVal m au ts will b mad

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Barbara Newman 3 February 16, 1988

continuoosl.y at wells instrumented with data loggers and periodically at other wells. The frequency of per.i.odic measurements will vary depending upon well location and time since the start or cessation of pumping.

The disc:harge water from the pumping tests will be treated prior to on-site disc:harge. For the duration of the aquifer pumping test, a temporary treatment system will be utilized to assure that the organic compounds present in the water are reduced to acceptable levels before the water is discharged into a stormwater ditch at the southeastem portion of the site. The temporary treatment system will oa1sist of a packed column air stripper followed by a liquid phase granular activated car:bcm (GAC) system. The tower and GAC system will meet the following specifications:

Packed Tower

Diameter 1011 Packed Bed 15 1 011 Water Flow 5 to 10 gpm Air to Water Ratio >150:1 Holding Basin 4 1H X 5 1 W X 8 1L

GAC System

Sump Pump 10 gpm @ 20' TDH No. of Units 2 Diameter 2011 Height 4011 Lbs. GAC/Unit Operation

225 lbs. Series

The packed tower will be mc:wrt:ed em the holding basin and the sump pump placed within the same basin. Water pumped from the wells being tested will flow t:lurugh the packed tower where from 9o-99% of the volatile oompcments will be :z:emaved: the water will cascade into the holding tan.k. once the level in the holding tank is suffident, the sump pump will be activated and pump the water to the GAC units which will be operated in series. From the carbon system, the water will flow t:lurugh a garden hose to the final discharge point.

This treatment system has been designed to assure that the levels of organics leaving the treatment system do not exceed 10 ppb total. The design is based en the historical water quality data available from monitoring well sampling and an assumed water flow rate of between 5 and 10 gpm for the period of the pumping tests.

Water Treatment svstem Evaluation.

cmcurrant with the piqX'l68d hydraulic testing, Hydro Group will evaluate three altemative water treatJnent systems. The three methods to be evaluated

Geol'rans,lnc.

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are: granular activated carbon, air stripping, and, if possible, an absotpt:ion,ldeoompositian method. Testing of the tlUrd method is dependent upon proper testing and pilot system availability.

a. The GAC pilot test will run for the duration of the pumping test. A flow totalizer will be used to record the volume of water treated, and daily samples of influent and effluent water for Unit #1 will be collected for use in full-scale system design. ·

b. The air stripping pllot study will consist of a one-day test on the last day of the aquifer test program. If the volume of water being generated during the pumping test is insufficient to ocn:luct the packed column pilot study (a 5 to 15 gpm flow is required), a closed tank will be filled with water the day before the pilot test. This water will be used to gather information for the fUll-scale system design. Air and water flows will be varied according to a pre-determined test program, and raw and treated water samples gathered for analysis. The data generated will then be used in the design process. A portable gas chromatograph will be used to monitor testing as it progresses.

c. The alternative absorption/decomposition method is a chemical process with carbon dioxide and water as end products.0

Treatment system performance will be evaluated by Gas Chromatograph (GC) analysis. GC analysis will be utilized at four major points in the aquifer; treatability study: temporary treatment system start-up, temporary system operation, GAC pilot study, and air stripper .pilot study.

During the first day of operation of the temporary treatment system, a portable GC will be used to evaluate the operation of the treatment system. Samples will be gathered during the first day of operation from the well discharge, after trestment by air stripping, before treatment by each of the GAC units, and before discharge to the groond. These samples will be screened using the field GC.

Each day that the temporary treatment system is q:>erating, samples will be collected from the well discharge for analysis by GC/mass spectrometery (GCjMS). Analysis tumaramd time will be chosen to ensure ocnsist:ent progress of the project: one and three week turnaround periods are anticipated. A sample of the final discharge from the f2 GAC unit will also be collected each day to assess the operation of the temporary system. This sample will be analyzed by Hydro GJ:OUp each day; 24-hour turnarcAlnds are anticipated. If the system is not operating as required for two consecutive days, a fresh GAC cannister will be installed.

The GAC pilot study will be running for approximately 30 days. Samples will be oollect:ed each day before and after the tl GAC unit. If the organic

GeoTrans,lnc.

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Ms. Barbara Newman 5 February 16, 1988

levels durinq the pumping test are close to the levels seen in the past, breakthralgh will occur in the first unit before the completion of the test. If breakt:lm:lugh shc:W.d occur in unit 4t2, it will be necessary to begin collecting addit.ialal samples from unit 4t2. GC analysis by EPA Methods 601/602 will be used.

During the air stripper pilc:C study, raw and treated water samples will be collected for eadl of eight different airflow/waterflow combinations. These samples will be analyzed by GC Methods 601/602.

The results of the Water Treatment System Evaluation will be used to prepare the final design of the m-site water treatment system to be used with the groundwater recovery system.

Schedule.

We propose to begin .install.atia1 of the four test wells within four weeks of receiving approval of this plan from EPA. If you have any questions regarding the proposed work, please call.

Sincerely,

~-~~ ~~~ :~esident JHG/&W 02080830 GEO/CB

cc: B. Martin, Hydro Group s. Maslansky, GeoEnvironmental Consultants G. Muench, us EPA, Office of Regional Counsel s. Ramsey, Sidley and Austin M. Stoler, W.R. Grace

barcode: *564254*barcodetext: SDMS Doc ID 564254