ATTACHMENT I

TECHNICAL MEMORANDUM -Scope of Work Additional Sampling for Feasibility Study Addendum Silresim Site, Lowell, Massachusetts WA # 10-IL22

Task 1.0 Project Planning

As requested per the Work Assignment Revision No.4, dated 5/20/91, CDM FPC will perform the necessary sampling activities to further define the nature and extent of the shallow ground water contaminant plume along the bordering residential area south of the site and its discharge to East Pond. This additional sampling data is necessary to ensure continued.protection of human health and the environment prior to site remediation. Ground water and surface water/sediment samples will be collected and analyzed, and a technical memorandum will be prepared and submitted to EPA, as described below.

Task 3.0 Field Investigation

Ground Water Samplioe:

A ground water sample will be collected at or near each of four existing monitoring wells: MW-503B, MW-201, MW-414, and MW-413. The well casing of MW-503B is presently under a paved road; the well will be located using a metal detector, the casing will be reset at finished grade, and the pavement will be repaired. To ensure characterization of the contaminant plume in the area of the residential dwelling at the northwest end of Main Street (the closest dwelling to the Silresim site), CDM FPC may alternately collect a ground water sample from well MW-403B (R) or from P-416. If appropriate wells cannot be reaccessed, one or two piezometers near the dwelling may also be installed. Water levels in all sampled wells will be recorded. Refer to Figure 1-1 for locations of the existing monitoring wells. Cross Section A-A' shows several of the well locations and depth to ground water between the dwelling and the site. All ground water samples collected shall be analyzed for Target Compound Ust (TCL) volatile organics (VOAs) using CLP regular analytical services (RAS).

Surface Watcr/Sediment Sampline:

One surface water and one sediment sample will be collected from each of two locations along the edge of East Pond as shown on Figure 1-1. The samples will be taken from the edge of the pond closest to the site. The samples will be collected by wading into the pond and will be taken from a depth of about 3 feet below the surface. All surface water and sediment samples collected shall analyzed for TCL VOAs using CLP regular analytical services (RAS).

77101().2 621911

Task 4.0 Sample Analysls/VaUdatlon

All sampling activities will be conducted in compliance with the approved Health and Safety Plan and the approved Quality Assurance Project Plan for the Silresim site. All analytical data will be validated according to EPA Region I guidelines.

.•. Task !.0 Data Evaluation

The sampling and analysis results will be compared with previous results from 1981, 1985 and 1988 and with the plotted VOA contours of the RIIFS. Any changes that can be ascertained will be noted for discussion in the technical memorandum.

Task 11.0 Report

A technical memorandum describing the results of the sampling effort and the conclusions drawn therefrom shall be prepared and submitted•

.. 77101~ 621911

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