SITE INFORMATION AND CORRESPONDENCE_FILE 1

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Mr. Russell F. Chapin, Sr. November 15, 1995 Page 3 • Operation and maintenance. • Not listed, but important as a separate task, are final design of the recommended system for mitigating contamination at the site, to include permitting as necessary, quarterly monitoring of four groundwater monitoring wells, verification sampling at the close of the remediation process, and reporting. MONITORING WELL CONSTRUCTION Agency comments have included a requirement for one additional groundwater monitoring well (see Site Plan, attached). We will drill one soil boring, collect and analyze two soil samples from the boring, and construct, develop, and sample one groundwater monitoring well using 2-in inner diameter PVC casing. No chemical cements, glues, or solvents will be used in well construction. The base of the well will be fitted with a threaded PVC plug. The screened portion of the well will consist of factory-perforated casing with 0.020-in-wide slots. The well screen will be set through the augers and will extend from the total depth of the boring to approximately 15 ft below the ground surface. The annular space of the well will be packed with sorted sand to a point approximately 0.5 ft above the top of the perforated casing. A 2-ft thick plug consisting of bentonite pellets or chips will be placed above the sand in the wells to prevent cement from entering the sand pack. The remaining annulus will be backfilled with a mixture of neat cement and powdered bentonite (<5%) to grade. Soil samples will be collected at maximum 5-ft intervals and at lithologic contacts in the boring using a California-modified split-spoon sampler fitted with clean brass sleeves. Soil samples designated for possible laboratory analysis will be sealed and placed in iced storage. A photoionizing organic vapor meter(OVM)will be used during sampling to detect potential hydrocarbon concentrations in the soil samples. Two soil samples from each boring will be analyzed for TPHg using EPA Method 8015 (modified) and for BTEX using EPA Method 8020. PROPOSED REMEDIAL SYSTEM The FRP called for construction of a 40-ft deep, 2-in air sparging well near the northeast corner of the site with a 5-ft slotted interval from 35 to 40 ft. Based on our understanding of the site, we recommend a significantly different system. We propose to install two additional vapor extraction wells; one which would replace the proposed air sparging well near the northeast 4058-P3 LUSH GEOSCIENCES