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Mr Russell F Chapin, Sr May 15, 1995 Page 3 • 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 We have also included estimated costs for quarterly monitoring of four groundwater monitoring wells, estimated costs for verification sampling at the close of the remediation process, estimated fuel costs during operation of the unit, and reporting costs PROPOSED INVESTIGATION Air Sparging Well i The request for proposal called for construction of a 40-ft deep, 2-in air sparging well near the northeast corner of the site, the well will have a 5-ft slotted interval from 35 to 40 ft 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 the boring will be analyzed for TPHg using EPA Method 8015 (modified) and for BTEX using EPA Method 8020 Based on our understanding of the site, we recommend a significantly different system than that recommended, in that we propose to install two additional vapor extraction wells, one of which would replace the proposed air sparging well (originally proposed for the northeast corner of the site) and the other of which would be located near the northwest corner of the site We would also attempt to make use of the wells near the southwest and southeast corners of the northerly parking area as vapor extraction wells and to make use of the existing air sparging well as the only sparging point at present It is our opinion that the design as previously presented would lead to additional migration of contaminants by forcing contaminants offsite to the east when air sparging is initiated at the proposed locations All vapor extraction wells will be constructed using flush-jointed, 4-in inner diameter, Schedule 40 polyvinyl chloride (PVC) casing set to depths of 25 to 30 ft No chemical cements, glues, or solvents will be used in well construction The base of each well will be fitted with a threaded PVC plug The screened portion of the well will consist of factory-perforated casing with 0 060-in-wide slots The well screen will be set through the augers and will extend from the total depth of the bonng to approximately 5 ft below the ground surface 4058-P2 LUSH GEOSCIENCES