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5.4 Well Survey A survey was conducted at the Department of Water Resources (DWR) to locate all groundwater wells within approximately 0 5 mile of the site Wells researched at DWR included domestic wells, wells for irrigation and industrial purposes, and groundwater monitor wells A total of six known wells were located within the search radius of the survey The closest well to the site appears to be a domestic well located approximately 500 feet to the north Information pertaining to these wells is presented on a Table shown on Figure 8 5.5 Vapor Extraction Pilot Test On June 10, 1994, a soil vapor extraction pilot test was conducted at the site to assess the suitability of subsurface soil conditions for soil vapor extraction as a possible option for site remediation The pilot test data was conducted to provide preliminary feasibility data including flow rate, changes in soil pore pressure, the effective radius of influence, and concentrations of extractable hydrocarbons in soil vapor Three temporary vapor wells (VW2 through VW4) were constructed at the site prior to performing the extraction test Each test well was constructed by drilling a soil boring to approximately 17 5 feet below the ground surface, removing the augers from the boring, and placing a 2-inch inner- diameter perforated (0 020-inch slots) PVC casing in the bore hole The annular space was sealed at the surface of the site with a mixture of bentonite powder and clean water The screened interval extended from the base of each boring to approximately 2 5 feet beneath the asphaltic-concrete covered ground surface A strong odor of petroleum hydrocarbons was detected in each of the temporary vapor wells The existing permanent 4-inch, inner-diameter vapor extraction well was intended for use as the extraction well and the three temporary vapor wells were to be used as observation wells, however, because of possible poor well construction, a vacuum could not be developed on the existing 4-inch vapor extraction well VW1 The internal combustion(IC) engine therefore, was used to extract vapor from temporary vapor well VW3 (Figure 9) Flow rates in feet per minute and vacuum in inches of water were monitored and recorded using Dwyer Series 2000 Magnehelic Gages Flow rates, converted to cubic feet per minute (cfm), were vaned during the test from approximately 26 to 71 cubic feet per minute The applied vacuum ranged from approximately 0 9 to 0 66 inches of water (Table 5) Changes in vacuum measured in inches of water were monitored at VW2 and VW4 during the pilot test The results of the soil vapor extraction test indicated that a change in pressure occurred between VW2 and the point of extraction(VW3), a distance of 22 feet, and between VW4 and the point of extraction (VW3), a distance of 28 feet The change in pressure, although not significant, was consistent and likely adequate for the effective removal of hydrocarbon vapor from the subsurface The pressure change may have been greater if not for the large bodies of pea gravel beneath the surface of the site and adjacent to the vapor extraction well The lower density pea gravel backfill material provided a preferential pathway for the flow of air induced by the applied vacuum The SEACOR 014-01-1 par 15 I