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r f f 30 August 2004 AGE-NC Project No 99-0592 Page 11 of 13 Since initiation of ground water monitoring in November 1999,ground water elevations have ranged ' I from approximately 25 2 to 44 4 feet below mean sea level The ground water table underlying thef site is generally flat and toward the northeast with a low gradient of less than 0 01 ft/ft (Figure �M'11 _� vY,, aoo4- --)vd4-o SW, 'I] Laboratory analysis of ground water samples detected petroleum hydrocarbon-imp4c ed water at the former USTs T-1 and T-2 locations (at borings MW-1 and B-2), only MTBE at 9 µg7l`r as detected ' at the western edge of the site (boring B-5) However, the detected concentrations in ground water MT-AL' samples collected from the former UST location (e g , MW-1)have remained stable since grounds 6 water monitoring began in November 1999, indicating that further migration of hydrocarbons from ha it*__ the source area is not occurring Furthermore, analytes of concern have not been detected above laboratory reporting limits in ground water samples collected from perimeter monitoring wells MW-2,MW-3 and MW-4 over the length ofthe quarterly monitoring and sampling events conducted to date The lateral extent of ground water contamination appears to be limited to the former UST area (MW-1) Typically, ground water would represent the migration medium for contaminants over significant horizontal distances However, sites located in up-gradient or cross-gradient directions from the subject property are not likely to be negatively impacted by the subject property In addition, first encountered ground water is not used for drinking or irrigation, although all ground water in the State of California is considered to be of potential beneficial use Drinking water at and near the site is supplied by private wells Two on-site domestic wells (DW-1 and DW-2) were identified during a sensitive receptor survey conducted during the Fourth Quarter 1999, DW-1 is located approximately 140 feet north and DW-2 was located approximately 90 feet southeast of the former UST system DW-2 reportedly had been out of service since 1978 due to sand infiltration problems and was destroyed under EHD oversight in December 2000 Groundwater in well DW-1 is sampled each quarter, and to date analytical results have been non-detect In addition to on-site well DW-1, ten other private wells and one public well were Identified within - a 2,000-foot radius of the site,the nearest off-site well is approximately 220 feet from the site Based on the lateral extent of contaminated ground water at the site, it is unlikely for off-site wells to be contaminated by impacted ground water from the site ' The subject property utilizes two septic systems, one is located approximately 90 feet east of the former UST system and the second system 1s located toward the front of the property,near the office Ibuilding, approximately 250 feet west of the former UST system Based on the lateral extent of contaminated soil and ground water,there is a low potential for the septic systems to act as conduits for subsurface migration of impacted ground water Advanced GeoEnviron mental,Inc I i I '