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From June 1999 through June 2000, ENSR operated a sod vapor extraction (SVE) system at the • site Initially, ENSR extracted from VW-11D, VW-1S, VW-2S,VW-3, and VW-4 After several months of operation, air sparging was initiated in MW-1 According to ENSR, the remediation system removed over 7,000 pounds of gasoline hydrocarbons from the subsurface In July 2000, ENSR decommissioned the system and removed the equipment from the site On November 28, 2000, Ramage Environmental published Environmental Site Investigation Report documenting the results of a sensitive receptor survey and the drilling of confirmation sod bonngs According to available records, three property parcels within 2,000-feet of the site had operating water wells These properties included the San Joaquin Catholic Cemetery (site), St Joseph's Hospital, and a residential dwelling at 1821 North Hunter Street The locations of the cemetery wells and hospital well are shown on Figure 3 To confirm the effectiveness of remediation efforts, soil samples were collected every 10 feet to a total depth of 100 feet directly beneath the former USTs The sod sample results indicated that except for 560 milligrams per kilogram (mg/kg) of Total Petroleum Hydrocarbons (TPH)-as- gasolme in sod at a depth of approximately 10 feet below ground surface (bgs), the vadose zone soil was remediated by the SVE system To delineate the vertical extent of impacted groundwater, discrete groundwater samples were collected with a cone penetration test (CPT) ng at 75, 90, and 125 feet bgs from soil borings located approximately 20 feet northeast (downgradient) of the former USTs The discrete groundwater sample results indicated that the vertical extent of impacted groundwater was mostly delineated Concentrations of MTBE declined significantly with depth and were absent in the 125-foot groundwater-bearing interval Only 1,2-dichloroethane (1,2-DCA)was detected in the 125-foot groundwater sample, at a low concentration of 0 5 micrograms per liter (µg11) i On May 2, 2002, Ramage Environmental published Report, Additional Site Investigation, which documented the drilling of CPT bonngs for discrete groundwater sampling at six additional locations, and the installation of a two-well monitoring well cluster(MW-8A and MW-813) The results of the project indicated that the extent of MTBE was defined and limited to the groundwater table northeast (downgradient) of the former UST Only low concentrations (0 5 to ' 1 2 µgll) of 1 2-DCA were detected in the 110 to 125 foot groundwater-beanng interval south and west of the former UST 4