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' 9110 Thornton Road, Stockton, California April 27, 1994 The Southland Corporation Page 2 assessment and remediation activities performed from April 1986 to the present are summarized below ■ Between 1986 and 1990, 24 groundwater monitoring wells, 4 recovery wells, 1 sod ' boring, and 4 vapor recovery wells were installed to delineate the lateral and vertical extent of petroleum hydrocarbons in soil and groundwater (Figure 2) Results of groundwater monitoring and sampling confirmed the presence of separate-phase (SP) and dissolved hydrocarbons in the groundwater • In September 1991, two off-site and one on-site groundwater wells (MW-16, MW-19, and MW-20) were installed to monitor groundwater quality Sal samples collected ' from MW-20 at 41 5 feet below grade contained 9 parts per million (ppm) total petroleum hydrocarbons-as-gasoline (TPH-G) Groundwater samples collected from monitoring wells MW-18, MW-19, and MW-20 did not contain TPH-G and benzene concentrations above the method detection limits (MDLs) ' • Three USTs and associated product dispensing lines were removed at the site during September 1991 ' ■ Sod samples collected below the USTs during removal did not contain TPH-G and benzene, toluene, ethylbenzene, and total xylenes (BTEX) above the MDLs Lead and ethylene dibromide (EDB) concentrations were also reported below the MDLs Two soil samples were collected from the product-line trench One sample was below MDL for TPH-G and BTEX, the other soil sample contained 2,100 ppm TPH-G ' • Between 1986 and April 1993, all site-related groundwater monitoring wells were monitored for depth to product and depth to water Initial high hydrocarbon concentrations and SP presence in some monitoring wells at the site has decreased to nondetectable levels of TPH-G and BTEX concentrations in groundwater samples collected from these wells ■ Between 1986 and 1993, off-site private domestic wells were routinely sampled on a monthly basis for TPH-G and BTEX concentrations Results of sampling indicated levels of hydrocarbon constituents have been at or below California action levels for drinking water since 1989 1 ' Between 1986 and the present, Southland has performed the following remediation activities • Between May 1986 and October 1990, a separate-phase hydrocarbon recovery ' system and a groundwater treatment system were installed and operated by Groundwater Technology Approximately 760 gallons of hydrocarbons were recovered Approximately 1 6 million gallons of groundwater were pumped and treated 1 '=j[41 GROUNDWATER j� TECHNOLOGY