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• TheCkoure So Report The Southlarsd Corporation,9110 Thornton Road Stockton CA December 5 19955 and remediation activities performed from April 1986 to the present are summarized below A list of references and reports are provided in Attachment 3 1.1 Stte Investigations ■ Between 1986 and 1990, 24 groundwater monitoring wells, 4 recovery wells, 1 soil boring, and 4 vapor recovery wells were installed to delineate the lateral and vertical extent of petroleum hydrocarbons in sod and groundwater (Figure 2) Results of groundwater monitoring and sampling confirmed the presence of liquid phase hydrocarbons (LPH) and dissolved hydrocarbons in the groundwater ■ In September 1991,two off-site and one on-site groundwater wells (MW-18, MW-19, and MW-20) were installed to monitor groundwater quality Sod 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 MWA 8, MWA 9, and MW-20 did not contain TPH-G and benzene concentrations above the method detection limits (MDLs) it Three USTs and associated product dispensing lines were removed at the site during September 1991 Soil samples collected below the USTs during removal did not contain TPH-G, benzene,toluene, ethylbenzene, and total xylenes (BTEX) above the MDLs Lead and ethylene dibromide (EDB) concentrations were also reported to be • 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, as a result of active remediation, all site-related groundwater monitoring wells were monitored for depth to product and depth to water Initial high hydrocarbon concentrations and LPH presence in some monitoring wells at the site had decreased to nondetectable or close 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 had been at or below California action levels for drinking water since 1989 Locations of domestic wells are shown on Figure 3 ■ During drilling at the site between 1986 and 1995, soils encountered to a depth of 50 feet were predominately sands with layers of clay, clayey silt, and silty sand Logs for confirmation bonngs are provided in Attachment 4, and well construction data is provided in Table 1 >t In July and September 1995, domestic wells were sampled TPH-G and BTEX constituents were not detected in any of the domestic wells SJCPHS-EHS distributed letters in October 1995 notifying domestic well owners that Southland will no longer be sampling the domestic wells and that bottled water service will be discontinued cimuraz ro(ST C4 v GWUNH V11ATM EIDE] TLCHNOI OCl' .