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1 <br />' Closure Report <br /> May 21, 1993 <br /> Southland Site No 20680, 9110 Thornton Road, Stockton, CA 4 <br /> ■ Sod samples collected below the USTs during removal reported TPH-G and <br /> benzene, toluene, ethylbenzene, and total xylenes (BTEX) below the MDLs <br />' Additional analyses for lead and ethylene dibromide (EDB) also reported <br /> concentrations below the MDLs Two soil samples were collected from the product- <br /> line trench, one sample was below MDL for TPH-G and BTEX concentrations, <br />' analytical results of the other soil samples reported 2,100 ppm of TPH-G <br /> 23 Remediation Activities <br /> 1 <br /> Between 1986 and the present, Southland has performed the following remediation activities <br />' Between May 1986 and October 1 - <br /> ■ y990, a separate phase hydrocarbon recovery <br /> system and a groundwater treatment system were Installed and operated by <br />' Groundwater Technology Approximately 760 gallons of hydrocarbons were <br /> recovered Approximately 16 million gallons of groundwater were pumped and <br /> treated <br />' • Between February 1987 and January 1991, a soil vent system was Installed and <br /> operated by Vapor Extraction Technology, Inc The soil vent system removed 576 <br />' gallons of separate-phase hydrocarbons <br /> 24 Routine Monitonng and Sampling <br /> • Between 1986 and April 1993, on-site and off-site groundwater monitoring wells were <br /> monitored for depth to product and depth to water Initial free-product recovery in <br /> monitoring wells at the site have decreased to nondetectable levels of TPH-G and <br /> BTEX concentrations in groundwater samples collected from these wells <br /> ■ Between 1986 and 1993 off-site private domestic wells were routinely sampled on a <br /> monthly basis for TPH-G and BTEX concentrations (Figure 3) Results of sampling <br /> Indicated levels of hydrocarbon constituents have been at or below California action <br /> levels for drinking water since 1989 <br /> California action levels for hydrocarbon constituents In drinking water are 1 part per billion (ppb) <br /> benzene, 100 ppb toluene, 680 ppb ethylbenzene, and 1,750 ppb xylenes Tables 1 and 2 <br /> summarize the 1991 through 1993 monitoring data and groundwater sampling analytical results A <br /> historical summary of the analytical results of Total Petroleum Hydrocarbons-as-Gasoline for the <br /> groundwater monitoring and domestic wells is presented in Appendix A <br /> I <br /> 1211 Ra13 <br /> GROUNDWATER <br /> Iy i TECHNOLOGY, INC <br />