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1 <br /> Closure Report May 21, 1993 <br /> Southland Site No 20680, 9110 Thornton Road, Stockton, CA 2 <br /> The analytical results of recent and historical groundwater quality data suggest that the remediation <br />' activities performed at the site have been effective In remediating groundwater (in the monitoring <br /> wells that have had sufficient water to sample) to the State of California drinking water levels for <br /> benzene, toluene, ethylbenzene, and xylene (BTEX) constituents <br /> The analytical results of soil samples collected from the borings drilled during the confirmation sod <br />' sampling program reported concentrations of benzene and total petroleum hydrocarbons-as- <br /> gasoline (fPH-G) below the method detection limits (MDLs) for the sod samples analyzed <br />' Based on the soil and groundwater data collected duringthe implementation of activities described <br /> p { <br />' in Groundwater Technology's Sde Closure Work Plan, dated March 1991, and in the Proposal to <br /> Implementation Site Cleanup Confirmation, dated July 7, 1992, and an amendment letter dated July <br /> 31, 1992) and on the historical data presented in this report, Groundwater Technology requests that <br />' the SJPHS forward a copy of this report to the California RWQCB, Central Valley Region, with <br /> recommendations for closure <br /> As of July 1, 1993, groundwater monitoring and sampling activities and domestic well sampling will <br />' be discontinued Well abandonment will be implemented when site closure or a no-further-action <br /> decision has been granted by the SJPHS and RWQCB <br /> 2.0 BACKGROUND <br /> A precision UST test conducted on March 28, 1986, indicated a failure of the unleaded fuel tank <br /> system at the site On April 2, 1986, the unleaded tank and the associated dispensing system were <br /> Ishut down Groundwater Technology was contracted by Southland in April 1986 to investigate the <br /> site's subsurface for evidence of petroleum hydrocarbons The site assessment and remediation <br /> activities performed from April 1986 to the present are summarized below <br /> I2.1 Site Conditions <br /> The site Is located in the central portion of the San Joaquin Valley at an elevation of approximately <br /> 12 feet above mean sea level (msl) The city of Stockton is located within the San Joaquin Basin, <br /> which has two main aquifers separated by an aqultard in the upper Mehnen Formation The <br /> 12118013 <br /> JC GROUNDWATER <br /> I _ _l TECHNOLOGY, INC <br />