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Project Quarterly Update Report February 21, 1992 Southland, 9110 Thornton Road, Stockton, California Page 7 The groundwater treatment system experienced a mechanical breakdown as reported In the April 1991 project Quarterly Update Report The system has not been reactivated at Southland's request ' because of the recent analytical results, which reported (1) no detectable TPH-as-gasoline concentrations in the samples from any of the monitoring wells, pumping wells, or nearby domestic ' wells for the period of January through December 1991, and (2) no detectable petroleum hydrocarbon constituents (i e, BTEX) for the same wells for the period of April through December ' 1991, except for domestic well 9172 during August and September 1991 Southland has submitted correspondence to the San Joaquin County Department of Health to place ' the groundwater treatment system in dormant status, with reactivation criteria based on changes in water quality data 4.0 DISCUSSION ! On-site well MW-20 was Installed In an area where petroleum hydrocarbons were previously detected In the soil Analytical results of these soil samples were used to confirm remediation in this area The absence of detectable BTEX compounds in all soil samples analyzed from the boring for MW-20 further supports the observation that remediation of the subsurface soils has been successful ! Petroleum hydrocarbons were not detected In groundwater samples from the new on-site (MW-20) and downgradient wells (MW-18 and MW-19) or from existing wells, suggesting that remedlation of ' the groundwater may also be complete The supplementary data collected during this reporting period supports observations presented in the March 1991 Site Closure Workmen, and the analytical results from the tank closure as reported in the October 4, 1991, correspondence to San Joaquin County Public Health Services It is ! apparent, based on this supplementary data, that defining and initiating steps toward site closure would be appropriate at this time 5.0 SUMMARY ' On September 18, 1991, three monitoring wells were Installed as proposed In the,$ite Closure Work Plan- hl tin 7-EI even Pr 9110 Th mt n Road, Stocktgn. Gel rf ml ! (March 1991) During drilling activities, four soil samples were collected for analyses from the sod boring for well MW-20 Analytical results indicate BTEX and 1,2-dibromoethane was not detected In GROUNDWATER ' TECHNOLOGY, INC