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SIIWFH FIL I= <br /> May 3, 1996 <br /> 94373 <br /> Ms Mary Meays <br /> San Joaquin County <br /> Environmental Health Division R <br /> P O Box 388 <br /> Stockton, California 95201-0388 <br /> Subject Workplan for Off-Site Subsurface Investigation at Former Thiemann's Service, <br /> 106 West Second Street, Ripon, California <br /> Dear Ms Meays <br /> Smith Environmental Technologies Corporation has prepared this workplan to perform a <br /> subsurface investigation and install two groundwater and three vapor wells at the subject site <br /> (Figure 1) The purpose of the investigation is to determine if the groundwater off-site has been <br /> impacted by the petroleum hydrocarbons, as required by San Joaquin County Public Health <br /> Services (PHS/EHD) correspondence received April 12, 1996 The vapor extraction wells will be <br /> used for a vapor extraction pilot test and potential firture soil remediation The details of the pilot <br /> test will be addressed m a subsequent workplan This report outlines procedures and practices to <br /> be utilized during field investigations <br /> SITE HISTORY <br /> In March 1991, three underground storage tanks (USTs) were removed from the site Analysis of <br /> soil samples collected from the excavation indicated that high concentrations of petroleum <br /> hydrocarbons were present in soil beneath the tanks Groundwater was not encountered in the <br /> excavation The location of the former USTs is shown on Figure 2 <br /> In July 1993, a subsurface investigation was conducted at the site to determine the extent of <br /> petroleum hydrocarbons present in soil and to determine if groundwater had been impacted This <br /> included drilling eight soli borings and collecting soil samples Three of these borings were <br /> completed as shallow groundwater monitoring wells (MW-1, MW-2 and MW-3) Analysis of soil <br /> samples indicated that the majority of petroleum hydrocarbons in soil were present from about 10 <br /> feet below ground surface (bgs) to groundwater at a depth of approximately 29 feet bgs and <br /> within a radius of 35 feet from the former UST pit <br /> w t943731rq.0m\wp0496 doc 1 <br /> I260 Graphics Qnvc - Nrtodesto,CA 95351-1502 (209)579-7271 Fax(209)579-2225 <br /> Engineering - Consulting Remediation Construction <br />