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SWUH f rtl Tl <br /> ENVIRONMENTAL TECHNOLOGIES CORPORATION C <br /> II <br /> May 3, 1996 <br /> 94373 <br /> Ms. Mary Meays <br /> San Joaquin County <br /> Environmental Health Division <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 future soil remediation. The details of the pilot <br /> test will be addressed in a subsequent workplan. This report outlines procedures and practices to <br /> be utilized during field investigations. <br /> i <br /> STI'E 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 Vocation 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 soil 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:\943731reports\wp0496.doc 1 <br /> 1260 Graphics Drive Modesto,CA 95351-1502 (209 579-2221 Fax(209)579-2225 <br /> Engineering Consulting - Remediation Construction <br /> Y <br />