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U U . <br /> WORK PLAN <br /> f SITE INVESTIGATION <br /> 4 C" SAN JOAQUIN COUNTY MOSQUITO AND VECTOR CONTROL DISTRICT <br /> L 7759 S. AIRPORT WAY FACILITY <br /> STOCKTON, CALIFORNIA <br /> i <br /> 1.0 INTRODUCTION <br /> i1 <br /> This work plan has been prepared in response to a letter dated February 3, 1994 from the San <br /> Joaquin County Public Health Services Environmental Health Division (EHD) to the San Joaquin <br /> County Mosquito and Vector Control District (SJCMVCD) which requested submission of a <br /> work plan for further investigation of soil and groundwater quality at the SJCMVCD facility <br /> located at 7759 South Airport Way, Stockton, California(Figure 1). The investigation work was <br /> requested to follow-up on conditions at the locations ofus reviounderground tank removals and <br /> p g <br /> a soil remediation project completed in early 1987. <br /> 1.1 Background <br /> .i <br /> In March 1987, the SJCMVCD removed several underground storage tanks from the Stockton <br /> service yard. Two 8,000 gallon underground storage tanks which had previously held light weed <br /> spray oils were removed from an area east of the shop building as shown on the plot plan map <br /> presented in Figure 2. Soil samples taken from below the tanks indicated extractable petroleum <br /> hydrocarbons (commonly known as total petroleum hydrocarbons - diesel fraction or TPH-D) <br /> were present in the soil. A remedial excavation was completed in April 1987 to an approximate <br /> depth of 27 feet below grade to remove impacted soils. Two confirmation samples were taken <br /> during the completion phase of the excavation at 20 and 27 feet below grade and a water sample <br /> was collected from a nearby water supply well to monitor groundwater conditions near the <br /> excavation. The analytical results for these samples are as follows: <br /> TABLE 1 <br /> Excavation Confirmation Sample Results <br />� I! <br /> " Soil Samples (mg/Kg) Water Sample (mg/L) <br /> Analytical Parameter , <br /> 20 feet 27 feet Water Well <br /> Benzene ND,., NDo.2 NDa_005 <br /> Toluene NDQ.2 ND1.2 NDO.005 <br /> Xylene NDo_2 NDu.2 N130.0w <br /> IJ <br /> Other Volatile Hydrocarbons ND,., ND1,0 NDo.02 <br /> Total Extractable Hydrocarbons (TPH-D) NDs.o 112 ND,.s <br /> IND = Nondetectable at the level of detection shown in subscript. <br /> I'I <br /> MUtPTSLSICMVCU.WP2 l 03/141% <br /> y <br />