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i <br /> CHRONOLOGY <br /> MANTECA UNIFIED SCHOOL DISTRICT . <br /> 2901 LOUISE AVE <br /> MANTECA, CA 95336 <br /> h <br /> 03/18/97 A 250-gallon diesel underground storage tank (UST) #39-505556 was removed at the <br /> above referenced site. Soil samples were collected from the excavation at 7 feet below <br /> surface grade (bsg) and from the stockpile.for laboratory analyses. <br /> 04/08/97 Analytical results of the soil sample from the former tank excavation was 130 parts per <br /> million (ppm) of weathered diesel. <br /> 04/16/97 Filed Unauthorized Release Report (UAR) #97-U15 and Prop 65 #97-056. ? <br /> 4 <br /> 01/08/98 Placed site into San Joaquin County Environmental Health Department (EHD) Local ! <br /> Oversight Program (LOP). Official Notice of Responsibility was mailed to Manteca ' <br /> Unified School District (MUSD) requiring additional work to investigate the extent of the <br /> contamination. <br /> 11/05/98 Advanced Geoprobe soil boring SB-1 in the middle of the former tank excavation to 17 <br /> feet bsg. Groundwater was encountered at approximately 13 feet bsg. Soil and grab <br /> groundwater samples were collected. { <br /> E <br /> 03/25/99 Received "Limited Soil and Groundwater Assessment" dated January 20, 1999 prepared by <br /> Kleinfelder. The highest analytical result of the soil samples was at 8 feet bsg at a <br /> concentration of 168 mg/kg of diesel, but concentration fell to 5.34 mg/kg of diesel at 13 <br /> feet, and non-detect at 18 feet bsg. Analytical result of the grab water sample was 389 <br /> µg/l of diesel. <br /> I <br /> 11/29/01 Installed monitoring well MW1, 2, and 3. Soil and grab groundwater samples were <br /> collected. <br /> 02/08/02• Received "Soil and Groundwater Investigation Report" dated February 3,2002 prepared <br /> by M.J. Kloberdanz &Associates (Kloberdanz). Analytical results of all soil samples were <br /> non-detect. Analytical results of the groundwater samples from MW-3 were non-detect <br /> for diesel, 0.3 µg/l of Benzene, 1.1 µg/l of Toluene, 0.4 µg/1 of Ethyl-benzene, and 3.0 <br /> pg/l of Xylenes. Results of groundwater samples from MW-1 and MW-2 were non-detect <br /> or below 1 µg/l. <br /> Direction of groundwater flow was calculated to be northwest. <br /> 2000 feet well survey indicated the presence of one drinking water well at approximately <br /> 150 feet south of the tank,and an irrigation well 175 feet southeast of the tank. <br /> Using soil sample results and contour assumptions, Kloberdanz calculated a total mass of <br /> 2.9259 pounds of diesel remaining in the soil. <br /> r - <br />