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ENVIRONMENTAL INVESTIGATION REPORT <br /> Unocal Service Station No 5886 <br /> 2701 West March Lane <br /> Stockton California <br /> Delta Project No D095-066 <br /> ' Page 12 <br /> 4.7 Tank Area Shorin>~, UST Removal, Soil and Ground Water Sampling, and Excavation <br /> On October 23, 1995, during the installation of shoring for the removal of the three 12,000 gallon USTs, <br /> ' an approximate 12-inch hole was punctured in the top of the east end of the diesel tank Ballast water <br /> present in the tank leaked from a level of 114 inches to a level of 8175 inches, representing <br /> ' approximately 2,760 gallons of released ballast water The calculation of the volume of water released <br /> is presented in Appendix G, Ballast Water Volume and Diesel Quantification Calculations <br /> ' Quantification of the volume of hydrocarbons released was accomplished by sampling the ballast water <br /> in the diesel tank and using the concentration and volume released, a volume of diesel was calculated <br /> Ground water samples from the two gasoline tanks were also collected and analyzed Samples collected <br /> from the tanks were analyzed for TPH as gasoline, TPH as diesel, and BTEX using the previously <br /> described methods The samples were also analyzed for corrosivity, ignitability, and reactivity for <br /> disposal options <br /> Water analyzed from the diesel tank (T3) was below the laboratory's limits of detection for benzene and <br /> ethyibenzene Concentrations of toluene, total xylenes, TPH as gasoline, and TPH as diesel were <br /> reported and are presented in Table 7 (Tank Removal and Tank Ballast Water Sample Results) Copies <br /> ' of the laboratory reports and chain-of-custody documentation are presented in Appendix C <br /> ' A calculated volume of 0 17 gallons of diesel fuel was released during shoring activities A copy of the <br /> calculations of the volume of water released and corresponding diesel fuel quantification is presented in <br /> ' Appendix G <br /> ' 4 7 1 Unauthorized Release Re orts <br /> On October 25, 1995, Unocal submitted an Underground Storage Tank Unauthorized Release (Leak) <br /> Contamination Site Report (URR, form HSC 05) to the SJCEHD Concurrent with this submittal, Delta <br /> submitted an additional report providing information regarding the release Delta prepared an additional <br /> Unauthorized Release Report dated October 25, 1995, addressing specific comments relating to the release <br /> as previously requested by SJCEHD <br /> RPT 160 SJS <br />