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r HISTORY OF SITE WORK <br /> ff_ 3 Initial UST Removal,Overexcavation,and Sampling Activities <br /> On April 21, 1993, two, 10,000-gallon capacity, leaded gasoline underground storage tanks and <br /> one, 5,000-gallon capacity, diesel underground storage tank (USTs) were removed from the <br /> k subject site. Evax Technologies, Inc. inspected the tanks and collected soil samples from beneath <br /> the ends of each leaded gasoline UST, and one sample from beneath the fill end of the diesel UST <br /> ' immediately subsequent to removal. All samples were retrieved from the floor of the excavation at <br /> --_' 13.5 feet below surface grade (bsg). Additionally, two soil samples were collected from the soil <br /> stockpile flanking the excavation. The stockpile was moved to the south end of the property. <br /> Analytical results of the soil samples revealed that elevated levels of Total Petroleum Hydrocarbons <br /> as gasoline (TPH-g); Total Extractable Petroleum Hydrocarbons as diesel (TEPH-d); volatile <br /> aromatics benzene, toluene eth lbenzene TE <br /> y , xylenes (B X); and lead were present in the samples <br /> collected from the excavation and from the stockpile. <br /> G_ The overexcavation of the former tank pit was undertaken on July 16, 1993 by W.W. Irwin, Inc.. <br /> The work was periodically supervised by Mr. Michael Collins, SJCPHS EHD Registered <br /> Environmental Health Specialist. As the excavation proceeded, soil samples were collected for <br /> f: lithologic analysis and organic vapor analysis (OVA) meter readings were taken in order to direct <br /> the excavation.. The excavation was expanded slightly in all directions from the original tank pit to <br /> an area approximately 35 square feet and to a depth of approximately 18 to 20 feet below surface <br /> grade(bsg). The excavation was Halted when the excavator reached the limits of its extension and <br /> the northern wall became inaccessible. Groundwater was not encountered. <br /> f An estimated 260 cubic yards of excavated soil was removed from the tank pit and stored at a <br /> location on the south side of the property, and separately from soil stockpiled during the tank <br /> removal operation. The excavation was backfilled in May of 1994 subsequent to collection of <br /> stockpile soil samples for single-sample-composite analyses. Backfilling was approved in a letter <br /> dated May 10, 1994 from Specialist Collins to Mr. Dwight Davis of the Pegasus Group. <br /> HydropunchTm Sampling <br /> =_ On April 8, 1994, three HydropunchTM boreholes (HP-1, HP-2, and 1HP-3 depicted on Figures 2 <br /> t_ <br /> and 3)were drilled near the north, east, and west flanks of the overexcavation. Groundwater was <br /> encountered at an average depth of 23.7 feet below surface grade(bsg). <br /> The groundwater sample collected and analyzed from HP-3 revealed benzene at 160 micrograms <br /> per liter (µg/L), prompting the SJCPHS-EHD to order the completion of three monitoring wells <br /> for groundwater direction and gradient determination, and possible definition of the contaminant <br /> migratory path. <br /> 2005-41.496 2 HORIZON ENVIRONMENTAL INC. <br /> i ; <br />