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Re-T.,-nal Off i <br /> INTERNATIOY TECHNOLOGY 4585 Pa--'--=--a Souievm' <br /> ® May 99 Mcxrttnez.Cal �.._ q4553-27-- <br /> CORPORATIONy <br /> � 2 1 6 <br /> 5 i 0-372-91 Cc <br /> F= =10-372-5220 <br /> IT Project NO: 765748 <br /> Mary Maeys _ <br /> F San Joaquin County Public Health Services <br /> Environmental Health Division <br /> �. PO Box 2009 I °j <br /> Stockton, California 95201 <br /> k <br /> Planned Overexcavation Adtivities <br /> Pacific Bell Tank Replacement Project <br /> 2300 Eight Mile Road; Stockton; California <br /> Dear Ms. Maeys: <br /> IT Corporation (IT) was retained by Pacific Bell to conduct oversite and verification sampling <br /> activities during the removal of two underground storage tanks fr66 the above referenced Pacific <br />{ } Bell Property. The tanks consisted of one 4,000 gallon diesel Biel tank and one 10,000 gallon <br /> unleaded gasoline tank, which were removed on May 2, 1996 by representatives of Aronson <br /> Engineering. Two separate excavations (one for each tank)were��&g, with two verification soil <br /> L- samples being collected beneath the diesel tank and three verification soil samples being collected <br /> beneath the unleaded gasoline tank. A mobile lab operated by Sparger Technology was onsite <br /> to analyze the verification samples. Analytical results indicated the presence of unleaded gasoline <br /> in two of the three samples collected from the gasoline rank excavationsam the le collected at ., # <br /> ( p <br /> the east end and the sample from the center of the excavatiod floor possessed the gasoline <br /> concentrations. Petroleum contaminants were not encountered id the diesel tank excavation. <br /> It is the intention of IT to conduct overexcavation and a second round of verification sampling <br /> E activities in the areas found to contain fugitive petroleum concentrations. A track excavator will <br /> be delivered to the site on May 2, 1996 in preparation for overexcavation efforts to begin on May <br /> 3, 1996 at 0700. TI' anticipates extending the depth of the excavation a maximum of 5.0 feet to <br /> I (resulting in a maximum excavation depth of 20.0 feet below grade). The excavation side walls <br /> l (east, and possibly north and south) may be extended a maximum of 2.0 feet beyond current <br /> limits, in the areas adjacent to the impacted soils. Overexcava l activities will be continued <br /> until no further visual, olfactory or field screening indications of troleum contamination exists <br /> or the limits of the excavating equipment have been reached] overexcavation activities will also <br /> f be halted if it appears that any onsite structure may be undermined. <br /> A mobile laboratory will be onsite to analyze the second 'round of verification soil samples. <br /> Samples will be collected from the center of each new wall1lor floor excavated at a rate of. 1/20 <br /> f - <br /> yd' of soil removed. The samples will be analyzed for total petroleum hydrocarbons (TPH) as <br /> gasoline and benzene, toluene, ethyl benzene and xylenes (BTEX) using detection limits of 1.0 <br /> PPM for the TPH as gasoline and 0.005 ppm for the BTEX constituents. All results will be <br />