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March 17, 1999 <br /> • Page 2 <br /> Soil samples collected from beneath the former UST complex were reported to contain <br /> concentrations of total petroleum hydrocarbons as gasoline (TPH-g) ranging from 130 to <br /> 5,800 parts per million (ppm) Benzene was reported to two of the six samples <br /> collected at concentrations of 0 52 and 3 6 ppm Methyl tertiary-butyl ether(MtBE)was <br /> reported in two of the six samples at concentrations of 0 19 and 3 6 ppm Lead was not <br /> detected in any of the samples analyzed <br /> SCOPE OF WORK <br /> To determine the lateral extent of dissolved petroleum hydrocarbon in the soil and <br /> groundwater the following scope of work was performed <br /> • Permits. IT obtained the appropriate soil boring and groundwater <br /> monitoring well permits from the San Joaquin County Environmental <br /> Health Department prior to initiating fieldwork <br /> • Geoprobe®. One Geoprobe® (GP-1)was advanced to a depth of <br /> approximately 40 feet below ground surface (bgs) on July 24, 1998 <br /> (Figure 2) <br /> • Monitoring Well Installation. IT drilled and installed two <br /> groundwater monitoring wells (MW-1 and MW-2) on August 21, <br /> 1998 During installation of Well MW-4, a mismarked City of <br /> Lathrop water main was broken by the drill ng auger Approximately <br /> 600,000 to one million gallons of water were discharged from the <br /> broken water main Work was stopped for the day On September <br /> 14, 1998 IT returned to the site to install wells MW-3 and MW-4 <br /> • Soil Sampling and Analysis. Selected soil samples collected from <br /> groundwater monitoring wells MW-1 through MW-4 and <br /> Geoprobe® GP-1 were submitted to a California State-certified <br /> laboratory and analyzed for the presence of TPH-g, benzene, toluene, <br /> ethylbenzene, and xylenes (BTEX), MtBE, diisopropyl ether(DIPE), <br /> ethyl tertiary-butyl ether(ETBE), tert-amyl methyl ether (TAME), <br /> and tert-butanol (TBA) Additionally, selected soil samples collected <br /> from the Geoprobe® (GP-1) and monitoring wells MW-3 and MW-4 <br /> were analyzed for methanol and ethanol A soil sample from Well <br /> MW-3 was submitted to a California-State certified laboratory and <br /> analyzed for moisture, bulk density, grain density, porosity,pH, total <br /> organic carbon, permeability, and hydraulic conductivity <br /> (Attachment B) <br /> • Groundwater Sampling and Analysis. All wells (MW-1 through <br /> MW-4)were developed and sampled by IT on October 8, 1998 <br /> Groundwater samples were analyzed for the presence of TPH-g, <br />