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1 <br /> A letter from the San Joaquin County Public Health Services - Environmental Health <br /> ' Division (PHS/EHD) dated March 7, 1994, stated that "the former underground storage <br /> tank(s) cannot be recommended for final closure without further investigation to determine <br /> the full extent of the soil and/or groundwater problem " In response to the letter from the <br /> ' PHS/EHD, GeoAudit was retained to assess soil and groundwater conditions at the site <br /> 2.3 Monitoring Well Installation and Sampling <br /> On April 27 and 28, 1994, eight soil bonngs were drilled at the site Three of the borings <br /> were completed as 2-inch groundwater monitoring wells Soil samples were collected at five- <br /> foot intervals during drilling Pan-Ag Environmental Labs analyzed fourteen soil samples for <br /> total petroleum hydrocarbons (TPH) as gasoline, TPH as diesel and volatile aromatics <br /> (BTE&X) TPH as gasoline was detected in ten samples at concentrations as great as 3,800 <br /> ppm (134-20), TPH as diesel was detected in twelve samples at concentrations as great as <br /> 9,000 ppm (138-20), Concentrations of benzene, toluene, ethylbenzene and xylenes were <br /> ' detected in eight of the soil samples The analytical results of the soil samples are <br /> summarized in Table 1. <br /> ' After installation, groundwater samples were collected from each well The samples were <br /> analyzed for TPH as gasoline, TPH as diesel and BTE&X TPH as gasoline was detected <br /> in MW-1, MW-2 and MW-3 at concentrations of 1,700 A&IL (ppb), 14,000 ppb and 2,600 <br /> ppb, respectively, TPH as diesel was detected in MW-1, MW-2 and MW-3 at concentrations <br /> of 2,400 ppb, 9,200 ppb and 6,900 ppb, respectively Concentrations of benzene, toluene, <br /> ethylbenzene and xylenes were also detected in the groundwater samples Analytical results <br /> of all groundwater samples are included in Table 3 <br /> ' 3.0 PROCEDURES <br /> 3.1 Monitoring Well Purge Procedures <br /> On November 14, 1994, groundwater monitoring procedures were performed at the <br /> referenced site The depth to groundwater was measured in each well relative to the top of <br /> ' the casing using a Solinst water level meter (Table 2) No free hydrocarbon product was <br /> observed in any of the wells. <br /> After water levels were measured, a 2-stage purge pump was used to remove approximately <br /> seven gallons of standing water from each well to stabilize temperature,pH, and conductivity <br /> ' (Appendix A) Groundwater parameters were measured at one-gallon intervals using an <br /> ICM water analyzer The purge water was stored on-site in 55-gallon DOT-approved di ums <br /> 3.2 Sample Collection and Analysis <br /> After purging, a water sample was collected from each well using a new disposable plastic <br /> ' a..bVwi A.&s« 6- 4 <br /> . wP..nm,s.rp.Gw,ni 4uvs3-s <br /> 1 <br />