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' Limited Soil and Groundwater Report-05/24/99 Page I Western Oil&SEreading Site Project No 024 9$ 1.0 EXECUTIVE SUMMARY On March 23 and 24, 1999 Gallardo&Associates advanced five six-inch diameter soil borings (B-1 ' through B-5) at 19256 N Highway 99 in Acampo, California (See attached Figure 1 for Site Location Map) The soil borings were advanced at the request of the San Joaquin County Environmental Health Division(SJCEHD)for the purpose of evaluating the condition of the soil and ' groundwater(inferred)crossgradient and (inferred) downgradient of the former UST cavity Based on the results of this investigation, SJCEHD should consider the site for closure ' Five exploratory soil borings were advanced to an approximate depth of 40 feet below grade surface (bgs) on March 23 and 24, 1999 (See attached Figure 2 for Borehole Site Map) After completing the site investigation, a total of 20 soil samples and one groundwater "Grab" sample had been collected for laboratory analysis The soil samples were analyzed for the following petroleum constituents the fuel Oxygenate Methyl tert-Butyl Ether (MTBE), total petroleum ' hydrocarbons as diesel(TPH-d),total petroleum hydrocarbons as kerosene (TPH-k), total petroleum hydrocarbons as gasoline (TPH-g), and the fuel constituents benzene, toluene, ethylbenzene, and ' xylenes (BTEX) The groundwater "Grab" sample was additionally analyzed for the Fuel Oxygenates Di-isopropyl Ether(RIPE), Ethyl tert-Butyl Ether(ETBE), MTBE, tert-Amyl Methyl Ether(TAME), and tert-Butanol(TA), (See Tables 1 & 2 for analytical results). lie The initial drilling depth to groundwater was not encountered during this investigation However, a shallow body of groundwater was detected at soil boring B-4 at an approximate depth of 29 314 feet bgs and after an hour stabilized at approximately 26 i/2 feet bgs Based on the data collected during this investigation, Gallardo do Associates concludes that soil ' sampling results collected from the five exploratory soil borings(B-1 through B-5) indicate that the sod located beneath the property at sort boring locations B-1, B-2, and B-4 has been impacted by moderate concentrations of TPH-g, TPH-d, and TPH-k. The Vertical extent of the impacted ' soil appears to end at approximately 34 %feet bgs at boring B-2, and approximately 29 %feet bgs at boring B-4. However, vertical definition was not defined at boring B-1. The impacted soil extended below the 40 foot maximum depth of the investigation as defined in the approved workplan. The horizontal extent of the impacted soil appears to be restricted to the area surrounding the 20,000-gallon UST's. No impacted soil was detected beneath soil boring B-5 located within the former diesel and gasoline UST's cavity. The highest concentrations of impacted soil appear to be centered beneath borings B-1 (TPH-d at 30,000 ppm and TPH-k at 18,000 ppm) and B-2(TPH-d at 13,000 ppm and TPH-k at 11,000 ppm) at an approximate depth ' of 29 %feet bgs. In addition, analytical results collected from soil boring B-4 indicate that concentrations of TPH-d at 1,800 ppm and TPH-k at 1,700 ppm exists at an approximate depth of 14 %feet bgs The depth to the true water table was not encountered during this investigation; ' however, a shallow perched water zone was detected beneath soil boring B-4 at an approximate depth of 29 '/z feet bgs and has been impacted by concentrations TPH-d, TPH-k, TPH-g, and . BTFX However, this shallow groundwater body was only detected in soil boring B-4. The extent of impact to this possibly perched groundwater could not be determined during this limited ' iii