Laserfiche WebLink
Ak <br /> EXECUTIVE SUMMARY <br /> On June 18 and 19, 1991,Artesian Environmental Consultants, Inc. (Artesian)conducted a Phase Il <br /> subsurface investigation at Exxon Service Station 7-3330 at 3128 West Benjamin Holt Drive in <br /> Stockton,California. 'The purpose of this Phase 1I Site Investigation was to evaluate the vertical and <br /> lateral extent of the hydrocarbons detected in the sail during the previous investigation and the lateral <br /> — extent of hydrocarbons in the groundwater. This investigation only evaluated on-site soil and <br /> groundwater conditions. No off-site sampling was performed during this investigation. <br /> Four soil borings,B-4 through B-7, were drilled on June 18, 1991 to a depth of 20 feet below <br /> ground surface. Groundwater samples were collected from B-4 through B-7 using hydropunch <br /> — sampling equipment. On June 19, 1991, three soil borings,B-I through B-3,were drilled can the <br /> northern and downgradient boundary of the site, near the sidewalk on West Ben Holt Drive. Soil <br /> borings B-1 through B-3 were subsequently converted into monitor wells, MW-4 through MW-6, <br /> respectively. <br /> - Soil samples were collected every five feet during the drilling of the soil borings. Total petroleum <br /> hydrocarbons as gasoline(TPH-g), were detected in soil samples collected from borings B-4 <br /> through B-6 at concentrations of up to 1,100 parts-per-million(ppm)in the sample from boring B-4 <br /> located northeast and downgradient from the underground storage tank area. The soil sample from <br /> 4� borin B-4 was collected at 16 ft.bellow g2und surface. This soil sr le also contained the highest <br /> concentrations of benzene,toluene,ethylbenzene and x lenes B . The soils were below <br /> r detectable limits for all analytes in samples collected from B-1 through B3 and B-7. <br /> t <br /> TPH-g concentrations at 120,000 parts-per-billion (ppb)were highest in the hydropunch <br /> groundwater sample from soil boring B-4. Concentrations of B`!TEX were also highest in <br /> hydropunch groundwater sample from boring B-4. <br /> 14 <br /> Installation of monitor wells north and downgradient of the underground storage tanks and pump <br /> y islands was done to detect and monitor the presence of hydrocarbons in the groundwater. An <br /> electronic oil/water interface probe was used to evaluate the wells for free product, upon completion, <br /> and at 7 and. 14 days following completion. No free product,sheens or odors were observed. <br /> Groundwater was below detectable limits for all analytes in monitor wells NIW-4 through MW-6, <br /> installed on June 19, 1991 and pre-existing wells MW-1 and MW-3. TPH-g and BTEX were <br />