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Atlantic Richfield Company 6 <br /> ARCO 4932,16 E Harding Way Stockton,CA June 7 2002 <br /> 1� <br /> . - Soil analytical data are summarized in Table 2 Field and laboratory procedures are <br /> presented as Attachment C Certified laboratory analytical reports and chain-of-custody <br /> documentation are presented as Attachment D <br /> Well Development, Surveying,Monitoring and Sampling, and Analysis <br /> After installation, wells DMW-1 and EW-1 were developed by West Hazmat on March <br /> 29, 2002 Well MW-4 was also redeveloped on March 29, 2002 The wells were <br /> rigorously surged over the length of the screen interval Approximately 10 casing <br /> volumes of water were bailed and pumped from each well at an approximate pumping <br /> rate of 10 gallon per minute (gpm) Approximately 305 gallons of purge water were <br /> ' transferred to the holding tank on-site, which was used to store additional groundwater <br /> generated during aquifer testing on April 2 and 3, 2002 Purge water and groundwater <br /> 1 generated from aquifer testing (approximately 6,300 gallons) were removed by Dillard <br /> Environmental Services (Dillard) of Byron, California from the site on April 3, 2002, <br /> and transported to InStrat Inc (InStrat) in Rio Vista, California for disposal Waste <br /> disposal confirmation sheets are included as Attachment E Monitoring well <br /> development field sheets are included in Attachment F <br /> ' The newly installed wells were also surveyed by Morrow Surveying of West <br /> Sacramento, California, a California-licensed surveyor Latitude and longitude <br /> coordinates, California state plane coordinates, elevation relative to mean sea level <br /> lie values, and a surveyor's site plan are included in Attachment G <br /> Depth to water was measured and groundwater samples were collected from the newly <br /> installed groundwater monitoring wells during the second quarter 2002 groundwater <br /> monitoring event on April 11, 2002 (Table 3) Depth to water was approximately 28 <br /> feet bgs Groundwater flow direction within the shallow zone was determined to be in <br /> ' the northeast direction, at a gradient of 0 002 foot/foot (Table 4) A groundwater <br /> elevation contour map is included as Figure 4 Groundwater flow direction within the <br /> deeper zone will be established utilizing water level data from well DMW-1, additional <br /> ' off-site downgradient deep wells scheduled for completion between June 10 and 14, <br /> 2002, and deep groundwater monitoring wells located at the Tosco service station, <br /> located downgradient of the site at 1502 North El Dorado Street (Figure 3) <br /> Simultaneous groundwater monitoring and sampling of wells located at the site and at <br /> the Tosco service station will be coordinated, beginning in the third quarter 2002 <br /> ' Groundwater samples from the newly installed wells were analyzed for TPHg and <br /> BTEX by the DHS/LUFT Method, and fuel oxygenates by EPA Method 8260B <br /> Elevated concentrations of petroleum hydrocarbons and MtBE were reported in <br /> extraction well EW-1 As a result of raised detection limits due to the presence of high <br /> concentrations of MtBE in EW-1, concentrations of TPHg and other fuel oxygenates by <br /> ' EPA Method 8260 were not quantified above the specified laboratory detection limits <br /> Concentrations of benzene and MtBE (EPA Method 8260B) were detected at 5,200 ugll <br /> and 520,000 ug/l, respectively Concentrations of benzene (DHSILUFT Method), and <br /> ' 11ARCOW9321Reports\Asmt&AgffrstRpt doc <br />