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a <br /> A SSOCIATES INC <br /> 2.0 METHODS AND PROCEDURES <br /> ' To investigate the extent of impacted groundwater and determine the groundwater gradient at the <br /> site, three soil borings were advanced in the vicinity of the former 10,000-gallon UST and <br /> completed as groundwater monitoring wells All field activities were performed in accordance <br /> with ATC's Workplan for Additional Subsurface Investigation at Continental Grain, 1805 <br /> Harbor Street, Stockton, California, dated May 15, 1998 This workplan was approved by <br /> PHS/EHD on May 22, 1998 with minor modifications <br /> 2.1 Soil Boring Advancement and Sam lin <br /> ' Drilling was conducted by V & W Drilling (State C57 license no 720904) utilizing a hollow stem <br /> auger drill ng The soil borings MW 1, MW2, and MW3 were advanced and completed as <br /> groundwater monitoring wells A field geologist logged drill cuttings and soil samples utilizing <br /> ' the Unified Soil Classification System Descriptions of soil types encountered and sample <br /> collection intervals are included on the boring/well construction logs contained in Appendix A <br /> ' The cored soil samples were collected at five-foot intervals or significant changes in lithology <br /> using a 2-inch diameter split-spoon sampler containing three brass tubes The cored samples and <br /> drill cuttings were characterized for soil type, moisture content, and visual evidence of petroleum <br /> hydrocarbons A flame ionization detection meter (FID) was used as a field screening device for <br /> the detection of petroleum hydrocarbon vapors in drill cuttings and cored samples Drill cuttings <br /> were temporarily stored on site in 55-gallon DOT approved steel drums <br /> 2.2 Soil Sample Analysis <br /> Selected soil samples were placed on ice, and transported under chain-of-custody to Sequoia <br /> Analytical (ELAP #1210) of Redwood City, California for analysis All soil samples were <br /> ' analyzed for total petroleum hydrocarbons as gasoline (TPHg), total petroleum hydrocarbons as <br /> diesel (TPHd), benzene, toluene, ethylbenzene, and xylenes (BTEX) utilizing EPA 8015 and 8020 <br /> methodologies, oxygenate fuel additives utilizing EPA 8260 methodology, ethyl dibromide (EDB) <br /> ' and 1,2-dichloroethane (DCA) utilizing EPA 8010 methodology, and total lead The analytical <br /> results for soil samples are summarized in Table 1 Laboratory data sheets and chain-of-custody <br /> documentation are included in Appendix B <br /> ' <br /> 13 Groundwater Monitoring Well Construction <br /> Soil borings MW1, MW2, and MW3 were subsequently completed as groundwater monitoring <br /> wells to assess impacted groundwater beneath the site, and to provide measurement points for the <br /> determination of groundwater flow direction and hydraulic gradient <br /> Each well was constructed with 2-mch PVC casing The screened interval of each well was <br /> positioned from approximately 5 feet above to 15 feet below the encountered water table to allow <br /> w 1625001rep*rU\sutwj doc 2 <br />