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1 <br /> Report on Additional Site Assessment and First Quarter 2000 Monitoring and Sampling Report 3 <br /> 7-Eleven lnc Store#19976 1399 N Main St Manteca California February 4 2000 <br /> 1 <br /> Groundwater analytical data trends over time indicate highest dissolved hydrocarbon levels are <br /> consistently present in well MW-2 (Table 2) Benzene, TPH-G, and MTBE concentrations in this well <br /> have ranged up to 6,990 micrograms per liter (Ng/L), 57,000 pg/L, and 885 pg/L, respectively Low to <br /> non-detectable concentrations in downgradient wells MW-5, MW-5A, and newly-installed MW-6 Indicate <br /> adequate lateral and vertical plume delineation (Figures 2 and 3) <br /> I30 ADDITIONAL SOIL.AND GROUNDWATER ASSESSMENT <br /> 31 Permitting/Site-Specific Health and Safety Plan <br /> I A permit for groundwater monitoring well Installation was obtained from the SJCPHS The existing <br /> site-specific Health and Safety Plan(as required by the Occupational Safety and Health Administration <br /> Standard Hazardous Waste Operations and Emergency Response guidelines 29 Code of Federal <br /> Regulations 1910 120) was used during recent activities The document was reviewed and signed by all <br /> IT Corporation personnel and subcontractors prior to commencement of work at the site <br /> I� <br /> 32 Soil Boring <br /> IThe boring for well MW-6 was drilled on December 22, 1999 to a depth of 30 feet below grade using a <br /> drilling rig equipped with an 8-Inch diameter hollow-stem augers All drilling equipment was steam <br /> cleaned prior to drilling each boring, and sampling equipment was washed in an Alconox® (detergent) <br /> solution and rinsed with water between sampling intervals All soil and rinse water generated during the <br /> drilling was placed In labeled Department of Transportation (DOT)-approved 55-gallon drums and left on <br /> the site pending transportation and disposal <br /> 33 Soil Sample Collection <br /> Soil samples were collected during drilling at 5-foot Intervals to 30 feet below grade using a split-spoon <br /> sampler lined with 2-Inch-diameter by 6-inch-long brass sample tubes The sample tubes were sealed <br /> with Teflon pads, plastic caps and tape, labeled, placed on Ice In an Insulated container, and submitted <br /> for analyses under chain-of-custody manifest to a state-certified laboratory for analysis Soil samples <br /> were field screened for hydrocarbon vapors using a flame-Ionization detector (FID) Soil was logged <br /> using the Unified Soil Classification System by a IT Corporation field geologist working under the <br /> supervision of a California registered geologist (Appendix A) <br /> 19976 3SA <br /> 1 <br />