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S E C 0 R 7-Eleven Store #32262 Site Assessment Report December 12, 2003 Page 3 x� SECOR prepared a site-specific Health and Safety Plan for well installation and sampling activities at the site as required by the Occupational Health and Safety Administration (OSHA) Standard "Hazardous Waste Operations and Emergency Response" guidelines (29 CFR 1910 120) The document was reviewed and signed by all SECOR personnel and subcontractors performing work at the site Prior to conducting subsurface work at the site, USA was contacted to delineate subsurface utilities near the site with surface markings In addition, a private utility locator service was contracted to clear each of the proposed drilling locations Soil Borings On October 15-17, 2003, SECOR supervised Cascade Drilling of Rancho Cordova, California, drill and install six groundwater monitoring wells at the locations shown on Figure 2 MW-1 through MW- 5 were drilled to an approximate depth of 17 feet bgs MW-6D was drilled to an approximate depth of 51 feet bgs. (Table 3) The five shallow wells were installed to 17 feet bgs using a truck-mounted drilling rig equipped with 8-inch-diameter hollow-stem augers (HSAs) Deep welt MW-6D was installed to a depth of approximately 51 feet bgs using 15-inch HSAs from ground surface to 32 feet bgs to allow for conductor casing installation, which is described below MW-613 was then drilled from 32 to 51 feet bgs using 8-inch HSAs through the conductor casing Soil Sampling Soil samples were collected continuously in borings MW-1, MW-3, MW-4, and MW-6D, and at five- foot intervals in MW-2 and MW-5, using a split spoon sampler lined with 2-inch diameter by 6-inch- long brass sample tubes Downhole drilling equipment was steam cleaned before drilling each borehole, and sampling equipment was cleaned between each sampling interval Each soil sample was screened for hydrocarbon vapors using a portable photoionization detector (PID) Soils encountered during drilling were logged using the Unified Sod Classification System by a SECOR field geologist, working under the supervision of a California Registered Geologist Selected sod samples were sent to Kiff Analytical in Davis, CA and analyzed for TPHg, BTEX, fuel oxygenates MtBE, TBA, TAME, ethyl-tert-butyl ether (EtBE), diisopropyl ether (DIPE), 1,2-dichloroethane (1,2- DCA), and ethylene dibromide (EDB) by EPA Method 82608 Lithology Based on the description of the soil samples collected from the six new wells, the lithology encountered consists mainly of silt, with minor amounts of gravel and clay, from ground surface to 17 feet bgs In MW-6, silt, with minor amounts of sand and clay, was encountered from ground surface to total depth (51 feet bgs) Groundwater was observed at approximately 10 feet bgs No obvious ' low permeability, confining layer of clay or silt was observed in the soil borings Copies of the sod boring logs are included in Attachment B Copies of the field notes collected during well installation are provided in Attachment C T 32262 Assessment Report SECOR International Incorporated x r