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6 l i <br /> Chevron U S A Products Company April 8, 1992 <br /> 02320 2241 Page 2 <br /> reviewed and signed by all Groundwater Technology personnel and subcontractors personnel and <br /> subcontractors performing work at the site <br /> Groundwater Technology conducted a technical review of all pertinent information prior to <br /> proceeding with assessment work at the site All applicable permits pertaining to monitoring-well installation <br /> were obtained <br /> 32 SOIL BORINGS/SAMPLING <br /> On March 3, 1992, Groundwater Technology drilled three sort borings using a truck-mounted drill <br /> rig equipped with 8-inch-diameter, steam-cleaned, hollow-stem augers The sod borings were drilled to <br /> depths ranging between 20 and 30 feet below grade to accommodate installation of two monitoring wells <br /> (MW-6 and MW-7) and a vadose well (VW-1) Drilling was supervised by afield geologist working under the <br /> direct supervision of a California registered geologist A continuous log of materials encountered while <br /> drilling was maintained by the field geologist using the Unified Soil Classification System (Appendix A) Sod <br /> from the borings was placed in 55-gallon drums for future disposal <br /> During drilling, sod samples were collected from the borings for MW-6 and MW-7 at 5-foot intervals, <br />. beginning at approximately 5 feet below ground surface (BGS) to the bottom of the boring VW-1 was <br /> continuously sampled from 15 to 20 feet BGS Samples were collected using a 25-inch outside diameter <br /> (O D ) split-spoon sampler, lined with three 2-inch-diameter by 6-inch-long brass sample tubes The sampler <br /> was driven 18 Inches ahead of the augers at each sample point Sod samples were field screened using <br /> a photo-ionization detector (PED) One sample from every 5-foot interval was sealed with aluminum foil, <br /> capped, taped, labeled, placed on ice in an insulated container and delivered under chain-of-custody <br /> manifest to State of California-certified Superior Precision Analytical laboratories <br /> Selected samples (based on PID readings) were submitted for analysis of benzene, toluene, <br /> ethylbenzene and xyienes (BTEX),and total petroleum hydrocarbons-as-gasoline (TPH-G) by Environmental <br /> Protection Agency (EPA) methods 5030/8020/8015 <br /> 33 WELL, INSTALLATION/DEVELOPMENT <br /> Groundwater monitoring wells were installed in two of the sod borings A vadose well was installed <br /> in the third boring All wells were constructed of 2-inch-diameter, schedule 40 PVC casing with flush threads, <br /> and 0 020-inch-slot well screen A sand filter pack was placed around each well screen to a height of <br /> approximately 2 feet above the top of the screen The wells were completed with a bentonite and neat- <br /> cement sea[, to grade The two monitoring wells are screened from 10 to 30 feet BGS in each well The <br /> vadose well is screened from 12 5 to 17 5 feet BGS Each wellhead was protected by a locking cap and <br /> 2241SUMi APT rEILI 11I GROUNDWATER <br /> TECHNOLOGY INC <br />