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& '�'i ^�^y-�'+* a ..a'�qr ,+;•fir .1+� ^°� •^ ,.� ,q- � 'r,�p Chevron U.S.A. Products Company April 8, 1992 02320 2241 Page 2 reviewed and signed by all Groundwater Technology personnel and subcontractors personnel and su'5contractors performing work at the site. Groundwater Technology conducted a technical review of all pertinent information prior to proceeding with assessment work at the site. All applicable permits pertaining to monhoring-well installation %,,re obtained. 3.2 SOIL BORINGS/SAMPLING On March% 1992,Groundwater Technology drilled three soil borings using a truck-mounted drill rig equipped with 8-inch-diameter, steam-cleaned, hollow-stem augers. The soil borings were drilled to depths ranging between 20 and 30 feet below grade to accommodate Installation of two monitoring wells (MW-6 and MVV-7)and a vadose well(VW-1). Drilling was supervised by a field geologist working under the direct supervision of a California registered geologist. A continuous log of matarials encountered while drilling was maintained by the field geologist using the Unified Soil Classification System(Appendix A). Soil from the borings was placed in 55-gallon drums for future disposal. During drilling,soil samples were collected from the borings for MW-6 and MW-7 at 5-foot Intervals, beginning at approximately 5 feet below ground surface (BGS) to the bottom of the boring. VW-1 was continuously sampled from 15 to 20 feet BGS. Samples were collected using a 2.5-Inch outside diameter (O.D.)split-spoon sampler,lined with three 2-inch-diameter by 6-inch-long brass sample tubes. The sampler was driven 18 Inches ahead of the augers at each sample point. Soil samples were field screened using a photo-Ionization detector(PID). One sample from every 5-foot interval was s9aled with aluminum foil, capped, taped, labeled, placed on Ice In an Insulated container and delivered under chain-of-custody manifest to State of California-certified Superior Precision Analytical laboratories. Selected samples (based on PiD readings) were submitted for analysis of benzene, toluene, ethyl benzene and xyfenes(BTEX),and total petroleum hydrocarbons-as-gasoline(TPH-G)by Environmental Protection Agency(EPA)methods 5030/8020/8015. 3.3 WELL INSTALLATION/DEVELOPMENT Groundwater monitoring wells were Installed in two of the soil borings. A vadose well was Installed In the third boring.All wells were constructed of 2-Inch-diameter,schedule 40 PVC casing with flush threads, and 0.020-Inch-slot well screen. A sand filter pack was placed around each well screen to a height of approximately 2 feet above the top of the screen. The wells were completed with a bentonite and neat- cement seal, to grade. The two monitoring wells are screened from 10 to 30 feet BGS In each well, The vadose well is screened from 12.5 to 17.5 feet BGS: Each wellhead was protected by a locking cap and 2241SUM1.AP7 --�f-�''��t CHOUN'U11'ATElt