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t T Environmental Assessment Report 2 Chevron U.S.A. Products Company, 139 South Center Street,Stockton,CA January 25, 1996 borings was placed on and covered with plastic sheeting. Soil and rinsate were temporarily stored on site pending removal by Integrated Wastestream Management, Inc. (IWM) of Milpitas. 2.3 Soil Sampling Soil samples were collected from boreholes MW-7, SB-6, SB-7 and SB-9 at 5-foot intervals during drilling, beginning at approximately 5 feet BGS. Samples obtained from boring SB-7 were collected using a 2.54nch O.O. split-spoon sampler, lined with three 2-inch-diameter by 6-inch-long brass sample tubes. Samples collected from borings MW-7, SB-6 and SB-9 were collected using a 1.75-inch O.D. pin sampler, lined with three 1.5-inch-diameter by 6-inch-long stainless-steel sample tubes. The sampler was driven 18 inches ahead of the augers at each sample point. Soil samples were field screened for hydrocarbon vapors using a photo-ionization detector (PID). Soil was logged using the Unified Soil Classification System by a Groundwater Technology field geologist working under the supervision of a California registered geologist(Appendix B). One sample tube from each 5-foot interval was sealed, labeled and placed on ice in an insulated container for transport under chain-of-custody manifest to Sequoia Analytical (Sequoia), a California state-certified analytical lab in Walnut Creek. Soil samples collected from each boring were selected for laboratory analyses (Tables 1 and 2) on the basis of lithology, first occurrence of groundwater and PID readings. Samples were analyzed for benzene,toluene, ethylbenzene and total xylenes (BTEX), and total petroleum hydrocarbons-as- gasoline (TPH-G), using U.S. Environmental Protection Agency(EPA) methods 5030/8020/modified 8015. Upon completion of drilling and sampling, a groundwater monitoring well was installed in boring MW-7, and borings S13-6, SB-7 and SB-9 were backfilled with a neat cement grout to surface. 2.4 "Grab" Groundwater Sampling "Grab"groundwater samples were obtained from borings MW-7 and SB-9 immediately after collection of the last soil sample from each boring. Groundwater samples were obtained from each boring using a disposable PVC bailer and were transferred into appropriate sample containers, sealed, labeled and placed on ice in an insulated container for transport under chain-of-custody manifest to Sequoia. Samples were analyzed for BTEX and TPH-G using EPA methods 5030/8020/modified 8015. 2.5 Groundwater Monitoring Well Installation/Development A groundwater monitoring well was installed in boring MW-7 on December 1, 1995. The monitoring well was constructed of 2-inch-diameter schedule 40 PVC blank casing and 0.020-inch slot well screen 00B B EAR.rpt lChv-641 LF GROLJJNDVWATER "TECHNOLOGY .