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139 South Center Street, Stockton, California January 21, 1994 _ <br /> Chevron U.S.A. Products Company Page 4 4 <br /> each interval was sealed with aluminum fail, capped, taped, labeled, placed on ice In an insulated <br /> container and delivered under chain-of-custody manifest to GTEL Environmental Laboratories in <br /> Concord, California. <br /> Seveni1 <br /> so samples from the sad boring were selected for analysis. Each sample was analyzed for <br /> benzene, toluene, ethylbenzene and xylenes (BTEX), and total petroleum hydrocarbons-as-gasoline <br /> (TPH-G) by Environmental Protection Agency (EPA) methods 5030/8020/modified 8015. <br /> 3.4 Groundwater Monitoring Weil Installation/Development <br /> One groundwater monitoring well (MW-6) was installed within the boring (Figure 2). The monitoring <br /> well was constructed of 2-inch-diameter, schedule 40 PVC casing with flush threads, and <br /> 0.020-inch-slat well screen. The well screen was installed from the bottom of the boring (60 feet <br /> BGS) up to 35 feet BGS. Sand was placed in the well annulus from the bottom of the well to <br /> approximately 2 feet above the top of the screen. The well was completed with a bentonite and <br /> neat-cement seal, to grade, and protected by a locking cap and a traffic-rated street box with a <br /> water-tight bolted lid. Well construction details are presented in the drill logs (Appendix B). <br /> Upon completion, the new monitoring well was developed to remove fine-grained sediments from the <br /> well and filter pack. On October 14, 1993, Groundwater Technology personnel purged approximately <br /> ten well volumes of water from MW-6, using a clean PVC bailer. "temperature, pH, and conductivity <br /> measurements, recorded while purging, stabilized after 10 well volumes of groundwater had been <br /> removed (Appendix C). Purge water generated during the development process was stored in a <br /> DOT-approved purge water trailer and transported to the Chevron refinery in Richmond, California for <br /> recycling. <br /> 3.5 Groundwater Monitoring <br /> On November 22, 1993, the six site-related groundwater monitoring wells were gauged to determine <br /> depth to water and the thickness of any separate-phase hydrocarbons (SP). Depth to water was <br /> measured using an ORS Environmental Equipment INTERFACE PROBC" Well Monitoring System, <br /> Cj GROUNDWATER <br /> _,__J 'TECHNOLOGY <br />