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ME PRELIMINARY HYDROGEOLOGIC ASSESSMENT WORT{PLAN 6441"F"Street,Banta,Canfornia Delta Project No.40-88-481 1-4 Page 8 o Properly develop the monitoring wells and collect ground water samples from each well for laboratory analysis. 1.3_Previous Work ETS Environmental(ETS)had been retained previously by Jerry Moore,of Moore Petroleum, Inc. to conduct a preliminary site assessment at this location. This site assessment consisted of the drilling of one soil boring, installation of one monitoring well, and the collection and analysis of soil and water samples from the soil boring and monitoring well. The results of the work performed by ETS is presented in the following sections. 1.3.1 Soil Borings and Soil Analvtiml-Results One soil boring was drilled by means of a hollow-stem auger to a depth of 20 feet and completed as a monitoring well. Soil samples were taken at five-foot intervals by means of a California modified split-spoon sampler. Figure 2 shows the location of the monitoring well, The boring log for the soil boring is included in Appendix A. . Soil samples collected from the soil borings were analyzed by a California-certified laboratory for benzene, toluene, ethylbenzene, xylenes (BTEX), 1,2-dichloreethane (EDC), ethylene dibrorrFide (EDB)and total petroleum hydrocarbons(TPH)by EPA method 524.2/8240. Results of the analyses are summarized in Table 1. Laboratory reports fcr soil analyses are presented in Appendix B. As shown in Table 1, the highest TPH level detected was 450 ppm in the sample taken at 10 feet below grade. BTEX constituents were either not detected or found at relatively Iow levels, with the exception of ethylbenzene and xylene which were detected in the 10-foot sample at concentrations of 4.8 and 8.5 ppm, respectively. 1.12 Monitoring Well Monitoring well (MW-1) was completed within the soil boring located immediately north of the -- underground storage tanks(USTs). This wel!was constructed of 2-inch diameter,Schedule 40 PVC blank casing and 2-inch diameter, Schedule 40 PVC well screen with 0.020-inch slots. The -----monitoring-well constructiondia ram for-this well-is included in- g Appendix A_The-mon i tori n g:veli--. -- _ T was developed by removing water from the well screen by purging with nitrogen gas.