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RECR December 6, 1994 Jeffrey S. Lawson -2- 943-7076 quarters of groundwater sampling; the evaluation of the threat that residual soil contamination,if any,will pose to the groundwater;and the preparation of a closure report in accordance with Appendix "B" of the Central Valley Regional Water Quality Control Board Tri-Regional Recommendations for Closure Reports. SCOPE OF WORK In preparing this work plan,Golder reviewed the Phase I Investigation Report, Brine Release, dated April 30, 1993 (WHF),Phase III Site Assessment-Report of Findings &Phase IV Additional Remediation Proposal,dated July 17, 1992 (WHF);the Phase IV Remediation Report of Findings, dated July 121994 (WHF);Groundwater sampling and analysis report dated December 15, 1993 (Levine Fricke);and the letter from Mary Meays addressed to Brent Larson, dated August 12, 1994 Health and Safety Plan Preparation Prior to initiating the field work,Golder will review the existing reports for information on expected contaminants at the site and their magnitude. Based on this information,Golder will prepare a health and safety plan for workers at the site. Groundwater Sample Collection Golder will measure the water level in and collect groundwater samples from all existing monitoring and extraction wells at the site for two quarters. As shown in figure 1,a total of fourteen wells will be sampled (MW-1S, MW-1D,MW-2S,MW-3S,MW-4S,MW-4D,MW-5S, MW-6S,MW-75,MW-8,MW-9,MW-10,MW-11,and MW-12). Prior to collecting groundwater samples,we will measure the depth to groundwater to the nearest 0.01 feet with an electronic water level meter and then we will purge each well. A minimum of three casing volumes of water will be purged from the wells. During purging, field parameters (pH, specific conductance, and temperature) will be monitored,and purging will continue until these parameters have stabilized. Each sample will be collected in an appropriate container and sent in a cooler with ice to Superior Analytical Laboratories, a State of California Certified analytical Iaboratory,under chain-of-custody procedures. A minimum of 1 blank sample, and 2 duplicate samples will be collected during each quarterly sampling round for QA/QC. QA/QC documentation will be retained and submitted with the Closure Report. Groundwater samples will be analyzed for extractable Total Petroleum Hydrocarbons as gasoline (TPHg) and benzene, toluene,ethyl benzene,and xylenes (BTEX)using EPA test methods Modified 8015 and 8020. Purge water generated during this task will be contained in labeled 55-gallon drums and stored onsite for subsequent offsite disposal by a licensed contractor. A letter report will be prepared for agency submittal summarizing the results of each quarterly sampling. Golder Associates