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• Monitoring Well Installation and VET Report—Former Unocal Station#2859,Stockton,CA July 30,2001 Groundwater Analytical Results MtBE was not detected in groundwater samples TPHg or benzene were not detected to wells MW-14, MW-16, MW-18, or MW-19, and benzene was not detected in well MW-17 TPHg range hydrocarbons were detected to wells MWA 1 (31,000 ppb), MW-12(3,100 ppb), MW-13 (87 ppb), MW-15 (3,100 ppb), and MW-17 (75 ppb), and benzene was detected in wells MW-11 (720 ppb), MW-12 (19 ppb), MW-13 (1 1 ppb), and MW-15 (9 0 ppb) 1,2-DCA was detected in wells MW-17 through MW-19 at concentrations of 200, 16,and 2 1 ppb,respectively WASTE DISPOSAL Soil cuttings generated during drilling activities were placed on and covered with plastic sheeting at the subject site and disposal confirmation sample SP-1(A-D) was collected (Table 1) Approximately 32 yards of soil cuttings were removed from the site on June 18, 2001 and transported to Forward Landfill in Manteca,California, for disposal A copy of the disposal confirmation form is included in Appendix B VAPOR EXTRACTION PILOT TEST . GR personnel performed a five-day vapor extraction (VE) test at the site from June 18 through 22, 2001 The VE system operated for a total of 39 hours and soil vapors were extracted from wells VW-1,VW-2,and VW-3 The purpose of the VE test was to evaluate the feasibility of the VE technology and collect needed site specific data for the design of a VE system if deemed necessary The VE test also provided GR with data to determine the area with the highest residual hydrocarbons in soil, and if there was enough hydrocarbon mass to wan-ant the re-installation of a VE system Soil Va or Extraction Test Eguil2ment A trailer mounted, propane powered internal combustion (IC) engine was used for the soil vapor extraction test The vapor extraction test was performed in accordance with the San Joaquin Valley Air Pollution Control District(SJVAPCD) source testing guidelines The SJVAPCD Notice of Consent Letter for a soil vapor extraction test is presented in Appendix B Laboratory confirmation samples were collected in Tedlar bags and submitted to Sequoia Analytical Laboratories for analysis (ELAP #1274) Vacuum observation wells, measuring the response to vapor extraction,were monitored with magnehelic gauges and the data recorded manually Pilot Test Procedure The VE pilot test was conducted from June 18 through 22, 2001, and consisted of extraction from the three vapor extraction wells at different times Vacuum observations were collected from vapor extraction wells VW-1,VW-2,and VW-3,and monitoring wells MW-1, MW-2,MW-3, and MW-6 The IC engine was set to operate at a constant motor speed (RPM) during the test The applied vacuum to the extraction wells was vaned automatically by the engine, based on influent petroleum concentrations The RPM was also manually stepped up during the course of the test each day,which also vaned the applied 24007204-1 5