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+1 . Mr Kyle Christie Project 0805-114 04 December 6, 1995 Page 3 The wellhead elevations of the monitoring wells at the site were previously surveyed by Morrow Surveying of West Sacramento, California The surveyed elevations and the depth to groundwater measurements, summarized in Table 1, were used to evaluate the potentiometnc surface beneath the site The groundwater flow direction on August 28, 1995, was to the northeast, with a hydraulic gradient of 0 001 (see Figure 3) The groundwater flow direction in the past has generally been towards the east to southeast Groundwater elevation data are presented on Figure 3 and in Table 1 Groundwater elevations decreased 167 feet from the previous sampling event (May 1995) Groundwater samples collected from wells MW-1 through MW-8 and MW-10 were analyzed for TPHG, and benzene, toluene, ethylbenzene, and total xylene isomers using California Department of Health Services (DHS) LUFT Method and Environmental Protection Agency (EPA) Method 5030/8020, respectively These samples were analyzed at Columbia Analytical Services, Inc , in San Jose, California The results of these analyses are summanzed in Table 2 Copies of the chain-of-custody records and laboratory analysis reports are presented in Appendix B . Dissolved hydrocarbons were detected in wells MW-1, MW-2, MW-5, MW-6, and MW- 10 TPHG concentrations ranged from below detection limits in wells MW-3, MW-4, MW- 7, and MW-8 to 650 ppb in well MW-2 Benzene concentrations ranged from below detection limits in wells MW-3, MW-4, and MW-6 through MW-8 to 84 ppb in well MW-2 TPHG and benzene concentrations are shown on Figure 2 OPERATION AND MAINTENANCE OF THE REMEDIATION SYSTEM EMCON began the operation and maintenance of the remediation system in November 1994 The system consists of an air sparging-enhanced vapor extraction system with catalytic oxidation treatment (AIREX KATOX 100) The system is connected to one air sparging well (AS-1) and 12 vapor extraction wells (VW-1 through VW-12) The system has been operating with VW-5, VW-7, VW-9, VW-11, and VW-12 closed (see Table 5) The air sparge system has operated in conjunction with the SVE system During the third quarter 1995, air sparge wells AS-2 and AS-3 were connected to the system EMCON performed monthly site visits to evaluate and optimize system performance Copies of the field data sheets are presented in Appendix C Analytical results of influent and effluent samples collected on July 17, 1995, indicated that the system was not meeting the required destruction efficiency The system was shut down immediately and the San Joaquin Valley Unified Air Pollution Control District was notified of the condition A source test was conducted on August 10, 1995, to reestablish system operating parameters and destruction efficiency The results of the source test indicated that the SVE system was in compliance and was restarted on August 27, 1995 The system was operational until October 6, 1995, when analytical results again indicated poor SAON\P1UA80M8051140 4Es-95\pas 1