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Fourth Quarter 1997-,Groundwater Monitoring Report Moore Petroleum,Inc.,5491 'T"Street,Banta,CA Page 2 exhaust. The system was set up such that soil vapors could be extracted from either vapor well VW-1 and/or monitoring well MW-1. The system was started on May 5, 1995, and has operated through October 4, 1995,. at which time it was temporarily removed from site. On November 27, 1995, the system was returned to the subject site and restarted. An air sparge system was installed for use in conjunction with the vapor extraction system. The air sparge system consists of a one horse power electric motor which powers a 10-cubic feet per minute (CFM) oil-less compressor. The compressor injects air through an air sparge point located midway between VW-1 and MW-1 (Figure 2). The air sparge system was started on May 31, 1995 and operated intermittently through August 30, 1995, at which time its operation began to coincide with the operation of the R.S.I. system. On April 29, 1997, Apex received permission from the San Joaquin County Environmental Health (SJCEH) to shut down the air sparge and vapor extraction system. As of April 29, 1997, the remediation system has extracted a total of 1,730 pounds of total petroleum hydrocarbons, as gasoline, and 19.9 pounds of benzene. In a letter dated April 29, 1997 from the SJCEH, the county concurred with an Apex's recommendation to conduct annual groundwater monitoring at the site, except that monitoring wells MW-1 and MW-4 will still be monitored on a quarterly basis. GROUNDWATER MONITORING Groundwater Levels On October 30, 1997, Apex personnel collected groundwater-level measurements from five of the six monitoring wells in accordance to the Apex Standard Operating Procedures (SOP) included as Appendix A. Monitoring well MW-3 was not accessible due to a vehicle parked over it. All groundwater elevations were measured to the nearest 0.01 foot, referenced to the surveyed top- of-casing elevations. Groundwater level measurements collected since January 1993 are summarized in Table 1. A groundwater contour map of the shallow water-bearing zone on October 30, 1997 is shown on Figure 3. Groundwater Sampling and Analysis On October 30, 1997, Apex personnel collected groundwater samples from monitoring wells MW-1 and MW-4 in accordance to the Apex SOP included as Appendix A. The samples were submitted, under chain-of-custody documentation, to California Laboratory Services of Rancho Cordova, California, a state-certified analytical laboratory. The samples were analyzed for concentrations of total petroleum hydrocarbons, as gasoline and diesel, by Modified EPA Method 8015; benzene, toluene, ethylbenzene and total xylenes by EPA Method 8020. The analytical results are summarized in Table 2. The samples were also analyzed for concentrations of five JY:D:1 PROJECTIE'S1ERA02.004-Moore Petroleum,Banta\Qmr11971QMRl 197.doc