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S First Quarter 1998 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.1. 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-I and MW-4 will still be monitored on a quarterly basis. Apex has included monitoring of five oxygenates (MTBE, TBA, DIPE, ETBE and TAME) in the third and fourth quarter, 1997 groundwater monitoring at the site. The additional monitoring was requested by the Central Valley Regional Water Quality Control Board. The analytical results indicated concentrations of all five oxygenates were at below laboratory detection limits, and therefore the oxygenates are no longer included in the quarterly groundwater monitoring at the site. GROUNDWATER MONITORING Groundwater Levels On January 16, 1998, Apex personnel collected groundwater-level measurements from the six monitoring wells in accordance to the Apex Standard Operating Procedures (SOP) included as Appendix A. 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 January 16, 1998, is shown on Figure 3. JY:D:1_PROJECTIE'STRA02.004-Moore Petroleum,BantalQmr0198_CRIQMR0198.doc