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Interim Remediation Plan and Second Quarter 2001 Groundwater Monitoring Report Moore Petroleum Bulk Plant,5491 F Street,Banta,California Page 4 PUMPING TEST RESULTS Preliminary Assessment As previously mentioned, during the Workplan preparation phase of the IRP,Apex recommended installing three groundwater recovery wells to effectively draw down the aquifer and control the potential offsite migration of petroleum constituents dissolved in groundwater. Groundwater flow in the shallow aquifer is from the southwest to the northeast as shown on the groundwater contour map presented as Figure 3. The recovery wells were positioned to provide a means of intercepting groundwater down gradient of the UST excavations and upgradient of the domestic well located at 5451 F Street. Apex anticipated that the former tank basin area would have to be significantly dewatered before any changes in groundwater elevations will be observed in wells MW-3, MW-9, and MW-12 located outside the former tank basin area(Figure 2). This is due to the relatively low hydraulic conductivity of the native soil at the site (0.0026 ft/min) as determined by Delta in their report entitled Preliminary Hydrogeologic Assessment Report dated September 8, `1989.� As previously mentioned, 8443 only wanted one recovery well installed for the pumping test and depending on the results, more recovery wells could be installed. Apex installed one groundwater recovery well RW-2 at the site for the purpose of conducting the pilot pumping test. Dewatering the entire former tank basin area was not necessary for the purposes of this pumping test. It was Apex's opinion that a pumping test using a rate of 10-gallons per minute (gpm) will produce sufficient draw down in the former excavation and provide sufficient hydrogeologic data to assess the possible effectiveness of groundwater extraction as a remedial alternative for the site. Based on 48-hours of pumping time,the test would produce approximately 28,800 gallons of water that would require proper disposal. Field Activities On March 26, 2001, Apex personnel lowered a one horsepower submersible pump into the recovery well RW-2 and installed pressure transducers in monitoring locations MW-3, MW-8, MW-9, and MW-12. The pretest was initiated to establish an appropriate flow rate. The pumping was initiated at 10-gpm and groundwater levels monitored at location RW-2 determined that this rate was too fast. The pump was turned off,the water table was allowed to recover and the pump was turned on again at 4-gpm, which was also determined to be too fast. The pump was turned off, the water table was allowed to recover and the pump was turned on again at 2- gpm, which was determined to be the appropriate flow rate for well RW-2. The pump was turned off and the groundwater levels were allowed to fully recover 18 hours.