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Former Beacon Station No 12419 March 18,2002 Stockton California Problem Assessment Report/Corrective Action Plan and 0 25 pound benzene were recovered from the aquifer during the 47 3-hour aquifer Pumping test Aquifer pumping test figures are contained in Appendix G 9.2 Soil Vapor Extraction Test A four-hour soil vapor extraction test (SVET) and an air sparge test (AST) were performed separately in October 1999 to evaluate soil vapor extraction and air sparging as remedial alternatives for the site Tabulated SVET and AST field data are contained in Appendix H Soil vapors were extracted from soil vapor wells VW-1 and VW-2 while monitoring for induced vacuum in monitoring wells MW-7 and MW-9 The daily TPHg mass extraction rate ranged from 21 0 to 292 pounds per day (ppd) The maximum flow rate achieved was 9I scfm from VW-I at a wellhead vacuum of 60 inches of H2O Vacuum influence ranging from 0 3 to 0 4 inches H2O were observed in well MW-9 Approximately halfway through the VET, a vacuum response ranging from 0 05 to 0 8 was observed in well MW-7 (4 f'b�� The vapor well VW-1 (screened interval 34-44 feet bsg) maximum extraction flow rate of 91 standard cubic feet per minute (scfm) at low vacuum, and measurable induced vacuum response at 56 feet (Figure 9) from extraction well, indicated vapor extraction is a feasible soil remedial alternative Vapor well VW-2 (screened interval 15-25 feet bsg) exhibited low vapor flow characteristics with a maximum flow rate of 14 scfm possibly due to finer- grained sediments in the screened interval The radius of influence for vapor well VW-2 is uncertain because no vacuum response was detected in the observation wells, but is estimated as less than 20 feet 9.3 Air Sparge Test An 8-hour AST was performed on October 20, 1999 and consisted of the injection of air into well air sparge well AS-I while monitoring pressure responses in wells MW-3 and MW-9 A measured injection flow rate of 13 actual cubic feet per minute (acfm) was established 419PARCAP3-02 doc 18 Project No 1419 23 HORIZON ENVIRONMENTAL INC.