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Beacon Station No 641 September 28, 1998 Stockton California Remedial Testing Report per million by volume (ppmv) and not detectable (less than 4 0 ppmv) 1n the effluent vapor stream Summarized results of the field vapor readings along with other pertinent data are shown on Table 1 The summarized laboratory results along with other pertinent data are shown on Table 2 Copies of the Iaboratory reports and chain of custody (CoQ records are included in Attachment B Based on the flow measurements obtained during the VET, the maximum influent flow rate from well VW-2 is calculated to be approximately 46 cfm with the average influent flow rate being approximately 33 cfm The calculated average removal rate was approximately 248 lbs/day of TPHg and 14 lbs/day of benzene According to data recorded by Horizon personnel, the abatement efficiency of the entire duration of the VET was 100% except during the last 30 minutes, after which the VET was shut down Magnahelic gauges were attached to the casing of wells VW-3, VW-4, VW-5, VW-6, and VW-8 to evaluate the possible radius of influence from the source well, VW-2 The source well VW-2 is screened between 21 and 36 feet, and vapor wells VW-3 (from 45 to 55 feet), VW-4 (25 to 40 feet), VW-5 (40 to 50 feet), VW-6 (22 to 32 feet), and VW-8 (22 to 32 feet) Differential pressure readings were recorded every 15 to 30 minutes when Horizon personnel were onsite for the duration of the VET (see Table 1) Vapor wells VW-3 and VW-4 showed almost immediate recorded influence from the beginning and throughout the VET Wells VW-5 and VW-6 showed some affects after approximately 45 minutes, but with no significant increase Magnahelic readings at well VW-3 ranged from 0 20 to 0 23- inch of water column at approximately 13 feet from the source well (VW-2) Influence recorded for well VW-4 ranged from 0 40 to 0 48-inch of water column at 13 feet away from the source Wells VW-3 and VW-4 are located in the same boring, except that well VW-4 is screened in the same approximate interval as the source well while well VW-3 is screened from approximately 45 to 55 feet bsg Wells VW-5 and VW-6 are located in the same boring approximately 18 feet from VW-2 Based on this data it appears that the effective radius of influence utilizing VW-2 as the source well is approximately 15 to 20 feet of radius at 100 inches of water column vacuum Influence was noted in well VW-8 which is located 26 feet from the source well, however this data indicates the effect was marginal and probably not effective for hydrocarbon removal utilizing only VW-2 Air_ Sparging Test An air-sparging test (AST) was conducted at the site on May 27, 1998 This test was conducted at the same time as the VET and was begun after approximately four hours into the VET Sparge well SW-1 was used to introduce air into the saturated zone using a Gast 1 horsepower oilless rotary vane compressor Well SWA is screened from 60 to 65 feet bsg The depth to groundwater at the time of the AST was 47 3 feet bsg During the AST, the magnahelic gauges utilized for the VET were monitored to record changes in vapor pressure at the selected well locations In addition, toward the conclusion of the AST, dissolved oxygen (DO) concentrations were measured in selected monitoring wells to compare to DO concentrations taken at these locations prior to any testing 1641-21 rpt 3 HORIZON ENVIRONMENTAL INC.