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r 16 GROUND ZERO ANALYSIS, INC. The induced vacuums recorded in the observation wells suggest the effective radii of influence for test wells VW-1, VW-2 , VW-3 , VW-4 , and VW-6 are approximately 25 to 30 feet � Laboratory Analyses and Results I Ground Zero initiated a chain--of--custody record that accompanied the vapor samples to Sequoia Analytical of Sacramento, California r (DOHS # 1624) The vapor samples were analyzed for total petroleum hydrocarbons as gasoline (TPHg) using EPA Method 8015, and for ' benzene, toluene, ethylbenzene, and total xylenes (BTEX) using EPA Method 8020 The results of the laboratory analyses are presented 1 i in Table 2 Copies of the chain-of-custody records and laboratory reports are included in Attachment 3 Results of the laboratory analyses of vapor samples collected from ' test wells VW-1, VW-2 , VW-3 , VW-4 , and VW-6 indicate that TPHg concentrations ranged from 11, 000 to 31 , 000 milligrams per cubic meter The analytical results of the IC engine effluent vapor samples collected to evaluate the breakdown efficiency of the ' engine indicate greater than 97k destruction efficiency Projected Gasoline Removal Rates The primary area of concern for this site is the former underground storage tank (UST) pit and the surrounding area The approximate lateral extent of gasoline hydrocarbons present in soil beneath the site is presented as Figure 5 If vapor extraction is chosen as the method of soil remediation for this site, Ground Zero proposes that test wells VW-1, VW-3 , VW-4 , and VW-6 be brought online for the proposed vapor extraction system (VES) These wells are screened at the same depth intervals as the residual gasoline hydrocarbons detected in the higher permeability soil at depths ranging from 50 to 60 feet below ground surface (bgs) in the vicinity of wells VW-1 and VW--4 , and at depths ranging from 30 to 60 feet bgs in the vicinity of wells VW-3 and VW-6 Ground Zero also proposes that test wells VW-2 and VW-5 be brought online for the proposed VES These wells are screened at the same depth intervals as the residual gasoline hydrocarbons detected in the I lower permeability soil at depths ranging from 35 to 45 feet bgs in the vicinity of well VW-2 , and at depths ranging from 14 to 42 feet bgs in the vicinity of well VW--5 ' Based on the test results, the effective radii of influence for the wells is estimated to average approximately 30 feet which should provide overlapping coverage of the area of gasoline impacted soil { beneath the site 7