ARCHIVED REPORTS_XR0007910 - Laserfiche WebLink

Home Browse Search

' SOIL VAPOR EXTRACTION PILOT STUDY REPORT San Toaqum County Mont omery Ward Auto Service Center Public Health Services Department 5400�Pacific Avenue, Stockton, CA Site Code 2163 ' Extracting from VEW-1B at 225 SCFM (Figure 24 Observation Slope Soil Point (in WC) Permeability (Darcies) SP-2 30 451 SP-3 41 330 ' SP-4 27 501 SP-8 22 615 Extracting from VEW-1A & VEW-1B at 210 SCFM (Figure 25) ' Observation Slope Soil Point (in WC) Permeability (Darcies) SP-2 81 156 ' SP-3 99 128 SP-4 65 194 SP-8 51 248 ' 8 1 3 Vapor Concentrations Vapor concentrations measured by field instruments are shown in tables included in Appendix K for each day of the pilot tests Figure 26 shows the graph of these data as a function of time for all the vapor extraction wells on site Figure 27 shows vapor concentrations versus time for all the soil vapor probes These graphs show a general trend of decrease in concentrations as the test proceeded However, there appears to be a slight increase on the last day of the test, a possible effect of the air sparging test as explained later Figure 28 shows the inlet concentration at the vapor extraction unit as a function of time There appears to be a distinct change in concentration levels from 11/19/1996 to 11/20/96 Samples were also obtained from two of the vapor extraction wells for laboratory analyses Results are tabulated in Table 12 and the laboratory data is included in Appendix L Results for well VEW-1A are shown in Figure 29 The data suggest a sharp decrease in vapor concentration between 11/18/96 and 11/21/96 The sharp drop in concentration beginning on August 20, 1996 is probably caused by the continued operation of the VES at high vacuum EAI suspects that the concentrations will have rebounded back to initial high concentration after a few days of equilibration I8.2 Results from Air Sparging Tests After completing the vapor extraction tests, EAI performed a test to assess the effectiveness of I air sparging in ground water Air sparging is a method of remediating ground water in situ by injecting air bubbles into the water and causing volatile contaminants to transfer into the van phase and travel up into the vadose zone A VES can then extract the contaminants and treat it accordingly Air sparging can also enhance bioremediation of contaminants in ground water In general, the air sparging test involved the introduction of pressurized air at a fixed depth below ground water and testing vapor and water concentrations, dissolved oxygen in water and vacuum at monitoring points An increase of dissolved oxygen and/or vapor/water concentrations after the air sparging starts, generally indicates that desired results (stripping contaminants from water and transferring into vapor phase in the vadose zone) are being I Project No 1232 - 13 - ENVIRONMENTAL AUDIT, INC