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' GeoHydrologic Consultants, Inc GHC recommends performing vapor extraction combined with groundwater extraction ' (by pumping) and treatment (MPE) as the preferred remedial solution for the shallow zone, with groundwater extraction only recommended for the deeper zone well (EW-513) The downhole pumps will not only extract the impacted groundwater for treatment but ' will also lower the water table thus exposing more soil to vapor extraction We believe that this technology will achieve the same remedial goals more quickly than dual-phase extraction and at a lower overall cost since this type of system has a significantly higher ' "up time" and once the vapor goals are reached beneath the Site the vapor extraction system can be shut down while the groundwater extraction portion of the system continues to capture and cleanup the groundwater plume, if needed Based on the multi-phase extraction pilot tests (average ROI approximately g pp ately 30 to 50 feet), GHC recommends using existing groundwater monitoring wells TB-3, TB-4, TB-6, TB-7, TB-10, MW-2, extraction well EW-5S, and vapor well VW-5 for conducting vapor extraction activities while simultaneously extracting groundwater from the six wells including TB-7, TB-10, MW-2, MW-4, EW-5D, and EW-5S (Figure 10) Since ' moderate to high concentrations of soil vapors were extracted during the most recent pilot tests which mostly consisted of TPHg in the vapor and dissolved phase, GHC recommends these remedial activities be performed with a fixed permanent vapor ' extraction and thermal/catalytic oxidation system, since these pilot test results are indicative of a moderate to large mass of hydrocarbons in the subsurface The strategy of remediation will be to concentrate contaminant removal efforts in the area of greatest contamination surrounding the previous tank cluster Based on available information, the current onsite Baker Furnace vapor extraction system ' consisting of a positive displacement blower capable of moving air at 250 scfm at about 15-inches of mercury vacuum will be sufficient for vapor extraction at the Site The treatment technology is currently anticipated to be a thermal/catalytic oxidizer based on ' the pilot test results The vapor phase will be treated and discharged under the existing Site specific permit issued by the APCD Currently wells TB-3, TB-4, TB-6, TB-7, TB- 10, MW-2, MW-4, and VW-5 are connected to the vapor extraction system, however, well EW-5s will need to be connected to the existing piping using 2-inch diameter schedule 40 PVC If this well is tied into an existing vapor extraction line, a valve should be placed inside the well box so that the newly added wells can be isolated for vapor ' sampling purposes if needed Groundwater will be extracted using downhole pneumatic pumps (six QED Hammerhead Pumps) powered by an above ground air compressor(15 cfm Ingersol Rand Continuous Duty Two Stage Air Compressor) Extracted groundwater is expected to be a combined flow rate of five to ten gpm The extracted liquids will be pumped into a 500-gallon ' settling tank and then the liquid stream will be routed through two 1,000-pound granular activated carbon vessels and a flow meter/totalizer before permitted discharge to the sanitary sewer This equipment should be able to be accommodated in the existing 15 ' foot by 20 foot remediation compound that already contains a secondary containment berm TOC 171 Pilot Study Page 25