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• The six additional wells will be drilled with a drill rig equipped with 8-inch diameter hollow stem augers The wells will be constructed with 2-inch diameter, flush threaded, schedule 40, 0 020-inch factory slotted PVC well casing and blank casing The vapor-extraction wells will be screened between 4 and 12-feet bgs The depth of 12-feet was chosen because that depth is dust above the shallowest depth of groundwater measured historically in on-site monitoring wells Blank casing will be installed above this screened interval Lonestar #2112 sand will be placed between the well casing and the boring from the bottom of the boring to 0 5-feet above the screened interval A 0 5-foot thick bentonite layer will be placed between the sandpack and the overlying cement sanitary seal A Portland cement sanitary seal will be placed above the bentonite layer t o prevent surface water from infiltrating into the well The wellheads will be piped to the proposed vapor-extraction piping manifold, which will then be piped to the abatement device (Figure 12) 6.2 Remediation System Coml2onents 6 2 1 Vapor Extraction Abatement Device The in-situ vapor extraction system will use a 300 cubic inch • displacement, six cylinder internal combustion (IC) engine (RSI or similar) unit to oxidize extracted hydrocarbons The IC engine will be equipped with a power take off (PTO)-driven blower-type vacuum pump (Roots #33 or similar) to extract volatile gasoline-laden air (soil gas) from the vapor extraction wells (Figure 12) The vacuum pump is rated to produce a maximum vacuum of approximately 200 inch water column (iwc) or 15 inches of Hg Under typical conditions for vapor extraction, the actual maximum vacuum for the IC engine unit with the blower is approximately 110 iwc with a flow rate of 50 to 60 cubic feet per minute (cfm) at 2,000 to 2,400 revolutions per minute (rpm) Note that the extracted soil gas may require dilution with atmospheric air in order to maintain operation of the IC engine if the soil gas oxygen concentrations are low due to in-situ bioremediation of the petroleum hydrocarbons in groundwater Therefore, the actual extraction rate from the vadose wells may be less than the throughput to the IC engine, especially during the initial few weeks of VE/AS system operation The IC engine will require a continuous supply of propane as supplemental fuel since the vapor levels of the extracted soil gas will most likely be t o o . low to sustain operation of the IC engine The use of supplemental fuel will also stabilize the operation of the IC engine because the vapor levels Frank's One Stop Remedial Action Plan — August 2001 -1s-