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v <br /> 4 <br /> ASSAT <br /> O C I ATE S I N C . <br /> gases but may be changed to vapor-phase carbon after concentrations are reduced. Additional <br /> costs to the client would be incurred for permitting, leasing, and installing the vapor extraction <br /> and air sparging equipment and treatment compound, and operation and maintenance of the <br /> system. The cost of this alternative is estimated to be between$100,000 and $150,000. <br /> ♦ Criterion S: <br /> This alternative should effectively remediate subsurface contaminants to acceptable regulatory <br /> levels within 1 year of implementation. <br /> ♦ Criterion 6: <br /> 4, Groundwater would be monitored periodically until soil and groundwater is remediated to <br /> ensure that concentrations of petroleum hydrocarbons are being reduced, which should be <br /> 4 effective in the long-term. <br /> L. <br /> ♦ Criterion 7. <br /> This alternative has some minor implementability problems due to the time involved in <br /> obtaining permits from the APCD for the vapor extraction system. Permitting could take as <br /> much as 180 days depending upon APCD work load, but is typically completed in 60 to 90 <br /> days. <br /> ♦ Criterion 8: <br /> Impact to the site occupants and surrounding businesses during installation and other site <br /> activities will be moderate. This method has been shown to be effective and regulatory <br /> acceptance is expected. <br /> 6.0 RECOMMENDATIONS <br /> ATC proposes utilizing high vacuum dual phase extraction in an effort to remediate the vadose <br /> and capillary fringe zone soils. High vacuum dual phase extraction will be conducted using <br /> existing monitoring and remediation wells MW1, MW2, VWl, and VW3 as source and <br /> L observation wells. The remedial action will be conducted during monthly events each of a <br /> duration of approximately five days. Vacuum influence and depth to water will be monitored at <br /> ` the observation wells to evaluate the radius of vacuum influence and groundwater draw down. <br /> L During the remedial action, the soil gas oxygen concentration will be monitored using a <br /> GasTechTM combustible vapor analyzer. The volatile fuel hydrocarbon (VFH) concentration will <br /> also be monitored with a photo ionization detector (PID). Soil gas samples will collected in <br /> �- TedlarTM bags or Summa canisters for laboratory analysis for volatile fuel hydrocarbons (VFH), <br /> BTEX and MTBE using EPA Test Method TO-14. <br /> 16- The total amount of groundwater recovered during the remedial action events will be recorded <br /> using a flow meter/totalizer. This will be used to determine the total number of gallons extracted <br /> -owe during the event. Depth to groundwater measurements will be collected from surrounding <br /> observation wells at periodic time intervals. Effluent water samples shall be collected during the <br /> S:IEnvironmenta11625771SCMCAPAdddoc 10 <br /> r� <br />