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31 January 2013 AGE-NC Project No. 02-0926 Page 14 of 21 systems are capable of removing both hydrocarbon vapors and, depending on soil type and stratification, liquid and dissolved phase hydrocarbons. DPE-vapors may be treated by catalytic oxidation, thermal oxidation, or by carbon bed filtration, while DPE-groundwater may be treated on site (i.e. air stripper, carbon media vessels), and discharged into either the sanitary sewer, storm drain system or by hauling off-site. Alternatively, impacted groundwater may be stored on site in a temporary tank for later recycling. 9.2.2. Duration Cleanup periods for dual phase extraction typically range from several months to several years. Based upon the plume size, and the general lithology beneath the site it appears that a 18- to 24-month period could be expected to complete soil and groundwater remediation at the site. 9.2.3. Estimated Cost The costs for installation, operation and general maintenance of a DPE remediation system is dependant upon the particular system utilized for destruction of the extracted hydrocarbon vapors (thermal destruction, carbon adsorption, etc.) and the established cleanup goals. Generally, the installation cost for a dual phase extraction system will range between $75,000 and $125,000. The approximate cost to operate, sustain, monitor and sample a DPE system could vary from $70,000.00 to $100,000.00 per year. 9.2.4. Feasibility High vacuum DPE can quickly remediate petroleum hydrocarbons present in the vadose zone, capillary fringe and upper portion of the saturated zone; typically trapped in fine grained soils. Due to the liquid burial of the adsorbed contamination, the dual phase system can often be more cost effective than groundwater extraction. The effectiveness of this technology is sometimes dependent upon sufficiently lowering the water table to allow vapor extraction to remove hydrocarbons from the capillary fringe and saturated zones. Deep screened wells must be utilized to adequately de-water the site. Currently, the site is not equipped with dedicated DPE wells and pumping tests have not been conducted at the site to evaluate the ability to draw down the water table and expose saturated zone soil impact at the site. Further, a dedicated system, which would need to include an air-stripping device (due to elevated dissolved hydrocarbon concentrations) would need to be installed at the site. Advanced GeoEnvironmental, Inc.