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N 30 January 2014 AGE Project No . 99-0682 Page 18 of 28 11 . 2 , DUAL PHASE EXTRACTION Dual phase extraction (DPE), or high vacuum groundwater extraction is a technology that simultaneously recovers adsorbed hydrocarbons from the vadose zone and the saturated zone subsurface by locally extracting groundwater and lowering the groundwater level to expose previously submerged soil strata to a high vacuum . 11 .2 . 1 . Principles Recovery of hydrocarbons from the saturated subsurface is often difficult due to the fact that hydrocarbons can exist in the vapor-, dissolved- and liquid-phase . Liquid-phase hydrocarbons both dissolve into ground water, and adsorb and/or vaporize into pore spaces between sediment grains . Dissolved phase hydrocarbons also vaporize into pore spaces until equilibrium is established between the liquid , dissolved , and vapor phases . Remediation methods effective in treating one phase may not be efficient for the remediation of other hydrocarbon phases. High-vacuum (vacuum pump capable of producing 25 to 30 inches of mercury) DPE systems are capable of removing both hydrocarbon vapors and , depending on soil type and stratification , capable of removing liquid and dissolved phase hydrocarbons. DPE- vapors may be treated by catalytic oxidation , thermal oxidation , or by vapor phase carbon bed filtration , while DPE-groundwater are typically treated on-site utilizing an air stripper or carbon media vessels , and discharged on-site to the sanitary sewer. Alternatively, impacted groundwater may be stored on-site in a temporary tank for later recycling . 11 .2.2. 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. The site conditions , which include buried (below water table) adsorbed soil impact, fine grained lithology in both the smear and saturated zones and the current water table depth make dual phase extraction a moderately favorable remedial alternative for the site . Advanced GeoEnvironmental, Inc.