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u � 30 March 2012 AGE-NC Project No. 97-0312 Page 4 of 8 Subsequent to the installation of the SVE wells, the well-head elevations and locations will be surveyed by a licensed surveyor. 2.3. HIGH VACUUM SOIL VAPOR EXTRACTION REMEDIATION The proposed remedial action includes the utilization of a high vacuum (20-25 inch Hg)soil vapor extraction (SVE) system intended to remove hydrocarbons from the vadose zone. Recovery of hydrocarbons from the subsurface is often difficult due to the fact that hydrocarbons can exist in the vapor-,dissolved-and liquid-phase and fine grained material are less permeable. High-vacuum (vacuum pump capable of producing 20 inches of mercury)soil vapor extraction systems are capable of removing both hydrocarbon vapors and, depending on site soil type and stratification, liquid and dissolved phase hydrocarbons. Extracted vapors may be treated by incineration in catalytic oxidation and later by carbon adsorption. AGE proposes to operate the SVE unit 24-hours daily to maximize the remediation potential; however, rebound evaluation will be required following successful progress of the hydrocarbon removal action.The HVSVE unit will be used to apply a vacuum to a minimum of five extraction wells at a time. The induced vacuum will be measured at a surrounding SVE well and several monitoring wells throughout the site. Additionally, the vapor concentrations from each extraction well, ground water depths and others SVE unit parameters (operation speed, air flow and vacuum) will be measured weekly during the start-up period. The extraction well vacuum, induced vacuum at monitoring points, extracted hydrocarbon concentrations and extraction flow rate will be measured at 30 minute intervals throughout the first day of operation and thereafter weekly. The data will aide to estimate the relative subsurface permeability for vapor extraction, radius of influence of the vapor extraction wells and the initial hydrocarbon recovery rate. Monitoring data from observation wells and the extraction wells will be collected on field logs. Data will facilitate in the evaluation of the SVE system and will be used to determine the number of vapor wells to operate and time line for modification of the SVE operation (e.g. catalytic oxidation to carbon adsorption). The SVE operation specifications are presented in Section 3.3. Four vapor samples will be collected from the extraction system during the first day of operation and thereafter semi-monthly. Sampleswill be collected at approximately two hour intervals on the first day.The samples will be collected in Tedlar bags and TO17 adsorbent charcoal tubes and stored in a cool container and transported under chain-of-custody to a CDPH-certified laboratory for analysis. Each vapor sample will be analyzed for: • Total petroleum hydrocarbons quantified as gasoline (TPH-g) in accordance with Advanced GeoEnvironmental,Inc.