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5) Performance Analysis Calculations <br /> a) Prepare vapor flow rate versus time graphs for each extraction well Are the vapor extraction <br /> rates the same as those in the design specifications? Have the vapor extraction rates changed <br /> since the initial period of operation? <br /> b) Construct vacuum isopleth maps of the site Is the vacuum distribution consistent with that <br /> predicted during design?Does the vacuum distribution (in three dimensions) indicate capture of <br /> vapors and prevention of migration to receptors9 <br /> c) Are monitoring points distributed adequately to determine vacuum distribution, flow paths, or <br /> containment? Are monitoring points distributed adequately to determine if adequate air flow or <br /> vapor capture is achieved in three dimensions9 (In most cases, vacuum monitoring points set at <br /> multiple depths are needed to verify vertical flow components) <br /> d) Construct concentration versus time graphs for all contaminants of concern in each extraction <br /> well Construct isopleth maps of the current soil gas concentrations for each contaminant of <br /> concern Have contaminant concentrations been declining in most of the target zone? <br /> e) Have individual wells or the system as a whole reached a consistent asymptote on the <br /> concentration versus time graph without significant rebound? ("Significant rebound" might be <br /> defined as an increase of 25-50% above the asymptote concentration value) <br /> Q Are the well depths and screened intervals adequate to optimally direct air through the target <br /> zone? Is there evidence of preferential flow paths or hydrogeologic boundaries that were not <br /> considered in the system design? (Prepare hvdrogeologic cross sections using available well <br /> boring logs, including the extraction wells, of cross sections of the area of concern are not <br /> available) <br /> 06ro7r9g <br /> Page 4 of 8 <br />