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h) Are monitoring points distributed adequately in cross section to determine if sufficient air contact is achieved in <br /> all three dimensions? (In most cases, monitoring points set at multiple depths are needed to venfy vertical air <br /> distribution) <br /> i) Are measurements of water table fluctuations made to determine the possible effects on the ISAS system <br /> performance?Are these measurements made with adequate frequency9 <br /> ,1) Have tracer tests been conducted to verify air flow paths and adequate travel tunes/velocities <br /> 5) Performance Analysis Calculations <br /> Every system is different and the evaluation of the performance data must be made with the specific objectives and <br /> system configuration in mind The following are general considerations that are common to most ISAS systems <br /> a) Prepare hydrogeologic cross sections using available well/boring logs, including the spargmg wells, if no cross <br /> sections of the area of concern are available Evaluate the potential for preferential flow paths or hydrogeologic <br /> boundaries not considered in design and which may affect system performance <br /> b) Prepare air flow versus time graphs for each injection well to determine if past flow rates differ significantly <br /> from current conditions <br /> c) Construct ground water concentration versus time graphs for the contaminants of concern at each monitoring <br /> point Have individual monitoring points reached a consistent asymptote on the concentration versus time graph <br /> without significant rebound? ( Significant rebound" might be defined as an increase of 25-50%above the <br /> asymptote concentration value at the time of shutdown of the sparging system) <br /> d) Construct ground water contaminant concentration isopleth maps of the site Do the contaminant concentrations <br /> indicate that the treatment is effective throughout the target zone? <br /> 6) Adequacy of Operations and Maintenance <br /> a) Has the entire system been operating with enough consistency to achieve its objective in a reasonable time? (A <br /> good operational target should be 90%uptime or better) <br /> b) Are the monitoring points constructed to yield reliable results (e g , short screens, checked for <br /> plugging/response)? <br /> 06/07/99 <br /> Page 3 of 6 <br />