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program and plotted against time. <br /> Step Testing <br /> The vacuum step test is designed to test a range of vacuum that can be imposed on the vadose zone <br /> extraction wells and to observe the vapor flow rate and vacuum radius. The goal is to determine the <br /> optimal vacuum to be used for the constant rate test. <br /> During the step test,a vacuum will be applied and gradually increased while monitoring the response <br /> at nearby observation wells. Vacuum and flow rate will be monitored at least every 15 minutes as <br /> the responses stabilize. The vacuum will be maintained constant until the recorded flow rate is <br /> maintained constant for more than one minute.The applied vacuum will be incrementally increased <br /> until the maximum blower capacity has been reached. <br /> The frequency and parameters to be monitored during the step test are: <br /> • Air pressure vacuum (every minute for first 10 minutes, every 5 minutes for next 20 <br /> minutes, then every 30 minutes in the SVE extraction and observation wells) <br /> • Air flow rate (every 30 minutes in the SVE wells) <br /> • Oxygen and carbon dioxide levels (every 30 minutes in the extraction well) <br /> • Organic vapor concentrations (every 30 minutes in extraction well) <br /> • VOC concentrations (at the end of extraction well step test) <br /> • VOC samples will be collected in Summa canisters and analyzed by for VOCs using <br /> USEPA Test Method TO-15. <br /> Constant Rate Test <br /> Constant-rate SVE testing will be performed in each of the four dual zone pilot test areas. Constant- <br /> rate testing will be used to evaluate the actual area of influence and efficiency of a SVE well or <br /> combination of wells for various test configurations. The blower vacuum setting for each test will <br /> be determined based on the highest flow rate determined from step-testing in the same area. <br /> M ain\D:AEnvironmentaI\LN CV\10152007.wpd 54 <br />