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The constant rate tests will allow collection of the following information: • Vacuum under steady-state conditions and radius of influence • Air permeability of the vadose zone • VOC concentrations and removal rate to design the vapor treatment system(for sizing of the granular activated carbon units for the permanent system). Constant-rate tests will be run longer than step tests (several hours to one day) to ensure transient effects are no longer present. The constant rate test will last until pressure has equilibrated at the observation wells. Generally equilibrium is reached rapidly(within minutes) but could take up to several hours. If equilibrium is not reached after several hours, a decision regarding the benefits of running the test for a longer period will be made in the field. The frequency and parameters measured during the constant rate test will include: • Air pressure/vacuum (every minute for first 10 minutes, every 5 minutes for next 20 minutes, then hourly in the SVE extraction and observation wells) • Air flow rate and temperature (every 30 minutes in the extraction wells) • Oxygen and carbon dioxide levels (every 30 minutes in the extraction wells) • Organic vapor concentrations (hourly in extraction and observation wells, and every 30 minutes in the blower effluent) • VOC concentrations (once at the end of the test of each SVE well and from the GAO effluent) • VOC samples will be collected in Tedlar bags or Summa canisters and analyzed for VOCs using USEPA Test Method TO-15. Laboratory samples will comprise a minimum of 10% of the number of field measurements. M ain\D:AEnvironmenta1\LN CV\10152007.wpd 55