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0 0 These measurements will be taken from the onsite wells that are part of the pilot test, including SP -1, MW-4RS, MW-4RD, MW -7S, MW -8I, MW -11D, and VW -2D. Shallow wells VW -1S, VS -2S, and VS -3S will also be checked for helium gas and vapor concentration. 4.2.1.2 Biosparge R0/ Test Upon completion of baseline measurements, testing will begin with airflow injection into the groundwater aquifer at SP -l. To avoid potentially over -pressurizing the aquifer, the initial injection pressure will be set to slightly above the hydrostatic pressure exerted at the well. Based on the average groundwater level observed at the site, the hydrostatic pressure at the test well SP -1 is expected to be approximately 10 psig. The first part of the pilot test will be the step pressure test. This test involves taking measurements at three injection pressure levels. The initial test pressures are 10, 15, and 20 psig; the higher pressure levels may be subjected to changes based on the results of the lower pressure tests. Each test will run for up to two hours or when the DO reaches a constant level in three consecutive measurements at the primary observation well at least 10 feet away from the sparge well, whichever occurs first. As previously noted, the initial pressure will begin around 10 psig. ' During each test, DO and water level from MW-4RS, MW-4RD, MW -7S, MW -8I, MW -11D, and VW -2D will be recorded at the following frequencies: II • 15 minutes for the first hour • 30 minutes thereafter for the second hour Measurements of wellhead vapor concentrations, helium gas concentrations, and air pressure will also be taken at VW -1S, VW -2S and VW -3S and recorded at the same frequencies. After completion of the step test, a constant rate test, in which air will be injected at the test well at a constant pressure and flow rate, will begin. The constant rate test will run for about 4 to 8 hours depending on the data stability observed throughout the first 4 hours. The test pressure will be determined based on the step test results. During the constant rate test, the same measurements will be taken but less frequently, usually once every hour or so. 4.2.1.3 Post -Test Measurement After completion of the constant rate test (i.e., immediately after shutdown of the air injection system), one round of field measurements will be taken from the same wells from which baseline data have been collected. These post-test measurements include: • Helium gas concentration (in headspace) • Well water level • Wellhead vapor concentration (by PID) Biosparge Pilot Test Final. doc 4-3 Shaw Environmental, Inc.