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i L ameO Lvalve, and flow meter as shown in Figure 4 Temporary aboveground piping connections will be used during the pilot scale test. The AS well head will be fitted with a tee to allow for air Linjection from the side and a threaded plug on the top to allow access for sampling or gauging. The blower will be capable of injecting a minimum airflow of 10 standard cubic feet/minute (scfm) and 25 pounds per square inch gauge (psig). L 4.4 PILOT TEST PROCEDURES LA step rate and constant rate test will be conducted at AS-1. Initially, a step rate test will be conducted by injecting air into the AS well at increasing flow rates (or steps). The first step in the step rate test will be conducted at the minimum pressure necessary to induce flow into the subsurface. This step will continue at this flow rate until pressure and flow rate readings have stabilized or for 2 hours, whichever occurs first. Following the initial step, three additional steps will be conducted at various pressures between the minimum pressure to induce flow and the maximum pressure of the compressor. LFollowing completion of the step rate test, the air injection flow rate and the injection pressure from each step will be compared to determine the optimal flow rate. The optimal flow rate is considered to be the point at which the air injection flow rate continues to increase steadily, with only a minimal increase in injection pressure. A 12-hour constant rate test will then be conducted at the selected optimal flow rate. The following field parameters will be measured Lin the field during both the step rate and constant rate test in accordance with Table 2: • Injection air pressure; L • Air injection flow rate; • Groundwater elevations in observation wells; • Dissolved oxygen (DO) in the AS and observation wells; LOxygen reduction potential (ORP)the AS and observation wells; • PID readings in observation wells; and • Helium in the observation wells (discussed in the following section). 4.5 HELIUM TRACER TEST Lab grade helium will be used as a tracer gas to identify the extent in`which injected air moves in the subsurface. During the constant rate test, helium will be mixed with air being injected at LAS-1 through a manifold at the well head (Figure 4). Helium will be added to the injection air stream at an appropriate rate to achieve a helium concentration of approximately 1 percent by AMEC Geomatrix, Inc. P:\Project\14000s\14443_Caltrans\TO 10\11000_PLANSWS WP—March 2010\AS WP.doc - 13