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r Geosyntec untiultam" 3. PILOT TEST OBJECTIVES AND APPROACH The primary objectives of this pilot test are to: 1. Demonstrate that ISB using biosparging can aerobically biodegrade sulfolane in groundwater near the BS W, the PS W and potentially upgradient of LWD-10; and 2. Determine design parameters (e.g., zone of influence, well spacing, air injection rates) required for full-scale design and implementation of biosparge barriers that can prevent further migration of sulfolane towards the supply wells. Based on historical Site data and preliminary results of the ongoing supplemental characterization, ISB pilot testing is proposed to be implemented at up to three locations. Pilot testing will be initially implemented near the BSW / Location 3 of the ongoing supplemental characterization (Figure 4a; Pilot Test Area A)and near the PSW/Boring Location 2 of the ongoing supplemental characterization(Figure 4b; Pilot Test Area B). Both tests will target the transmissive well-graded sand and gravel zone immediately above the Corcoran clay,at depths ranging from approximately 240 to 270 feet bgs. Pilot testing may also be conducted at Location 1 upgradient of LWD-10 (Figure 4c; Pilot Test Area Q. An initial groundwater sample from Location 1 did not contain sulfolane above its detection limit (<3.3 µg/L). When LWD-10 is not operating and LWD-6 is operating (the current condition), the hydraulic gradient in this area is generally to the north. Should sulfolane be detected at Location Ithen pilot testing at Pilot Test Area C would likely be initiated. Because the groundwater flow direction varies depending on which water supply wells are operating in the area, Geosyntec is proposing to install three pilot test wells at each pilot test area (PTA). Installation of the wells at PTA A and B will proceed upon receipt of necessary approvals. Installation of wells at PTA C would proceed if pilot testing is required, as discussed above. The wells will be spatially arranged so that the pilot test can be conducted using any one of the wells as a sparge point and the other wells as observation wells to evaluate zone of influence(ZOI)and biosparging performance, depending on groundwater flow direction at the time of the test. As air(or oxygen-enriched air') is introduced to the subsurface through a biosparge well,air flows into the pore space of the soil. At the air-water interface within the pore space, oxygen dissolves from the air into the groundwater. Therefore, in biosparging applications, rapid increases in dissolved oxygen (DO) are used to approximate the ZOI of a biosparge well. According to the United States Army Corp of Engineer's (USACE) guidance for in-situ air sparging and biosparging, the ZOI for dissolved oxygen from biosparging can range from 5 feet in dense, low- permeability soils composed of silts and clays to 25 feet or more in transmissive soils comprising Atmospheric air contains approximately 21%oxygen by volume.Oxygen-enriched air produced by an oxygen generator typically contains 85-95%oxygen by volume(this is achieved by removing nitrogen from atmospheric air through adsorption via Zeolite).The use of oxygen-enriched air allows for efficient delivery of oxygen to the subsurface for aerobic degradation. In-Situ Bioremediation Pilot Test Work Plan—GSH Lathrop 6