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Geosyntec sands and gravels (USACE, 2013). As biosparge wells are operated over time, the groundwater within the injection ZOI,now with elevated DO concentrations,moves downgradient.This slower migration of DO downgradient of the biosparge point is not included as part of the well ZOI; however, these elevated DO concentrations are still expected to promote the biodegradation of sulfolane in groundwater beyond the initial ZOI. Because sulfolane is present in the highly transmissive zone, a ZOI ranging from 15 to 25 feet around the sparge point is expected.The ZOI may also be enhanced laterally by two factors: 1)the confinement of the transmissive zone by overlying lower-permeability silts and clays, which will likely limit vertical movement of the injected air; and 2)high groundwater velocity in the vicinity of the test areas due to ongoing pumping in the area. Therefore, placing the wells at different distances from each other allows for flexibility to conduct the pilot test with various groundwater flow directions and horizontal gradients. The proposed well layout at each PTA is shown on Figures 4a, 4b and 4c. Please note these well locations are approximate; exact locations will be adjusted in the field depending on access constraints and existing above-ground and underground utilities. Each of the proposed biosparge/observation wells will be screened to monitor and/or deliver air within the primary sulfolane transport pathway zone in the well-graded sand and gravel at depths of approximately 240 to 270 feet bgs. Using this pilot test well layout near the new supplemental characterization wells installed at locations 1, 2 and 3, Geosyntec will confirm biosparge ZOI, evaluate the persistence of DO, and confirm ability to aerobically biodegrade sulfolane. In addition, Geosyntec will evaluate effects of biosparging on geochemical parameters including ammonia, sulfate, nitrate and total and dissolved iron and manganese and aesthetic parameters such as color that may affect water quality. These data will help design potential future full-scale biosparge injection and monitoring well spacings. Based on the data and results of the ongoing laboratory microcosm study, it is possible that nutrient amendment (likely diammonium phosphate) and/or bioaugmentation (with sulfolane degraders from either the BSW area or a commercial culture) may be necessary to promote aerobic sulfolane degradation. Should this be necessary, Geosyntec would pursue the required Waste Discharge Requirement(WDR)approval. Operation and performance monitoring of the pilot test is initially proposed to be conducted for approximately 2 to 3 months to demonstrate feasibility of ISB at PTA A and B (and possibly PTA C),and to evaluate the need to optimize ISB for full-scale design, if necessary. If biosparging is successful, the pilot test may be extended coincident with development of a full-scale approach to offer continued protection of the downgradient supply wells. In-Situ Bioremediation Pilot Test Work Plan—GSH Lathrop 7