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-- -"SOMA Working To Restore Nature in the evaluation of the significance of water-level changes observed during the later pumping test. The analysis of the pumping data from the site yields the following conclusions: o The water-bearing zone from approximately 48 to 60 feet bsg is heterogeneous, anisotropic, and unconfined o The transmissivity of this zone is approximately 0.1 to 0 2 feet/minute and the specific yield is approximately 1 to 3 percent. o The production well exhibited negligible non-linear head losses, suggesting a high ' efficiency and proper design. o The groundwater gradient at the site is irregular and has shifted in magnitude and direction. Therefore, calculation of a steady state capture zone is not valid. To evaluate remediation feasibility, a conservative approach, which greatly underestimates potential capture zone, was used This approach uses the steepest observed gradient moving away from the tank area (0.04 in a northeast direction) which yields an estimated limit of the steady-state capture zone downgradient of well RW-1 of 12 feet for a pumping rate of ' 3.5 gallons per minute (gpm). It is likely that the gradient direction reversals observed at the site over four separate monitoring events result in an average annual gradient that is relatively flat. This would result in a much larger potential capture zone. Longer ' term static monitoring at the site would be needed to define the capture zone more precisely. ' 4.0 SUMMARY OF SOIL AND GROUNDWATER CONDITIONS 4.1 Extent of Hydrocarbon-Lnpacted Soil ' The lateral extent of gasoline hydrocarbons in soil is delineated by borings B-6 and B-7 on the ' west, boring B-5 on the south, boring B-4 on the east, and boring B-15 on the north. The highest concentrations of residual gasoline hydrocarbons appear to be north and west of tank T3, ' from approximately 15 feet bsg to the top of the groundwater surface (42 feet bsg). 38009-88009-8 FRP 9 1