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A Wellhead Protection Area (WHPA) is the surface and subsurface area, delineated by fixed radius, hydrogeologic/geomorphic mapping, analytical, semi-analytical or numerical flow/solute transport methods, which contributes water to a PWSS well and through which contaminants are likely to move through and reach the well over a specified period of time. The delineation of the WHPA is based on the physical processes governing ground water flow. The Indiana WHPA delineation is based on time of travel (TOT) criteria or distance criteria. The TOT is the distance traveled by a drop of water through an aquifer to the well or well field for a specified period of time. The TOT for calculating the WHPA is determined by the PWSS, with a minimum five year TOT allowed. The WHPA size and shape will vary, depending on hydrogeological features, including ground water divides, surface water features, hydraulic gradient, and specified TOT. |