STOCHASTIC APPROACH TO DELINEATING WELLHEAD PROTECTION AREAS

Delineating the wellhead protection area (WPA) is a vital component in the development of a comprehensive wellhead protection program. WHPA is a series of computer programs developed for the U.S. Environmental Protection Agency to delineate WPAs. In the state of Tennessee, the WP A is delineated using a two-dimensional particle tracking code (GPTRAC ) in a leaky-confined aquifer, or a modified containment front trackin g code (RESSQC) in an unconfined aquifer. Both WHPA delineation method s require constant values for all model parameters. To overcome the di fficulty of estimating values for each input parameter and to provide some measure of the uncertainty in the size and shape of wellhead prot ection zones, the Environmental Protection Agency WHPA models are inte grated into a parallelized Monte Carlo (MC) simulation. The MC-WHPA mo del is used to compute a discrete two-dimensional cumulative distribut ion function for a WPA. MC-WHPA uses a parallel virtual machine comput ing environment developed over a network of computers. The MC-WHPA mod el is used to delineate the wellhead protection and management zones f or two wellfields in western Tennessee.