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mandated DPR to detect and regulate ground water contaminants. One aspect of DPR’s implementation of the PCPA is the creation of Pesticide Management Zones (PMZs) which are one square mile sections of land where one or more pesticides have been detected in ground water and where the contamination was determined to result from legal agricultural use. Agricultural uses of a subset of detected pesticides are allowed in PMZs, but a permit for use must be obtained from the County Agricultural Commissioner (CAC). Advisories outlining best management practices must accompany the permit. To date, pesticide use is regulated in 489 square miles of land designated as PMZs of which 311 are located in Fresno and Tulare Counties (Figure 1). The DPR, in cooperation with various universities, local and county agencies, and growers has conducted studies to determine the processes by which pesticides move to ground water. An empirical analysis of spatial vulnerability related pesticide movement to areas where coarse soils were predominant or to areas where soils contained a hardpan (Troiano et al., 2000). In the coarse soil condition, movement was related to leaching of residues from the soil surface. This is the most recognized process associated with movement of pesticides to ground water. I