ECONOMICS OF SCREENING FOR PESTICIDES IN-GROUND WATER

In the United States, millions of dollars are currently spent to monit or water quality for a whole suite of organic compounds. However, resu lts of several surveys conducted in the past decade indicate that only a few pesticides occur in a small proportion of wells. Screening meth ods based on historical evidence of contamination patterns and knowled ge of the locales will have significant potential to reduce these cost s and effectively identify contamination problems. In this paper, the economics of utilizing two screening methods, sequential analysis and sample compositing, in the design of monitoring strategies is captured in the form of mathematical models and illustrated for a state-level monitoring program. When the two methods are adopted, the total analyt ical cost to conclusively identify contaminated wells in a network of 4,000 wells is shown to range from $12,500 to $1,575,000 depending on the extent of contamination. In contrast, the total analytical cost of a conventional program where all the wells in the network are sampled and tested for a standard suite of pesticides at a cost of $250/sampl e is one million dollars. Given such wide range in costs, it is pruden t to incorporate the screening concepts presented in this paper in the development of cost-effective monitoring programs.