Pesticides in selected water-supply reservoirs and finished drinking water, 1999-2000; summary of results from a pilot monitoring program

Abstract

In 1999, a pilot monitoring program was initiated by the U.S. Geological Survey and the U.S. Environmental Protection Agency to provide information on pesticide concentrations in drinking water and to assist in the implementation of the Food Quality Protection Act of 1996. Drinking-water utilities that withdrew from reservoirs were sampled because reservoirs are vulnerable to pesticide contamination, integrate pesticide loading from their watersheds, and show smaller temporal variations than streams. Sampling frequencies were designed to measure long-term mean and short-term peak concentrations of pesticides in drinking water. Samples were collected quarterly throughout the year and at weekly or bi-weekly intervals following the primary pesticideapplication periods. Water samples were collected from the raw-water intake and from the finished drinking-water tap prior to entering the distribution system. At some sites, samples were also collected at the reservoir outflow.Twelve water-supply reservoirs were sampled, ranging in size from 120 to 92,600 acre-feet normal capacity, with contributing watersheds ranging from 3.3 to 784 square miles. The sites are in California,

Water‐soluble pesticides in finished water of community water supplies

“…The systems also exhibited variation in both their method of disinfection and the point in the treatment process where disinfection occurred. The method of filtration as well as the type of adsorption also varied among systems in this study, and some of these processes varied seasonally at certain facilities (Blomquist et al, 2001).…”

“…), Waxahachie Water Treatment Plant (Texas), and Western Berks Water Authority (Pa.). Ten of the sites were selected to represent agricultural land use, with total agricultural land ranging from 24.4 to 94.9% of the surrounding watershed (Blomquist et al, 2001). The other two sites (Elsinore and Edmond) were selected because urban areas were deemed to be the predominant influence on the water quality in these basins.…”

“…*Table modified from Blomquist et al (2001) who conducted interviews with the plant staffs to determine treatment stages.…”

“…In order to adequately compute exposure levels of the general population to pesticides, USEPA needs information on pesticide concentrations in drinking water on a national scale. However, there are only a few data sets that contain information on pesticide concentrations in drinking water, and these generally cover only selected compounds or local areas (Blomquist et al, 2001).…”

“…The study focused on the occurrence and distribution of 43 water‐soluble pesticides and 4 pesticide degradates in the source and finished water of 12 community water systems (CWSs) in the United States and compared pesticide concentrations in source waters with pesticide concentrations in finished waters (after the treatment process). A detailed description of the sampling methods, frequency, and quality‐assurance and quality‐control procedures as well as a more thorough discussion of the treatment processes and the chemical and physical properties of the source water can be found elsewhere (Blomquist et al, 2001).…”