9753074 Hering The "provision of safe, palatable, and ample public water supplies", a core mandate of the environmental engineering profession, has always been particularly challenging in the arid southwestern United States. In contrast to the past focus on delivery of water, which has been manifested in the western U.S. in massive hydraulics works, the present regulatory climate emphasizes water quality. Increasingly stringent drinking water standards place an increased burden on municipalities and water suppliers; this problem can be particularly severe for groundwater systems, which have traditionally required minimal treatment of source waters. A specific example of this problem is provided by the City of Hanford, CA population ca. 39,000), which relies on groundwater for its municipal water supply. Elevated concentrations of arsenic occur naturally in the groundwater at Hanford. Arsenic concentrations in local wells frequently exceed the current drinking water standard (50 g/L); compliance with the standard is achieved, in the average, by dilution within the distribution system. The proposed project will focus on the Hanford groundwater supply system as a case study of the issues that are likely to become increasingly prevalent in the future of water supply in the U.S. Specifically, the project will emphasize the issues of risk estimation and compliance options within the framework of both the regulatory drivers and the physical constraints of the local hydrogeology and the existing distribution system. ***
