The half-acre Vancouver Water Station #4 (WS4) site is a public water supply wellfield in Vancouver, Washington, located a half-mile north of the Columbia River. The wellfield has been owned by the city for over 50 years. The site is defined as the wellfield and includes several support buildings, six production wells, two air stripping towers and one capped well. In 1988, the Washington State Department of Health sampled the production wells at WS4 under guidelines provided by the Safe Drinking Water Act (SDWA) and discovered perchloroethylene (PCE) at levels exceeding federal standards. The sample also showed very low levels of other volatile organic compounds (VOCs). The city took WS4 out of service in October of 1989. Dry cleaners are a suspected source. Following construction of the site�s remedy, operation and maintenance activities and monitoring are ongoing.