SITE VULNERABILITY ASSESSMENT FOR WELLHEAD PROTECTION PLANNING

A methodology is presented for assessing the relative risk of a given chemical inventory to produce a ground-water contamination event in accordance with wellhead protection (WHP) planning. Modeled after the U.S. Environmental Protection Agency's hazardous ranking system, the approach is one based on a vulnerability assessment incorporating factors for chemical quantity, storage, toxicity, and fate and transport characteristics. The ground-water vulnerability scoring system (GVSS) tool provides a means for ranking the various chemical holders within a delineated WHP (capture) zone with respect to their likelihood to produce a ground-water contamination event. The information generated by GVSS may be useful to land-use planners and water quality regulators in the development of future planning of commercial/industrial activities within a delineated WHP area and is a valuable tool for educating the general public regarding the issues of long-term preservation of the quality of ground-water supplies. In highlighting the utility of the tool, an application is presented using select contaminant holdings located in Spokane County, Washington.