Probabilistic Hazardous Materials Contamination Model for a Municipal Water Source

Abstract

In 1997 conditional probability was used to assess the frequency of contamination of the Truckee River by hazardous material (hazmat) released during a rail or highway accident. A Great Basin stream originating at Lake Tahoe, Calif., and terminating at Pyramid Lake, Nev., the Truckee River is the principal water source for the Reno–Sparks (Nev.) metropolitan region. The 1997 probabilistic assessment was based on sparse to nonexistent data for accident frequency and other factors. Assumptions made during the 1997 study were reassessed in 2007 using a significantly more comprehensive database for rail and highway accidents and hazmat incidents. The 2007 assessment confirmed that estimates of hazmat contamination probability (likelihood) were reasonable and even low. Consequently, the operational plan to be implemented, should a hazmat contamination occur, relies on estimates of arrival times coupled with the ability to shut down water treatment plants and rely on groundwater resources during such an emergency.