Development of Salmonid-Specific Water Quality Effects Thresholds to Evaluate Wastewater Impacts. D. Lester, J. Simmonds, B. Cooper, D. Williston, and C. Wisdom; King County Department of Natural Resources and Parametrix, Inc.
Water quality criteria (WQC) developed under the Federal Clean Water Act are intended to protect aquatic resources. Due to the complex life history of salmonids (e.g., smoltification, migration), however, there is a growing concern these criteria may not be sufficiently protective of species listed as threatened or endangered under the Endangered Species Act (ESA), which mandates no "harm" may come to these species. King County, which includes the metropolitan Seattle area, is in the process of developing a Habitat Conservation Plan for wastewater discharges, for which impacts to ESA listed salmon are a key concern. To determine if constituents associated with wastewater effluent discharge have the potential to adversely impact salmonids, salmonid-specific water quality effects thresholds were developed using available data from the scientific literature. Development of these thresholds involved a two step process that included an initial screening using conservative assumptions, followed by a more detailed assessment. Salmonid-specific water quality thresholds were developed for 25 of 137 constituents detected in secondary treated effluent. These thresholds were then applied to site specific exposure concentrations of constituents expected to be present in wastewater discharges. In most cases, salmonid-specific water quality effects thresholds were not lower than current water quality criteria.
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