A "Screening Approach" for Nutrient Criteria in Virginia: Report of the Academic Advisory Committee for Virginia Department of Environmental Quality

Under the Clean Water Act (CWA), criteria are components of water quality standards that are intended to protect designated uses for waters of the U.S. Nitrogen (N) and phosphorous (P) (“nutrients”) are common water contaminants that challenge conventional methods for establishing water quality criteria for an essential designated use, the protection of aquatic life. Unlike many water contaminants for which criteria have been established, nutrients typically do not exert primary effects on aquatic life by acting as toxicants. Excess nutrients in freshwater streams stimulate growth of algae that can impair stream communities by causing oxygen depletion and through other pathways. Because excess nutrients in surface waters are well known as stressors that impair aquatic life and impact other uses, the U.S. Environmental Protection Agency (EPA) is requiring CWA agencies throughout the U.S. to establish criteria for nutrients. The Academic Advisory Committee (AAC) to the Virginia Department of Environmental Quality (DEQ) has recommended a screening approach for nutrient criteria in Virginia as an alternative to single fixed-concentration numeric criteria as is commonly employed for conventional toxicants. Here, we investigate the potential to establish nutrient criteria using a screening approach by seeking to derive screening parameters from analyses of Virginia DEQ water monitoring data.