North Carolina addresses nutrients using several strategies, including specific criteria and special programs, special use classifications, and basin management plans to achieve restoration and protection of lakes and reservoirs. This approach provides the flexibility necessary to develop management strategies for the wide variety of responses to nutrient loading seen in the state’s lakes and reservoirs.
In the 1970s, North Carolina adopted a chlorophyll a standard of 40 µg/L for warm waters and 15 µg/L for cold waters as part of its water quality standards. The state included a narrative that allows prohibition or limitation of any discharge into surface waters that would contribute to exceedances of the chlorophyll a standard.
North Carolina also established an algal bloom program that studies phytoplankton, chlorophyll a, nutrients, and other parameters from lakes, reservoirs, and slow-moving rivers throughout the state. Data collected through the program resulted in a legislative ban on phosphate detergents for the entire state.
The development of the Nutrient Sensitive Waters (NSW) supplemental classification allows the state to control point and nonpoint source nutrient inputs upstream from a priority water body through rule-making. There are six areas that have been declared NSWs in North Carolina.
In addition, North Carolina is addressing eutrophication of its waters within the basinwide water quality management process and plans. For example, to address eutrophication in Lake Wylie, the state adopted a point and nonpoint nutrient control strategy for the Lake Wylie watershed. The basis for those actions was the chlorophyll a standard and its caveat allowing the director of the Division of Water Quality to require nutrient controls at his or her discretion (USEPA 2000a).
Reference:
USEPA. 2000a. Nutrient Criteria Technical Guidance Manual: Lakes and Reservoirs. EPA-822-B-00-001. U.S. Environmental Protection Agency, Office of Water, Office of Science and Technology, Washington, DC. Accessed October 2016. https://nepis.epa.gov/Exe/ZyPDF.cgi/20003COV.PDF?Dockey=20003COV.PDF.