National USEPA Clean Watershed Needs Survey WWTP nutrient loads 1978 to 2012

This dataset contains tabular data for U.S. Environmental Protection Agencys (EPA) Clean Watersheds Needs Survey (CWNS) wastewater treatment facility information. Literature-based average total nitrogen and total phosphorous concentrations were substituted for wastewater treatment levels reported for each facility because little or no concentration data is reported in the CWNS. Concentrations were based on the treatment levels of raw, primary, secondary, and advanced. Concentration and effluent flow-value data gaps were filled in through simple linear assumptions, based on each facilitys responses to the survey in years bracketing the data gap or were based on an un-bracketed single year survey response. Unlike the McMahon and others (2007) method used to complete the EPA Permit Compliance System/Integrated Compliance Information System (PCS/ICIS) dataset where data from similar facilities was used to fill the data gaps, treatment level and flow data unique to each facility were used to complete the Clean Watershed Needs Survey dataset. [McMahon, Gerard, Tervelt, Larinda, and Donehoo, William, 2007, Methods for estimating annual wastewater nutrient loads in the southeastern United States: U.S. Geological Survey Open-File Report 2007-1040, 81 p., https://pubs.usgs.gov/of/2007/1040/] The Clean Watershed Needs Survey data were collected by the EPA for the years 1978, 1980, 1982, 1984, 1986, 1988, 1990, 1992, 1996, 2000, 2004, 2008 and 2012, and total nitrogen and total phosphorous loads were calculated using reported annual flows and nutrient concentration values substituted from literature for reported treatment levels from the CWNS. The long-term nutrient loads are provided as supportive information for studies being conducted by the USGS National Water Quality Assessment (NAWQA) Project.