Water Quality Data Assessment
What is the 303d list?
The 303(d) list is a list of Category 5 impaired waters that require a TMDL. If water quality data exceed a surface water quality standard the waterbody is considered impaired and can be assigned an integrated reporting category number of 5. The reporting of these impaired waters is required under section 303(d) of the Clean Water Act of 1972.
Does the 303(d) list show all impaired waters in the state?
No, the 303(d) list only shows category 5 impaired waters that require a TMDL. Category 4 waters are also considered impaired but either already have an EPA approved TMDL or fall into another category 4 description listed below.
What is an Integrated Reporting Category?
Integrated Reporting Categories represent varying levels of water quality standards attainment, ranging from Category 1, where monitored parameter(s) meets a water quality standard, to Category 5, where a pollutant impairs a water and a TMDL is required. Integrated reporting categories are based on EPA guidance. Each waterbody in North Carolina that has been assessed is assigned at least one of the following Integrated Reporting Categories. The North Carolina Integrated Reporting Category definitions can be viewed here.
Who collects the data?
Data used for water quality assessment is primarily collected by DWQ's Ambient Monitoring System, NPDES Discharge Monitoring Coalitions , and Biological Assessment Unit, the NC DENR Division of Environmental Health, and the United States Geological Survey. Local governments and environmental groups as well as industry, municipal and university coalitions also provide data. Submitted data sets must include an approved Quality Assurance Project Plan (QAPP) to assure that the data were collected in a manner consistent with agency data. A standing solicitation for data is listed below.
Where to find data
DWQ stores data from the Ambient Monitoring System on EPA's STORET online database. Guidance on how to search and download data is available on the DWQ AMS homepage.
How you can submit data
DWQ invites all interested parties to submit water quality data and information. The quality and reliability of data submitted determines the programs and projects for which the data can be used. DWQ uses only the highest quality data for regulatory decision-making and water quality assessment.IF YOU INTEND TO SUBMIT DATA FOR DWQ USE, PLEASE CONTACT US BEFORE BEGINNING DATA AND INFORMATION COLLECTION, TO ENSURE THAT WHAT YOU SUBMIT IS USABLE FOR ITS INTENDED PURPOSE.
What pollution sources are causing the impairment?
DWQ Basinwide Planning Reports are an excellent resource for finding detailed information on the probable sources of pollution for 303(d) listed waterbodies.
How are waters removed from the 303(d )list?
Waters are removed when either a TMDL is completed or when monitoring data shows that the waterbody is in compliance with water quality standards. Waters that are suspected to be impaired due to natural conditions may be removed with approval from the US EPA with appropriate documentation.
303(d) and Integrated Report Files