303(d) Impaired Waterbodies List

303(d) list reporting is required under Section 303(d) of the Clean Water Act. 

The 303(d) list is comprised of category 5 waters of the water quality assessment. Category 5 waters are those that require a TMDL or TMDL alternative. These Category 5 waters are assembled in a single document (the 303(d) list) and sent to EPA on April 1st of every even numbered year, per 40 CFR 130.7. EPA must approve, disapprove, or partially approve each 303(d) list. 303(d) files can be found here.

For information on the broader water quality assessment please visit the water quality assessment page

What are impaired waters? 

Impaired waters are where water quality samples for a particular parameter on a waterbody exceed water quality standards and the assessment methodology has determined that the waterbody is indeed impaired for the particular parameter. Impaired waters are grouped into two categories:

  • Category 4 assessments are those that do not need a TMDL, these are not included in the 303(d) list.
  • Category 5 assessments are those that do need a TMDL and this is the 303(d) list.

How are water quality standards made and do they change?

To learn about all about water quality standards please visit the water quality standards page.

How is the assessment methodology made and does it change?

The 303(d) listing methodology is a subset of the overall assessment methodology. The overall assessment process is set to be consistent with North Carolina water quality standards and EPA guidance. For more information on the overall assessment process and data collection click here.

How are waters removed from the 303(d )list?

Waters are removed when either a TMDL, or TMDL Alternative, 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.