South Carolina 303(d) List of Impaired Waters & TMDLs | South Carolina Department of Environmental Services

South Carolina's Draft 2024 List of Impaired Waters

The South Carolina Department of Environmental Services (SCDES) is updating its list of impaired waterbodies requiring TMDLs pursuant to Section 303(d) of the Federal Clean Water Act. The list includes waterbodies not meeting the State’s water quality standards after application of existing required controls for point and nonpoint sources of pollution.

The public comment period for the draft list, methodology and restoration priorities closed August 12, 2024, and SCDES is no longer accepting comments. The final list will be posted upon approval by USEPA.

Water Quality Information Tool

This application can assist stormwater managers in preparing a Notice of Intent (NOI) for stormwater management planning. Use this tool in conjunction with the statewide list of Sites Covered Under an Approved TMDL and Corresponding WQ Attainment Status (pdf) to determine the water quality attainment status at each monitoring location. This application and table are updated as TMDLs are approved and as changes in water quality status are determined.

SC Watershed Atlas

The Watershed Atlas brings 90 layers of the Agency's most current watershed and water quality information into a user-friendly application. This searchable atlas includes watershed boundaries, Bureau of Water permits, advisories, public water supply, water quality monitoring stations and assessments, water classifications, floodplains, Municipal Separate Storm Sewers (MS4s), TMDL information, and more.

303(d) List of Impaired Waters

Development of the 303(d) List

South Carolina's 303(d) Lists, 305(b) Report, and Supporting Documents

Water Quality Standards, Classifications, and Designated Uses

Total Maximum Daily Loads (TMDLs)

Approved TMDLs

TMDLs Under Development

Implementation of TMDLs

TMDLs and Stormwater Permittees

Contacts

303(d) List of Impaired Waters

The 303(d) list is a list of water quality sampling sites where water quality standards have been violated. South Carolina, along with all other states, is required to update this list of impaired waterbodies every two years. This requirement comes from Section 303(d) of the Clean Water Act, hence the common name for the list. The purpose of the list is to identify impaired waters so that the sources of the impairments can be described, and corrective actions can be developed to improve water quality. You may also see the 303(d) list referred to as The Integrated Report (IR). The IR includes both the 303(d) list (IR Part I) and the 305(b) report (IR Part II). The 305(b) report is an overview of the health of the state’s waters. It makes use of the same data used to compile the 303(d) list. Links to current and past 303(d) lists and 305(b) reports may be found below.

Development of the 303(d) List

The 303(d) list is compiled using five years' worth of water quality sampling data. For the 2024 list, data from 2018-2022 were used. SCDES developed the methodology used to assess these data and it has been approved by EPA Region 4. Every two years, the assessment methodology is reviewed and updated as needed and it is available for public comment, along with the 303(d) list.

Data Sources

SCDES requests and considers all existing and readily available water quality data, including non-SCDES data, in developing South Carolina's 303(d) list. Outside data (not sourced from SCDES) are accepted for consideration at any time during the listing cycle; however, only data submitted before May of each odd-numbered year will be considered for the following year's 303(d) list (for example, data for the 2026 list must be submitted by May 1, 2025). To be considered for the 303(d) list, data must be representative of current water quality conditions and comparable to state water quality criteria. Organizations submitting data should use laboratories certified by the SCDES Office of Environmental Laboratory Certification for the test methods used.

Non-SCDES data should be accompanied by an approved quality assurance project plan (QAPP). If you wish to collect water quality data for SCDES to use in developing the 303(d) list, you are encouraged to contact the Department’s Quality Assurance Manager for more information on developing a QAPP prior to initiating sampling.

If you have data that you would like SCDES to consider in developing South Carolina's 303(d) list, please e-mail Susan Waldner. Data must be submitted electronically using an appropriate format. See Data Template (xls) for a downloadable Excel file.

Removal of Sites from the 303(d) List

If a water quality sampling site has been included on the 303(d) list, it will need to meet one of three criteria to be removed from a subsequent list:
1.    The state’s water quality standard has been attained at the sampling site
2.    The site was listed in error
3.    A Total Maximum Daily Load (TMDL) has been developed and approved

TMDLs must be developed and approved by EPA for all sites listed on the 303(d) list unless they are removed for one of the first two reasons above. Sites that have been included in a TMDL are not listed, even if they have still not attained the water quality standard.

South Carolina's 303(d) Lists, 305(b) Report, and Supporting Documents

Supplement Pb Technical Document to the 2018 303(d) List - January 2020 (pdf)
Supplement Pb Technical Document Update to the 2018 303(d) List - October 2020 (pdf)

Supplement to the 2000 303(d) List - January 2001 (PDF)
Supplement concerning Enoree River (BE-017) - October 2001 (PDF)
Supplement to the 2000 303(d) List - January 2002 (PDF)

1998 303(d) List (pdf)

Water Quality Standards, Classifications, and Designated Uses

Water quality standards for South Carolina (R.61-68 and R.61-69) are promulgated by the SC General Assembly, approved by EPA, and implemented by the South Carolina Department of Environmental Services. The standards are designed to protect water quality for the waterbody’s designated uses.

Federal water quality standards regulations require that States, Tribes and Territories specify appropriate water uses to be achieved and protected. Appropriate uses are identified by taking into consideration the use and value of the waterbody for public water supply, for the protection of fish, shellfish, and wildlife, and for recreational, agricultural, industrial, and navigational purposes. Some of the designated uses we protect are:

•    Contact recreation (swimming or primary and boating/wading or secondary)
•    Aquatic life (the survival and propagation of a balanced indigenous aquatic community of fauna and flora)
•    Shellfish harvesting and crabbing
•    Fish consumption
•    Drinking water supply

When a waterbody does not meet the water quality standard set to protect these uses, we say the use is ‘not supported’ and the water quality monitoring site is listed on the 303(d) list for the pollutant that is exceeding the standard.

Total Maximum Daily Loads (TMDLs)

A Total Maximum Daily Load, or TMDL, is the maximum amount of a pollutant (such as bacteria, nutrients, or toxics) that can enter a waterbody on daily basis without exceeding the water quality standards set by the State. The development of TMDLs is a requirement of Section 303(d) of the Clean Water Act. If a site is included on the 303(d) list of impaired waters, a TMDL must be developed for the pollutant(s) at that site. In South Carolina, TMDLs are developed by SCDES, made available for public review and comment, and then forwarded to EPA Region 4 for final approval.

The term "TMDL" refers to both the calculation of the current and allowable amount of pollutant entering a waterbody and the document that describes these calculations, along with pollutant source assessments, watershed and land use information, and the percent reduction goals, load allocations, and general implementation information required to restore water quality.

TMDLs are calculated as the sum of the allowable loads of a single pollutant from all contributing point and nonpoint sources. TMDLs also include a margin of safety. The margin of safety provides assurance that the TMDL will protect water quality despite any uncertainties in the calculations.

Expressed mathematically, the TMDL equation is:

TMDL = ΣWLA + ΣLA + MOS

WLA is the wasteload allocation, LA is the load allocation, and MOS is the margin of safety. Point sources will be allocated a WLA and nonpoint sources will be allocated a LA.

Developing a TMDL is just one step in the process of restoring water quality. The TMDL will identify potential pollution sources, calculate and quantify the necessary reduction of those sources, and provide general implementation information. After the approval of the TMDL, a detailed implementation plan can be developed to realize the goals of the written TMDL document.

SCDES's TMDL Regulations may be found here: SC R. 61-110

Approved TMDLs

A link to all of South Carolina’s approved TMDLs may be found below. The documents are listed by waterbody, pollutant (parameter) and water quality monitoring site.

South Carolina's Approved TMDLs

Sampling sites included in a TMDL document may or may not be meeting the water quality standard. The complete list of sites covered under TMDLs and whether the sites are meeting water quality standard for the pollutant of concern may be helpful to prospective permittees in finding out if a waterbody is impaired. This information is included in document at the link below.

Sites in Approved TMDL Watersheds and their Status

TMDLs Under Development

SCDES continues to develop TMDLs for impaired sites across the state. When work on a new TMDL has begun, this is announced on the following webpage: TMDLs Under Development

Implementation of TMDLs

After a TMDL is approved, implementation is the next step in the restoration of water quality. A TMDL implementation plan serves as a pathway to water quality improvement. It lets community members and regulated entities know what needs to be done to improve and restore impaired water bodies. The TMDL quantified pollutant loading, identified sources and determined the pollutant reductions needed to meet water quality standards, however, to have an effect on water quality, it must be implemented.

Point sources are regulated by permits. After a TMDL is approved State and local water quality management plans should be updated and control measures implemented.

Non-point sources are not regulated by permits and TMDL implementation is voluntary. In South Carolina, funding may be available for the implementation of TMDLs through Section 319 Grants administered by SCDES. These funds are available for TMDL implementation activities that are not otherwise required under a permit. Learn more about the Section 319 Nonpoint Source grant program here: Section 319 Nonpoint Source grant program

When a TMDL has been implemented, the local community becomes a better place to live because water quality has improved. The water is cleaner so swimming, boating, fishing and other water-based recreation are safer. Landowners can take pride in addressing and solving resource issues at the local watershed level. If you are a landowner or a stakeholder interested in finding out more about TMDLs or how to implement one in your area, contact your Watershed Manager. You can learn more about SCDES's watershed management program here: Watersheds Program

TMDLs and Stormwater Permittees

The Municipal Separate Storm Sewer (MS4) program is a permitting program that regulates stormwater discharges from municipalities. MS4 stormwater discharges are considered point sources, and they are required to obtain NPDES permit coverage in order to discharge into Waters of the State. There are also construction and industrial stormwater dischargers operating under NPDES permits in South Carolina.

TMDL wasteload allocations for MS4s are usually stated as a percent reduction goal for the pollutant. The MS4 operator must incorporate the requirements of the TMDL into their stormwater management plan and implement them accordingly to the maximum extent practicable. For more information on stormwater management, visit Stormwater Management