TMDL Information for the Lowcountry Stormwater Partners

What is a TMDL? A total maximum daily load is the amount of a pollutant (such as phosphorus) that can enter a waterbody on a daily basis, still allowing for the waterbody to meet state water quality standards. Every two years, SC DHEC must submit a list of monitored waterbodies that do not meet water quality standards for one or more parameter (the "303d list"). From that list, it is determined what pollutants and impairments can be fixed through the TMDL process or other means. Therefore, "TMDL" may refer to the calculation of a pollutant entering a waterbody as well as a document which outllines potential sources of that pollutant within a watersed, information on the calculation, and relevant information including maps, figures and pictures.

The TMDL process is a regulatory process, and therefore, there are many ways in which a TMDL can play a role in local government decision-making. For our regional education effort, the TMDL process is an important consideration as the consortium decides what priority pollutants should be addressed through education and public involvement.

DHEC has developed a web application to assist operators of construction activities, industrial facilities, and Municipal Separate Storm Sewer Systems (MS4), subject to the NPDES stormwater program, with identifying water quality information necessary to comply with their permit. This tool will assist the user in determining the classification of receiving waters, location of water quality monitoring stations that receive stormwater discharges from the facility, and status of assessed water quality monitoring stations, including impairment and TMDL status. It is necessary to use this tool in concert with the applicable permit to determine requirements for best management practices, monitoring, etc., found in NPDES stormwater permits. For program assistance, please refer to the DHEC’s stormwater website ( Suggestions or comments on the web application can be emailed to

For best view of application the recommended browser is Internet Explorer 7 or higher with a screen resolution at 1024 x 768 or greater. Please note in the ‘Water Information’ form the final tab visible should be ‘Report’. If this is not visible, temporarily disable unnecessary toolbars associated with your browser or change the resolution of the screen. Applicant must see this tab to report and print assessed data associated with the permit application.