A total maximum daily load (TMDL) is the amount of pollutant loading that can occur and have a water body meet water quality standards. A TMDL may be written as an equation which allocates pollutant loading to four separate categories:
TMDL = WLA + LA + MOS + RC
where WLA is wasteload allocation, LA is load allocation, MOS is margin of safety, and RC is reserve capacity. WLA includes pollutant loading from sources covered by a NPDES permit (often called point sources), LA includes sources not covered by a NPDES permit (often called nonpoint sources), MOS accounts for uncertainty in the estimates of WLA and LA, and RC allows for future growth.
- Overview of TMDLs
- Summary of TMDL requirements in stormwater permits
- Forms and guidance for TMDLs
- Summary of data received from permittees on MS4 TMDL permit reporting forms
- Links for TMDLs
- Visit the MPCA TMDL Project page for information on specific projects across the state