Total Maximum Daily Load (TMDL) Studies
What is a TMDL?:
- The federal Clean Water Act (CWA) requires states to adopt water quality standards to protect waters from pollution. These standards define how much of a pollutant can be in the water and still allow it to meet designated uses, such as drinking water, fishing and swimming.
- A TMDL or Total Maximum Daily Load is a scientific study conducted on impaired waters to determine how much a pollutant needs to be reduced in order for the waterbody to meet water quality standards.
- The CWA requires states to identify waters that do not meet water quality standards, establish TMDLs for pollutants causing the impairments, and set pollutant reduction goals needed to restore waters.
- In MN, this responsibility is delegated to the Minnesota Pollution Control Agency (MPCA). More information on TMDLs can be found on the MPCA website at:http://www.pca.state.mn.us/
MCWD’s role in the process:
The MCWD acts as a local partner to the MPCA for TMDLs that are completed in the District. Our role is primarily to:
- Provide technical support through local knowledge, modeling and water quality data.
- Serve as a liaison between the MPCA and local communities/stakeholders by providing technical and process updates to staff, policy makers and other affected stakeholders.
- Ensure consistency, where possible, between the TMDL, the District’s Comprehensive Water Resources Management Plan, and communities’ Local Surface Water Management Plans.
Connection to District’s Plan & Local Water Management Plans:
- The District's Comprehensive Water Resources Management Plan was structured like a TMDL as a proactive way to begin addressing existing impairments in advance of the State’s completion of TMDLs and to prevent future impairments.
- The District Plan provides the District and local communities with a head start on identifying and implementing strategies to address impairments.
- The TMDL will build on the District Plan’s existing modeling and use similar methodology for assigning allocations in an effort to avoid duplication of efforts and contradicting requirements for cities.
Upper Minnehaha Creek Watershed TMDL
This study addressed all waterbodies in the western portion of the Minnehaha Creek Watershed that are currently identified as impaired, including: 20 lakes/bays that are impaired for nutrients, specifically phosphorus, and Painter Creek, which is impaired for E. coli bacteria.
Minnehaha Creek and Lake Hiawatha TMDL
This study addressed Minnehaha Creek, considered impaired for E coli, and Lake Hiawatha, considered impaired for nutrients.
This study addressed Lake Nokomis, Parley Lake, Lake Virginia, and Wassermann Lake.
- Read the report (approved by the EPA on April 25, 2011
- Site-specific standard of 50 ug/L for Nokomis approved by EPA on November 7, 2013