How are Impaired Waters Determined? 

• Review Water Quality Standards
• Evaluate Monitoring Data
• Identify waters for Impaired Waters List 303(d)

The Clean Water Act requires states to publish an updated list of streams and lakes that are not meeting their designated uses because of excess pollutants every two years. The list, known as the 303(d) list, is based on violations of water quality. 

How are TMDL's (Total Maximum Daily Load) Developed?

An impaired listing triggers a regulatory response to address the causes and sources of impairments.  This process is called a TMDL study.  TMDL stands for Total Maximum Daily Load.  Essentially, a TMDL is the amount of pollution a body of water can handle and still meet water quality standards.  A TMDL study identifies sources of pollution and reductions of the particular pollutant needed to attain water quality standards.  Keep in mind that rivers and streams may have several TMDL's, each one determining the limit for a different pollutant.

Minnesota and TMDL's

Minnesota's 2008 TMDL list contains 1,475 impairments on 336 rivers and 510 lakes.  However, this is not the complete list of all impaired waters.  The Inventory of Impaired Waters includes 2,575 impairments needing a TMDL plan as well as those for which a plan has already been developed and approved by US EPA.

Major Steps in a TMDL Study

After a water body is listed, a TMDL study must be conducted to evaluate why impaired waters are not meeting standards and to set pollutant reduction goals that will eventually restore them to their designated uses.  Major TMDL steps are: 1) Monitor water quality, 2) Determine load allocations, 3) Determine sources of pollutant, 4) Determine required reductions. 

Implementation

Upon completion of this study, a detailed implementation plan will be developed.  During this phase, local elected officials and dedicated staff will work toward developing effective strategies.  However, it is important to note that much work is already underway to reduce pollutants from reaching our surface waters.  This work has been and will continue to progress as TMDL goal setting is completed. 

Additional information on impaired waters can be found on the following links:

     - Minnesota's Impaired Waters and TMDL's
     - Faribault County 2008 Inventory of Impaired Waters Map  PDF