Reasonable Assurance

The MPCA has worked with stakeholders in the TCMA to develop a plan to restore and protect waters impacted by chloride. The TCMA CMP incorporates water quality assessment, source identification, implementation strategies, monitoring recommendations and measurement and tracking of results into a performance-based adaptive approach for the 7-County TCMA. The goal of the CMP is to develop the framework to assist local partners in minimizing chloride use and provide safe and desirable conditions for the public. The CMP will guide and assist agencies, local governments and other TCMA stakeholders in determining how best to restore and protect water resources impacted by elevated chloride levels while balancing the need for public safety, level of service considerations, as well as water softening needs. The CMP is not intended to resolve all issues. Rather, it provides understanding and guidance for management activities over the next 10 years.

Significant progress has already been made by many entities, including MnDOT, a number of cities including Prior Lake, Shoreview, Richfield, and Waconia, as well as the UMN (see section 3.5 of the TCMA Chloride Management Plan for examples). Their efforts have demonstrated that salt use can be reduced without detrimentally impacting the level of service, as well as showing the economic benefits of improved winter maintenance practices. Funding mechanisms are available to entities interested in investing in better equipment and enhanced education efforts. This is includes the Clean Water, Land, and Legacy Fund which has several grant and loan programs that could be used for implementation of BMPs, education and outreach, and WWTP modifications. Additional discussion of implementation strategies is included in Section 8 of this TMDL as well as in the TCMA CMP.

Tracking Implementation Efforts

Measuring water quality in the TCMA and monitoring chloride loads in the lakes, wetlands, and streams is critical to understanding progress toward the ultimate goal of restored and protected lakes, wetlands, and streams. However, these types of measurements alone will not be sufficient to demonstrate the progress made in implementing individual salt reduction efforts and accomplishments taking place throughout the TCMA to reduce chloride. Tracking of implementation activities is needed to assess the related benefits to water quality, take credit for making progress, and identify areas where additional effort is needed.

The approach to tracking implementation efforts will vary by the source type. The Winter Maintenance Assessment tool (WMAt) will be an option available to any winter maintenance group and will support a consistent approach to tracking and reporting winter maintenance activities.


Permits issued under the NPDES program are required to have effluent limits consistent with the assumptions and requirements of the WLAs in this TMDL. Compliance with the WLAs, as developed and presented in this TMDL, is assumed to ensure meeting the water quality standards for all of the chloride 303(d) listings. Sections 8.1 and 8.2 of this TMDL report present a brief summary of the permit programs that exist to put into place requirements consistent with the WLAs. For the MS4 Permits, conditions will be included to document winter maintenance practices, establish goals for improving winter maintenance practices, and track improvements as part of the MS4 Storm Water Pollution Prevention Plan (SWPPP). While existing loads and the necessary percent reductions have not been estimated for this TMDL, the expectation for the MS4s is to track progress from the year that implementation of salt reducing BMPs began for each individual winter maintenance organization and reporting that progress to the MPCA as part of their annual reporting. The two previously completed chloride TMDLs in the TCMA, Nine Mile, and Shingle Creek estimated reductions of 60%-70% in existing chloride loads and may be used as an example target to work towards. However, the progress made already will vary greatly as well as the local chloride loadings and target reduction/BMP implementation goals should be established at the local level using the best available information. For wastewater sources, permits will initially include monitoring requirements to assess chloride loadings. Upon permit renewal, effluent limits and/or other permit conditions will be included to address chloride loadings that exceed the WLAs in this TMDL. A number of municipalities within impaired watersheds for chloride are not currently MS4s but are expected to have an MS4 permit by or before 2020. The future MS4 Permits are included in the categorical WLA for MS4s.


Non-permitted non-point sources of chloride will be addressed through the combined efforts of the MPCA, watershed districts (WD) and watershed management organizations (WMO), soil and water conservation districts, natural resources conservation service programs, and municipalities. Organizations that conduct winter maintenance activities and education and outreach programs will experience the benefits of improved practices whether or not they are within an MS4.

Adaptive Management

Implementation of a TCMA CMP, which includes 186 cities and townships and seven counties as well as colleges, universities, private industries, commercial property owners, school districts, private homeowners, and others, can only be accomplished by maintaining flexibility and adaptability within the overall approach. It should be understood that the water quality goals and chloride loads presented in this TMDL are estimates based on the best available science.

Adaptive management is an approach that allows implementation to proceed in the face of potentially large uncertainties. Adaptation allows for the implementation plan to be adjusted in response to information gained from future monitoring data and new or improved understanding of related issues. The adaptive implementation process begins with initial actions that have a relatively high degree of certainty associated with their water quality outcome. Future actions are then based on continued monitoring of the TCMA water resources and an assessment of the response to the actions taken.

The TCMA Chloride TMDL is a prime candidate for an adaptive implementation process for a number of reasons. First, the scale, complexity, and variability of chloride sources within the area make a traditional implementation plan (i.e., one that identifies the specific implementation activities required to attain the TMDL) impractical. Second, there will likely be a time lag between reduction of external loads and the response of the system, and there will be year‐to‐year variability in the monitoring results. Finally, the TMDLs focused on the problem of high chloride loads and its current sources. However, restoration and protection of the TCMA water resources will require a planning framework that recognizes potential future threats such as changing deicing products, driver expectations, climate change, and population increases. For these reasons, implementation of the TCMA Chloride TMDL will be conducted within an adaptive framework.

The NPDES permitting requirements will be reviewed and revised as part of the adaptive management approach. As described above, the detection of improved water quality conditions will in many cases occur some years after the implementation, which further justifies the need for an adaptive management approach to the permitting requirements and continued stakeholder input.

This page was last edited on 23 November 2022, at 15:58.