Addressing the issue of the environmental impacts of chloride in the TCMA is a long-term endeavor. Water quality improvements may take time to observe, due to historical loadings, groundwater inputs, variable residence times, and other complicating factors. Continued monitoring of the TCMA lakes, wetlands, and streams for chloride is critical, along with documenting changes in winter maintenance activities, point source discharges, and water softener usage. Continued water quality monitoring along with improved source tracking will allow adaptive management and inform the future steps to restore and protect the TCMA waters. This CMP is intended to be revisited and revised within 10 years based on improved understanding. The update of the CMP will also include new waterbodies that are identified as impaired by chloride.

Water quality monitoring

Addressing the issue of chloride impacts on the environment in the TCMA is a long-term endeavor and it may take some time before water quality improvements are seen due to historical loadings, groundwater inputs, variable residence times and other complicating factors. Therefore, continued monitoring of the TCMA lakes, wetlands, and streams for chloride is critical as well as the need to document changes in winter maintenance activities, wastewater source discharges, and water softener usage. Continued water quality monitoring, along with improved understanding of the sources of chloride will allow adaptive management to take place and inform future steps needed to restore and protect TCMA waters. The CMP is intended to be revisited within 10 years and revised based on improved understanding.

There are a number of organizations across the TCMA that monitor water quality or partner with others to conduct monitoring. In addition the MPCA, Metropolitan Council and the USGS also collect data throughout the TCMA. Incorporating the recommendations below into existing local water monitoring programs will provide valuable data to assist with tracking progress and meeting water quality goals. Monitoring should take place at the existing sites for consistency and comparison purposes. However, since monitoring activities are lead at the local level it will be dependent on available resources and local priorities. We encourage local monitoring data be shared with MPCA by routinely submitting data to the MPCA’s water quality database, EQuIS. The monitoring that MPCA conducts across the state follows the 10-year monitoring strategy as described in Minnesota’s Water Quality Monitoring Strategy report.

The MPCA has worked with the MSG to develop monitoring guidelines for lakes, streams, wetlands and storm sewers. Monitoring guidance documents are available on the MPCA TCMA chloride project website. The key components of continued monitoring to support the implementation of the CMP include:

  • Collect samples during the critical periods for elevated chloride concentrations: January through May for lakes and December through April for streams. However, always put safety first when assessing conditions for collection of samples through the ice.
  • Analysis of chloride should also be included in typical summer season sampling. Analysis for chloride is relatively inexpensive and should be included if the effort is being made to collect samples for analysis of other parameters.
  • In lakes with potential for stratification collect a bottom sample and surface sample.
  • Maintain consistency in sampling. Chloride concentrations may vary from year-to-year depending on the winter conditions. Assessment of long-term trends will have greater confidence with consistent, yearly datasets.
  • Collect a matching conductivity reading with each sample taken for chloride analysis.
  • Expand the sampling program to additional lakes, streams, and wetlands as resources allow. Many waterbodies in the TCMA have not been sampled sufficiently to make a reliable assessment of potential impairment by chloride.

High risk monitoring recommendations

The MPCA has developed specific guidance for monitoring of the TCMA waters not currently impaired but showing a high risk of impairment. The chronic standard of 230 mg/L for chloride concentration applies as a four-day time average. In practice, impairment is often judged from monthly sampling results when these show a clear pattern of prolonged concentrations exceeding the standard. Weekly or twice-weekly sampling would provide the basis for a clear determination. Long-term sampling at such high frequencies is unreasonably expensive in most cases. Therefore, the MPCA suggests the following guidance for additional monitoring of high risk waters:

  1. Identify dates or periods of past chloride concentrations that were either:
    1. Exceedances (exceeded the chronic chloride standard), and
    2. High occurrences, defining high as less than, but within, 10% of the chronic standard (thus >207 mg/L)
  2. Select a four-week period centered on each such date or period, and for each:
    1. Sample for chloride weekly, always on the same day of the week
    2. Sample at the same depth or depths as in past sampling
  3. If an electrical conductivity meter is available, take and record a matching conductivity reading with each lab sample taken:
    1. matching = from the same primary sample that provides the lab subsample, if the primary sample is a sufficiently larger volume than the laboratory bottle used; or otherwise
    2. matching = same location and depth as the lab sample
  4. Possible expanded effort:
    1. Monitor twice weekly rather than once, always on the same days of the week (e.g., Mon and Thu) including, as resources permit:
      1. Chloride sample and conductivity measurement if possible
      2. Chloride sample only if lacking conductivity meter
      3. Conductivity measurement only on the increased frequency if laboratory costs limit sampling but a meter is available

To clarify, sampling for chloride at least weekly during the selected four-week period(s) is the necessary minimum effort for ensuring the value of this additional monitoring; conductivity measurements alone will not suffice at present. This could change in the future if a reliable and accurate relationship between chloride and conductivity is developed for an individual waterbody or for an area including the waterbody.

Impaired monitoring recommendations (tracking progress)

In order to assess high risk waters and waters without data, the MPCA recommends monitoring waters already identified as impaired for chloride less frequently. It is recommended that efforts focus on collecting samples during critical periods. For instance, if the impairment is a result of winter maintenance activities, chloride sampling should be conducted during January through May for lakes and wetlands, and December through April for streams. If the impairment is caused by effluent with high chloride concentrations from WWTPs, monitoring during low-flow periods in the streams should be targeted. If long-term monitoring data has already been collected, less frequent monitoring during critical conditions (monthly or twice monthly) is recommended. If monitoring efforts are limited by costs and a site-specific chloride-conductivity relationship has been established, the MPCA recommends collecting conductivity measurements during the critical period to track progress.

General monitoring recommendations for waters without data

At a minimum, collect monthly chloride and conductivity data for waters without data during the critical period. If possible, expand the effort to weekly sampling during the critical period, and include chloride in typical summer season sampling efforts. For lakes with a potential for stratification, collect a bottom and a surface chloride sample. If it is determined that these waters meet the high risk criteria, the MPCA recommends following the monitoring guidelines for high risk waters.

Tracking and reporting 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 WMAt will be an option available to any winter maintenance group and will support a consistent approach to tracking and reporting winter maintenance activities.

Treatment facilities holding an NPDES Permit will be required by permit to monitor for chloride for an initial term. If the effluent shows no reasonable potential to contribute to or cause violations of the chloride criteria, monitoring requirements may be dropped. For facilities where monitoring shows elevated chloride concentrations, the MPCA will work with the individual facility to determine a course for reducing chloride loads. Where residential water softeners are a major contributor to elevated chloride concentrations, educational and outreach efforts and implementation of water softener buy-back programs should be documented.

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 plan 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. Adaption allows 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 CMP 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 CMP will be conducted within an adaptive framework. The primary steps in the adaptive management framework are presented in Figure 30. Measurement and evaluation of progress in early years of implementation will be critical to success.

This graphic shows Adaptive Management Framework
Adaptive Management Framework


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This page was last edited on 18 May 2018, at 19:07.

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