TCMA Chloride Management Plan - TCMA Chloride Conditions
TCMA Chloride Conditions
Chloride data across the TCMA was compiled and assessed to support the development of the CMP. As part of the TCMA Chloride Project, the MPCA worked with local partners to develop and implement a chloride monitoring program. The objective of the monitoring program was to better inform an understanding of chloride conditions across the TCMA, including seasonality, trends over time, and the potential for high chloride concentrations in the deepest part of lakes. Seventy-four lakes, 27 streams, and eight storm sewers were monitored as part of this effort from 2010-2013. The Chloride Monitoring Guidance for Lakes and Chloride Monitoring Guidance for Streams and Stormsewers were developed by the MPCA and local experts from the TCMA Chloride MSG and can be found on the MPCA’s TCMA Chloride Project website. The monitoring guidance provides recommendations on sample collection, times of the year to sample, as well as guidance for monitoring high risk waters. In addition to data collected in 2010-2013 following the TCMA Chloride Project monitoring program, chloride data from a host of other sources and timeframes were compiled. The data were collected by several local organizations including the MPCA, the United States Geological Survey (USGS), Capitol Region Watershed District (CRWD), Metropolitan Council Environmental Services (MCES), Minneapolis Park & Recreation Board (MPRB), Minnehaha Creek Watershed District (MCWD), Mississippi Watershed Management Organization (MWMO), Ramsey County Environmental Services, Ramsey-Washington Metro Watershed District (RWMWD), Rice Creek Watershed District, Scott County Watershed Management Organization, and Three Rivers Park District. A large portion of the data were compiled and submitted to the State of Minnesota’s Environmental Quality Information System database (EQuIS). All data collected by Metropolitan Council are available on their Environmental Information Management System (EIMS) database, and data collected by USGS are available on their water-quality data for the Nation database: waterdata.usgs.gov/nwis/qw.
The impacts of climate change create uncertainty related to winter salt application and chloride levels in TCMA waters in the future. Predictions provided by the United States Global Change Research Program for the TCMA area include warmer winter temperatures by 5 - 6 degrees Fahrenheit, longer freeze-free seasons increasing by 20-30 days, greater winter precipitation, and the likelihood of more frequent extreme events (Kunkel et al. 2013). On the one hand, these predictions of climate change may result in reduced salt use. On the other hand, more frequent snow events, more extreme events, and potentially more frequent ice storms may result in greater needs for deicing roads. Continued monitoring of climate change and chloride concentrations in the TCMA waters, tracking of salt use on all paved surfaces, and an adaptive process will be needed to restore and protect the TCMA waters from chloride impairments with the prospects of a changing climate.
The remainder of this section will present an overview of the assessments conducted based on the available data, including determinations of impairment, time and spatial trends in chloride concentrations, the TMDLs developed for impaired waters, and waters showing a high-risk for future impairment.
Condition Status
This section describes the current status of water resources within the TCMA with respect to applicable chloride criteria. The status of surface waters including lakes, wetlands and streams is presented first. The status of groundwater resources is presented second.
Surface Water
The MPCA’s approach to determining whether or not a stream, lake, or wetland is impaired by chloride relies on an assessment of available data. The MPCA conducted an assessment for chloride in the TCMA waterbodies in 2013. Two or more exceedances of the chronic criterion of 230 mg/L within a three-year period are considered an impairment. One exceedance of the acute criterion of 860 mg/L is considered an impairment. The 2013 TCMA chloride assessment resulted in 29 new chloride impairments (6 streams, 19 lakes, and 4 wetlands) added to the 2014 draft impaired waters list, resulting in a total of 39 chloride impairments in the TCMA. Shingle Creek and Nine Mile Creek were previously listed as impaired with completed chloride TMDLs. Approximately 11% of the 340 waterbodies assessed were determined