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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.

Information: A STREAM, LAKE OR WETLAND IS IMPAIRED BY CHLORIDE IF Two or more samples exceed 230 mg/L within a three-year period; Or, One sample exceeds 860 mg/L.

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.

TCMA Chloride Management Plan - TCMA Chloride Conditions - Condition status

TCMA Chloride Management Plan - TCMA Chloride Conditions - Chloride sources

TCMA Chloride Management Plan - TCMA Chloride Conditions - Chloride trends

TCMA Chloride Management Plan - TCMA Chloride Conditions - TMDL summary


TMDL summary

The Total Maximum Daily Loads (TMDLs) were developed for each of the lakes, wetlands and streams in the TCMA impaired for chloride, with the exception of Shingle Creek and Nine Mile Creek which already have existing TMDLs. A TMDL quantifies the allowable pollutant loading to a lake, wetland, or stream that will result in water quality standards being attained. The water quality target for the TMDLs was set to the chronic water quality criterion for chloride of 230 mg/L. The total allowable load, or TMDL, is allocated to the various sources contributing chloride as well as consideration of a margin of safety and reserve capacity. Margin of safety is intended to account for uncertainty in the development of the TMDL. Reserve capacity is intended to set-aside a portion of the TMDL for future growth. For the TCMA chloride TMDLs, reserve capacity was set to zero assuming that any further development and additional impervious surfaces would be expected to have the same level of best management practices (BMPs) implemented for winter maintenance activities as for the remainder of the watershed. The complete details of the TMDL development are presented in the TCMA Chloride TMDL report (see Appendix A).

A total of 39 waterbodies are listed as impaired by chloride, and TMDLs for Shingle Creek and Nine Mile Creek have already been prepared under separate projects. A total of 37 TMDLs were completed as part of this project. Summaries of the TMDLs are presented in the Summary of TMDL and Components for Impaired Lakes and Wetlands in the TCMA table for lakes and the wetlands and the Summary of TMDL and Components for Impaired Streams in the TCMA table.

Summary of TMDL and Components for Impaired Lakes and Wetlands in the TCMA
Link to this table

Lake/Wetland AUID Watershed Area (ac) TMDL and Components (all values in lbs/yr of chloride)
Loading Capacity (TMDL WLA LA Margin of Safety
MS4 Categorical Wastewater Sources1 Non-Permitted Aggregate Natural Background
Battle Creek Lake 82-0091-00 4,326 2,153,699 1,766,033 0 0 172,296 215,370
Brownie Lake 27-0038-00 452 341,418 279,963 0 0 27,313 34,142
Carver Lake 82-0166-00 2,242 1,071,123 878,321 0 0 85,690 107,112
Como Lake 62-0055-00 1,850 994,078 815,144 0 0 79,526 99,408
Diamond Lake 27-0022-00 744 486,017 398,534 0 0 38,881 48,602
Kasota Ponds North 62-0280-00 10 6,234 5,112 0 0 499 623
Kasota Ponds West 62-0281-00 6 5,742 4,708 0 0 459 574
Kohlman Lake 62-0006-00 7,533 4,839,183 3,106,733 1,050,484 0 303,096 378,870
Little Johanna Lake 62-0058-00 1,703 1,224,242 1,003,879 0 0 97,939 122,424
Loring Pond (South Bay) 27-0655-02 34 9,764 8,007 0 0 781 976
Mallard Marsh 62-0259-00 16 9,851 8,077 0 0 788 985
Parkers Lake 27-0107-00 1,064 1,431,262 528,161 787,163 0 51,528 64,410
Peavey Lake 27-0138-00 776 205,995 165,889 3,692 0 16,184 20,230
Pike Lake 62-0069-00 5,735 3,591,268 2,943,971 1,059 0 287,217 359,021
Powderhorn Lake 27-0014-00 332 218,588 179,242 0 0 17,487 21,859
Silver Lake 62-0083-00 655 370,011 303,409 0 0 29,601 37,001
South Long Lake 62-0067-02 114,785 26,334,624 21,534,261 4,030 0 2,106,448 2,633,059
Spring Lake 27-0654-00 39 15,600 12,792 0 0 1,248 1,560
Sweeney Lake 27-0035-01 2,439 1,456,271 1,194,142 0 0 116,502 145,627
Tanners Lake 82-0115-00 1,732 826,520 677,746 0 0 66,122 82,652
Thompson Lake 19-0048-00 178 134,340 110,159 0 0 10,747 13,434
Valentine Lake 62-0071-00 2,404 1,165,072 955,359 0 0 93,206 116,507
Wirth Lake 27-0037-00 426 1,095,000 897,900 0 0 87,600 109,500

1 WLA=0 in the wastewater sources column means that there is no wastewater discharges in that watershed


Summary of TMDL and Components for Impaired Streams in the TCMA
Link to this table

Stream AUID Watershed Area (ac) TMDL and Components (all values in lbs/yr of chloride)
Loading Capacity (TMDL WLA LA Margin of Safety
MS4 Categorical Wastewater Sources1 Non-Permitted Aggregate Natural Background
Bass Creek 07010206-784 5,434 1,746,399 1,432,047 0 0 139,712 174,640
Bassett Creek 07010206-538 25,209 9,334,219 6,642,961 1,233,048 0 648,094 810,117
Battle Creek 07010206-592 7,246 2,328,721 1,909,551 0 0 186,298 232,872
Elm Creek 07010206-508 66,382 21,332,410 17,386,888 0 105,688 1,706,593 2,133,241
Judicial Ditch 2 07030005-525 1,587 510,115 418,294 0 0 40,809 51,011
Minnehaha Creek 07010206-539 109,151 35,997,083 28,679,140 1,004,128 0 2,806,140 3,507,675
Raven Stream 07020012-716 42,750 15,023,193 442,771 1,284,983 10,822,561 1,099,057 1,373,821
Raven Stream, East Branch 07020012-543 14,751 6,025,349 442,093 1,284,983 3,445,007 379,229 474,037
Rush Creek, South Fork 07010206-732 13,844 4,470,069 3,646,696 21,010 1,532 355,925 444,906
Sand Creek (South) - includes 07020012-662 07020012-513 175,578 59,480,179 4,402,547 3,056,425 41,864,932 4,513,900 5,642,375
Unnamed creek (Headwaters to Medicine Lk) 07010206-526 6,447 2,071,959 1,699,006 0 0 165,757 207,196
Unnamed creek (Unnamed ditch to wetland) 07010206-718 793 254,852 208,979 0 0 20,388 25,485
Unnamed Stream (Unnamed lk 62-0205-00 to Little Lk Johanna) 07010206-909 1,627 522,817 428,710 0 0 41,825 52,282

1 WLA=0 in the wastewater sources column means that there is no wastewater discharges in that watershed


Protection of surface and groundwater

Protection is an opportunity to prevent waters from continued degradation which may result in impairment. Prevention or protection is often more easily accomplished than the restoration of an impaired waterbody. Protection efforts also may eliminate the need for additional permit and other regulatory requirements to reduce pollution. Successful protection efforts rely on understanding how current practices or conditions may be contributing to water quality conditions.

High risk surface waters

Preventing a waterbody from being contaminated with chloride is easier and more cost effective than restoration. Chloride is a conservative ion and will not break down over time but rather it accumulates in waters. Therefore, efforts should be made to protect waters that show an increasing trend in chloride concentration or have been shown to have chloride concentrations approaching the water quality criteria. Lakes, wetlands, or streams with at least one sample within 10% of the chronic water quality standard within the last 10 years have been identified as a high risk waterbody (one exceedance of 207 mg/L chloride). Proactive actions to reduce chloride loads to these high risk waterbodies should be pursued. Proactive actions similar to actions listed for impaired waters should be explored to protect high risk waters. These waters are considered to be approaching the water quality standard and if no actions are taken, they will likely reach impairment status in the near future. The TCMA lakes and streams identified as being at high risk for potential chloride impairment are shown in the High Risk Lakes in the TCMA table and the High Risk Streams in the TCMA table, respectively.

It should be noted that there are potentially many more high risk waters in the TCMA that have not been identified because there is limited or no monitoring data available for those waters. For this reason, similar proactive approaches to chloride management should be taken to prevent chloride contamination.

All surface waters and groundwater

In addition to the high risk waters listed above, protecting all surface waters and groundwater from further degradation due to chloride is important. By implementing salt reducing practices throughout the TCMA, both the need to restore those waters already impaired and also protect those waters not yet exceeding the standard are addressed. The practices necessary for protection of groundwater are the same as those for restoring and protecting surface waters. Through targeting and prioritization a starting point can be established. Management practices and BMPs used for impaired and high risk waters can be the same for all waterbodies and should provide the same level of protection and chloride reduction.

High risk lakes in the TCMA
Link to this table

Lakes AUID
Beaver Lake 62-0016-00
Bennett Lake 62-0048-00
Calhoun Lake 27-0031-00
Centerville Lake 02-0006-00
Crosby Lake 62-0047-00
Crystal Lake 27-0034-00
Fish Lake 19-0057-00
Gervais Lake 62-0007-00
Hiawatha Lake 27-0018-00
Johanna Lake 62-0078-00
Keller Lake (Main) 62-0010-02
Lake Of The Isles 27-0040-00
McCarron Lake 62-0054-00
Medicine Lake 27-0104-00
Ryan Lake 27-0058-00
Taft Lake 27-0683-00
Unnamed Lake 62-0278-00
Wabasso Lake 62-0082-00
Wakefield Lake 62-0011-00


High risk streams in the TCMA
Link to this table

Streams AUID
Bevens Creek 07020012-718
Bluff Creek 07020012-710
Classen Lake Creek 07010206-703
Clearwater Creek 07010206-519
County Ditch 17 (Spring Brook) 07010206-557
Credit River 07020012-517
Diamond Creek 07010206-525
Dutch Lake Outlet 07010206-678
Fish Creek 07010206-606
Painter Creek 07010206-700
Rush Creek 07010206-528
Unnamed Creek 07010206-704
Unnamed Creek 07010206-740
Unnamed Creek (Pleasure Ck) 07010206-594
Unnamed Stream (Perro Ck) 07030005-612
Unnamed Stream (Sand Ck) 07010206-744
Unnamed Stream (Trib To Long Lk) (Furgala Creek) 07030005-765
Unnamed Stream In Plymouth 07010206-738
Unnamed Stream Receiving Wtr From Medicine Lk 07010206-785