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Poplar River TMDL

 Poplar River TMDL Summary:

Mouth of the Poplar River

Mouth of Poplar River into Lake Superior. (2002) Click to enlarge.
Photo credit: S. St. Louis County SWCD

Recent water quality monitoring on the Poplar River has found that the lower section of the river is officially impaired because of excessive turbidity (cloudiness or “muddiness” of the water). Because of this, the river was put on the state’s list of impaired waters (also known as the 303d list) by the Minnesota Pollution Control Agency (MPCA) in 2004. This listing mandates the MPCA to complete a study to determine what’s known as a Total Maximum Daily Load (TMDL). A TMDL is a calculation of the maximum amount of a pollutant that a waterbody can receive and still meet water quality standards.

The TMDL study commenced in 2006 and was originally to be completed by January of 2008. Needs for additional modeling, timeline adjustments with contracts, and public feedback to the process required a timeline and contract deliverables adjustment. The EPA contractor completed a turbidity assessment report in March 2008 and the Natural Resources Research Institute (NRRI) completed a biological monitoring report in September 2008. Progress to date by the contractors have included reviewing and compiling existing water quality information and data, analyzing this data, performing biological sampling and laboratory analysis for macroinvertebrates, reviewing an existing model, updating and improving the model, conducting a physical channel assessment, and estimating loading values.

Public participation is encouraged in the TMDL process. The first public meeting was held on June 7, 2007 and focused on the review of existing information and analysis of water quality data. A Technical Advisory Committee (TAC) meeting was held on August 27, 2007. The second public meeting was held February 28, 2008. A third public meeting was held on September 16, 2008 and focused on the biological monitoring on the river, a fishery summary report and educational information on hydrology and watershed science. Other public communication tools include a comment form on this web page and a “listening log” of comments received via phone, e-mails or office visits. University of Minnesota Sea Grant staff has summarized comments. Additionally, once a draft TMDL has been completed it is noticed in the state register and there is an official 30-day public comment period. Check this website or MPCA TMDL web pages for information on the progress of the Poplar River TMDL project.

For information about the process, see the contacts below. If you would like to be added to an E mail list for Poplar River TMDL updates, please e-mail your request to Cindy Gentz at cindy.gentz@co.cook.mn.us.

What is a TMDL?

A TMDL or Total Maximum Daily Load is a calculation of the maximum amount of a pollutant that a waterbody can receive and still meet water quality standards, and an allocation of that amount to the pollutant's sources.

Water quality standards are set by States, Territories, and Tribes. They identify the uses for each waterbody, for example, drinking water supply, contact recreation (swimming), and aquatic life support (fishing), and the scientific criteria to support that use.

A TMDL is the sum of the allowable loads of a single pollutant from all contributing point and nonpoint sources. The calculation must include a margin of safety to ensure that the waterbody can be used for the purposes the State has designated. The calculation must also account for seasonal variation in water quality.

The Clean Water Act, section 303, establishes the water quality standards and TMDL programs.

Source: US EPA http://www.epa.gov/owow/tmdl/intro.html

 Why is the Poplar listed as an impaired water?

The Minnesota Pollution control Agency has been monitoring water quality in the Poplar river since 2002 at two locations, one above the ski hill (photo 1), and another near Lutsen Lodge near the mouth of the river (photo 2). Turbidity criteria for the Poplar River, a designated trout stream, are set at 10 NTU’s. The upper monitoring station has seen only 3 of 73 samples above 10 NTU’s, but the lower monitoring station has had 32 out of 92 samples (35%) above 10 NTU’s. This elevated turbidity can cause serious problems for fish and other aquatic organisms, as described here.

The cause of the increased turbidity is mainly suspended sediment particles, such as clay. The TMDL study will carefully evaluate each source of sediment to determine how much is coming from each different source, such as eroding banks, roads, ski trails, and the golf course. Once this is known, an evaluation will be made of which sediment sources need to be reduced, and by how much, so the Poplar River turbidity will meet the state’s water quality criteria and can be removed from the impaired waters list.

Implementation may take several years, as additional Best Management Practices (BMP’s) may need to be installed, or other changes may need to take place. Implementation will be addressed after the TMDL study is complete.

Poplar River - at the upstream monitoring station Poplar River - at the downstream monitoring station
Upstream and downstream sites on the Poplar River, July 31, 2001 after a large rainfall

Photo credits: Minnesota Pollution Control Agency 2002


Observed Turbidity, Lower Poplar River Upstream Station 2002 - 2006


Observed Turbidity, Lower Poplar River Downstream Station 2002 - 2006

Project Contacts:
Ilena Berg
Cook County Water Planner
Minnesota Pollution Control Agency:
Karen Evens
MN Pollution Control Agency
Pollution Control Specialist
Watershed Unit
525 S. Lake Avenue  Suite 400
Duluth MN 55802
United States Environmental Protection Agency:
Julianne Socha
77 West Jackson Boulevard
Mail Code: WW-16J
Chicago, IL 60604-3507