Coeur d'Alene Tribal TMDLs | Region 10 | US EPA

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Coeur d'Alene Tribal TMDLs

Lake Creek Water Quality Clean-Up Plan for Sediment on the Coeur d’Alene Reservation

The U.S. Environmental Protection Agency (EPA) and Coeur d’Alene Tribe (CDAT) with significant participation from Idaho Department of Environmental Quality (IDEQ) are working together to improve Lake Creek’s water quality and have developed a water quality improvement plan TMDL for sediment.

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TMDL at a Glance
Why Does Lake Creek Need a TMDL?
What is a TMDL and What Does it Look Like?
What is the Analytical Approach and Bottom Line?
What Happens Once the TMDL is Finalized?
Final Water Quality Improvement Plan (TMDL) September 2005 (pdf file, 75 pp.,2051 Kb)

Lake Creek Maps
Local Map (pdf file, 1 pp, 71 Kb)
Regional Map (pdf file, 1 pp, 342 Kb)
Regional/State Map (pdf file, 1 pp, 108 Kb)

More About TMDLs (pdf file, 3 pp, 18 Kb)

For More Information

Other Websites of Interest
EPA approves Coeur d'Alene Tribe's application (for treatment-as-a state) to set water quality standards for certain Reservation waters

Lake Creek Sediment TMDL at a Glance
WaterbodyLake Creek (on the Coeur d'Alene Reservation), Idaho
Water Quality-limited?Yes
Hydrologic Unit Code17010303 (Coeur d’Alene Lake)
Criteria of ConcernNarrative criteria for sediment
Designated Uses AffectedCold water aquatic life
Environmental IndicatorsInstream total suspended solids (TSS) concentration
Major Source(s)Cropland erosion and mass wasting
Loading Capacity4,894.1 tons/year
Wasteload Allocation16.1 tons/year
Load Allocation4,878.0 tons/year
Margin of Safety0 tons/year (included implicitly)
Necessary Reduction55%

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Why Does Lake Creek Need a TMDL?
Lake Creek is located in the Coeur d’Alene basin in Northern Idaho. This basin consists mostly of agricultural and forested lands. The portion of the Lake Creek which lies entirely within the Coeur d’Alene Reservation has been identified as an impaired waterbody because of excessive sediment in the creek and in need of a water quality improvement plan or Total Maximum Daily Load (TMDL).

This excessive sediment has reduced the quality of pools necessary for fish spawning and survival in the winter. Good spawning pools have gravel or small cobble bottom suitable for digging redds. Sediment and fine sands can cement together to create a hard bottom preventing the building of nests. The sediment also can fill spaces between the gravel, reducing oxygen necessary for the developing fry and trapping the fish. Too much sediment can prevent fish from seeing food in the water and clog their gills.

Erosion from agriculture (crop lands) is the primary cause of sediment in the creek.

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What is a TMDL and What Does it Look Like?
EPA and CDAT, with significant help from IDEQ, have developed a TMDL that determines the maximum amount of sediment that can enter Lake Creek and still protect the fisheries (cold water aquatic community and salmonid spawning).

The CdA Tribe has adopted water quality standards (WQS) for the waters within its Reservation. EPA has not yet approved the CdA Tribe’s WQS. Both the tribal and state’s WQS contain narrative criteria for the protection of waters from excess sediment. This TMDL is developed to meet both the state’s and CDAT’s criteria and protect designated uses in Lake Creek for both the state and Tribe (essentially cold water aquatic community and salmonid spawning) based upon agreement from the involved agencies (CDAT, USEPA Region 10, Idaho DEQ). EPA, CDAT, and IDEQ have developed a draft TMDL, or Total Maximum Daily Load, which is required by the federal Clean Water Act. This draft TMDL determines the maximum amount of sediment that can enter Lake Creek and still protect the fisheries (cold water aquatic community and salmonid spawning).

The TMDL is like a “pollution budget” for Lake Creek. It is the sum of how much individual point sources can discharge, how much nonpoint and natural sources can discharge. Pollution that generally comes out of a pipe or an activity that has a wastewater or stormwater permit is called a point source. Pollution that are diffuse and do not have a single point of origin is called a nonpoint source. Examples include runoff from row-crop agriculture, pasture, ranges, forested areas, and roads. This TMDL:

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What is the Analytical Approach and Bottom Line?
The TMDL uses numeric instream total suspended solids (TSS) targets of 40 mg/L during the high flows (usually the fall and spring) and 25 mg/L during low flows (usually in the summer) designed to maintain good fisheries and recommends future monitoring to assess improvements in aquatic habitat quality. The TSS targets are established from a range of values typically maintaining good or moderate fisheries, based on literature values [European Inland Fisheries Advisory Commission Report (1965) and the Environmental Studies Board, National Academy of Sciences Report (1973)].

With TSS, turbidity and flow data, this TMDL uses statistical analysis that determined 4894.1 tons/year was the maximum amount of sediment that Lake Creek could receive and still protect the cold water aquatic community and salmonid spawning. Over 99% of this entire loading capacity was given to nonpoint sources of sediment and less than 1% was given to Idaho Transportation Department while they are constructing Highway 99. These amounts represent over 55 percent reduction in existing sediment loading into the creek.

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What Happens Once the TMDL is Finalized?
Once the TMDL is finalized, the Coeur d’Alene Tribe intends to develop an implementation plan with extensive involvement from IDEQ, local agencies and the community. The main focus of the implementation plan is likely to focus on reducing sediment inputs from agricultural erosion, restoring riparian zones, augmenting base flow with storage reservoirs, and mitigating flow disturbance and sedimentation due to forest roads. The Tribe has already held two meetings to discuss implementation options. The Coeur d’Alene Tribe plans to continue water quality monitoring to track water quality improvement.

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For More Information....
Please contact agency representatives if you have any questions. All relevant TMDL documents, including the draft TMDL and a fact sheet, is available on this EPA’s web site or by contacting:

Jayne Carlin
EPA Region 10
1200 Sixth Ave, Suite 900
Seattle, WA 98101
(206) 553-8512

Scott Fields
Coeur d’Alene Tribe
401 Anne Antelope
Plummer, Idaho 83851
(208) 686-0252
Email: or

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