Water Quality Improvement Projects
Pend Oreille River Area


The Pend Oreille River begins at the outlet of Lake Pend Oreille in northern Idaho and is part of the Clark Fork-Pend Oreille Basin, which drains western Montana and northern Idaho. The river enters Washington State near the city of Newport and flows 72 miles north through the Kalispel Tribe of Indians' reservation to the Canadian border. After flowing about 15 miles in British Columbia, Canada, the Pend Oreille River joins the Columbia River. The Pend Oreille contributes approximately 10% to the total flow of the Columbia River.

There are two hydroelectric projects on the Pend Oreille River in Washington:

  • Box Canyon Dam is owned and operated by the Pend Oreille Public Utility District. Box Canyon Dam received a new Federal Energy Regulatory Commission (FERC) license in 2005. For more information please see their web site: www.popud.com/license.htm.
  • Boundary Dam is owned and operated by Seattle City Light, which is in the process of relicensing Boundary Dam. You can obtain additional information from Seattle City Light’s web site: www.seattle.gov/light/tours/boundary/.

Two other dams influence the Pend Oreille River in Washington State. Albeni Falls Dam is located just upstream of the Washington-Idaho state line in The U.S. Army Corps of Engineers owns and operates Albeni Falls Dam, which controls river flows in Washington. Another major dam in the basin is Cabinet Gorge Dam, which is located upstream of Lake Pend Oreille.

Pend Oreille River.  Photo courtesy of David T. Knight, WA Department of Ecology.


Water quality issues

The Pend Oreille River does not meet Washington State’s water quality standards. As a result, Ecology listed the Pend Oreille River on the 1998 list of impaired water bodies (also called the 303[d] list) because it did not meet temperature and total dissolved gas (TDG) water quality standards. On the 2004 Category 5 303(d) list, the Pend Oreille River is also listed for Aldrin, pH and total PCBs. Some tributaries to the Pend Oreille River are also listed for fecal coliform bacteria, dissolved oxygen, and temperature.


Why this matters

When water temperatures are too high it can make the streams uninhabitable for fish and other aquatic animals. Many salmon and trout species will suffer a variety of ill effects, ranging from decreased spawning success to death, when waters are too warm. The optimal temperature for most salmon and trout species is between 12-14˚C (54-57˚F), and temperatures in the range of 23-25˚C (73-77˚ F) can be lethal, depending on the species.

Water temperature can also affect how much oxygen is dissolved in the water. Fish need this dissolved oxygen (DO) to breathe. The warmer the water the less DO it can hold. The warmer temperatures also tend to speed up the metabolism of the fish so that they require more oxygen for biological functions.

Total dissolved gas is air that gets trapped in water as a result of waterfalls or water plunging over a dam. When rivers have excess total dissolved gas, the gas can form bubbles inside the fish, often in the eyes or near fins. This condition is known as gas bubble disease and can be fatal.

Chemicals such as aldrin and PCBs can build up in fish. If the level of chemicals in the fish is high enough, it can become unsafe for people to eat a large amount of the fish.

For more information, please see our Environmental Importance of the Different Impairments page.

Status of the projects

Beginning in 2004, Ecology has worked to develop two TMDLs for the Pend Oreille River: Total Dissolved Gas and Temperature.

Temperature TMDL

Since 2005, Ecology has coordinated with the Environmental Protection Agency (EPA), the Kalispel Tribe, the Idaho Department of Environmental Quality (IDEQ), and the Tri-State Water Quality Council to evaluate water temperature throughout the basin.

The agencies have worked with a watershed advisory group (WAG). The WAG is made up of citizens, cities, organizations, and businesses in the watershed. In August 2007, the WAG reviewed the first draft of the TMDL. WAG members had numerous comments and concerns about the technical analysis. As a result, from the summer of 2008 to early fall of 2010, Ecology worked to address concerns and edit the draft TMDL. During this time, Ecology also held meetings with the agencies and sent updates to the WAG.

Ecology held a public comment period for the temperature TMDL from October 1 - November 30, 2010. A public meeting was held on October 14, 2010 at the Pend Oreille Public Utility District office in Newport, WA. Ecology received ten comment letters, which you can read in full text by clicking on one of the links in the table that follows. From December 2010 until March 2011, Ecology worked to respond to the comments and edit the TMDL. Ecology sent the final TMDL to EPA for approval on April 6, 2011.

EPA Idaho Dept. of Environmental Quality
Kalispel Tribe of Indians Pend Oreille Clean Water Alliance
Pend Oreille Public Utility Department Ponderay Newsprint
City of Sandpoint Seattle City Light
U.S. Army Corps of Engineers U.S. Forest Service

See the Technical information page for additional information about the TMDL.

On April 28, 2011, the Department of Ecology received a letter from Seattle City Light requesting Ecology to initiate a dispute resolution process in response to the TMDL submittal. The Pend Oreille County PUD initiated a similar request on May 6, 2011.

Total Dissolved Gas TMDL

On March 26, 2008, the Environmental Protection Agency (EPA) approved the Total Dissolved Gas TMDL for the Washington portion of the Pend Oreille River. The next step is to develop a water quality implementation plan. The implementation plan is on hold until the temperature TMDL is completed so that only one plan, covering both parameters, will be written. Implementation of this TMDL will reduce the amount of air trapped in the water due to operating dams on the river in Washington.

Technical information

Related information

Idaho Dept. of Environmental Quality’s web site for the Pend Oreille TMDL

WRIA 62: Pend Oreille Watershed Information (Water web site)


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Last updated May 2015
  Water resource inventory area (WRIA) 62 map, Washington State.


WRIA: #62 (Pend Oreille)
Pend Oreille

Water-body Name:
Pend Oreille River

Total dissolved gas

# of TMDLs:
Total dissolved gas - 2

Total dissolved gas - approved
Temperature - submitted to EPA
Dispute resolution initiated for temperature TMDL

Contact Info:
David T. Knight
Phone: 509-329-3590
Email: David.T.Knight@ecy.wa.gov

Eastern Region
Department of Ecology
N 4601 Monroe
Spokane, WA 99205-1295