Spokane River snippet

Spokane dissolved oxygen TMDL

Project Background

Ecology began working on a Dissolved Oxygen Water Quality Improvement Project (TMDL) in 1998. In the fall of 2000, Ecology contracted with the U.S. Army Corps of Engineers (USACE) to apply the CE-QUAL-W2 model to the Spokane River and Lake Spokane system. The USACE collaborated with Portland State University. A report (Cusimano, 2004) on the water quality study and modeling effort was completed in 2004 (see the Modeling Information page for a link to the report).

In October 2004, Ecology released a draft TMDL for public comment. Prior to the release, entities that discharge to the Spokane River (the Dischargers) developed a Use Attainability Analysis and submitted a petition for rule making to revise the dissolved oxygen water quality criteria for the Spokane River and Lake Spokane. Shortly thereafter, Ecology and the Dischargers agreed to withdraw the petition, put the draft TMDL on hold and develop an implementation plan for the TMDL. This led to the creation of the Spokane River TMDL Collaboration (Collaboration).

The Collaboration included Ecology, the Dischargers, local governments, Idaho Department of Environmental Quality (IDEQ), the U.S. Environmental Protection Agency (EPA), the Spokane Tribe of Indians, environmental groups, and Avista Utilities. The Collaboration developed the Foundational Concepts for the Spokane River TMDL Managed Implementation Plan. The agreement was formalized through a Memorandum of Agreement signed on March 7, 2007.

During 2007, Ecology worked with Portland State University to run some additional model scenarios to incorporate modifications to the modeling approach as a result of the Collaboration. The dissolved oxygen TMDL has been revised to reflect the Foundational Concepts and the new modeling. The draft report was distributed for a 45-day public comment period in September 2007 and additional public comment periods in early 2008.

In late 2008, EPA determined that the 2007/08 draft TMDL reports did not adequately account for draft permit limits they developed for Idaho dischargers (see EPA letter).

Following this reversal, EPA and Ecology re-established the TMDL advisory process and discussions with stakeholders to comprehensively account for all pollutant sources (point, nonpoint source, and hydroelectric dams) in an equitable manner throughout 2009, culminating with a final TMDL approved by EPA in May 2010. The same model was used and developed by Portland State University in partnership with Ecology and EPA. A dispute resolution hearing took place in April 2010 and permits for Washington Dischargers were issued in November 2011. See the Implementation Schedule and Actions page and Older Status links on that page for more details on the development history of the Spokane River DO TMDL. Details on the TMDL can be found at the What Does the TMDL Do? page and modeling information for all efforts can be found at the Modeling Information page.

Last updated December 2012