November 17, 2022
Contact: Thea Wickersham, Water Quality Coordinator, thea.wickersham@deq.idaho.gov
BOISE — The Idaho Department of Environmental Quality (DEQ) is advancing three water quality improvement plans—known as total maximum daily loads—designed to control pollutants in the Beaver-Camas subbasin, Lower Clark Fork River, and Spokane River.
These efforts will help ensure that the three water bodies meet Idaho’s water quality standards and support their beneficial uses, including aquatic life, recreation, and domestic water use.
Beaver-Camas Subbasin Total Maximum Daily Load
The Beaver-Camas subbasin is one of the several “sinks drainages” in the Upper Snake River Basin, meaning all streams naturally flow subsurface into the Snake River Plan Aquifer rather than flowing into the Snake River. The Yellowstone Cutthroat Trout is a native species of concern in the subbasin.
In 2005, DEQ developed temperature and sediment TMDLs to address water quality criteria exceedances in eight different stream segments, including the mainstem segments of both Beaver Creek and Camas Creek.
On August 12, 2022, DEQ submitted the Beaver-Camas Subbasin TMDL to the US Environmental Protection Agency (EPA) outlining steps to manage temperature, Escherichia coli (E. coli), and sediment. EPA approved the plan in September 2022, which outlines the maximum pollutant levels for 16 water bodies to ensure the subbasin supports cold water aquatic life, salmonid spawning, recreation, and domestic water supply.
In its review, EPA determined that DEQ’s criteria will protect the most sensitive beneficial uses, as well as less sensitive beneficial uses, and protect water quality downstream and adjacent to the subbasin.
- DEQ regional contact: Alex Bell, Regional Water Quality Manager, alex.bell@deq.idaho.gov
Lower Clark Fork River
The 320-mile Clark Fork River flows from Butte, Montana, to Lake Pend Oreille in Idaho, accounting for 92% of the lake’s annual inflow. The river’s main tributary, Lightning Creek, is also home to a regionally significant Bull Trout population and supports many other native fish.
Sediment and temperature are the main pollutants of concern in the tributaries to the lower Clark Fork River. In 2007, DEQ developed TMDLs for instream sediment, metal, and temperature, with the goal of maintaining or restoring cold water aquatic life and salmonid spawning. Implementation work has continued into 2022, when DEQ developed revised TMDLs for 22 temperature impaired assessment units using a new methodology.
EPA approved the updated TMDLs in June 2022. The revised TMDLs and implementation plans establish pollutant allocations at a level that will help ensure the river meets state water quality standards and supports cold water aquatic life, salmonid spawning, recreation, and domestic water supply.
- DEQ regional contact: Craig Nelson, Water Quality Analyst, craig.nelson@deq.idaho.gov
Spokane River
The Spokane River is in the Upper Spokane subbasin in Kootenai County, Idaho, and drains into the Coeur d’Alene basin.
Historic mining practices discharged an estimated 64.5 million tons of tailings into the Coeur d’Alene River and its tributaries. The tailings primarily contained lead, cadmium, and zinc, and were transported and deposited throughout the basin’s tributaries, lakes, and wetlands, including the Spokane River.
The river has been listed as impaired since 1994 due to high levels of cadmium, lead, and zinc. DEQ developed TMDLs in 2000 and 2008 to address these pollutants of concern, and successfully removed cadmium as a cause of impairment in 2016.
In 2022, DEQ submitted a revised TMDL for lead and zinc to EPA, which was approved in April 2022. The 2022 TMDL includes pollutant allocations necessary to protect and support a variety of beneficial uses and includes implementation strategies necessary to ensure progress towards improving water quality throughout the Spokane River.
- DEQ regional contact: Kristin Lowell, Water Quality Coordinator, kristin.lowell@deq.idaho.gov
Background
The Clean Water Act § 303(d) requires states and tribes to identify and prioritize water bodies that do not meet water quality standards. Under the law, Idaho must develop a water quality improvement plan, called a total maximum daily load (TMDL), for water bodies not meeting water quality standards. A TMDL sets the maximum amount of a pollutant that a water body can receive and still meet water quality standards.