Water Quality Improvement Project
Spokane River Area:
Dissolved Metals


A 1998 study showed that the Spokane River had elevated levels of zinc, and frequently had elevated levels of lead and cadmium. At the time of the report there were seven wastewater treatment facilities with permits to discharge into the river. Five segments of the Spokane River were listed in the 1998 Section 303(d) list of impaired surface waters because they did not meet the state's water quality standards for dissolved metals including cadmium, lead, and zinc.

Why this matters

Zinc can be found everywhere, from cyclone fences to metal roofs. Zinc is the fourth most commonly used metal, after iron, aluminum, and copper.

Cadmium is a by-product of zinc production. It is also used in nickel-cadmium batteries, pigments, plastics, and other synthetics. It can enter the water from runoff from roads and parking lots.

Both cadmium and zinc are harmful, even at relatively low concentrations, to threatened and endangered salmon, and aquatic life. They can bio-accumulate in fish tissue. Zinc and cadmium can bind to fish gills and cause suffocation. Zinc may prevent fish from "smelling" their spawning grounds. Also, it may cause toxic effects to the kidneys, bone defects, high blood pressure, and reproductive effects.

Status of the project

The Washington State Department of Ecology (Ecology) developed a Total Maximum Daily Load (TMDL) for the Spokane River for dissolved cadmium, lead, and zinc. It addresses impairments due to potential toxic effects of these metals on the five segments of the river. EPA approved the TMDL in August 1999.

Ecology is currently considering how to effectively address multiple toxic substances in the Spokane River, including dissolved metals. Such a strategy will likely include updated technical studies to assess sources and concentrations of dissolved metals.

Technical information

Spokane River Dissolved Metals Total Maximum Daily Load -- Submittal Report (Ecology publication)

Cadmium, Lead, and Zinc in the Spokane River Recommendations for TMDL and Waste Load Allocations (Ecology publication)

Related information

WRIA 54: Lower Spokane Watershed Information (Environmental Assessment Program web site)


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Last updated May 2010
  Water resource inventory area (WRIA) 54 map, Washington State.


WRIA: #54 (Lower Spokane)
County: Spokane

Water-body Names:
Spokane River

Dissolved metals

# of TMDLs: 5

Approved by EPA

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

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