Protecting Public Health and the Environment.

Cottonwood Creek Subbasin

Subbasin at a Glance

Hydrologic Unit Code 17060305 (part of the South Fork Clearwater River hydrologic unit)
Size 124,439 Acres
§303(d) Listed Stream Segments Cottonwood Creek (upper and lower), Red Rock Creek, South Fork Cottonwood Creek, Long Haul Creek, Shebang Creek, Stockney Creek
Beneficial Uses Affected Secondary contact recreation, agricultural water supply, cold water biota, salmonid spawning
Pollutants of Concern Sediment, temperature, nutrients, dissolved oxygen, pathogens, ammonia, habitat, flow alteration
Major Land Uses Cropland, pastureland, rangeland, forestland, urban/industrial
Date Approved by U.S. EPA June 2000
EPA Approval Letter

Overview

Cottonwood Creek is a second order tributary of the South Fork Clearwater River, located in Idaho County, Idaho. Cottonwood Creek has been designated a high priority water quality limited segment. Portions of Cottonwood Creek lie within the Nez Perce Reservation. TMDLs for the remainder of the South Fork Clearwater River hydrologic unit were completed in 2004.

Both fine sediment and coarse sediment impair salmonid spawning and rearing in Cottonwood Creek. TMDLs were developed for both. A TMDL was also developed for temperature to protect steelhead salmonid spawning and other cold water aquatic life. The temperature TMDL established percent reduction targets that are linked to percent increase in shade.

Nutrient and dissolved oxygen TMDLs were combined. An assumption was made that by meeting the instream nutrient target the dissolved oxygen standard will also be met.

A TMDL for bacteria was developed. The Cottonwood wastewater treatment plant was not a significant source of bacteria loading; therefore, its wasteload allocation was left at its existing permitted limit. Significant sources of bacteria in the watershed include animal wastes, septic tank failures, and cattle in streams.

An ammonia TMDL was developed that requires a five percent reduction in total ammonia during November through April. The ammonia TMDL only addresses the toxicity effects of ammonia; the nutrient effects of ammonia are evaluated in the nutrient TMDL.

Flow and habitat are identified on the §303(d) list; however, the TMDL does not address these issues as they are currently not required to be addressed under the Clean Water Act.

Streams and Pollutants for Which TMDLs Were Developed

Long Haul Creek
Fine sediment, coarse sediment, temperature, total inorganic nitrogen, total phosphorus, bacteria
Lower Cottonwood Creek
Fine sediment, coarse sediment, temperature, total inorganic nitrogen, total phosphorus, bacteria
Red Rock Creek
Fine sediment, coarse sediment, temperature, total inorganic nitrogen, total phosphorus, bacteria
Shebang Creek
Fine sediment, coarse sediment, temperature, total inorganic nitrogen, total phosphorus, bacteria
S. Fork Cottonwood Creek
Fine sediment, coarse sediment, temperature, total inorganic nitrogen, total phosphorus, bacteria
Stockney Creek
Fine sediment, coarse sediment, temperature, total inorganic nitrogen, total phosphorus, bacteria
Upper Cottonwood Creek
Fine sediment, coarse sediment, temperature, total inorganic nitrogen, total phosphorus, bacteria, ammonia

Subbasin Document