Protecting Public Health and the Environment.

Boise - Mores Creek Subbasin

Subbasin at a Glance

Hydrologic Unit Code 17050112
Size 625 square miles (400,000 acres)

Water Bodies with EPA-Approved TMDLs (Category 4a)

Clear Creek, Grimes Creek, Lucky Peak Lake, Macks Creek, Mores Creek, Smith Creek, Thorn Creek

Beneficial Uses Affected Cold water aquatic life, salmonid spawning, primary contact recreation, domestic water supply

Major Land Uses

Forest, rangeland
Date Approved by EPA

February 2010
EPA Approval Letter

Subbasin Characteristics

The Boise-Mores Creek subbasin is located in southwest Idaho, about seven miles east of Boise, Idaho, predominantly in Boise County with small parts in Ada County and Elmore County. The subbasin includes Mores Creek, Grimes Creek, and all tributaries upstream to the headwaters as well as Lucky Peak and Arrowrock Reservoirs and the Middle Fork Boise River to the confluence of the North Fork Boise River. Of the 400,000 acres in the watershed, 81.5 percent are forest and 17.4 percent rangeland. Idaho City and Placerville are the only recognized cities in the watershed. Other incorporated cities in Boise County include Horseshoe Bend, Crouch, Garden Valley, and Lowman.

2009 Subbasin Assessment and TMDL

TMDLs were developed for the two §303(d)-listed streams (Mores and Grimes Creeks). A sediment TMDL has been developed for all segments of Mores Creek and two segments of Grimes Creek. Another TDML addresses temperature impairment of Mores Creek and thermal contributions of its tributaries including Smith Creek, Thorn Creek, Elk Creek, Grimes Creek, Granite Creek, Macks Creek, Daggett Creek, and Robie Creek. Part of the Boise River is recommended to be added to the §303(d) list due to temperature impairment.

No TMDLs were completed for habitat alteration or flow alteration in accordance with DEQ and EPA policy. However, DEQ proposed listing certain segments of Mores Creek, Elk Creek, Grimes Creek, and Granite Creek in the next Integrated Report for habitat alteration and flow alteration due to impacts from historic placer mining.

2009 TMDL: Streams and Pollutants for Which TMDLs Were Developed

Mores Creek
Temperature, sediment
Smith Creek
Thorn Creek
Elk Creek
Grimes Creek
Temperature, sediment
Macks Creek
Daggett Creek
Robie Creek

Subbasin Document