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Boise – Mores Creek Subbasin

Data Details
Hydrologic Unit Codes 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 southwestern Idaho, about 7 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% are forest, and 17.4% are 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, Thorn, Elk, Grimes, Granite, Macks, Daggett, and Robie Creeks. 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, Elk, Grimes, and Granite Creeks 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

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

Subbasin Documents

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DEQ Boise Regional Office
1445 N. Orchard St.
Boise, ID 83706
Ph: (208) 373-0550
Fax: (208) 373-0287
Toll Free: (888) 800-3480

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