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Payette River (Middle Fork) Subbasin

Data Details
Hydrologic Unit Codes 17050121
Size 292 square miles (186,880 acres)
Water Bodies with EPA-Approved TMDLs (Category 4a) Upper and Lower Middle Fork Payette Rivers
Beneficial Uses Affected Cold water aquatic life
Major Land Uses Forestry, agriculture, urban
Date Approved by EPA July 2000 EPA Approval Letter
Date Addendum Approved by EPA December 2007 EPA Approval Letter

Subbasin Characteristics

The Middle Fork Payette River is a 4th-order tributary of the Payette River located in the northern part of Boise County and the southern part of Valley County, Idaho. Beneficial uses in the mainstem Middle Fork Payette River include salmonid spawning, cold water biota, primary and secondary contact recreation, domestic water supply, agricultural water supply, and special resource water (only cold water biota was found to be affected by pollutants).

1999 Subbasin Assessment and TMDL

Results of a water body assessment for the Middle Fork Payette River indicate that the lower reaches of the river (below Bulldog Creek) are not fully supporting cold water biota due to high levels of sediment and subsequent changes in channel morphology. The tributaries to the Middle Fork Payette River and the upper sections of the river were found to be meeting their beneficial uses and were removed from the §303(d) list.

A TMDL for sediment for the lower Middle Fork Payette River was prepared. A TMDL for habitat modification (changes to channel morphology) was not prepared, as habitat alteration is considered “pollution,” but not a “pollutant,” and TMDLs are not required for water bodies impaired by pollution. A TMDL is only required when a pollutant can be identified and in some way quantified.

1999 TMDL: Stream and Pollutant for Which TMDLs Were Developed

Stream Pollutants
Middle Fork Payette River (Bulldog Creek to mouth) Sediment

2007 Addendum

This document addresses one water body (four assessment units) in the Middle Fork Payette River subbasin, the main stem river itself, placed on Idaho’s §303(d) list. This document addresses the temperature TMDL for the Middle Fork Payette River. Twelve tributaries to the Middle Fork Payette River were examined along with the river as sources of solar loading. These tributaries were chosen based on stream volume. Effective shade targets were established for these waters based on the concept of maximum shading under potential natural vegetation resulting in natural background temperature levels. Shade targets were derived from effective shade curves developed for similar vegetation types in the Northwest. Existing shade was determined from aerial photo interpretation field verified with Solar Pathfinder data. TMDLs were approved for the Middle Fork Payette River, and informational TMDLs were developed for the 12 tributaries.

2007 Addendum: Stream and Pollutant for Which TMDLs Were Developed

Stream Pollutants
Middle Fork Payette River Temperature

Subbasin Document(s)

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