![]() ![]() ![]() ![]() ![]() ![]() ![]() ![]() Return toList of Subbasin Assessments, TMDLs, and Implementation Plans in Idaho See Also Upper Hangman Creek
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Surface Water: Upper Hangman Creek
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| The Subbasin at a Glance | ||||||||||||||
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| Background | ||||||||||||||
The federal Clean Water Act requires that states and tribes restore and maintain the chemical, physical, and biological integrity of the nation's waters. States and tribes must adopt water quality standards necessary to protect fish, shellfish, and wildlife while providing for recreation in and on the waters whenever possible. Section 303(d) of the Clean Water Act establishes requirements for states and tribes to identify and prioritize water bodies that are water quality limited (i.e., water bodies that do not meet water quality standards). States and tribes must periodically publish a priority list of impaired waters, currently every two years. For waters identified on this list, states and tribes must develop water quality improvement plans known as total maximum daily loads (TMDLs) that establish allowable pollutant loads set at levels to achieve water quality standards. |
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| Overview | ||||||||||||||
The upper Hangman Creek watershed is located where the rolling hills of the Hangman Creek valley meet steep mountain sides. The watershed is primarily forested, although there have been some openings created for other land use activities. The land is primarily privately owned with only a small amount of national forest lands. The primary land use is timber management, with some residential development along major roads and some livestock grazing activity at lower elevations. Sediment was determined to be in excessive quantities and impairing the cold water aquatic life use designation. Sediment generated from roads, mass failures, and stream bank erosion was characterized to determine the amount of sediment load reduction needed to restore beneficial uses. The target load capacity was set at 50% above natural background. Temperature TMDLs were written because of exceedances of Idaho's numeric water quality temperature standard. Solar radiation was determined to be the factor most easily controllable and manageable in reduction of stream temperatures. A decrease in solar radiation requires an increase in shading of the streams. Bacteria TMDLs were written because water quality monitoring data indicated that the beneficial use of secondary contact recreation was not being fully supported. The source of bacteria is unknown. Further monitoring will be needed to determine the source of contamination. Known possible sources include domesticated and wild animals, and/or human contributions from recreation or septic systems. Some water bodies in this watershed were also listed for habitat alteration and/or nutrients. No TMDL was completed for habitat alteration as a matter of DEQ policy. It is being recommended that listing for nutrients be removed due to recent data showing low levels of total phosphorus. |
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| Streams and Pollutants for Which TMDLs Were Developed | ||||||||||||||
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| Subbasin Assessment and TMDLs | ||||||||||||||
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