Protecting Public Health and the Environment.

Hangman Creek (Upper) Subbasin

Subbasin at a Glance

Hydrologic Unit Code 17010306
Size Approximately 10,000 acres
§303(d) Listed Stream Segments Hangman Creek, South Fork Hangman Creek, Bunnel Creek, Hill Creek, Conrad Creek, Martin Creek, Tenas Creek
Beneficial Uses Affected Cold water aquatic life, secondary contact recreation, salmonid spawning
Pollutants of Concern Sediment, temperature, bacteria, nutrients, habitat alteration
Major Land Uses Timber management, residential development, livestock grazing
Date Approved by U.S. EPA

September 2007
EPA Approval Letter

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.

Streams and Pollutants for Which TMDLs Were Developed

Hangman Creek
Sediment, temperature, bacteria
S. Fork Hangman Creek
Sediment, temperature, bacteria
Tenas Creek
Sediment, temperature, bacteria
Martin Creek
Sediment, temperature, bacteria
Conrad Creek
Sediment, temperature, bacteria
Hill Creek
Sediment, temperature, bacteria
Bunnel Creek
Sediment, temperature, bacteria

Subbasin Document