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.

The Portneuf River Subbasin has numerous documented water quality problems that affect beneficial uses. Twenty-seven stream segments in the subbasin were listed on the 1994/1996 §303(d) list, including the mainstem Portneuf River, 16 tributaries, and Hawkins Reservoir. All segments include sediment as a pollutant of concern and roughly half are listed for nutrients. The mainstem Portneuf River is also listed for bacteria, flow alteration, and oil and grease. Hawkins Reservoir is listed for dissolved oxygen. Evidence indicates that other pollutants, such as temperature, metals, and PCBs, may also be impairing the waters in the Portneuf River Subbasin.

Information collected through the Beneficial Use Reconnaissance Program indicates that several streams on the §303(d) list (Gibson Jack, Mink, Walker, Bell Marsh, Goodenough, upper Garden, Dempsey, Pebble, and Toponce Creeks) are supporting their beneficial uses; it is recommended that these streams be removed from the §303(d) list.

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DEQ is currently seeking public comment on a revised assessment of water quality in the Portneuf River Subbasin and TMDLs to ensure water quality standards are met.
The document addresses pollution in water bodies that are on Idaho’s 2008 list of impaired waters and carryovers from previous lists, including the entire Portneuf River and its major tributaries.

In the Portneuf River (Marsh Creek to the Fort Hall Reservation Boundary), TMDLs are proposed to address excess sediment, E-coli, total phosphorus, and oil and grease.

In Hawkins Reservoir, TMDLs are proposed for dissolved oxygen, total phosphorus, and nutrients.

In addition, TMDLs are proposed to address the following pollutants in these assessment units:

• Sediment: Beaverdam Creek, Marsh Creek (upper), Kinney Creek (headwaters to Mink Creek), and South Fork Pocatello Creek (headwaters to Pocatello Creek.
• E. coli: Cherry Creek (three assessment units), Dempsey Creek (lower), Garden Creek (lower), Indian Creek, Marsh Creek (lower middle and upper), and Mink Creek (lower).
• Nutrients: Marsh Creek (upper).

The document also proposes delisting some water bodies in the subbasin for certain pollutants that no longer pose a threat to water quality. Two segments of Cherry and North Fork Pocatello Creeks, Yago Creek, and Rapid Creek (lower) are proposed to be delisted for sediment. A segment of Cherry Creek would also be delisted for nutrients.

› View draft October 2009 Revision and Addendum (pdf 3.1 mb, 364 pages).

› Submit written comments by 5 p.m. MST, Friday, December 4, 2009.