The majority of the Rock TMDL Planning Area (TPA) is located in Granite County, with a small portion in Missoula County. The total extent of this TPA is 569, 320 acres, or approximately 890 square miles, and it comprises the Rock Creek watershed. Waterbodies in this TPA flow through both publicly-owned (United States Forest Service, State of Montana and Bureau of Land Management) and privately-owned land. The streams in the Rock TPA are within the 4th code HUC17010202, and they have been assigned a B-1 beneficial use classification (ARM 17.30.623). Rock Creek is located in the Pend Oreille River Basin (Accounting Unit 170102) and drains from the Anaconda Range to the Clark Fork River near Clinton. The watershed is located on the border between the Middle Rockies and Idaho Batholith Level III Ecoregions. Flow in Rock Creek is reduced by inter-basin diversion from East Fork Rock Creek into Trout Creek, a tributary of Flint Creek.  

The Montana Department of Environmental Quality has identified 25 waterbody-pollutant impairments in the Rock TPA for sediment, temperature, nutrients, and metals. They are shown in the table below. The TMDL planning process for this TPA incorporates a combination of water quality sampling and hydrologic modeling to further identify and quantify sediment, temperature, nutrients, and metals contributions from all significant sources.   

Sediment, temperature, nutrient, and metals TMDLs are intended to be included in the same final document; however, nutrient and metals TMDLs will either be included in a separate project plan or added as a modification to this project plan at a later date.  

The table identifies which streams have sediment, temperature, nutrients, and metals listed impairments. For complete information on each stream's probable impairment causes and sources, see DEQ's Clean Water Act Information Center. To view the most recent information, click on "Begin Search" and then select "Rock" in the TMDL Planning Area drop-down list under "Step 2." You do not need to select anything else in Step 1 or Step 2.