Publication Summary

South Prairie Creek, downstream of the town of South Prairie, and Spiketon Creek/Ditch, located southwest of Buckley, do not meet the fecal coliform bacteria Class A water quality standard, and reductions in bacteria loads are required. The mouth of Wilkeson Creek does meet the water quality standard and does not require bacteria reductions.

South Prairie Creek from the town of South Prairie downstream, Spiketon Creek/Ditch, and Wilkeson Creek exceed the numerical Class A temperature standard. A variety of management activities are necessary to meet the temperature standard under extreme hydrologic conditions.

The South Prairie Creek watershed covers 90.7 mi2 (235 km2) and includes all or portions of the towns of Wilkeson, Buckley, South Prairie, and Burnett. The creek, a Class A water body, is a tributary to the Carbon River, located in the Puyallup River watershed. Segments of South Prairie Creek or its tributaries were placed on the 303(d) list of impaired waters for fecal coliform, temperature, and copper.

Historical fecal coliform bacteria concentrations along lower South Prairie Creek exceeded water quality standards, resulting in inclusion on the 1996 and 1998 303(d) lists. The present study identifies and quantifies the sources of fecal coliform bacteria from Spiketon Road in Buckley to the confluence with the Carbon River. The South Prairie Creek load allocations call for fecal coliform bacteria load reductions downstream of the town of South Prairie. In addition, fecal coliform loads must be reduced in Spiketon Creek/Ditch and in the unnamed tributary leaving the town of South Prairie.

Continuous temperature monitoring in 2000 and 2001 indicated that some segments of South Prairie Creek and its tributaries exceed the Class A temperature standard. Wilkeson/Gale Creek was placed on the 303(d) list for temperature based on monitoring conducted in 1997 by the Muckleshoot Tribe. The temperature assessment uses effective shade as a surrogate measure of heat flux to fulfill the requirements of the federal Clean Water Act. Effective shade is defined as the fraction of the potential solar shortwave radiation that is blocked by vegetation and topography before it reaches the stream surface. The present study recommends load allocations equivalent to mature riparian vegetation throughout the watershed. The South Prairie and Wilkeson wastewater treatment plants should not increase stream temperatures significantly at the edge of the mixing zone.

A recent re-evaluation of the copper listing on Wilkeson Creek found that waters are within water quality standards for copper during critical conditions (Golding and Johnson, 2001) and recommended that the listing be removed. Therefore, no TMDL analysis was conducted.

Link to EIM data for User Study ID SPC TMDL