Parsons Creek 303d Evaluation


Parsons Creek is on 303d list, listed in 2002 and updated in 2006. The TMDL was completed and approved by EPA (Sept. 28,2007), however the state found the TMDL incomplete and needs to be updated by the state and re-submitted to EPA due to the need to solicit more public comments. Problems include sediment, nutrients, degraded habitat. Sediment (specifically TSS) is the pollutant that must be addressed to attain the designated use. Fine sediment covers the stream substrate and fills in pools, reducing the suitable habitat for fish and macroinvertebrate communities. Filling-in of pools reduces the amount of available cover for juvenile and adult fish. Sedimentation of riffle areas reduces the reproductive success of fish by reducing the exposed gravel substrate necessary for appropriate spawning conditions. Streambank erosion also widens the streams, resulting in reduced cover for fish. Sedimentation also increases turbidity, reducing light penetration necessary for photosynthesis in aquatic plants. Increased turbidity also reduces the feeding efficiency of visual predators and filter feeders, and lowers the respiratory capacity of aquatic invertebrates by clogging their gill surfaces.

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