Peterson Creek Aquatic Organism Passage Improvement

This project replaced an 8.0-ft failing culvert where Miami Foley Road crosses Peterson Creek, a tributary of the Miami River (Tillamook Bay Watershed, Tillamook County, Oregon). The culvert was undersized and perched during low water conditions. The original designs included culvert removal and construction of a 48-ft open span, concrete bridge. Prior to construction, the contractor suggested modifying the design. The resulting value-engineered design accomplished the project objectives and lengthened the bridge span 5-ft and the low chord elevation to 68ft. This allowed the bridge to pass 100-year flood flows, whiile the original design did not. Construction was completed ahead of schedule and with a lower total project cost than proposed.

Peterson Creek is within the range of several Pacific salmonids including Oregon Coast coho, Chinook, and chum salmon; and steelhead and cutthroat trout. ODFW spawning distribution maps depict fall Chinook, coho, chum, and winter steelhead in mainstem Peterson Ck and its tributaries. Coho, steelhead and cutthroat trout were documented during summer, snorkel surveys focused on juvenile coho.[1] This report states that the creek has excellent spawning opportunities for coho and high channel sinuosity and habitat complexity. It also indicates that the stream had low rearing densities relative to habitat quality and worried that further degradation of the culvert at the mouth could limit temperature dependent juvenile migration during summer low flows. The stream is also within the range of Pacific, river and western brook lamprey. Distribution maps depict Pacific lamprey in the mainstem Miami above Peterson Creek and western brook lamprey are known from the basin. The existing culvert has been identified as a partial barrier to juvenile salmonid passage through the use of a recognized barrier determination model (BLM Coarse Screen Filter for Juvenile Salmonid Passage Assessment, Version 2.2). The proposed project will replace the existing 8-ft circular culvert with a 48-ft open-span, concrete bridge. In other words, the replacement structure will be greater than 1.5 times as wide as the active stream channel and will include a wide channel with a streambed composed of natural substrate. As a result, the replacement structure will be much less susceptible to catastrophic failure and it will not impede transport of streambed materials, organic matter or nutrients. Further, the replacement structure will allow unimpeded passage to six miles of stream habitats for all life stages of all salmonid and lamprey species that occur in the Miami River Watershed.