The City of Lake Forest Park proposes to replace the culvert (L-80) conveying Lyon Creek beneath 35th Avenue NE, which is approximately 198 stream meters (m) south of its crossing of Ballinger Way NE. The existing 47-foot-long structural plate steel (SPS) arch culvert is undersized for conveyance of peak flows and debris, and is identified as a partial barrier to fish passage due to slope and velocity according to 2017 and 2010 WDFW Level A culvert assessments.The City proposes to replace the existing L-80 culvert to improve fish passage with a 22-foot span by 8-foot rise by 65-foot long four-sided concrete box culvert and natural stream channel. The replacement culvert will meet WDFW Stream Simulation Culvert Design Criteria for channel width, culvert bed slope, stream bed material gradation, depth of stream bed materials, and capacity to convey the 100-year design flow and debris. The culvert and associated stream bed sediment will be installed with a 1.0% slope. Average 2-year flood slope upstream is 0.9% over a channel distance of 63 m.; the replacements slope of 1.0%  will meet WDFW slope ratio criteria. Large woody debris and root wads will be installed to provide aquatic habitat.Fish species benefited by this project include Chinook, coho, steelhead, searun cutthroat, and resident trout.