Muddy Hollow Culvert Removal: Compliance report for Coho Salmon and Steelhead Trout Restoration Project

Point Reyes National Seashore, National Park Service

Muddy Hollow Creek lies within the central California coast Evolutionarily Significant Unit (ESU) and provides critical habitat for steelhead trout (Oncorynchus mykiss), a federally threatened species. National Park Service (NPS) surveys within Muddy Hollow Creek confirmed the presence of O. mykiss in 1997. It is likely that some component of the surveyed population is oceangoing. Prior to NPS acquisition of the land in the 1960’s, an 80’ culvert was installed to pass an access road over Muddy Hollow creek. Over time the culvert failed, creating fish impediments, elevating sediment load, and diminishing streambed stability. Removal of the culvert, or daylighting, was performed to restore hydrologic connectivity and to reduce the long-term maintenance requirements associated with culvert operation. The National Marine Fisheries Service (NMFS) designed a 2-step vortex boulder weir fish passage that was used to replace the culvert. As well as enhancing fish migration routes, the design allows for stream gradients to be maintained, stabilizes banks, and provides habitat for developing juvenile salmonids. The culvert was removed and recycled, and 1 to 4 ton boulders were installed to attain the desired intent of the project. Mitigating actions taken by NPS included the removal of all fish from the project site, diversion of water flow from direct impact, and the installation of fish fences upstream and downstream of project site to prevent fish access during the project. Revegetation and erosion control efforts included sprigging of willow stakes, alder and Juncus sp. transplants, installation of curlex bundles, and the redistribution of leaf litter and debris to break surface water flow patterns. The purpose of this report is to summarize the hydrologic performance and effectiveness of the fish passage structure in its first year of operation. Since project completion, NPS has monitored the following parameters at the project site: flow conditions, stream levels, structural integrity, the fishery resource, revegetation, and sedimentation. NPS staff will continually monitor the project site in coming winters and will prepare a similar document in 2002 and 2003.