Background

Dunn Creek is a tributary to the North Fork Cottaneva Creek near the town of Rockport in Mendocino, County. Dunn Creek is a second order stream that drains a two-square mile watershed. The creek supports anadromous steelhead trout (Oncorhynchus mykiss) and coho salmon (Oncorhynchus kisutch). About ¾ of the land ownership within the Dunn Creek sub-basin is managed for sustainable timber production.
Three culverts on private land were complete barriers to fish passage. They included:

•  A 36-inch diameter culvert located 60-feet south of the lower bridge crossing was removed and the tributary stream was rerouted through a newly constructed side channel with two boulder weirs.
• An 8-foot diameter culvert at the middle crossing was removed and replaced with a 16-foot wide by 40-foot long bridge.
• A 7-foot diameter culvert at the upper crossing was removed and replaced with a 16-foot wide by 50-foot long bridge.
• In addition, six boulder weirs were installed in the channel.

All three culvert upgrade sites (Figures A–F) are located upstream of another site and fish passage barrier remediation project along CA-1 that improved passage conditions for juvenile and adult salmon and steelhead in 2013. The site had a nine-foot diameter steel plate pipe culvert that created a six-foot vertical drop and barrier to fish passage downstream. The culvert was removed and replaced with a 134-foot long concrete slab bridge.

Project Purpose

The purpose of the project was to improve adult and juvenile fish passage, and enhance salmonid rearing by upgrading three road crossings on Dunn Creek, restoring access to habitat for coho salmon and steelhead-trout in the Cottaneva Creek watershed.

Monitoring Timeline

Pre-project surveys, consisting of streambank observations and electrofishing, were conducted for several years prior to the planning and implementation of this project. Adult spawner surveys were conducted in 2015.