Woodcock Creek & Grimm Road Fish-Passage Project

An existing 10’ wide box culvert in Clackamas County between Colton and the City of Molalla carries Woodcock Creek under Grimm Road. Woodcock Creek is a tributary of Milk Creek, which flows into the Molalla River. This culvert is the remaining complete fish passage barrier on Woodcock Creek and prohibits access to 11 miles or more of high-quality habitat. The existing box culvert is undersized and perched approximately 16” on the outfall end, making it a partial or complete barrier to fish passage. Additionally, the culvert has a flat concrete floor which creates a sheet flow with an average depth of two inches at lower flows and with extreme velocities at higher flows. The proposed solution is to replace the culvert with a modular bridge. Also, much needed habitat complexity will be added by installing large wood and boulders. Riparian invasive species will be removed and new riparian planting will occur throughout the project area. Partners include Molalla River Watch (MRW), ODFW, and Clackamas County Department of Transportation & Development (CCDTD).

Molalla River Watch, CCDTD, and ODFW have categorized the Grimm Road crossing on Woodcock Creek in the Molalla River Watershed as a priority culvert replacement to restore fish passage to upstream habitats for all aquatic species. This project will replace a perched, concrete-bottom undersized culvert that is a fish passage barrier with a modular bridge that is 1.5 times bank-full width. The proposed project will also install several pieces of large-wood, boulders, native plantings, and vegetated swales. These actions will increase habitat complexity and diversity and will restore natural stream processes to this reach of Woodcock Creek. This project will help to restore the hydrologic processes that will increase habitat area, complexity and quality for ESA threatened Upper Willamette ESU spring Chinook, threatened upper Willamette DPS listed winter steelhead, along with non-ESA-listed coho, and native cutthroat trout. With technical assistance from Clackamas SWCD’s riparian specialist, we plan to replant the riparian area adjacent to the project site with trees that will shade the stream, prevent erosion, reduce fine sediment loads, filter road runoff, and eventually provide nutrients and natural wood recruitment to improve stream complexity. Once the fish passage impediment at Grimm Road is removed, access to the upstream forested areas with cooler water temperatures will provide high-quality spawning and rearing habitat. Those properties include Port Blakely, immediately upstream of the project site, and Ramsdell at the headwaters of Woodcock Creek, which are managed forests with commitments to improve fish habitat quality.