The Road to Salmon RecoveryRecovery by design — King County Roads' projects that improve salmon habitatRock Creek (SE 248th Street) ProjectWhen the roadway on SE 248th Street began cracking and sinking, crews from the King County Road Services Division discovered that the 100-year-old wooden culvert that carries water from Rock Creek under the road was decaying and creating a partial barrier to fish migration. So, from early June through mid-September, approximately 250 feet of SE 248th Street where it meets Rock Creek and the Cedar River Trail was closed to replace the trestle and culvert crossings. As part of the project, the County also repaired some degraded stream banks and restored instream habitat on Rock Creek. New concrete box culvert The contractor installed the new three-sided concrete box culvert in early July. The new culvert is 26 feet wide, eight feet tall, and 140 feet long (inside dimensions). The installation began with the placement of six footings weighing 33,400 pounds each. Streambed gravel and boulders were placed inside the footings to a depth of about five feet. The new culvert provides some key features for salmon habitat. Sockeye salmon, coho salmon, chinook salmon, coastal sea-run cutthroat trout and possibly bull trout will benefit from the new culvert. The wider culvert, lower water velocities, and increased roughness through and at both ends of the culvert provide upstream-migrating fish with resting places and more room to maneuver as they move through. Potential obstacles to upstream migration posed by the deteriorating timbers of the old culvert are no longer a concern with the new culvert. The new culvert is wider, more stable, and has no vertical jumps. New trail trestle The Cedar River Trail trestle was replaced with a longer span concrete and steel structure. The longer span was needed in order to place the wider culvert under the road. The previous timber trestle had vertical supports immediately adjacent to the old wooden culvert walls, which severely constrained the size of the culvert. The new trestle fits well into the rural neighborhood. Bank stabilization and restoration Downstream from the culvert where the banks were eroding, King County staff stabilized the stream bank using boulders and trees with root wads from the demolition at the inlet of the new culvert. Additional trees and boulders that are native to the general area were brought in for the bank stabilization and restoration work. Railroad ties and sand bags were removed along the eroded stream bank adjacent to two houses downstream of Rock Creek. These were replaced with logs and boulders to provide habitat complexity and stream flow variation. Fish use logs for cover; i.e., they hide under them for protection from predators. The logs and boulders create pools that fish use for resting during their upstream migration. On Monday, October 20th, King County staff braved a major rainfall to observe a good number of salmon in Rock Creek, migrating upstream through the new culvert and utilizing newly placed logs for cover. For more information about the Rock Creek Project contact: Janel London, Environmental EngineerKing County Department of Transportation Road Services Division Engineering Services Section 206-205-0575 E-mail: janel.london@kingcounty.gov |
The timber culvert at Rock Creek.
Enlarged view, 80K 
Downstream view at old culvert inlet with SE 248th Street and Cedar River Trail trestle.
Enlarged view, 124K 
October 2003 view of Cedar River Trail and new culvert.
Enlarged view, 104K 
Existing conditions downstream.
Enlarged view, 106K 
Sockeye in Rock Creek.
Enlarged view, 68K 
Placing large woody debris downstream of culvert.
Enlarged view, 257K |
= external link