WSDOT’s Fish Passage Barrier Removal Program
Salmon and other fish need access to freshwater habitat for feeding and spawning. |
Salmon and other fish need access to freshwater habitat for spawning and juvenile rearing. Washington State Department of Transportation (WSDOT) recognizes that removing fish barriers is important to the restoration of fish habitats and salmon recovery efforts.
WSDOT’s Fish Passage Barrier Removal Program began in 1991 to identify and remove barriers to fish passage caused by culverts under state highways. This is a cooperative effort with the Washington Department of Fish and Wildlife (WDFW).
How do we determine the number of blocking culverts?
WSDOT works with the Dept. of Fish and Wildlife to identify and prioritize fish-bearing streams and fish passage problems. |
WSDOT works with WDFW to evaluate culverts for fish passibility in all fish bearing stream crossings. Physical habitat surveys are conducted upstream from fish barriers to help us prioritize corrections that have the most benefit to fish.
The state wide inventory of WSDOT’s highway system (7,045 miles) was completed in September 2007. The data from the final inventory is still being tabulated. The next report will be available in the spring of 2008.
Data from our May 2007 Fish Passage Inventory reported:
- 6,210 culverts have been inventoried statewide
- 3,142 culverts in the state system are in fish-bearing streams
- 1,676 of the culverts in fish-bearing streams were identified as barriers
- 1,266 WSDOT–owned fish passage barriers that are in need of modification or replacement were identified as having significant habitat gain.*
*Significant habitat gain can be described as adding more than 200 meters (or 218 yards – approximately two football fields) of upstream habitat by removing a barrier from a fish bearing stream.
How culverts can be a barrier:
This culvert on SR 109 is an example of a fish passage barrier because the opening of the culvert is too high for fish to jump into and prevents fish from reaching upstream habitat. |
- Culvert outlet is too high – exceeds the jumping capabilities of the fish
- Water velocity through the culvert is too fast – exceeds the swimming capabilities of the fish
- Water depth inside the culvert is too shallow – not enough water for fish to swim through
- Debris blocks access or creates turbulence that exceeds the swimming capabilities of fish
How we address the problem – our three-pronged approach:
- Fish barriers are corrected through highway projects, whenever a hydraulic permit is required
- Stand-alone projects fix high priority barriers on highways that will not be addressed by a highway construction project anytime soon
- Some barriers are corrected through our Maintenance program, which replaces a failing culvert with a fish passable structure
How are culvert projects prioritized?
Stand-alone fish barrier corrections are prioritized to provide the largest habitat gains for the greatest number of “at risk” fish species, for the best value.
Prioritizing factors include:
- Amount of habitat gained for spawning and rearing
- Quality of the habitat gained
- The number of species that benefit from the habitat
- Cost of the project – Costs for barrier corrections cover a wide range – from solutions that modify existing culverts in place to those that entirely replace a culvert with a bridge.
How are culverts designed to provide fish passage?
When a fish passage barrier is identified and scheduled for correction, WSDOT works with WDFW to pick the best alternative for correcting the fish passage problems. Culvert designs are based on the latest edition of WDFW’s Design of Road Culverts for Fish Passage Manual. This design manual provides a variety of culvert correction options. WSDOT's and WDFW's goal is to select a design that maximizes fish passage for the species found in a particular stream, and can be successfully constructed at that location.
Where feasible, WSDOT and WDFW prefer to use a type of design called “stream simulation” to correct culvert barriers because it best mimics the conditions found in the natural streambed at the culvert site. Culverts designed to simulate natural streambeds are constructed wider than the existing stream channel width, and sloped at a similar gradient as the existing natural stream. Our approach to a stream simulation culvert is a bottomless culvert placed over a natural streambed. Use of stream simulation culverts is based on the principle that, if fish can migrate through the natural channel, they can also migrate through a man-made culvert that simulates the stream channel.
What’s been done so far?
Above: An undersized 11 foot culvert at Mill Creek on US 2 near Stevens Pass was a total fish barrier because the outfall drop was too high.
Below: In 2006 the culvert was replaced with a 38 foot bottomless arch culvert. The new structure restores access to over seven miles of upstream habitat for chinook salmon, steelhead, resident cutthroat trout and bull trout.
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- Since 1991, WSDOT completed* 205 culverts that were barriers to fish opening 480 miles of habitat
- We’ve spent $46 million since 1991 for inventory and correction of fish barriers: $20 million for inventory and $26 million on correction
- In 2006 and 2007, 32 fish passage projects were completed, which included 10 high priority stand-alone projects. More information on those projects can be found on our Fish Passage web page.
* Follow up monitoring is used to track progress. This shows that some of these projects require additional work to be fully functional for fish passage.
What still needs to be done?
As reported in the May 2007 Fish Passage Inventory , statewide:
- 1,676 - the number of fish passage barriers
- 1,266 - fish passage barriers with significant habitat gain
- 205 - the number of barrier removal projects that have been completed
Where are we heading?
WSDOT is committed to doing its part for the environment by removing barriers to fish habitats. Our strategy is to continue correcting barriers as part of highway construction projects where we have in-stream work; and to spend money provided by the legislature for the “stand-alone” projects on the highest priority corrections.
Need more information?
For more information on WSDOT’s Fish Passage Program, call Jon Peterson, WSDOT Fish Passage Coordinator, at 360-705-7499.