Bridge Construction

an example

Fire-truck Rated Bridge

This project was completed on a tributary to North Creek near the Bothell city limits.  The objectives of this project were to remove the invasive vegetation choking the stream, place two weirs for grade control, remove an undersized culvert that was a barrier to fish passage, and replace the culvert with a load-bearing bridge.  The final stage of planting the riparian area with native vegetation is yet to be completed.

The bridge decks were recycled from the old Hewitt Avenue Trestle and were provided by the Washington State DOT.  Engineering designs for the bridge were completed by Snohomish County Conservation District.  All construction was completed to specifications by Adopt-A-Stream staff.

Channel prior to construction (looking upstream).

This stream flows under the fence. Originally, it was choked with reed canary grass, disguising the actual volume of water flowing through the channel.

Looking down from the culvert outfall.

This culvert had nearly a three foot drop at its outlet. It was found to be a barrier to fish passage in a previous AASF stream survey.

Pre-bridge crossing.

The white water in this photo gives some indication of the velocity and volume spilling from this undersized culvert.

Cutthroat.

Prior to construction, we moved aquatic life downstream of the project area.

New bridge, looking downstream, prior to planting.

Looking upstream, toward the fence.

Once opened up, this channel proved to carry a large volume of water. The final phase of this project is to plant the riparian area with native vegetation to provide shade. This photo was taken after construction was complete, at the first rainfall of the season. Note the muddy water from urban run-off upstream.

Bridge for Private Crossing

During a routine stream survey, AASF identified this triple culvert as a barrier to fish migration in this salmon-bearing stream.  A wooden bridge was the perfect solution for this landowner who only needed occasional access for a personal vehicle.  Once the plans were drawn, the bridge took very little time to complete.  Construction was made somewhat easier as this channel is dry during the summer months.

Project site, prior to bridge installation looking upstream.

This undersized triple culvert was identified during a habitat survey by AASF. The landowner agreed to replace it with a bridge, adequate for a personal vehicle to drive over.

Project site prior to bridge installation, looking downstream.

By the time the project began, the stream had cut through to the left of where the person is standing.

Completed bridge deck, looking upstream.

Construction materials included salvaged timbers used for stringers and non-treated cedar decking to keep hydrocarbon-based chemicals out of the water.

Completed bridge deck.

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