Poorman Creek Culvert Replacement

Phase 1: Culvert Replacement

The objective of this project was to restore access to habitat for threatened Upper Columbia River (UCR) steelhead trout (Oncorhynchus mykiss) and endangered UCR spring Chinook salmon (Oncorhynchus tshawytscha) by replacing a barrier road culvert on Poorman Creek with a bottomless steel plate arch and engineered streambed. Threatened Upper Columbia bull trout (Salvelinus confluentus) have not been observed in Poorman Creek, but they are present in the Twisp River immediately downstream of the project area. An irrigation diversion immediately below the culvert was also a partial barrier and was replaced with a rock weir structure that allows passage at all flows. The project also improves downstream habitat in the creek by restoring bedload and wood transport through the culvert.

This project removed the last fish passage barrier on Poorman Creek. The project complements two prior fish passage barrier culvert replacements on National Forest lands upstream of this project site, and restores access to 2-3 miles of habitat above the Poorman culvert site.

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Out With the Old

The old corrugated metal culvert was too small, and created a barrier to fish passage at high and low flows.

The contractor dug a bypass canal to re-route the creek flows around the worksite during construction. This created a dry work area for culvert removal and replacement.


 

 

Laying the Foundation

Six inches of gravel were placed and compacted to create a base for the concrete culvert footings. An outside engineering firm came to the site to perform a compaction test of the base to make sure that it met specifications for the footings.

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Placing the Footings

The contractor used an excavator to lift the pre-cast concrete footings into the trenches.

Workers on the ground helped guide the heavy footings into place.


Installing the Culvert

An excavator lifted the sections of culvert into place, and workers bolted the sections together.

A series of grade control boulder weirs were installed under the arch and downstream of the culvert. The weirs will help make sure that the downstream flows through the culvert meet fish passage criteria.

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Rebuilding Poorman Creek Cutoff Road

Once the culvert was in place, the contractor rebuilt the road surface and placed rock riprap to stabilize the bank around the arch.

 


Fish Passage in Poorman Creek

The finished culvert allows fish passage to 2-3 miles of habitat upstream in Poorman Creek.

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Following construction, the site is restored to pre-project condition or better


 

 

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