Aquatic Contracting LLC, was contracted by the Lower Columbia Watershed Council and the Natural Resource Conservation Service to replace two aging culverts with a large arch bridge, improving fish passage and tidal influence on Conyers Creek.
Under a strict timeline, Aquatic Contracting constructed a large coffer-dam in order to keep the project work area dry. The dam kept tidal fluctuations as high as 9 feet out of the project area. 2000 cubic yards of soil were excavated and the old culverts removed. 2000 tons of stream bed gravel was placed to create a new channel and provide stability and habitat.
For the bridge construction, piling were driven to provide support for the footings. A concrete slab was poured underneath the footing to provide additional stability in the tidal environment. Footings were then poured and the bridge placed. To provide slope stability along the bridge wing walls, log jams were constructed and soil lifts placed on top.
The project was completed in 40 days, inside the allocated window. Shortly after completion the project survived the December 2007 flood. Had the project not been completed, it is likely the culverts would not have sustained the storm and flood damage, and the road would have been washed away.
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