SCOPE OF WORK:
A 1,400’ cofferdam using AquaDam® to protect the dredging of a new channel, removal of existing culverts, and the construction of a new bridge.
PROJECT PARTNERS:
- Layfield
- Cascade Bridge LLC
- Seton Construction Inc.
- AquaDam Inc.
Background Information and Challenge:
The North Olympic Salmon Coalition (NOSC) and the Washington State Department of Transportation (WSDOT) aimed to restore the historic tidal channels and fish runs between southern Kilisut Harbor and Oak Bay in Jefferson County, Washington. By removing outdated culverts and installing a new bridge, they sought to create approximately 2,300 acres of productive fish habitat in the Puget Sound.
The first phase of this project involved restoring the channel on the north side of the highway (State Route 116). However, dredging in a marine environment can be expensive and time-consuming. To reduce costs and expedite the operation, engineers and contractors turned to Layfield for a unique solution. Layfield USA provided a critical component of the project by supplying an AquaDam® temporary cofferdam capable of holding back local tidal waters, which can reach as high as 9 feet. Some of the diverse site challenges included working with the tide schedule, the inability to move equipment into optimal locations due to the risk of disturbing protected marsh areas, water supply distances during low tide, and the project’s quick timeline.
Solutions and Results:
Layfield proposed using the AquaDam® product due to its durability as a cofferdam and its quick deployment method compared to other cofferdam methods. The AquaDam® product is also less expensive than installing a standard sheet piles cofferdam. The systems used on this project were specially designed for the site to address its unique tidal influx. The AquaDams delivered to the site varied in height from 4 to 12 feet when filled. The 12-foot AquaDam® was placed at the end of the channel excavation to provide maximum protection.
The AquaDam® products were easy to install as they were delivered on rolls, which the contractor could roll out onto the existing ground, thus avoiding any disturbance of the protected marsh area. Once rolled out, the AquaDam® was filled with water from onsite sources using pumps. A few extra lengths of hose were needed to reach the water during low tide.
After deployment, the contractor had a relatively dry working area protected from the harsh tide. They were then able to excavate the channel using standard equipment, significantly reducing the cost of dredging from a barge. Layfield’s high-level service and quick supply turnaround resulted in a successful project for the client with minimal impact on the environment while working around the harbor.
