We are preparing to moor the pontoons that will be built as part of the Pontoon Construction Project.
What is moorage? Why is WSDOT storing the pontoons in water?
Pontoon moorage is a method of anchoring the pontoons for storage in Grays Harbor until they are needed for the bridge replacement. Because the largest pontoons are a football field in length and weigh 11,000 tons each, they must be stored and transported in water.
Where in Grays Harbor will the pontoons be moored and how will they get there?
The pontoon moorage area is located on the south side of the Grays Harbor navigation channel. This location is approximately 1.5 nautical miles from the Grays Harbor shoreline near the Johns River. The moorage area is about 1 mile long, 700 feet wide, and set back 200 feet from the navigation channel. When each batch of pontoons is complete, the casting basin will be flooded and the pontoons floated out of the basin using tug boats and taken to the moorage location where they will be secured and stored.
Why was this moorage location selected?
We worked with regulatory agencies, tribes and the local marine community to identify the pontoon moorage location. This location was selected because it met key requirements, including:
- Adequate water depth
- Adequate protection from wind and waves
- Clearance of charted navigation channels
When will the moorage occur and how will the pontoons be moored?
We are hiring a contractor to conduct the pontoon moorage work. This fall through the end of the year, the contractor will make arrangements to install anchors, anchor chains, buoys and mooring lines to accommodate up to four rafts of two to four pontoons at one time in the Grays Harbor moorage area.
There will be approximately 300 feet of separation between the rafts. The moorage area will be ready to receive pontoons before the first batch of six pontoons is ready in spring 2012.
What measures will WSDOT take to ensure the pontoons are moored safely?
Maintenance crews will conduct routine inspections to ensure safety.
- WSDOT will outfit the pontoons with navigation lighting in compliance with U.S. Coast Guard requirements.
- During moorage, we will conduct routine inspections of the chains and lines to help ensure that the pontoons are moored safely. The anchoring system is designed to keep the pontoons secured and limit drifting.
- We will monitor the pontoons and anchors regularly to ensure they remain securely in place.
- Pontoons will always float at least 7 feet above the harbor bottom, even during the lowest tides.
Where will the pontoons go next?
The pontoons will be towed to their moorage location by a tug boat
Pontoons will be moored until needed for the construction of the new SR 520 floating bridge. The pontoons would then be towed from the moorage site to Lake Washington where they will be assembled to form the floating foundation of the new bridge.