Twenty new east-half Hood Canal Bridge anchors are being constructed by WSDOT and Kiewit-General (K-G) at Todd Shipyards in Seattle, Wash. Anchors are large, concrete, bowl-like structures that sit on the bottom of Hood Canal and keep the Hood Canal Bridge from moving side to side. The anchors are connected to the bridge by long, steel anchor cables.
On this page, you can find out about:
Anchor Construction
Anchor Dimensions
Anchor Launch
Anchor Setting
Anchor Construction
In August 2006, crews started getting a dry dock ready for anchor construction and began assembling wood anchor forms. Actual anchor construction, marked by setting the first wood form in place, began in September 2006. The first cycle of ten anchors was completed and launched from the dry dock in February 2007. The second and final cycle of ten anchors was completed in June 2007.
Hood Canal Bridge East-half Anchors
| Diameter |
Number |
Weight for Each |
Total weight |
| 46 feet |
12 anchors |
995 tons (1,989,400 lbs) |
11,940 tons |
| 56 feet |
7 anchors |
1,328 tons (2,655,140 lbs) |
9,296 tons |
| 60 feet |
1 anchor |
1,385 tons (2,769,660 lbs) |
1,385 tons |
| TOTAL |
20 anchors |
|
22,621 tons |
Each 29-foot tall anchor was made up of just five concrete pours:
Pour #5: The upper spokes inside the anchor
Pour #4: Final 11 foot upper anchor wall section
Pour #3: Fourteen-foot lower wall section, which includes setting in pipe and teardrop anchor cable openings
Pour #2: Two-foot high base slab section
Pour #1: Two-foot tall lower spokes and anchor footing section
Casting the anchors in this manner helped WSDOT maintain the overall project schedule and to provide the opportunity to re-use the wood forms.
Anchor Launch
Anchors were launched in February and June in the following sequence:
1. Dry dock was submerged 15 feet underwater
2. WSDOT and Kiewit-General made final inspections, then
continued submerging the dry dock
3. Anchors began floating, dry dock was submerged to 35 feet
underwater
4. Anchors were towed from Pier 5 into Elliot Bay
5. Anchors were towed from Elliot Bay in Seattle to Port Gamble Bay in Kitsap County near the Hood Canal Bridge. The anchors were moored there until they were set at the bottom of Hood Canal.
See photos of the February launch, tow and mooring in the Photo Gallery. See time-lapse footage of the June launch:
Anchor Launch Time-lapse Footage (Windows Media Player)
Anchor Launch Time-lapse Footage (Real Video)
Anchor Setting
WSDOT and K-G crews began placing anchors at Hood Canal in May and completed in July 2007. The tenth anchor was submerged and placed at the bottom of the Canal on May 31, and the final 20th anchor was set on July 10.
The anchors were submerged by a large derrick barge with a custom-made transition truss. The operation to lower each anchor 80-340 feet to the bottom of the Canal took one to two days. The anchors were filled with water and slowly lowered under the water.
Several sensors monitored the anchor's tilt, turn and geographical location. When the anchor reached the bottom, it was filled with crushed rock with machinery on another derrick barge.
Now that anchor setting is complete, the twenty new anchors for the east half of the bridge are waiting until they are secured to the new east-half of the bridge in May-June 2009. These anchors are larger and stronger than the current anchors securing the east half.
For more information, check out the Media Kit. See photos of the anchors placed in May in the Photo Gallery.
Fun Anchor Facts
|
Each anchor weighs more than 1,000 tons, equivalent in weight to about 167 male African elephants. |
|
Each anchor is the same height as a two-story building. |
|
If all 20 anchors were stacked on top of each other, they would be almost as tall as the Space Needle. |