New SR 520 floating bridge named America’s top engineering feat

520 floating bridge

Originally posted here

SEATTLE — Precisely one year after opening to traffic, the new State Route 520 floating bridge on Tuesday, April 25, received one of the country’s highest engineering awards: the 2017 Grand Conceptor Award from the American Council of Engineering Companies (ACEC).

The annual award was presented the Washington State Department of Transportation during ACEC’s conference in Washington, D.C. to honor the nation’s best overall engineering achievement.

“This is an incredible honor for a remarkable project,” said Julie Meredith, Administrator of the SR 520 Bridge Replacement and HOV Program for the Washington State Department of Transportation. “An amazing, collaborative group of people deserve credit for this.”

Meredith made special note of HDR, the general engineering consultant on SR 520 reconstruction program; Kiewit/General/Manson, the new floating bridge’s design-builder; and KPFF, the bridge’s lead design consultant.

The floating bridge was one of 162 projects throughout the world vying for ACEC’s top engineering award. The new bridge opened to traffic on April 25, 2016, and is the longest floating span of highway in the world, at 7,708 feet. Its predecessor on Lake Washington – opened in 1963 – measured 130 feet shorter.

“This is one of the great engineering feats of our time,” said Secretary of Transportation Roger Millar. “The new bridge is an example of how our state is working to build a resilient, world-class, multimodal transportation system that will serve generations to come.”

Lake Washington’s extreme depth and soft lakebed required the construction of a floating bridge rather than a conventional fixed bridge. The new floating bridge, supported by more, bigger and stronger pontoons than the old bridge, is designed to withstand much stronger windstorms and waves. Moreover, the new bridge provides greater transportation mobility for the region, with bus/carpool lanes in both directions and a cross-lake bicycle-pedestrian path. Its design also allows it to be retrofitted for light rail if the region pursues that option in the future.

When reconstruction of the entire SR 520 corridor is complete, the bridge and connecting highway will carry about 10 percent more vehicles and 17 percent more people during peak traffic hours, while reducing rush-hour, cross-lake commutes between Seattle and Bellevue by about a half hour.

Recent past winners of ACEC’s Grand Conceptor Award are the San Francisco Air Traffic Control Tower (2016); the San Francisco-Oakland Bay Bridge East Span (2015); Wacker Drive/Congress Parkway Reconstruction (Chicago 2014); Kauffman Center for the Performing Arts, (Kansas City, 2013); Lake Borgne Storm Surge Barrier (New Orleans, 2012); and the Hoover Dam Bypass (2011).

A brief video documentary and online booklet – both posted on the new bridge’s April 25 one-year anniversary – provide more information about the structure’s design and construction. You can also follow the SR 520 project on Twitter.

Box Canyon Dam

Box Canyon Dam Upstream Fish Passage Project

As per of the FERC Relicense Process, Box Canyon Dam, which is located on the Pend Oreille River near Ione, WA is required to provide upstream passage for the Bull Trout, West slope Cutthroat, and the Mountain Whitefish.  Associated Underwater Services is providing the dive support for the project working for the General contractor, J.W. Fowler and the cofferdam subcontractor, Pacific Pile and Marine.  Multiple dive crews are required to complete the work scope which includes rock removal, sheet pile burning, installation of a steel dewatering structure, and underwater concrete placement.  Construction began in June 2016 and is scheduled for completion by October 2017.

Twin Falls Powerhouse

tfAUS conducted a survey of the Twin Falls Powerhouse tail race tunnel between August 6 and August 8,
2013. The condition of the tunnel was documented by ROV video and scanning and imaging sonars. The
tunnel was found to be in good condition with no significant evidence of sediment accumulation or ceil

Yellowstone River Cofferdam

Wilson Brothers of Cowley, Wyo., and Associated Underwater Services of Spokane, WA build a coffer dam as work continues Tuesday on new water intake in the Yellowstone River for the city of Laurel.

Sep 21, 2016

BY: Casey Page, Gazette Staff

A contractor crew and a specialized underwater construction subcontractor helped guide heavy equipment on Tuesday, sinking 3,200-pound sand bags into the Yellowstone River.

They worked three miles upstream from Laurel atop a man-made rock weir — a miniature peninsula that juts halfway across the river. The sandbags will form a cofferdam around the weir, allowing workers to install the long-awaited water intake.

The current unit, dubbed the 2003 intake, sits below the Highway 212 bridge south of town. It’s been plagued with issues since a flood swept through the area in 2011 and changed the riverbed topography.

Now in its ninth week, the $12 million intake project is underway. The work has been a long time coming for city officials. Laurel Public Works Director Kurt Markegard said that it defines critical infrastructure — a working intake brings millions of gallons of water to its residents, as well as the CHS refinery.

“This is probably one of the most important jobs we’ve done since 2003,” Markegard said.coffer-dam-2

Once the cofferdam is finished, pumps will pull out the remaining water, and the intake infrastructure will be installed. Markegard said surveys identified that upstream spot as one that’s more unlikely to be ruined by a flooding event.

Large blue piping will carry water back to the city’s treatment plant, which sits at shore near the old intake. Nick Wilson of Wilson Bros. Construction said that the pipes will sit an average of 14 feet underground. But it’s a gravity-fed system, so the pipes will gradually get deeper as they reach town.

About 25 trucks have arrived to pile up the pipes at the job site, Wilson said. About 75 more are expected.

A Wyoming firm, Wilson Bros. is the contractor. Montana-based Great West Engineering is handling the engineering work. Representatives from those companies meet each week with the city of Laurel and others involved in the project to discuss progress.

Meanwhile, temporary rock weirs were built just downstream from the Highway 212 bridge to keep the river level up above the old intake. Since the 2011 flood eroded the riverbed, the intake has suffered from ice jams in the winter and summer water levels that are too low.

Much of the construction cost will be covered by the Federal Emergency Management Agency, which approved nearly $43 million in public assistance to Montana after a 2011 disaster declaration.

The funding requires a local match of 25 percent of the project cost. Finding a source for that 25 percent has kept the Laurel project at bay before, and it’s likely to persist in the future.coffer-dam

Laurel officials had a rocky road to find $3 million for 25 percent of the intake project. The funds didn’t make it to a vote in the 2011 or 2013 sessions of that Montana Legislature. In 2015, the infrastructure bill failed.

Gov. Steve Bullock directed his office to piece together various money streams for the project, but it was announced in October 2015 that the money was no longer available — gone toward other projects.

So Laurel took out a $1.7 million loan from the State Revolving Loan Fund Program and used $1.3 million in city reserves, according to City Councilman Tom Nelson. But it wasn’t an easy pill to swallow, as the town neared its borrowing capacity.

“They gave us the loan. We had to take it,” Nelson said. “We had no choice.”

Nelson expressed some rancor over the 2.5-percent-interest loan, because he felt the state was obligated to pay the 25-percent match of FEMA funds as Laurel recovers infrastructure from the flood.

He’s not the only city official who felt that way. At a July 12 city council meeting, Councilman Douglas Poehls said Bullock’s office “essentially betrayed the city,” according to meeting minutes. City Chief Administrative Officer Heidi Jensen said at that meeting that the governor hasn’t given an official written statement about the state’s responsibility to the funds.

Nelson traveled to Helena in August to talk to state officials. Accompanying him were Billings state Rep. Kelly McCarthy, Laurel Civil City Attorney Sam Painter and Laurel state Rep. Vince Ricci.

Ricci declined to comment on the meeting. The governor’s office didn’t respond to a request for comment on Tuesday afternoon.

Nelson said Monday that Andy Huff, Bullock’s chief legal counsel, and Adam Schafer, Bullock’s policy director, heard him out on the manner. He said he requested an answer within two weeks but didn’t get one.

“The government’s still responsible for it,” he said. “The state still requested the emergency declaration from the president. That was given.”

The city’s hopes are pinned to the 2017 legislative session, when repayment for the state loan could end up tied to an infrastructure bill.

coffer-dam-3Ultimately, officials see it as a welcome sign that earth is moving west of town, near the end of Red Bridge Road.

Work is expected to be completed around April.


Ryan Dam

In the winter of 2014, AUS spent 2 1/2 months in Great Falls, MT overhauling the waste gates at Ryan Dam.

Ryan Dam

We removed the gates and gate stems, installed new gate guides and replaced the reworked gates and stems.


Utilizing Nitrox breathing mixture throughout the project, we made 194 dives to a depth of 66′. 120 No-D dives and 74 decompression dives.



520 Bridge Now Open

After nearly six years of construction, AUS is proud to announce the opening of the new highway 520 floating bridge that helps travelers across Lake Washington.
The new route 520 bridge is the world’s longest floating bridge at 7,710 feet long, bringing it 132 feet longer than the old highway 520 bridge.

Once the new pontoons were established, AUS assisted in the development of the bridge from the water line down during construction. With the ability to utilize the old 520 anchor cables, AUS welded and installed deviation frames to hold the new 520 in place. Other responsibilities included all joining steps like preparing the pontoons to be mated together by through bolts and repairing rock spall in the concrete. Inspecting, cleaning and overall maintenance of the anchor cables were crucial responsibilities for AUS as well.

The new 520 bridge offers six lanes compared to the old bridge which only had four, allowing for a HOV lane in both directions. See more details on Washington State department of Transportaion webpage 520 – Floating bridge facts.