In about a year and a half, people in Vancouver, Washington, will be able to walk out onto a 100-foot-long pier over the Columbia River, look deep into the water directly below and view Mount Hood in the distance.

What people won’t see is the complex engineering that makes such an experience possible.

The cable-stayed pier, a star attraction of the new Vancouver Waterfront Park, will be one of a kind and stay true to an artist’s design for a great pedestrian experience. It will also be environmentally sensitive to the river below and able to withstand a major earthquake.

Art merges with engineering

Shane McCormick, project manager and principal of engineering firm Martin/Martin of Lakewood, Colorado, said his firm has worked on many projects with the Studio of Larry Kirkland, the pier’s designer.

Kirkland, based in Washington, D.C., has a bachelor’s degree in environmental design from Oregon State University.

“Larry is very collaborative in working with other experts to come up with a design that makes sense from an artist’s point of view and from an engineering point of view, to come up with something that’s unique and special,” McCormick said.

Martin/Martin is handling the engineering for the above-ground portion of the pier, while BergerABAM is tackling the underground portion. Both firms have worked for months designing the various pier elements, which won’t be evident to people who walk out onto the wooden deck of the triangular-shaped, 2,500-square-foot structure.

For instance, the pier will appear to be lightweight, McCormick said, but post-tensioned concrete will be included underneath the wooden flooring.

“It’s very durable and will last a long time, but is also very stiff,” he said.

BergerABAM landscape architect David Sacamano added, “It was very important to have this very thin profile so it felt light and airy and hovered over the water.”

Pedestrians will have an unobstructed view from the north shore of the river and be able to look down through a 1,500-square-foot hole in the center. The opening serves an aesthetic viewing purpose, Sacamano said, but also makes the structure lighter and satisfies regulatory agencies such as the U.S. Army Corps of Engineers and the Washington Department of Fish and Wildlife.

The reason, he said, is that deep shadows cast over the water give predators more places to hide and feast on young – and possibly endangered – aquatic life.

More good news for river inhabitants is that the original design won’t be used; it relied on steel pilings rather than overhead cables for support. The act of pile driving in a riverbed is bad for fish and marine mammals, according to BergerABAM senior project manager Howard Wells.

“Fish don’t have ears but are sensitive to sound waves, so the pounding on a pile causes pressure waves,” he said. “That’s harmful to young fish in particular and also to marine mammals. They don’t like it and it can alter their behavior.”

Designed to endure an earthquake

Seismic stability of the pier will be ensured by extensive underground work at the shoreline, Wells said. This will be accomplished by drilling 27 five-foot-diameter shafts of reinforced concrete that will extend more than 60 feet under the river bank, creating a “massive and very strong anchor system,” he said.

“Because the pier cantilevers 100 feet over the water and the deck is held up by cables, something has to hold everything down so it doesn’t tip over into the water,” he said. “It’s like a real big kid on end of teeter-totter and small kid on other.”

A rectangular cofferdam of corrugated steel will allow construction below the water level, he said. Most of the cofferdam will be removed, but the back portion will remain as part of the pier’s permanent infrastructure, adding to seismic stability.

Once the shafts are drilled down into the shore, a concrete pile cap will be cast to form the base of the pier’s abutment, he said, which will then have 30 ground anchors attached and drilled back into the bank of the river.

“The purpose of the anchors in one wall of the sheet pile is to resist lateral spreading and (liquefaction) that can result from an earthquake,” he said. “With structures near the water – in Japan we saw quite a bit (during an earthquake) – the ground liquefied and started to flow.”

The ground anchors and cofferdam wall will form a bulkhead to hold the ground in place during a seismic event.

“The drill shafts will keep the pier in place vertically and the ground anchors and back wall of the cofferdam will keep it from sliding into the river,” Wells said.

A prominent, unique structure

Above the deck of the pier, 16 cable stays will be attached around the opening in the middle, descending from a tapered, slightly angled 65-foot pole on the shore, McCormick said. The cable stays will in turn be attached to smaller micro piles, similar to the drills shafts that will be driven deep into the riverbank.

“The pole is of steel pipe, with four plates on the outside that taper and create this sculptural shape,” McCormick said. “The tapering was artistically driven, and though the plates act as anchors for the cable, that’s part of the art that’s also functional.”

Martin/Martin has a long history of working on cable-stayed structures, McCormick said, and has performed civil and structural engineering work for many large-scale, cable-supported structures. He believes a cable-supported pier of this size is the first of its kind, though he downplayed the complexity of engineering involved.

“The pier is pretty unique and I’m not aware of anything quite like this being done before,” he said. “But it’s just physics.”

Ground will be broken on the pier today. Construction is scheduled to finish in December 2017. When people walk out onto the completed pier, they will be able to look back toward the 7.3-acre Vancouver Waterfront Park and, eventually, 35 acres of private development – apartment buildings, hotels, restaurants and many retail businesses.

Vancouver Parks and Recreation Director Julie Hannon said she’s pretty excited about the pier, which will be the signature element of the new park.

“I think it will be spectacular to have that over-water experience, to be able to see the river through the cutout, and you can see Mount Hood from there,” she said.

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