Portland’s proposed MLB stadium could help Tilikum Crossing survive ‘The Big One’: Expert

PORTLAND, Ore. ( KOIN ) — Securing a Major League Baseball team could help Portland’s Tilikum Crossing survive the next big Cascadia Subduction Zone earthquake, one earthquake expert says.

Completed in 2015, the car-free crossing was celebrated as the first bridge of its kind in the U.S. to solely serve pedestrians, cyclists and public transit. The bridge, owned by TriMet, is also Portland’s first river crossing capable of withstanding a catastrophic earthquake. However, while it’s true that Tilikum Crossing’s structure is built to withstand “The Big One,” its approaches are not.

Multnomah County Transportation Division Director and county engineer Jon Henrickson confirmed with County commissioners during a Sept. 12 meeting , that the western half of the roadway leading to Tilikum Crossing is expected to give way during a large earthquake. The damaged road would make the bridge temporarily inaccessible following a devastating earthquake.

“That part of it would have to be reconstructed before it would be accessible [again],” Henrickson said.

The issue? Much of the land in and around the Willamette River basin is made up of soft, sedimentary soil .

During a major earthquake, that wet, loose soil is expected to undergo a process known as liquefaction, where the water occupying the space between the bits of sand is shaken up and the ground temporarily enters a liquid state, Oregon Department of Geology and Mineral Industries Geology Hazards Specialist Lalo Guerrero told KOIN 6.

“Say you happen to go to the beach,” Guerrero said. “If you stand right along the edge of the [water] where the sand is wet and glistening, you can start replicating what happens with liquefaction if you start shanking your legs or start jumping up and down, you start sinking into the sand. That is what happens with liquefaction. It’s basically quicksand.”

What does this have to do with baseball?

On Sept. 24, the Portland Diamond Project, the private group leading the charge to bring an MLB team to Portland, announced that it had signed a letter of intent to purchase the Zidell Yards located on Portland’s South Waterfront . In the announcement, the group revealed its intention to one day build an MLB stadium on the property, located between the west end of Tilikum Crossing and the Ross Island Bridge.

In order to build a stadium on the South Waterfront property, the Portland Diamond Project will likely have to stabilize the ground, Portland State University Professor Emeritus of Geology, Scott Burns told KOIN. The process would likely involve drilling deep into the bedrock and implanting pilings made of steel, concrete, and gravel into the ground.

“These things are very very strong and they will be able to bend in an earthquake,” Burns said.

The addition of the pilings would likely stabilize the surrounding area, including the western approach to Tilikum Crossing, he said. If true, Tilikum Crossing could join the list of earthquake-resilient bridges that the City of Portland and Multnomah County hope to amass before the next major earthquake hits.

However, extensive geological tests will need to be performed before any plans for a stadium can move forward, Burns said. If the soil quality is similar to the rest of the South Waterfront, where a number of towering apartment buildings have been erected in recent years, ground-stabilizing pilings would be a likely option.

“They would have to drill and see what they have,” Burns said. “If they build the stadium, they would probably have to have some very big pilings in there. On the South Waterfront, that was all liquefiable soil, so all of the [new apartment buildings] have pilings going down almost as deep as they are up in the air.”

The Portland Diamond Project spokesperson Connor McCarthy declined to comment on the group’s potential construction plans at this time.

“We are still in the early stages of this project, and we are excited to share more information down the road,” McCarthy said. “Right now, we are focused on the letter of intent’s due diligence phase.”

KOIN 6 contacted TriMet on Sept. 24 about the possible positive effects the proposed stadium could have on Tilikum Crossing. As of Oct. 2, TriMet has not provided an official statement.

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