IT'S TRUE. The Northwest can expect a magnitude 8.0 or larger earthquake in the coming decades, or maybe tomorrow. And one very likely victim of that quake could be Portland's harbor wall—bad news because a busted wall might further cripple two Willamette River bridges already teetering on quake-related collapse.

That's a warning some scientists are keen to get out. But on a recent city tour dedicated to earthquake preparedness, that's not something you would've heard.

Emails obtained by the Mercury through a public records request reveal that a debate on how to characterize the wall's vulnerability was waged almost up to the minute before the tour started. And in the end it was agreed that the city's in-house engineer—not the nationally recognized expert with strong concerns about the wall—would have the final say.

The city and several outside engineers held the media-only tour on April 18. Focused on Old Town, it visited three seismically retrofitted structures, the Mercy Corps building, the Burnside Bridge, and Fire Station No. 1. It also stopped at the seismically vulnerable harbor wall. And while the tour itself was collegial, a heated debate about the wall had been brewing between Yumei Wang, a geotechnical engineer and nationally recognized earthquake expert at the Oregon Department of Geology and Mineral Industries, and David O'Longaigh, the structural engineer at the Portland Bureau of Transportation who oversees the wall for the city.

"In my opinion, it's important to be realistic as professional engineers," Wang wrote to O'Longaigh an hour and a half before the tour, still urging a more robust statement on the wall's vulnerability. "As the vice chair of an engineering committee that sends out teams after every major earthquake, there's a collective body of knowledge that's compiled that is important to recognize."

O'Longaigh wrote to Wang: "Just because a seawall failed in an earthquake in Japan does not mean it will fail in Portland."

The fight left the Portland Bureau of Emergency Management (PBEM) to act as referee. Emails show bureau spokesman Randy Neves working to keep the two talking, in hopes of reaching some kind of compromise that accommodated both messages. But refereeing between strong-willed scientists isn't easy, and at one point, O'Longaigh accused Neves of overstepping his bounds: "Please leave the engineering assumptions to the city's supervising engineer."

On the tour, Wang's comments on the wall were circumspect, while O'Longaigh's remarks were muted.

Despite previously telling the Mercury that the harbor wall would burst in a quake ["The First Four Minutes," Feature, March 15], potentially taking down some of the bridges, Wang said none of that during the tour. There was no mention of the bridges in connection to the wall. And while Wang talked about the failure of other cities' harbor walls, she was careful not to talk directly about Portland's. That task went to the city engineer.

On the tour, O'Longaigh acknowledged that when the wall was built in the 1930s, seismic vulnerability was not a concern—but his statements were careful. "The wall is really in superb condition," he told members of the media. When asked by the Mercury how Portland's wall might handle a major earthquake, he said: "I don't want to speculate doom and gloom because we haven't studied it."

But, as the emails show, that might be missing the point.

At the center of the engineering fight is something called liquefaction, an earthquake phenomenon in which solids, when shaken, behave like liquids. Wang—who has seen liquefaction's effects in a number of earthquakes, including both Chile's and Japan's—believes the same thing will happen to Waterfront Park's soils, putting critical pressure on the harbor wall.

That was the message Wang hoped to get across on the tour—worried the media might not understand that Portland's wall will probably collapse in a big quake. But as the email exchange shows, O'Longaigh was adamant about not comparing Portland's wall to others, collapsed or not.

Even after the tour, Wang was concerned. In an April 20 email to PBEM Director Carmen Merlo, Wang reiterated: "The harbor wall will likely have poor seismic performance due to its construction type."

Asked why she emailed Merlo, Wang said, "Because there was back and forth [in the emails], I think the main point might not have been clear. That's why I sent that email to Carmen—just to kind of make that one point that she knows what earthquake engineers like me think about the seawall."

Merlo, when asked about debate, said, "We have made it abundantly clear that all of the city's infrastructure is vulnerable."

She said right now the harbor wall was a low priority, but that she wasn't privy to any discussions about the harbor wall's connection to the bridges. High on the agency's list, Merlo said, are the untold number of Portland buildings likely to collapse on their occupants.

As to what effect the collapsed wall might have on the bridges, this also was a matter of debate.

The emails show the engineers arguing about whether a fallen harbor wall would entail a "house of cards" scenario in which the quake-damaged Burnside and Morrison Bridges might take another hit. In the end, it looks like Wang largely conceded this matter to O'Longaigh.

Wang's email to Merlo states that while she expects the wall to fail in a large earthquake, "This is not to say that a wall failure would have bad impacts (to other infrastructure like the Burnside Bridge or Front Avenue [Naito Parkway])." However, the final draft of the tour guide, vetted by both Wang and O'Longaigh, tells another story. The guide notes that if the wall did succumb to liquefaction, it could, "induce additional lateral forces to the existing [bridge] abutments along the Waterfront, causing some damage to their foundations." Wang also told the Mercury that she thought a collapsed harbor wall still posed a danger to the neighboring bridges.

O'Longaigh declined to answer questions over the phone or via email, submitting a statement that said debates among engineers are common. But on the tour, O'Longaigh also noted the city isn't planning to study either the wall or liquefaction in the park.

Wang also said it's normal for engineers to argue, especially when they come from different technical backgrounds. "My approach is different from his," she says. But, she followed, "Having been on earthquake reconnaissance trips, my professional judgment is you don't always need to crunch the numbers."