Bob Ortblad suggests that the IBR halt future preliminary engineering for its expansion and instead consider innovative, cost-saving design-build alternatives, including an immersed tunnel

Editor’s note: Opinions expressed in this letter to the editor are those of the author alone and do not reflect the editorial position of ClarkCountyToday.com

The Interstate Bridge Replacement Program (IBR) has been using a video that depicts the current I-5 bridges collapsing into the Columbia River. For the past four years, IBR has relied on this video to instill fear in the public and government officials to promote the construction of a new bridge. This video was likely produced by one of the several public relations consultants under contract for $23 million.

My suspicion that this video lacked supporting engineering analysis was confirmed by my Public Disclosure Request. I obtained the “I-5 Columbia River Crossing (CRC) Design Ground Motions Report,” a 1,622-page document prepared 14 years ago by Shannon & Wilson, geotechnical engineers who were paid over $6 million. This report analyzes the seismic behavior of the riverbed for a new bridge, but it does not address the seismic resilience of the current bridges. On page 742, there is a graphic that illustrates potential liquefaction to a depth of 50 feet for a 475-year return period.

Each of the existing bridge piers is supported by approximately 90 closely spaced wooden piles that extend about 100 feet into the riverbed, which is 50 feet deeper than any potential liquefaction risk. A Japanese engineering study states that when piles are tightly grouped, “the degree of compaction is increased by 106% by the log piling method” and that this method is “fail-safe against liquefaction damage.”

IBR plans to demolish these seismic-resistant bridges at a cost of around $200 million. Preserving these bridges would maintain six lanes for local traffic and bus rapid transit, while constructing an upstream six-lane immersed tunnel could add an additional six lanes for freeway traffic. This alternative is less costly, faster to build, and has environmental benefits.

Over a decade ago, the CRC spent $200 million on a 1960s-style freeway expansion and massive bridge project. The IBR has spent an additional $200 million to revive the CRC design, which is still too low for U.S. Coast Guard requirements. Now, the IBR seeks an additional $433 million for two more years of preliminary engineering, a request that raises questions about its necessity. The IBR claims to be at 30% design completion — the level needed to solicit design-build bids — but currently has only one potential bidder. I suggest that the IBR halt future preliminary engineering for its expansion and instead consider innovative, cost-saving design-build alternatives, including an immersed tunnel.

Bob Ortblad MSCE, MBA
Seattle