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Engineers and commenters press IBR team on bridge design, immersed‑tube tunnel and lift‑span tradeoffs
Summary
At a virtual SEIS hearing, commenters pressed the project team on geotechnical risks, the pros and cons of an immersed‑tube tunnel versus a high fixed bridge (including steep grades and lift-span operational impacts), and raised questions about how the project’s design options were evaluated.
Speakers at a virtual public hearing for the Interstate Bridge Replacement draft SEIS raised technical objections to the currently studied bridge configurations and urged the project team to more fully evaluate an immersed‑tube tunnel.
Bob Ortblad (public commenter) argued the riverbank soils at the replacement site are “basically mush” and said an immersed tunnel would be “much safer, more earthquake resistant, much more economical.” He told the panel that, in his view, the IBR’s previous tunnel evaluation was flawed, saying it “produced a fraudulent, tunnel evaluation” and that the consultant’s dredging estimates had been overstated in the study.
Bob also raised safety concerns about proposed grades and profiles, saying on the Vancouver side the project would create “a 4% slope with an S curve” that would be “extremely dangerous” in black‑ice and fog. He said proposed cloverleaf interchange grades were wrong for safe traffic operation and criticized a planned 80‑foot‑high transit station, warning elevators and 80‑90 foot spirals would be impractical for many users.
Supporters of the bridge alternatives pointed to the project’s multimodal features. Lucas Kerber praised the inclusion of light rail from Expo Center to Vancouver and said bicycle and pedestrian connectivity are major selling points, but asked for early Coast Guard input on lower‑deck options to avoid last‑minute design reversals.
Project staff on the call did not provide technical rebuttals during the hearing; Gitlin reiterated that the session was for public comment only and that technical office hours are available at interstatebridge.org/calendar for detailed follow up. Several commenters asked that independent peer review be documented in the record and that numerical estimates (dredging, parking costs) be substantiated in the final SEIS.
Status: commenters presented specific technical claims and recommended further study; the hearing record captures assertions and requests but did not include in‑session technical responses from staff, leaving several claims unresolved on the record.
