Engineers present two concept paths to address seismically vulnerable Big Creek dams

Engineers from Jacobs Engineering told the Newport City Council on April 6 that both Big Creek dams are not seismically stable and that the city must choose a path forward with the state soon. "OWRD has also asked that to agree to a selected option or a path forward by May 1," Nathan McCullough, a consultant with Jacobs Engineering Group, said as he summarized the alternatives analysis and regulatory timeline.

Jacobs presented two concept-level alternatives for further development. Alternative 3A would remediate both dams (stabilizing berms and ground-improvement columns) and retain current storage capacity. Alternative 3B would remove Big Creek 1 and remediate Big Creek 2, restoring roughly a mile of stream channel but reducing on-site storage and increasing reliance on the Siletz River. McCullough said remediation-only costs (without fish passage) were roughly $29.4 million in Jacobs’ high-level estimate, while adding fish passage could raise combined project totals substantially. He cautioned the estimates are order-of-magnitude only and that costs could range from roughly half to twice the numbers presented.

Counselors pressed on specifics including whether the state would allow lower-hazard reclassification, the feasibility of lowering pools to reduce remediation needs, and what tradeoffs would mean for water supply. Brad Phelps, also on the Jacobs team, framed the problem: "You have a right now issue and a now issue," emphasizing the immediate life-safety and seismic concerns followed by long-term water-supply needs.

Staff said they will bring a financial overview to the April 20 council meeting and that the alternatives will be advanced to concept-level design and additional study if council directs. The council closed the public portion of the work session and moved to executive session after the presentation; Jacobs will return with more detailed cost and permitting analyses and consultations with state agencies.