Update

Bridge Seismic Resilience in Lane County

By Rob Zako
June 21, 2024

An ODOT engineer talked about protecting bridges along state highways but a city councilor asked about keeping critical lifeline routes open.

Old Finn Rock Bridge. Source: Curtis Irish

At the Metropolitan Policy Committee (MPC) meeting on June 6, 2024, ODOT Bridge Program and Standards Manager Bert Hartman presented high level findings from the 2023 Bridge Condition Report and the status of the Seismic Program in the Central Lane region.

The report summarizes bridge condition ratings on state highways and performance measures based on National Bridge Inventory and ODOT data submitted annually to the Federal Highway Administration. Mr. Hartman provided an update to seismic projects on Oregon Highway 58 and also an approach to addressing seismic resiliency on the Interstate-5 corridor from Eugene northward.

But Eugene City Councilor Randy Groves asked: What is ODOT doing to ensure that bridges along routes to the area’s major hospital would still be passable after a major earthquake?

Prior work

As it happens, the Natural Hazard Mitigation Plan, adopted by local officials in 2020, identified five high priority and two additional bridges that are critical to keeping lifelines open:

4.7.4 Lifelines and Critical Bridge Evaluations

In 2017 the Oregon Department of Transportation (ODOT) has asked Lane County to complete these two tasks:

  1. Review locations of seismically vulnerable bridges along the ODOT lifelines and identify alternate routes that can be used if an earthquake occurs before the necessary bridge work is completed. Assess the feasibility, seismic vulnerability and corrective cost of these alternate routes.
  2. Identify local lifelines and assess corrective costs of any vulnerable bridges. Prioritize the replacement/rehab work to remove seismic vulnerabilities in a reasonable timeline. There will be priorities placed on bridges along these routes needing retrofitting or replacement. Some of these bridges can be avoided using alternate routes, saving money for other bridges that cannot be avoided. (See the Lane County Bridge Resiliency in the Event of an Earthquake Study, by the Engineering and Construction Services Division 4/1/2017.)

The Cities of Eugene and Springfield understand the main ODOT routes in our area are Hwy 58 to I-5; which will be critical lifelines during a Cascadia event. However, just as critical will be the need to get equipment, personnel, and supplies from these routes to the City’s internal transportation routes, supplying our Points of Distribution and Staging Areas. To this end we selected the bridges for upgrades to the ODOT routes. The Cities of Eugene and Springfield can support each other in many ways, but without these critical lifeline bridges we are virtually cut off from one another. The most glaring example is the only two major hospitals that support the area reside in the City of Springfield. This alone will put more than 165,000 people without access to a major medical facility.

The following is the recommendation submitted to the State on April 1, 2017:

The conclusions of this report identify the Eugene and Springfield’s minimum number of bridges needed to be operational after the Cascadia Seismic Event.

Methodology

Eugene and Springfield have identified detour routes around most bridge structures on their critical response routes. Detour routes are not presented in this report. This report addresses only the critical route bridges lacking realistic detour routes.

Several assumptions set the context of this memo:

  1. ODOT has determined that HELP will come from Eastern Oregon via HWY 58;
  2. Overcrossings over I-5 that may collapse onto I-5 will be driven around or pushed out of the way;
  3. Beltline Interchange at I-5 is anticipated to be operational directly after the seismic event;
  4. Riverbend Peace Health and McKenzie-Willamette Hospital will be operational and the triage point for mass casualties;
  5. The Eugene Airport will be a critical lifeline for transportation, response personnel and equipment, medical personnel, pharmaceuticals, and water purification needed almost immediately (and long into the recovery effort) after the event;
  6. There will be no help from Salem or Portland because they will be caught in the same event; yet Eugene-Springfield will be the gathering point for refugees from the coast and the south.
  7. Eugene Springfield have a combined Fire and EMS department needing access across the Eugene, Springfield, and surrounding area.

Conclusion

Bridges that must be Operational after the Event

  1. 08638: Beltline over Willamette River – Sufficiency rating= 74. Cost to upgrade = $2,000,000.
  2. 08705: Debrick Slough WB On Ramp to Beltline – Suff [Sufficiency] rating = 64. Cost to upgrade = $450,000.

The following three bridges are critically needed to bring HELP from I-5/HWY 58 to the southern end of Springfield and Eugene. The Glenwood area is planned to be a freight off-load and redistribution point.

  1. 016329: Glenwood Blvd over UPRR [Union Pacific Railroad] – Suff [Sufficiency] rating = 93. Cost to upgrade = $300,000.
  2. W6099C: Franklin Blvd over HWY 1 W and UPRR [Union Pacific Railroad] – Suff [Sufficiency] rating = 55. Cost to upgrade =$2,000,000.
  3. 08051: Main Street over Willamette River (Springfield) – Suff [Sufficiency] rating = 76. Cost to upgrade = $2,250,000.

There is one bridge in each City that provides a critical intercity link over a river or a HWY that needs to be operational to access a hospital or other vital resource:

  1. 6648: Ferry Street Bridge over the Willamette (Eugene) – Suff [Sufficiency] rating = 31. Cost to upgrade $2,000,000.
  2. 09596: Mohawk Blvd over HWY 126 (Springfield) – Suff [Sufficiency] rating = 64. Cost to upgrade = to be determined.

The 5 high priority bridges in the list above total $6,700,000. The phase 2 intercity bridges above are estimated at $2,000,000 plus.

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