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I-5 Viaduct Retrofit

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The next generation Medford Viaduct may include wider, safer shoulders and a more stable foundation.  That’s the recommendation of a multi-year I-5 Medford Viaduct Planning and Environmental Study.

“There is no funding identified for construction,” said ODOT Planner Lisa Cornutt, who briefed the Medford City Council on the study last month. “And the next step is to search for the funding—about $85 million—which we hope we’ll secure in the next decade.”

The multi-year study looked at rerouting Interstate 5 or replacing the nearly 60 year-old structure, but the consultant and local teams soon looked at the more feasible – and financially reasonable – retrofit of the bridge.

The nearly half-mile long bridge that runs through Medford and east of downtown carries more than 51,000 vehicles a day. It’s not only a main connector for Medford and Rogue Valley traffic, it’s also a critical north-south freight route for the West Coast.

Operational problems

When opened in 1962, the viaduct carried far less traffic than today, even in the summer.  It was built with two 12-foot travel lanes in each direction. Shoulders were three feet wide, not enough for a stopped vehicle in an emergency. Guardrail, not concrete barrier, separated the travel lanes.

Surprisingly, the crash rate is higher on either side of the viaduct than on the structure itself. Traffic engineers attribute that to drivers being their best—and not passing—while on the bridge. Yet it’s not without its problems.

“Given the increased growth in Medford and along the I-5 corridor, we’re looking forward to identifying a funding source for further design and construction of this project,” said ODOT District Manager Jerry Marmon.

Recommendations

Under the study’s recommendation, the viaduct would be widened to the east by 28 feet, thus avoiding properties and Bear Creek to the west. A new vertical support would be built.

When complete, the viaduct would continue to have 12-foot travel lanes, but emergency shoulders on the right would be 12 feet wide. Inside shoulders would be eight feet wide.

Future widening of the interstate through Medford to three lanes could see the viaduct widened, too, by restriping the structure.  Travel lanes would be narrowed by 1 foot and allow the emergency shoulder to narrow to 8 feet.

Seismic Hazards

The other portion of the study looked at retrofitting the existing viaduct footings by widening and strengthening. The concern is a strong subduction zone earthquake, in which the entire viaduct could simply tip over.

The initial analysis showed the existing soils at the viaduct would require a greater level of design to withstand a greater level of shaking during a seismic event.  Additional analysis would be needed for that portion of the project, according to the study.

To read the entire project summary and recommendations, go to:
www.medfordviaduct.org.

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