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Work on Sheep Creek Bridge rolling right along

 

September 6, 2016

WORKERS prepare a “beam set” at “Bent Five,” a “joint” between bridge decks, for placement of the slider, the metal piece lying across the top of the new Sheep Creek Bridge. Beams will sit on top of the slider and the abutment at the east end of the bridge crossing this gap. Asphalt is laid across the tops of those beams.

Under normal circumstances, a bridge that slides isn’t a good thing.

But that’s not the case with the new bridge being built on Highway 20 at Sheep Creek.

The east end of the new Sheep Creek Bridge is designed to roll across its eastern abutment as a major landslide continues its slow progression under the bridge.

Highway 20 has been closed since Aug. 2 as the Oregon Department of Transportation is rebuilding the eastern end of the bridge to cope with the active landslide.

In 1993, 2006 and 2011, the east abutment of the previous bridge was adjusted for the movement.

Until about 2010, the earth movement was measured at approximately one inch per year. Since then, the movement has increased to 6 to 7 inches per year, ODOT officials say.

The bridge, located about 26 miles east of Sweet Home on Highway 20, milepost 56.6, is scheduled for completion by Sept. 30.

The original bridge, built in 1962, was designed to move with the slide, but it had reached the point where it could no longer safely move and needed partial replacement.

Last year, 50-foot beams were buried in the slide north of the eastern end of the bridge last year to divert the slide away from the bridge.

In the current phase, Wildish Construction Co. of Eugene has removed the eastern-most bridge deck, between what is called “Bent Five” and the eastern abutment, called “Bent Six.” It has replaced the abutment with two pre-formed and pre-stressed concrete slabs.

Spanning the distance from Bent Five to the abutment will be nine beams with 3 inches of asphalt over the top, said Phil Lane, senior inspector for ODOT, Region 2, Area 4, based in Corvallis.

The end of the bridge will remain in place, sliding across the abutment, while the abutment moves with the slide.

When necessary, ODOT will be able to lift the eastern end of the bridge and slide new concrete slabs under the bridge, Lane said.

“It’s on time,” Lane said. “This job has an incentive to the contractor to finish early. So far, so good. It is going as well as can be expected.”

Wildish could gain a bonus for finishing up to 14 days early, Lane said, and that’s possible at this point.

ODOT maintenance employees have been taking advantage of the closed highway, repairing and resurfacing sections of the roadway.

Previous to this project, ODOT adjusted the bridge back into place, but now it can adjust no further. Further movement of the landslide had damaged the bridge, although it has remained usable over the past year.

The current construction phase is intended to stabilize the existing structure and eliminate further sliding. The new bridge span and abutment will be built to ride on top of the slide if it keeps moving, making the impact to the bridge more consistent, predictable and manageable.

Highway 20 remains open between Sweet Home and about 1 mile west of the bridge and from the Santiam Junction to the east end of the bridge.

Campgrounds and recreation areas remain open and accessible.

Access to popular trailheads in the Middle Santiam Wilderness and to Shedd Camp Shelter is available via Forest Service roads 2047 (Sheep Creek) and 2041 (Soda Fork). To get to Iron Mountain and Cone Peak trails, visitors will need to access Highway 20 from the east. All campgrounds located along Highway 20 are open.

At left, Dan Brown of Carlson Testing of Salem, prepares a “pull test,” which tests the strength of epoxy and bolts used in the construction of the bridge.

Forest Services officials do not recommend attempting to get around the project using forest roads. Motorists who choose to take Forest Service roads to get around the highway closure do so at their own risk. Remote Forest Service roads are not maintained for passenger car travel and are generally narrow with blind corners and few pull outs. When traveling on Forest Service roads, motorists should carry a detailed map of the area and be vigilant for log trucks, other vehicles and hazards.

As a public safety measure, Forest Service Road 2043 is closed to public use and reserved for emergency service access during the highway closure.

Further information is available at https://www.oregon.gov/ODOT/HWY/REGION2/Pages/US-20-Sheep-Creek-Bridge-Phases-1-and-2--.aspx.

To obtain maps or directions to recreation areas on the east and west side of the closure, stop by or call the Sweet Home Ranger Station at (541) 367-2367 or visit http://www.fs.usda.gov/willamette/. Stay up-to-date on Forest activities by following us on Twitter and Facebook @willamettenf. Additional information can also be found at http://www.linnparks.com/hwy-20-closure-and-access/.

 
 

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