Development
Posted June 17, 2010
Bridge Construction Put On-Hold
Bridge construction on ODOT’s $215 million U.S. 20: Pioneer Mountain-Eddyville project in
The Design Builder’s original calculations have been in question since columns at two bridge locations tilted out-of-plumb. The movement of the columns was discovered during a routine survey in February.
The design engineering firm, URS Corporation, working as a sub-contractor to the project’s Design Build contractor, Yaquina River Constructors, has determined that it needs to monitor ground forces at four bridge locations while its engineers reanalyze their original calculations.
The delay in construction will mean a delay of project completion but it remains uncertain at this time how long the delay might be.
Other Construction Continues
The delay of bridge construction does not mean a complete halt to construction of other aspects of the project.
Still underway is:
- The new alignment’s eastern and western intersections with the existing U.S. 20 will be complete this summer, meaning no more 20 minute delays while other construction continues;
- The remaining 920,000 cubic yards of excavation work;
- All remaining culvert and stormwater system work;
- Revegetation with native plants and seed mixes of the disturbed areas; and
- Paving will be completed on about 2.5 miles of the new alignment.
Project to enhance travel and safety on
The project is building a six-and-a-half mile section of new road that bypasses a ten mile stretch of substandard highway with no passing opportunities and many curves where the speed limit is 35 miles-per-hour. The new road will have wider travel lanes and shoulders, and will create miles of passing lanes.
A significant part of the project is the construction of ten bridges along the new alignment. All but four bridges are essentially complete.
The four bridges where construction has been delayed are:
- Cougar Creek Bridge- A 600 foot long structure that spans Cougar Creek
- Crystal Creek Bridge- A 1,100 foot long structure that spans
- Eddy B Bridge- A 750 foot long structure that spans Eddy Creek Tributary B
- Eddy C Bridge- A 600 foot long structure that spans Eddy Creek Tributary C
Bents, (the vertical support columns) have moved at only two bridge locations-- Cougar Creek and Eddy B--but because the Design Builder’s engineers are modifying their design parameters related to soil strength across the project site, construction may be delayed at these four critical bridges until they do more subsurface monitoring to confirm their design assumptions.
Project Background
The
Work was halted in July, 2007 after the discovery of ancient, massive landslides changed the scope of the project.
Work resumed in May, 2008 after Yaquina River Constructors and ODOT agreed on how the effects of landslides would be mitigated in construction.
Mitigation included construction of:
- Buttresses-In simple words, a buttress is a man-made mound or hill of soil or rock placed at the toe of the slope. The buttress increases the resisting forces and thus prevents material from moving towards the toe of the slope.
- Shear-keys-In simple words, a shear-key is a trench excavated into the stable soil so that the new fill placed over the natural slope firmly keys into the existing soil.
What happens next?
Engineers will now determine if landslide areas are continuing to move and if the ability of bridge components to withstand the earth pressure has been miscalculated.
If the construction methods have not stopped the slides, the Design Builder and their engineers and ODOT will determine how best to proceed. Options include:
- Constructing new buttress and shear-key configurations
- Readdressing the amount of fill material placed in some locations
- Creating longer bridge spans to replace bridge abutment fill material
- Consider different bridge construction techniques
Second
Meantime, work on the U.S. 20: Pioneer Mountain
The $8.5 million project will realign the curves near Sam’s