Residents of Clark County no longer fear the prospect of crossing the Muddy River at Cooper Street when heavy rains come. They travel safely along a new bridge with an elevated road—and may even spot a sensitive species of bird that was protected during the construction.
Those are just a few of the positive outcomes of the Cooper Street Bridge project in Overton. Harris provided full construction management support for this important initiative, including:
- One construction manager
- Two inspectors
- Administrative support
- A scheduler
- Material sampling and testing
This project entailed more than raising Cooper Street above flood level. It also included the daunting prospect of diverting and widening the Muddy River itself. Clark County upgraded the channel with wide-body gabion baskets, rip-rap and a cast-in-place post tension girder bridge system.
This approximately $13.6 million project included:
- A two-span post-tensioned box girder bridge
- Clearing and grubbing for channel excavation
- Rectangular and trapezoidal concrete-lined channel
- Gabion structures
- Cattle ramps
- Type II asphalt
- A storm drain system
- PVC pipes
- Driveway relocation
- Street lights
- Traffic control
- Dust palliative
- Traffic signs
- Relocation of 20-inch irrigation system, pump facilities and overhead electrical
- Removal of two residential homes
The bridge abutment and center pier foundations entailed construction of 36 three-foot drilled shafts 70 feet below grade for abutments and three six-foot drilled shafts 86 feet below grade for the piers.
The abutments and center pier drilled shafts were cast in place using a biodegradable polymer slurry, which was constantly tested for pH, viscosity and density. The polymer slurry supported the shaft walls to pump the concrete by tremie while displacing the slurry for reuse. After the shaft concrete was placed, cross-sonic logging was used to confirm its soundness.
Beyond the Blueprints
This project was intended to protect more than the area’s human residents. Before construction began, an environmental survey was conducted to document and remove any pre-nesting or nesting birds in order to safeguard the endangered southwestern willow flycatcher and other protected migratory bird species. Only after the environmental team declared the area environmentally cleared was the project allowed to continue.