Item(s) of Interest: Bridge foundation currently consists of spread footings in the water. Heavy current at this locale -- highest flood reading was 98,000 CFS. Bridge subjected to severe scour that caused the foundation to partially sink and rotate. Bridge is currently closed and a major scour retrofit and rehabilitation is underway. Retrofit utilizes micropiles as part of the foundation retrofit (bents 1-3). Eight 7 5/8" Micropiles per footing were installed, pile caps will be poured over them. Bent will not be re-rotated. Probably will rehab bridge rail and joint at rotated bent. During retrofit procedure, inspectors were monitoring rotation of pier with tiltmeters (inclinometers) and crack monitors. Access utilized about 2000 tons of rip-rap for the causeway. Wright Archer working with contractor to leave in cofferdam/sheet piles and will use rip rap from causeway for scour counter measures. Bent 5 was on rock and Bent 4 was on half rock/half weathered rock, so retrofit for these piers was unnecessary.
Observations and Points of Discussion:
Repairs almost complete and the bridge is scheduled to re-open to traffic the day of the visit (5/9/06)
Barrier rails closed expansion joint over bent when bent rotated.
Proposed to cut barrier rail to reopen expansion joint and alleviate further cracking.
Lessons learned:
Good use of micro piles.
Good inter-Unit coordination.
Time to let could have been improved – permit issues, rework contract.
Emergency permitting, contracting. First contract placed liability on contractor. Revised contract reduced the scope of work and included more shared risk.
Recommendations:
Respond quickly when we declare emergency.
Develop criteria for emergency permit, which may include:
How critical is this bridge?
Economic damage to area?
Emergency access risk?
NC DOT
NC DOH
NC GOV
