BRIDGE REPAIR/REHABILITATION FEASIBILITY STUDY

Boaters requesting that the bridge be raised to the maximum extent possible to maximize the
horizontal clearance have reportedly been told by the bridge operator that the bridge cannot be
fully raised due to safety concerns. The bridge operating equipment reportedly struggles to raise
the bridge and shudders, creaks, and vibrates significantly as the bridge operates. The tight fit
between the bascule span and approach spans has reportedly resulted in the bascule leaves to
periodically become stuck in the lowered position.
The stainless steel pins and sleeves that the bridge pivots about are not readily accessible for
inspection, but is not a reported item of concern.
The electrical conduit throughout the bridge exhibits surface corrosion and the hardware used to
secure the conduit to the bridge is severely corroded. There is at least one location where
hardware and conduit have failed.
The operating equipment is mounted on the sidewalks, which reduces the clear width of the
sidewalks to less than the minimum clear width of 3’-0”.
Repair Scope: Based on the reported reliability and safety concerns and the evaluation of the
current design of the operating ropes, sheaves, pulleys and winch drums, it is recommended that
the operating equipment be replaced with a design that meets current design standards. The new
operating equipment would include new winch assemblies, operating ropes, pulleys, deflector
sheaves and associated clevises and mounting hardware. It is also recommended that the
electrical power and controls be replaced for compatibility with the new operating equipment
and to address the deteriorated condition of the conduit.
Rehabilitation Scope: The Rehabilitation Scope is similar to the Repair Scope with the addition
that the new operating winches and sheave poles will need to be moved outward approximately
2’-0”in order to provide the required minimum clear sidewalk width of 3’-0” around the
operating equipment and to accommodate the new wider crash tested timber traffic railings.
Functionality and Safety: Replacement of the operating equipment will improve the reliability
and safety of the bridge operation, but will not address the accessibility concerns. Relocation of
the operating winch proposed in the Rehabilitation Scope will improve accessibility.
Load Capacity: The operating winches, cables, pulleys and deflector sheaves do not meet
current AASHTO LRFD Movable Highway Bridge Design Specifications (AASHTO Movable)
including the following:
• The existing operating equipment was designed for an unbalanced load only and does not
consider the force effects of ice load, friction, and wind loads, which are required in
AASHTO Movable (Article 5.4.2) and are known to be significant on bascule type
movable bridges. The current design of the operating equipment is implied in the 1980
Plans, which specifies that the counterweight be adjusted such as to produce a force of
5,000 pounds in each operating rope. The Plans also specify that the operating ropes be
sized for a force of 5,000 pounds. If the operating equipment were designed for the
Repair/Rehab. Feasibility Study March 10, 2011
Bridge No. C-07-001 (437) 31 Final Report