BRIDGE REPAIR/REHABILITATION FEASIBILITY STUDY

Functionality and Safety: The timber masts have no significant affect on functionality and
safety. Shifting the masts in conjunction with the replacement of the operating equipment will
improve accessibility.
Load Capacity: The timber masts may be undersized for operating forces meeting current design
standards (see 4.3.6 below). Replacing the masts with a larger members or strengthening the
masts with carbon fiber can be used to address this potential concern.
Maintenance: Installation of FRP sheets to the sides of the masts may increase maintenance as it
may be necessary to provide minor maintenance including reapplication of protective coatings,
repair of adhesives and/or periodic replacement of the carbon fiber.
Replacing the masts now would reduce maintenance in the short-term by reducing the need to
make periodic repairs to the deteriorating masts or to reapply in-place preservative treatments.
Visual Impacts: Replacing the timber masts in-kind would not introduce a visual impact.
The addition of FRP sheets to the exterior surfaces of the timber masts may introduce a visual
impact.
4.3.5 Paint/Coating (Steel Counterweight Box)
NBIS Condition Rating: 5 (Fair)
Condition Description: The rear third of the steel counterweight box that contains the concrete
and steel ballast exhibits moderate to heavy surface corrosion with minor overall corrosive
deterioration and localized areas with moderate section loss. The bolts used to secure the
counterweight to the underside of the timber stringers also exhibit moderate to heavy corrosion
with minor overall section loss. The galvanized coating on the steel box and mounting bolts no
longer adequately protects the steel from corrosion as much of the zinc that cathodically protects
the steel has been consumed. The corrosion of the steel is largely attributed to the dipping of the
rear end of the counterweight box into the saltwater each time the bridge is raised at high tide
and low clearance above the saltwater.
Repair Scope: As a minimum, the steel counterweight box should be sand-blasted and recoated.
It is recommended that the new coating also contain zinc (similar to that of the previous
galvanizing.) Zinc can be field applied as either a paint coating or by way of hot spray
application (metalizing). Metalizing has a higher initial cost but is known to have a longer
service life than zinc paint coatings. In addition, it is recommended that the portion of the
counterweight that dips into the water also be sealed with a coal tar epoxy or polyurea coating
that limits exposure of the counterweight to the saltwater. The corroded mounting bolts for the
counterweight should be replaced.
Alternatively, the counterweight can be replaced with a new counterweight fabricated using
stacks of stainless steel plate (in lieu of a combination of concrete and steel) and stainless steel
mounting bolts. This will reduce maintenance and extend the service life of the counterweight.
Repair/Rehab. Feasibility Study March 10, 2011
Bridge No. C-07-001 (437) 29 Final Report