BRIDGE REPAIR/REHABILITATION FEASIBILITY STUDY

sidewalk widths that do not meet accessibility requirements and substandard pedestrian railings.
The bridge does not operate reliably and the operating equipment does not meet standards for
safety and maintainability. The current navigation opening is also inadequate to serve the needs
of the boating community. Doing nothing or performing only normal maintenance will not
correct the functional and safety concerns.
Although technically feasible to repair or rehabilitate the existing bridge, all feasible schemes
have significant consequences or leave significant deficiencies. Although some of the
consequences and deficiencies individually may be considered minor, the cumulative impact of
these is significant. Specific consequences of maintaining, repairing or rehabilitating the existing
timber bridge include the following:
• The effort to maintain the existing timber bridge will continue to be a significant effort
and a burden to the Town of Chatham in terms of maintenance cost and disruptions to the
traveling public with continual piecemeal replacement and/or repair of timber members.
• Although not all timber elements of the bridge currently need to be replaced, it is not cost
effective or technically feasible to repair, strengthen or replace certain elements without
removing other elements. Although certain timber members can be replaced on an
individual basis (e.g. wearing surface, railing, curbs, bracing, fender system, sheave poles
and lifting beam) other major elements (e.g. structural deck, stringers, cap beams, and
piles) cannot be replaced without removal of a significant number of other elements.
• Continued replacement, repair and strengthening of the timber cannot be sustained
indefinitely as this work will eventually weaken members and create conditions that
promote further decay. As such, all timber members will eventually need to be replaced.
• Modern strengthening methods such as fiber reinforced polymer (FRP) sheets or pile
jackets are expensive relative to the cost of the timber, do not have a long-term
performance history for use in salt water environments, and may introduce visual
impacts.
• Extending the service life of the existing timber members using in-place preservative
treatments is not prudent due to the need for frequent reapplication of the treatment and
because of significant environmental and human health concerns. The currently available
treatment techniques and chemical preservatives have limited effectiveness and require
frequent reapplication (every 5 to 10 years). Some of the treatment would require
removal of significant portions of the bridge to provide access for the retreatment.
Because of the human health and environmental contamination risks, there is a risk that
this treatment will not be permitted for use in this environment.
• Repair or rehabilitation will not fully address the limited navigation opening. Navigation
through the bridge continues to be a challenge and a safety concern for the boating
community. As such, the boating community has requested improvements to the
navigation opening with a preferable minimum horizontal clear opening width with
unlimited vertical clearance of 25’-0”. Evaluation of the existing bascule span geometry
confirmed, with the existing constraints, modifications to the bascule span would at best
yield only a 19’-4” wide navigation opening with unlimited vertical clearance. A major
repair or rehabilitation effort that replaces the majority of timber components throughout
the bridge may be viewed by the US Coast Guard as more of a bridge replacement and as
Repair/Rehab. Feasibility Study March 10, 2011
Bridge No. C-07-001 (437) 3 Final Report