BRIDGE REPAIR/REHABILITATION FEASIBILITY STUDY

the exception that the drilled holes for internal treatment will not significantly reduce the pile
capacity. In-place preservative treatments can only be applied above the waterline and as such,
they would only be effective in treating the piles above the waterline. The risk of contamination
from the toxic chemicals is far greater with the piles than the other elements due to the closer
proximity to the water and the potential for the chemicals to leech out through the interconnected
network of splits and checks that extend above and below the waterline. As such, in-place
preservative treatments are not recommended for the timber piles.
As a number of existing piles contain significant loss in section, the deteriorated sections of the
piles should either be strengthened or replaced, or the piles completely replaced.
The piles can be strengthened using fiber reinforced polymer (FRP) composite jackets that
completely wrap the piles and then are filled with epoxy grout (see Appendix F.) In addition to
restoring the strength of the piles, the jackets provide the additional benefit of preventing decay
and marine borer attack by limiting the opportunity for fungal spores and marine borers to access
the piles. In order to provide full protection of the piles from both marine borers and decay, the
FRP jackets should extend from several feet below the mudline to the top of the piles. The tops
of the piles should be adequately sealed with a bituminous coating to prevent moisture from
absorbing into the pile from the top.
The current pile arrangement introduces some installation challenges for the jackets. In many
bents, there are instances where two piles are immediately adjacent to each other and in other
bents there are battered piles that butt into the side of the adjacent plumb piles. The piles may
need to be temporarily separated by jacking in order to provide sufficient clearance to install the
jackets. In addition, the piles in Bent 10 that contain the 12x12 timber build-up spliced in line to
the top of the piles will likely require larger jackets to fully encapsulate the splice and build-up.
After the jackets are installed, new holes will need to be drilled through the jackets and piles in
order to connect piles together and to attach the new timber bracing members. Previous unused
holes will be covered so as not continue to pose a problem. However, precautions will need to
be taken to ensure that the new holes do not eventually become open holes including the use of
corrosion resistant bolt material.
Although a relatively new technology, the FRP jackets have been successfully used on a number
of bridge, pier and wharf foundations with timber piles over the last decade. As it is a relatively
new technology, long-term performance data in the extremely aggressive salt water environment
is not available and thus the predicted service life of the jackets is somewhat unknown. The FRP
material and associated adhesives, grout and coatings are potentially susceptible to wear from
abrasion, impact damage, delaminations due to freeze-thaw, and degradation due to ultraviolet
light and exposure to the salt water.
Installation of the jackets requires that the piles be thoroughly cleaned to remove barnacles and
any decayed timber material. This work will expose the full extent of the deterioration, which
will not otherwise be known in detail until the work is performed. It may be found that some of
the piles contain too much deterioration to repair with the FRP jackets (i.e. there may be
inadequate pile capacity even with the jackets or insufficient sound material in the piles for the
jackets to connect.) This scenario is possible given that the marine borer attack is primarily on
Repair/Rehab. Feasibility Study March 10, 2011
Bridge No. C-07-001 (437) 39 Final Report