Bridge Piers Rehabilitated to Prolong Life

Lake Pend Oreille in the northern Idaho Panhandle is the largest lake in the state. It acts as a drinking water reservoir with the level of water fluctuating throughout the year.

A bridge crosses the lake and is supported by nine 100-year-old concrete piers. Over the decades the piers deteriorated and needed to be repaired. 

It was determined that the piers, which are almost entirely exposed during the winter months, did not require additional strengthening, but the existing concrete substrate showed extensive wear. To ensure the continued longevity of the bridge, concrete repair and the application of FRP were proposed.

The repair needed to be completed during the winter, when as much of the piers as possible, were above the water line. This meant the contractors had to construct heated hoarding shelters on floating platforms for each pier that was being wrapped. The team also had just four-months to complete the project due to subsequent works scheduled to take place.

The substrate of the piers was poor and required significant repair prior to the FRP installation. 

A layer of epoxy paint was applied over the majority of the installation that is typically submerged when the lake is full to offer additional protection. 

FRP was identified as a good fit for this project as it added a protective jacket around the piers, could be installed in a short period of time, and required only a small footprint for installation. A more traditional rehabilitation, such as shotcrete would have been more time consuming, and the dust particles created are typically harder to contain. Containment was vital due to the reservoir being used for drinking water supplies.

An important objective for the repair was to limit water intrusion into the piers; FRP is the ideal solution to meet this objective.

Although not specified, the installed FRP also adds some marginal strength to the pier. Other waterproofing membranes do not offer the hardness and durability of FRP.

In summary, FRP was the ideal solution for this project over other repair methods due to the constrained working environment, environmental sensitivity, allowed installation duration, and the Tyfo product's impermeability.