The rehabilitation of Troy’s 95-year-old seawall enhances the resiliency of the city’s waterfront business corridor against rising flood levels and protects an adjacent wastewater interceptor sewer. And the jobsite couldn’t have been more challenging.

Limited landside space required most construction work to be performed from barges in a river where daily tidal changes of up to 7 ft complicated the scheduling of drilling and other precision work. Underwater visibility was frequently limited due to combined sewer discharges, seasonal rain and snowmelt.

Photo courtesy CHA Constulting Inc.

Along with repairing the existing concrete seawall face and raising the height of a potentially vulnerable 1,000-ft-long section, the project team constructed a new precast concrete panel system supported by steel piles and tiebacks. Galvanized steel soldier piles were installed within 30-in.-dia pile casings drilled up to 9 ft into bedrock. After anchoring the piles with an underwater concrete poured streambed, 9-in.-thick precast concrete panels—25 to 32 ft high and 11 ft wide—were erected in front of the existing wall between the piles. In areas where the bedrock was deeper, the panels could be only 7 ft wide. The panels were prestressed to minimize cracking and maintain concrete compression during the erection process.

Photo courtesy CHA Constulting Inc.

An adjacent restaurant further complicated the project. The team used plans and physical inspection to locate the building piles and spaced the drilled tiebacks beneath the restaurant to integrate seawall support elements without conflicting with any pile. Given the limited access around the building, concrete to fill the void behind the wall was pumped over the restaurant, which remained in operation throughout the project. 

Verifying the quality of the underwater concrete repair work required specially trained hardhat dive inspections. High-definition cameras and video streams allowed land-based inspectors to follow the inspection in real time and to instruct divers to address specific issues as needed.

Photo courtesy CHA Constulting Inc.

The payoff of overcoming these challenges is a hardened seawall that’s credited for helping to spur development, including a new hotel, parklands and shared walkways that improve river access and connections to waterfront businesses.