The National Railroad Passenger Corporation (Amtrak) is replacing the 1907-era two-track bascule bridge over the Niantic River between East Lyme and Waterford, Connecticut, along the heavily traveled Northeast Corridor. Prestressed concrete sheet pile retaining walls were selected to support the new higher approach embankments along both the east and west approaches to the new bridge. Along the west approach a two-tiered wall design was utilized to support a new recreational walkway elevated above the 100-year storm surge elevation for the Niantic Bay, while at the same time keeping the walkway below the level of the adjoining tracks. The design of the two-tier wall system needed to take into account two simultaneous Cooper E-80 train live loads, the influence of electric traction catenary structure foundations along the wall alignment, and live load surcharge from maintenance vehicles at the walkway level, while at the same time minimizing long-term impacts to the public beach. The concrete sheet pile wall was designed to support the upper prefabricated modular T-WALL® along with all imposed loads, while at the same time protecting the railroad embankment from the scour and wave action of a 100-year storm event in Long Island Sound, and taking into consideration challenging subsurface conditions
