By 2017, the 70-year-old seawall guarding the waterfront of Seattle, Washington was in desperate need of repair. Constant exposure to the ravages of the sea, and even earthquakes, had withered away the old wooden supports that held the structure together. A new, modern seafront was required that could withstand the immense pressure of the Pacific Ocean while providing an attractive amenity to the residents of this modern metropolis – and a habitat for the abundant marine life of Elliot Bay.
An immense seawall that protects public safety
Oldcastle Infrastructure in Auburn, Washington produced 400 immense Z-shaped superstructure segments and 400 20-foot-tall face panels for the new Elliot Bay seawall.
The design and engineering of the specialty Z-shaped concrete segments and fascia panels were essential to the seawall’s stability, and a critical step in acting as the concrete backbone of the new seawall’s cantilevered sidewalk.
To meet the limitations of the constrained working environment, and a tight construction schedule, Oldcastle Infrastructure provided a high quality, durable precast concrete. This allowed for quicker and easier installation, improved constructability, and lowered life-cycle costs, solving the interesting construction challenge and providing the most efficient and durable solution for the City of Seattle.
Designed specifically to promote biodiversity beneath its surface
As a result, the seawall wasn’t just replaced. It was reinvented.
The Elliot Bay seawall now provides a natural defence for the city during storms, and a recreational space for city residents during calmer weather. But the real innovation lies beneath the surface. When the old seawall was first built, much of Elliot Bay’s existing wildlife habitat was cleared – the sloping beaches, the many crevices and a vegetated seabed in which biodiversity thrived. The new seawall aims to correct this biodiversity loss through, for example, the inclusion of a grooved, textured face to promote algae growth, rock beds for fish to hide and forage and in which marine plants can take root.
Most impressive of all, the seawall features light-penetrating surface panels in the sidewalk above, enabling juvenile salmon to see their way through the water on their annual migration.
Seven years after its completion, the seawall has brought fresh life to the shore — to the people and businesses above it, and the marine species below. This is a structure that doesn’t just stand up to the elements, but enhances the environment, and helps it endure.