Riverton Creek, a freshwater stream that runs into the Duwamish River, is a spawning habitat for coho salmon and sea-running cutthroat trout. At the project site, the creek runs through the parking lot of an industrial area.

The project’s goal was to contain the stream in its urban setting while enhancing the spawning habitat and providing a barrier to withstand tidal fluctuations. That was accomplished by building a contained streambed 1,000 feet long and 20 feet wide with engineered retaining walls.

The mechanically stabilized earth walls consist of interlocking precast concrete blocks made from recycled concrete. Each 2-ton block measures 2.5-by-2.5-by-5 feet.

Concrete blocks were used for versatility, ease of installation and speed. They were installed with heavy equipment because of their size.

The height of the blocks allowed construction to move high enough, and fast enough, to avoid problems with tidal fluctuations like bank erosion. Due to the nature of the interlocking blocks, minimal excavation was needed during installation.

Using interlocking blocks resulted in less environmental impact while saving 15-50 percent over other product options.