Port of Tacoma staff celebrated Earth Day April 22 by planting four downspout treatment boxes last week at the administration building in an effort to keep pollutants from flowing into Commencement Bay.

Anita Fichthorn, Port of Tacoma’s water quality project manager, designed the boxes to filter the heavy metals picked up by rainwater coming off the roof. The boxes were engineered and built by Port facilities development and maintenance staff, using materials readily available at local hardware and building supply stores. The boxes—nicknamed Coho, Steelhead, Chum and King—cost about $600 each to build. They mimic the natural environment to filter pollutants. Nestled in a bioretention soil mix of sand and compost that controls the flow of water, the plants take up zinc and other pollutants to use during photosynthesis.

“The boxes play a key role in our efforts to control heavy metal releases from our industrial properties,” said Fichthorn. “They also help us comply with the terms of our stormwater permit.”

The boxes were tested last year at Pierce County Terminal and the Port of Tacoma’s maintenance facility. Those pilot boxes removed 99 percent of metals, particularly zinc and copper, according to Port of Tacoma officials.

To see additional photos of the boxes, click here. To watch a two-minute video of how they work, click here.