The Port of Seattle has announced the results from a pilot project by environmental groups to reduce the amount of polluted runoff reaching Puget Sound. The Port has hosted a study site for two metal boxes that have bloomed into rain gardens to help reduce pollutants called Moving Green Infrastructure Forward. This effort is in partnership with King Conservation District, Sustainable Seattle, Gealogica and Splash Boxx.

“Reducing levels of zinc from storm water run-off is one of our toughest challenges. We thank our partner organizations and agencies in these efforts,” commented Stephanie Jones Stebbins, environmental and planning director at the port.

Two large steel boxes, called Splash Boxxes, were installed at Terminal 91, with results gathered every four weeks. These boxes are described as a blend of rain garden and cistern, two practices referred to as low impact development, or LID.

Literally a large “rain garden in a box” and a special soil mix with local, volcanic sands, water quality from a roof in an industrial port area was tested before and after going through the boxes to see how these two techniques performed.

“After eight months of sampling, the zinc levels are 1000 times lower at the Boxx output than the roof input after going through the soil and plants in the boxes,” said Alessandra Zuin of Gealogica, the project lead.

The information from this study will help shed light on the potential for these bio-retention planter boxes to improve water quality of polluted runoff in commercial/industrial areas and whether soil mixes used in rain gardens and bioswales could be improved.