Port of Seattle pilot project aims to reduce polluted runoff

'There is no single solution to saving Puget Sound, no silver bullet, but there are hundreds of different things we can do and this is one of them,' port commissioner Bill Bryant said Monday.

Moving Green Infrastructure is a research/demonstration project to test the water quality performance of two innovative stormwater treatment techniques, 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 will be tested before and after going through the boxes to see how these two techniques perform. 

The project is part of growing efforts to reduce the amount of polluted runoff reaching Puget Sound, which is estimated to receive between 14m and 94m pounds of toxic pollutants every year. Two large steel boxes, called Splash Boxxes, are being installed at Terminal 91, the location of Smith Cove Cruise Terminal. These boxes are a blend of rain garden and cistern, two practices referred to as low impact development (LID).

'LID works,' said Amy Waterman of Gealogica, adding that the result is a 98% to 99% reduction in runoff volume and an 83% to 99% reduction in key pollutants.

The information from this study will help shed light on the potential for these bioretention 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. One box will have a soil mix with volcanic sands and the other will be a typical rain garden soil mix.

King Conservation District in partnership with Seattle Public Utilities supported the project with a grant for $49,700.

The water going into each box from the roof runoff will be tested once a month.