The health of Puget Sound is a pressing environmental issues facing Washington State. Because stormwater is one of the major sources of pollutant inputs for these waters, development and implementation of ecologically rigorous best management practices (BMPs) for stormwater treatment is a priority.

Phytoremediation and compost-based biofiltration are two emerging technologies with the potential to provide effective, economical alternatives to conventional stormwater BMPs. Both technologies use living systems of plants and soil to capture, filter, and clean stormwater. Phytoremediation seeks to use living plants to filter runoff and, in some cases, to absorb and even utilize or biodegrade contaminants of concern. In contrast, compost-based biofiltration focuses on the ability of compost to sequester these contaminants in the soil. The roles of plants and soil substrate relative to one another in such systems are not fully understood, but our goal is to complete analyses that will help to elucidate these important design factors.

Admiralty Inlet at Ebey’s Landing on Whidbey Island is an excellent location for testing these approaches. The area is ecologically rich with salmon, shellfish, and abundant aquatic habitat, including an economically important shellfish community. It is also the site of a strong ongoing effort to preserve and honor the local, historic culture and its resources. Stormwater outflows to Admiralty Inlet have been shown to contain elevated concentrations of fecal coliform bacteria, nitrogen, phosphorus, and heavy metals. This observation prompted a pilot project testing phytoremediation as a possible means of improving the water quality of outflows to Puget Sound in a manner that is cost effective, ecologically sound, and consistent with the values of the local community.