Floating Treatment Wetland Build

The Snoqualmie Tribe Floating Treatment Wetland (FTW) Project was made in partnership with volunteers, Tribal staff, Herrera, and Biomatrix. This installation is located on the Tribe’s largest stormwater treatment pond, which is roughly 4/5 of an acre. The installation occurred over multiple days and required an inflatable boat to pull the rafts out into place and anchor them.

Sixty-two rafts make up the design, with gaps between some rafts with the intention of not trapping wildlife underneath them. Each raft includes non-toxic, fully recyclable substrate that can adapt to a variety of plants. The raft system is also robust and strong enough to hold people for maintenance, withstand a crushing or impact force of >770 pounds, and resist damages from waterfowl.

The floating treatment wetland is part of a larger stormwater treatment system on the Snoqualmie Tribe reservation. Improvements to that system are always considered with the FTW’s efficacy to treat contaminants in mind. Located next to the Casino & Hotel’s employee parking lot, this stormwater pond works in tandem with the bio-swales between rows of employee parking which were installed in 2011. The water quality of the reservation and maintenance of this system is routinely checked as the Tribe takes the drainage of stormwater from the reservation to Kimball Creek, a Snoqualmie River tributary, very seriously.

Kelsey Payne, Snoqualmie Tribe Water Quality Manager, pictured next to the Tribal Reservation’s Floating Treatment Wetland.

Floating Treatment Wetland Plants

Native aquatic and emergent wetland species, including grasses, rushes, sedges, and a few small woody shrubs and/or herbaceous plants were chosen with inputs from multiple Tribal departments. Plants with cultural significance to the Snoqualmie people were prioritized. Some of the selected plants include tule, twinberry, checkermallow, willow, red osier dogwood, and monkeyflower. These plants will be tended with care as they benefit the greater Snoqualmie community.

The substrate of the rafts was built thin enough to expose the roots of these plants to the water below. These roots then create a biofilm of beneficial microbes that can break down nutrients and filter sediments and pollutants. This floating wetland system is similar to Indigenous Knowledge of wetlands that can be found in different parts of the world. The success of the Snoqualmie Tribe’s floating treatment wetland ability to filter contaminants will need to be tested over time.