In November of 2023, volunteers helped the Snoqualmie Indian Tribe’s Environmental & Natural Resources (ENR) Department plant and install Floating Treatment Wetlands, or FTWs, in the retention pond on the Tribe’s reservation. Thanks to the work of our partners, the Washington Conservation Corps and volunteers, these constructed wetlands will improve water quality for the many life forms that live here. At the Snoqualmie Casino, the FTWs add to other functioning green storm water infrastructure (bioswales and retention ponds), which slow storm water run-off before it flows into local streams and wetlands, eventually joining the Snoqualmie River.
The Snoqualmie Tribe’s Floating Treatment Wetland (FTW) next to the parking lot and ecosystem from which water drains into the pond.
Checkermallow blooms on the floating wetland
The Tribe’s FTWs, designed by ENR’s Water Quality Program, Biomatrix Water, and Herrera Environmental Consultants, host a over 2000 wetland plants, including 12 different species. These plants will create shade to cool the water and contribute to larger wetland ecologies, filtering crude metals, oils, and excess nutrients from the water.
Floating Treatment Wetlands are meant to mimic the many benefits wetlands in the landscape bring to aquatic habitats. Wetlands are a part of our ecosystem where everything slows down – sediments and pollutants in water settle out and are removed from flows, plants create habitat for all sorts of wildlife, and diverse vegetation captures sunlight above the water, helping keep water cold. Colder water holds more oxygen, meaning fish can breathe easier. There are many other benefits wetlands bring to ecosystems, but at least these three major benefits are also created by the constructed FTWs on the Snoqualmie Tribe’s reservation.
This FTW is especially important in this processes because it is capturing storm water from the casino and surrounding parking lots. Thanks to these treatment strategies, some water quality issues that are present in this pond are not echoed downstream.
The benefits are not exclusive to wildlife. These ecological benefits also reach to human ecologies. Clean water is obviously of value to everyone, but the Tribe also designed the FTWs with culturally significant plants in mind. The shoots of willows and dogwoods (Salix and Cornus species) are valuable weaving and construction materials. Tule (Schoenoplectus acutus) is used for weaving, and cattail (Typha latifolia) is useful as both a food and weaving material. The pollinators visiting wildflowers help produce both seeds and honey. This is a place where culture, biology and ecology again become interwoven experiences. No plant is insignificant in this sense, but these wetlands have been designed with consideration to their ecological and cultural functions as part of the Snoqualmie Tribe’s larger landscape. More information about these plants can be found on the Native Plant Signs on the ENR website.
The many benefits that floating wetlands bring aren’t a completely new idea or technology, but are a concept that has only recently made its way to the Pacific Northwest. Although the Snoqualmie Tribe’s water quality data hasn’t shown this local result yet (it’s only been a year since the FTWs were installed), data from other floating wetland projects have shown promising results.
From what others have observed, the roots coming from FWTs trap sediment and organic particles in the water, making the water clearer. These roots and associated organisms are also important because they assist in absorbing nutrients from the water, their sole source of food. Studies suggest that this is why FTWs are able to remove water-borne nitrogen, phosphorous, copper, zinc, as well as other excess nutrients and pollutants present in stormwater ponds.
Roots growing under the floating treatment wetland start to form a mass which captures pollutants and excess nutrients.
Willow leaves on the floating treatment wetland.
So far, this description matches our FTWs too! Most of the plants are growing in well, and root masses are quickly establishing under the FTW structure. Tule and other emergents are growing tall in special submerged structures where underwater plants can grow. Tule has been shown to add oxygen to the water it grows in. Rushes, sedges, and silverweed were also added to these submerged FTW as we continue to experiment with which plants will do best in this local environment.
Willows are also growing quickly, as you can expect willows to do, making both roots and shoots. Much of the green you see from a distance are the willow leaves.
The Snoqualmie Tribe will continue to maintain and care for this project, replanting if needed. As these wetland plants grow in, we expect the water quality data will tell a story of improving aquatic habitat for everything that calls this place home. The life of water continues to be an important part of the Snoqualmie Tribe’s culture and history as outlined in the sdukʷalbixʷ – ʔəshəliʔ ti qʷuʔ Water is Alive Hub and our past ENR blog post The Water Connects Us.