WTD employees are developing new ways to protect the ponds in the North 40 natural area at the Brightwater Treatment Plant site.

The 70 acres of nature trails and ponds are a popular walking area with the local community – as well as an education tool for the thousands of students taught at the Brightwater Education Center every year.

A team is building floating wetlands designed to shade pond water, reducing temperature and nutrients that decrease oxygen. This effort will  improve oxygen levels and health of fish and other aquatic organisms, creating a healthier ecosystem.

“When ponds and shallow rivers and streams get too much sun, they can heat up, creating an unhealthy environment for fish, insects and frogs,” explains Matt MacDonald, water quality planner. “At Brightwater’s Lower Pond, trees planted around the shoreline of the Lower Pond will someday help shade the water, helping to keep the water cool.  While they are growing and maturing, the pond will need a little extra help.”

The floating wetlands are made of living willow branches that grow and become part of the pond ecosystem. Unlike other approaches that involve shade cloth to block the sun, these willow rafts are made of natural materials. When they need to be replaced, the material will break down and return to nature, rather than going to a landfill.
“The wetlands help us protect the ecosystems we created in the North 40 nature area and help us meet our permit requirements,” said Chris Tiffany, capital project manager for King County WTD. “This technology could be very helpful to other agencies who need to meet similar permit conditions.”

The project team will monitor the success and benefits of this unique and sustainable approach to a healthy pond environment, and we’ll be sharing what we learn so other agencies can learn from our work.