Truly House Demonstration Rain Garden

Guest post by Bachelors of Applied Science in Sustainable Practices student Oluwa Jackson

A rain garden has been installed behind Truly House as a BASSP capstone project by Oluwa Jackson. The purpose of a rain garden is to slow and filter stormwater flowing from impervious surfaces, in this case the Truly House roof. The garden has already been effective in preventing flooding on the lawn during heavy rain events.

A circle ten feet wide and two feet deep was cut in the lawn, and seven tons of native soil (which consists of red and blue clay glacial till, including lots of gravel as well as large rocks) was replaced with a bioretention soil mix. The soil comes from Cedar Grove, and consists 70% sand and 30% compost. Sand allows water to infiltrate rapidly, and compost provides nourishment to plants. A bowl shape was created, and then surrounded by a berm about a foot high. A rocky inflow leads from one of the house’s rain gutter downspouts to the garden, where it will be absorbed and filtered.

The garden is planted with native species such as common rush, Douglas iris, tufted hair grass, snowberry, swamp rose, red flowering currant, and red-osier dogwood. The shrubs are still young and are expected to grow significantly in the next few years. In the meantime, an irrigation system has been installed to nurture the young plants through the dry summers while their root systems develop. The flowers will provide food and habitat for pollinators.

Soon a sign will be installed explaining what rain gardens do so that passers-by can learn more, which will link to a website with even more information: https://trulyhouseraingarden.blogspot.com/

Hopefully this demonstration will serve as inspiration for people to put a beautiful rain garden in their own yards. The more rain gardens are installed in neighborhoods to slow and filter stormwater, the less pollution and sediment will be washed into our streams. This is important for the health of the ecosystem, particularly salmon and other important native species, and for the health of the Puget Sound.

This project is funded by the King County Wastewater Treatment Division