Rain Garden: Designed for Success

Dionne Talia, PBR Hawaii

Volunteers till in soil amendments including some composted invasive seaweed that has been pulled from nearby Maunalua Bay. This is a perfect example of the problem (invasive seaweed) becoming part of the solution (rain garden).

Faced with the challenge of dealing with rain runoff at a Honolulu high school, Songscapes took on the task of installing a rain garden to address a flooding problem.

After heavy storms, muddy rainwater would run downhill from the Henry J. Kaiser High School cafeteria parking lot into the art building plaza. This problem presented the opportunity to build a rain garden.

Songscapes, a local landscape contracting company led by Young Song (a Kaiser High School alum) took the lead in managing and directing the work of all the volunteers and helpers.

Donating time and services to this project were PBR Hawaii, Malama Maunalua, Songscapes, Hawaii Kai Rotary Club, student volunteers and community members from the neighborhood.

Hawaiian Earth Products supplied mulch and soil amendments; Steve Nimz donated Filtrexx Erosion Control Soxx; and Malama Maunalua provided informational signage.

For local organization Malama Maunalua, the situation at the high school presented the perfect opportunity to launch a pilot rain garden project. Malama Maunalua is dedicated to protecting east Oahu’s fragile ecosystems, including streams, beaches and Manalua Bay. Implementing a rain garden at the school fit well with their mission of keeping the surrounding beaches clean by preventing pollutants from ever reaching the ocean. After securing funding and generous donations of material and supplies from local groups and organizations, dedicated volunteers broke ground on October 29, 2011. Malama Maunalua members, energetic teenagers from Kaiser High School and Niu Valley Intermediate School, and others all joined forces to provide labor.

The first day included digging up the area to build the ground depression around the storm drain, which would now be the new over flow drain. A small excavator helped the volunteers avoid the most strenuous work and all excavated dirt was reused to build a continuous berm (earth mound) along the low side of the garden to help retain the storm water.

After about half a year, the school has maintained the natural look of the garden allowing the native plants to become well established, creating a re-naturalized habitat for insects and birds.

Repairing and deepening trench drain proved more difficult than expected, as over the years tangled roots from a nearby tree had grown throughout the trench. Eventually a volunteer with a mini chain saw managed to remove the majority of the roots. A continuous erosion control sock lined the base of the built-up soil berm to help maintain its shape.