Kaiser High School Rain Garden

Drainage problems at Kaiser High School in Hawai‘i presented the perfect opportunity for a community organization and a local landscape architecture firm to create a rain garden. Malama Maunalua teamed with PBR HAWAII to design a rain garden.

PBR HAWAII’s rain garden design required three key elements. First was creating a graded recessed area (maximum of 12” depth) around an existing, underutilized catch basin to redirect and collect storm water from the upper cafeteria parking lot. Excellent percolation tests of the soil around the catch basin reinforced that this was the right location.

The design team also verified that there were no underground utilities in the areas to be graded. The second element was repairing and deepening a clogged trench drain under a nearby sidewalk to allow water from the upper parking lot to flow through the trench, and not on to the surrounding sidewalks.

The third element was the inclusion of low maintenance, Native Hawaiian groundcover plants and shrubs to assist in absorbing and filtering the collected rainwater. The rain garden design and rainfall data calculations were all done by computer, allowing the electronic plans to be easily distributed via email for review and comment during the design process.

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, staff from Songscapes (a local landscape contracting company), and others all joined forces to provide labor.

The completed rain garden now serves as an educational tool, with students collecting data on the growth of the native plants, monitoring the progress and health of the garden, and measuring storm water runoff.