Durham Neighborhood Rain Catchers Project
One of the projects that we have been busy with this summer at Dragonfly is the installation of around 50 rain gardens in a neighborhood in the City of Durham. The project is funded through grants from the North Carolina Division of Water Quality and the Clean Water Management Trust Fund in an effort to help clean Durham water, specifically Ellerbe Creek! Residents in the area volunteered space in their yards in an effort to catch and treat storm water.
The size and location of each of the rain gardens was determined by engineers depending upon the size of the area of runoff, volume of runoff, and topography of the land. Rain gardens collect water for storage and then slowly treat and release it. Once a rain garden is complete, it is less than a foot deep, but upon construction, a larger amount of earth is removed. This deeper section is then filled with bioretention mix, which allows for better filtration of the water, while also allowing plants to grow. A layer of mulch is then placed on top of that and appropriate plants are then added. As water is collected, the plants and other biomass work to absorb some of the extra nutrients and chemicals before the water reaches a nearby creek or other body of water.
Other important elements of the system include the downspout, dissipator pad, berm, and weir. The downspout is where the water enters the rain garden during and after a storm. The dissipator pad consists of cobble and reduces the energy of the entering water to minimize erosion. The weir is on the opposite side of the rain garden as the water entrance area and allows for water that exceeds the storage space of the rain garden (in the case of a large storm) to flow out of the space and away from the home or other protected area. The berm is the raised area around all edges of the rain garden, which helps to keep water in the rain garden to be treated, rather than running down the slope.
Currently, we are working on excavating and filling the rain gardens, as well as setting up the downspouts, berms, dissipator pads, and weirs. We will install the plants later in the summer and early fall. It’s exciting to be part of this large project to improve water quality in Durham!