Charlottesville, VI Raingarden
Source File: http://www.charlottesville.org/Index.aspx?page=563
What is a Raingarden?
A "raingarden" is a low impact development (LID) stormwater management technique designed to improve water quality by filtering out and uptaking pollutants, promoting on-site infiltration and groundwater recharge, and reducing peak stormwater flow. By slowing water flow, a raingarden allows greater infiltration into soils, and gives plants in the garden time to process and remove pollutants from the water before it flows into local waterways.
The Greenleaf Park raingarden was funded through a grant from the Environmental Protection Agency's Chesapeake Bay Program and the Virginia Department of Conservation and Recreation. Its purpose is to showcase a "natural" method for addressing stormwater management that is appropriate in existing sites as well as new developments. The publicly accessible and central location of Greenleaf Park also serves to provide a long-term educational opportunity to a wide target audience and is supported through the development of two permanent interpretive signs. Construction of the raingarden began on September 19, 2005 and was completed by the end of October.
Greenleaf Raingarden Construction:
The raingarden is located in a natural swale, which drains approximately 40,000 square feet, including the park's parking lot and turf areas. In order to properly design the raingarden, the site was first surveyed to determine the size of the drainage area. The final size of the raingarden was calculated based on the amount of runoff expected from the drainage area and the magnitude of storm event it will be able to capture.
Next, the raingarden was designed based on the survey and drainage data and the landscaping was planned. The site was then excavated in accordance with the grading plan. Silt fences and other erosion control measures were installed to prevent stormwater runoff from eroding the area and depositing sediment in the adjacent streams. Once this was complete, a layer of sand was distributed around the bottom of the excavation and filter fabric was secured around the walls to prevent erosion and enhance stability. Next, layers of gravel and an underdrain system consisting of filter stone layers and perforated pipes was installed which helps to remove water that has filtered through the raingarden. The drain system was covered with a biofilter soil mixture, a layer of rich organic compost, and erosion control matting.
Local volunteer groups, such as Lexis Nexis and UVa's Students for Sustainable Communities, played a vital role in the completion of the garden.
Finally, the landscaping was completed with decorative river stone and native plants, ranging from trees, woody shrubs, herbaceous plants and seed mixes, which were selected based on aesthetics as well as their ability to function in the raingarden.
This project received funding from the Environmental Protection Agency's Chesapeake Bay Program and the Virginia Department of Conservation and Recreation, via grant agreement number Bay-2004-14-SR.