On Monday, June 26th, representatives from Montgomery Parks joined ANS for a tour and discussion of the newly installed rain garden at Woodend Sanctuary. Although the rain garden won’t have its ribbon cutting ceremony until later this year, it is rapidly approaching completion. With the perfect warm weather for such an outing, staff members, volunteers, and high school Conservation Campers strolled around the garden, listening as those involved with the project explained the thoughts behind it.
When the mansion at Woodend was first built, the attitude at the time towards rainwater management was to redirect it away from built areas as quickly as possible. Over time and with increased development in the surrounding area, this approach has led to erosion and flooding and seriously impacted nearby Rock Creek. In an effort to limit these issues, ANS, with support from grant funders including the Chesapeake Bay Trust, Montgomery County Department of Environmental Protection, Wallace Genetic Foundation, and Cornell Douglas Foundation, invested in the new rain garden to slow the flow of surface runoff from the Woodend parking lots and mansion roof.
ANS’s Tree-Safe rain garden was built with tree preservation in mind, because established root structures are essential for soil retention and water uptake. Mature trees are the best kind of stormwater management. Many rain gardens have underground gravel pits, because the larger spaces between rocks can hold more water during storms. But, digging out the soil to create a gravel layer would have damaged some of the Sanctuary’s important trees, including a notable Black Walnut, so the rain garden includes very little digging. However, saving these roots, and adding new ones by planting native herbaceous and woody plants, breaks up the soil and creates channels the water can follow to infiltrate into the ground over time.
In addition to root preservation, the rain garden uses compost berms, logs, and rip rap rocks contouring the hillside to act as speed bumps slowing the water’s flow. The slower moving water is unable to pick up as much sediment, reducing erosion. Other components of the rain garden, including the sandy and compost soils, the mulch layer, and the native plants increase the porosity of the soil so the pools of rainwater the berms produce can be absorbed into the ground. The compost berms are made of special “Nutriloxx Soxx” materials that filter pollution out of the water as it slowly passes through them. Completion of the rain garden is expected to trigger the emergence of exciting improvements as it matures and further establishes itself.