Kelly Muller’s Ecology class at Albany Options, an alternative high school, set out to solve the problem of a persistent muddy and wet area on their campus. After researching the situation, they decided to create a bioswale to increase the infiltration rate of rainwater, improve the quality of runoff water, and restore wildlife habitat. Without excavation equipment, they removed sod and dug the bioswale by hand but were unable to install gravel, sand and topsoil at the bottom to increase drainage. After creating a berm around the swale to increase its capacity to hold rainwater, the class planted the sides and bottom of the swale with native plants that are tolerant of wet conditions, effective in filtering pollutants, and attractive to native wildlife.
In adapting this project for other sites, it is important to identify local soils to determine whether a bioswale or a rain garden is indicated. (Bioswales require excavation and replacement of clay soils at the bottom of the swale with gravel, sand and topsoil. Rain gardens are located in areas with soils that drain well and do not require excavation and soil amending). The project Kelly Muller’s class completed is essentially a rain garden, despite the diligence of students in digging it deeper in the style of a bioswale. The class discovered that soils in the area do not drain well and that their rain garden would have functioned better if they had been able to excavate and amend the soil.
Planting a rain garden requires no excavation and can take advantage of existing low lying areas, ditches or swales. (Note: Please take care not to destroy existing creekside vegetation to plant new plants, as the loss of roots will contribute to erosion). Other projects to consider include building rain barrels or green infrastructure including low-lying below grade planter beds, tree planting, roof gardens, and paths and parking lots with permeable surfaces.
•Shovels, trowels, and planting tools (for class)
• Soil test kits (or soil sample bag to send to state extension service for analysis)
• Earth-moving equipment to dig swale deeper
• Gravel, sand and topsoil to bury at bottom of swale
• Native Plants (see lists) that can tolerate wet conditions and absorb pollutants