A Dirt, Gravel and Low Volume Road Program Grant from The Blair County Conservation District help fund this unique project. Day Contracting completed this in the summer/fall of 2017. A rain garden is a planted depression (or a hole) that allows rainwater runoff from impervious urban areas, like roofs, driveways, walkways, parking lots, and compacted lawn areas, the opportunity to be absorbed. ... Rain gardens can cut down on the amount of pollution reaching creeks and streams by up to 30%.