A Rain Garden is a planted depression that collects and infiltrates rainwater back into the ground. Recently adopted PA DEP regulations (NPDES Phase 2) require the infiltration of a portion of the stormwater generated by the project. Rain Gardens are one of the design tools that can be used to meet these regulations. When designing a Rain Garden it is important to understand the geology and soils present on the site, particularly in areas of limestone bedrock or clay soils. When the soils are not permeable enough to let water drain and filter properly, the soil in the bottom of the garden is replaced with a mixture of sand and compost (typically 60%/ 20%), and topsoil (20%). Rain Gardens are typically planted with native vegetation, often largely consisting of perennials which require only seasonal maintenance (mostly spring and fall clean up of older vegetation), and that can withstand the fluctuation of wet and dry conditions. While not a new idea, the advent some of the new stomwater regulations has created an acceptance for Rain Gardens and similar design ideas by local municipalities.