Rain gardens perform bioretention services but do not have an engineered subgrade. Rain gardens rely on healthy soils with good infiltration and percolation rates to manage ponded runoff water. A thorough soils investigation is needed to ensure a proposed rain garden site has soils with adequate percolation rates. Rain gardens are typically used in residential settings to manage runoff from smaller impervious surfaces like roofs. In some residential development, soils are altered and compacted and require an engineered subgrade to ensure drain down time of 12 to 24 hours.