In this subtitle the following words have the meanings indicated. “Environmental site design” means using small–scale stormwater management practices, nonstructural techniques, and better site planning to mimic natural hydrologic runoff characteristics and minimize the impact of land development on water resources. “Environmental site design” includes: Optimizing conservation of natural features, such as drainage patterns, soils, and vegetation; Minimizing use of impervious surfaces; Slowing down runoff to maintain discharge timing and to increase infiltration and evapotranspiration; and Using other nonstructural practices or innovative stormwater management technologies approved by the Department. “Impervious surface” means a surface that does not allow stormwater to infiltrate into the ground. “Impervious surface” includes rooftops, driveways, sidewalks, or pavement. “Precipitation data” means historical data that describes the relationship between precipitation intensity, duration, and return period.