Stormwater Management

When it rains, stormwater either infiltrates into the ground or flows directly into the storm system.  Pervious paving and landscaping allow water to be absorbed into the ground, percolating through natural filters and into aquifers.  Impervious surfaces, such as sidewalks and roofs, force storm water to flow directly into the storm drain.  This can lead to combined sewer overflow during times of significant rainfall.  Additionally, excess storm water may collect contaminants prior to entering the storm drain, and depending on the location, may drain into natural waterways without being treated.

The Energy Independence and Security Act of 2007 (§438) requires federal agencies to maintain the pre-development hydrology of the property with regard to the temperature, rate, volume, and duration of flow, to the maximum extent technically feasible. See EPA's 2009 technical guidance for more information.

https://www.epa.gov/greeningepa/epa-facility-stormwater-management