Outfall

An outfall is the discharge point of a waste stream into a body of water; alternatively it may be the outlet of a river, drain or a sewer where it discharges into the sea, a lake or the like.

In the United States, industrial facilities that discharge storm water which was exposed to industrial activities at the site are required to have a multi-sector general permit. Issuing permits for storm water is delegated to the individual states that are authorized by the EPA. Facilities that apply for a permit must specify the number of outfalls at the site. According to the EPA's 2008 MSGP (final version), outfalls are locations where the stormwater exits the facility, including pipes, ditches, swales, and other structures that transport stormwater. If there is more than one outfall present, measure at the primary outfall (i.e., the outfall with the largest volume of stormwater discharge associated with industrial activity).