Stormwater Permitting for the Rest of Us: The Use of USEPA's Residual Designation to permit Commercial, Industrial, and Institutional Properties Not Already Covered Under a Stormwater Permit

The Industrial Multi-Sector General Permit (MSGP) and its state-specific versions currently regulate stormwater discharges from specific industrial sectors as defined by their SIC/NAICS codes. Municipal Separate Storm Sewer (MS4) permits regulate MS4 agencies, typically cities and incorporated areas, and generally require that cities implement a range of Best Management Practices (BMPs), including in some cases, inspection and enforcement of discharges from commercial and industrial land uses that are not covered under an MSGP. In two U.S. Environmental Protection Agency (USEPA) regions, the regulatory approach of residual designation has been used to develop new stormwater permits specifically for Commercial, Industrial, and Institutional (CII) land uses, which require owners/operators of such properties to implement BMPs to reduce the discharge of pollutants from their properties. The first CII permit in EPA Region 9 in California is currently under development. This permit is for two watersheds Los Angeles County and will capture CII properties of 5 or more acres that are currently not covered in the California’s Industrial General Permit (IGP) and portions of properties covered under the IGP that are excluded (e.g. rooftops and parking lots). This includes the Ports of Los Angeles and Long Beach as well as a range of other CII land uses. The permit includes requirements for operators to implement BMPs, including potentially structural treatment control BMPs, to meet Water Quality Based Effluent Limits (WQBELs) that are specified for certain receiving waters within the permit. Permittees may participate in a regional stormwater capture and retention project or construct their own stormwater capture and retention system in lieu of meeting WQBELs. The permit has not yet been finalized and these conditions are subject to change.