National Pollutant Discharge Elimination System (NPDES)

EPA's Residual Designation Authority

EPA and the authorized states regulate stormwater discharges from regulated municipal separate storm sewer systems (MS4s), industrial activities, and construction sites under section 402(p) of the Clean Water Act. These stormwater discharges require NPDES permits. In addition, EPA can use its "residual designation" authority to regulate and require NPDES permits for other stormwater discharges on a case-by-case or categorical basis under 40 CFR 122.26(a)(9)(i)(C) and (D) (PDF)(23 pp, 224 K, About PDF). Small MS4s that are not already required to have NPDES permit coverage can also be designated for regulation under 40 CFR 123.35(b) (PDF)(2 pp, 135 K, About PDF).

Stormwater Petitions

areas petitioned for residual designationIn July 2013, EPA regions 1, 3, and 9 received petitions requesting EPA to use its residual designation authority to regulate stormwater discharges from commercial, industrial, and institutional sites that discharge certain pollutants to waters listed as impaired for those pollutants. The identified pollutants were lead, zinc, copper, phosphorus, nitrogen, sediment, biological oxygen demand, and chemical oxygen demand.

Each region conducted an analysis to consider:

  • The likelihood that the pollutants would be exposed to precipitation at sites in the source categories specified in the petition.
  • Whether sufficient data were available to evaluate the contribution of stormwater discharges to water quality impairment from the specified sources.
  • Whether the specified sources already were adequately addressed by other environmental programs.

Regions’ Responses

In March 2014, the three EPA regions responded to the petitioners.

Regions 3 and 9 declined to designate the stormwater discharges for permitting to designate these stormwater discharges for permitting because the regions did not have sufficient data available to link discharges from the sites to specific water quality impairments and there are existing programs underway to address these discharges. The regions plan to evaluate the progress of these programs and may decide at a later date if any designations are needed.

Region 1 is neither granting nor denying the petition, but will evaluate specific watersheds to determine whether site specific information will support such designations. Stormwater discharges pose a serious threat to the nation’s water bodies. EPA is committed to working with the states and its partners to ensure effective programs and activities are implemented to meet water quality objectives.

The regions’ responses and other information regarding these petitioners can be found at: