Stormwater Permits

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What is an MS4?

A municipal separate storm sewer system.

A conveyance or system of conveyances (including roads with drainage systems, municipal streets, catch basins, curbs, gutters, ditches, man-made channels, or storm drains):

Owned or operated by a State, city, town, borough, county, parish, district, association, or other public body;
Designed or used for collecting or conveying stormwater;
Which is not a combined sewer; and
Which is not part of a Publicly Owned Treatment Works.

District of Columbia MS4 Green Infrastructure Enhancement

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Which Discharges Need Permits?
Municipalities with MS4 Permits

Which discharges need permits? The NPDES stormwater permit regulations, put into law by the EPA, cover 3 classes of stormwater discharges on a nationwide basis:

Municipal Separate Storm Sewer Systems (MS4s)

Operators of MS4s located in “urbanized areas.” This means cities and towns like Philadelphia and Baltimore that own or operate municipal conveyance systems (includes roads, drainage systems, municipal streets, curbs and gutter, and storm drains).

Industrial

Industrial facilities in any of the 11 categories that discharge to an MS4 or to rivers and streams.

Categories include: hazardous waster treatment, storage, or disposal facilities, steam electric power generating facilities, sewage treatment works, and landfills.
If an industry’s materials and operations are not exposed to stormwater, stormwater permit coverage may not be necessary (must apply for a “no exposure” certification).

Construction

Disturb 1 or more acres of land.
Less than 1 acre if part of a larger development.

**Mid-Atlantic Municipalities With Separate Storm Sewer (MS4) Permits**
State	Permitting Authority	Permit Name	Phase*
Delaware	DE DNREC	New Castle County	I
	DE DNREC	Del DOT	II
	DE DNREC	City of Newark	II
	DE DNREC	City of Dover	II
	EPA Region 3	Dover Air Force Base	II
District of Columbia	EPA Region 3	District of Columbia	I
Maryland	MD DOE	Anne Arundel County	I
	MD DOE	Baltimore City	I
	MD DOE	Harford County	I
	MD DOE	Prince George's County	I
	MD DOE	Baltimore County	I
	MD DOE	Carroll County	I
	MD DOE	Charles County	I
	MD DOE	Frederick County	I
	MD DOE	Howard County	I
	MD DOE	Montgomery County	I
	MD DOE	MD State Highway Administration	II
	MD DOE	Statewide Small MS4	II
	MD DOE	Statewide Small MS4 (State & Federal Facilities)	II
Pennsylvania	PA DEP	Philadelphia	I
	PA DEP	Allentown	I
	PA DEP	PA DOT	II
	PA DEP	PA Turnpike Commission	II
	PA DEP	Statewide Small MS4	II
Virginia	VA DEQ	Arlington County	I
	VA DEQ	Fairfax County	I
	VA DEQ	Prince William County	I
	VA DEQ	Chesterfield County	I
	VA DEQ	Henrico County	I
	VA DEQ	Chesapeake City	I
	VA DEQ	Hampton City	I
	VA DEQ	Newport News	I
	VA DEQ	Norfolk City	I
	VA DEQ	Portsmouth City	I
	VA DEQ	Virginia Beach City	I
	VA DEQ	Statewide Small MS4	II
West Virginia	WV DEP	Statewide Small MS4	II
* Phase I - sources of stormwater runoff that have the greatest potential to negatively impact water quality Phase II - stormwater discharges from: certain regulated small municipal separate storm sewer systems (MS4s) and construction activity disturbing between 1 and 5 acres of land

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