Skip to Page Content Governor | General Assembly | Courts | Elected Officials | State Agencies
  Photo: Featured Delaware Photo
  Phone Numbers   Mobile   Help   Size   Print   Email

Skip Navigation LinksDNREC : Division of Water : Information : Surface Water Discharges Information : MS4


DNREC Web Reboot Project Logo

This page has been updated and replaced as part of the DNREC Web Reboot Project.

The new location for this page is

Please update your links and bookmarks.

Learn more.

Individual NPDES Permit for Municipal Separate Storm Sewer Systems (MS4s)

SamplingUrban stormwater runoff is commonly transported through Municipal Separate Storm Sewer Systems (MS4s), and is often discharged, untreated, into local waterbodies. To prevent harmful pollutants from being washed or dumped into an MS4, operators must obtain a NPDES permit (Phase I or Phase II) and develop a stormwater management program. This permit type is based on population. For additional information, please refer to the EPA’s MS4 Website

  • Phase I, issued in 1990, requires medium and large cities or certain counties with populations of 100,000 or more to obtain NPDES permit coverage for their stormwater discharges.
  • Phase II, issued in 1999, requires regulated small MS4s in urbanized areas, as well as small MS4s outside the Urbanized Areas (UA) that are designated by the permitting authority, to obtain NPDES permit coverage for their stormwater discharges.

Phase I MS4 Permits

Phase II MS4 Permits

General NPDES Permit for Small Phase II Municipal Separate Storm Sewer Systems (MS4s)

The Phase II Final Rule established under the Federal Clean Water Act requires nationwide coverage of all small MS4s that are located within the boundaries of a Bureau of the Census-defined “urbanized area” (UA) based on the latest decennial Census.  The 2010 Census results expanded the UA area within Delaware which in turn requires DNREC to expand the universe of municipalities requiring NPDES Phase II MS4 permit coverage.  Currently the four Phase II MS4 permits in Delaware are individual permits; however, as our permitted universe continues to expand DNREC has decided to move Phase II MS4 coverage to a General Permit Program. 

Below please find links to Draft Phase II MS4 General Permit and Draft Phase II MS4 General Permit Fact Sheet. DNREC-SWDS is soliciting comments/feedback on the below drafts from current MS4 permittees, newly identified permittees, the general public and any other interested parties from now through January 31, 2016.  This is not an official public notice draft, but rather an informal solicitation for comments and feedback. The DNREC-SWDS will assess all comments received and make any necessary changes to the draft general permit prior to proceeding to official public notice during Spring of 2016.  Also below you will find a Map and Table detailing all 2010 Census defined “urbanized areas” in Delaware and the associated jurisdictions identified as needing NPDES MS4 permit coverage.  We have also included a couple of useful links to EPAs website for additional information on NPDES MS4 Programs.  

The Department is in the process of reviewing comments for the Phase II General Permit.  A response to the comments and any changes to the MS4 Phase II General Permit will be provided online.


The Delaware Department of Natural Resources (DNREC) Surface Water Section would like to invite you to an informational MS4 workshop.

 The workshop will focus on the following topics.

1)     Revisions made to the Department’s Draft NPDES Phase II MS4 General Permit.

2)     The Department’s Draft Waiver Policy for the Draft General Permit, under 40 CFR Section 122.32.

3)     Information on how to develop a realistic and budget friendly MS4 program in your community presented by the Center for Watershed Protection.

This event is open to the public and will include communities identified as requiring permit coverage under the 2010 Census, communities with an existing MS4 permit, and non-permitted communities.

The MS4 Workshop will be held at the Cheer Center, 20520 Sand Hill Road, Georgetown, DE 19947 on Thursday, June 15, 8:30 to 1:00.  A light breakfast and lunch will be served.

MS4 Workshop Flyer

Department Presentation


Revised Pre-Notice Draft Phase II MS4 General Permit (now two distinct permits):

Please note that the Department reserves the right to revise the pre-notice draft permits and fact sheets prior to the start of the formal public notice period based on additional comments received from stake holders.

If you have any additional questions please contact the Department by email (  or by phone at 302-739-9946. Preliminary Draft Phase II MS4 General Permit from November 2015

If you wish to provide comments on the Draft Phase II MS4 General Permit, please direct comments to Beau Croll via email at or via U.S. Postal Mail to:

DNREC - Surface Water Discharges Section
Attn: MS4 Program
89 Kings Highway
Dover, DE 19901

DE MS4 Permitted Universe

MS4 Useful Links

MS4 Training Opportunity

MS4 Training

  • January 28, 2016 League of Local Governments Presentation


Contact Us

For more information please email Jennifer Roushey.

site map   |   about this site   |    contact us   |    translate   |