Municipal Separate Storm Sewer System (MS4)


The U.S. Environmental Protection Agency (EPA), under the Clean Water Act, promulgated the National Pollutant Discharge Elimination System (NPDES) municipal separate storm sewer system (MS4) regulations in two phases beginning in 1990. The Phase I regulations established requirements for stormwater discharges for 11 categories of industrial activity and for MS4s serving populations of 100,000 or greater. In December 1999, the EPA promulgated the Phase II MS4 regulations to address pollution discharges from small MS4s in urbanized areas (UA). Maryland expanded its MS4 permit program by issuing two general permits, one for municipalities (2003) and one for state and federal agencies (2004) operating small MS4s. These permits were reissued in 2018. During the 2010 Census, certain areas of Queen Anne’s County were categorized as urban areas and QAC was subsequent issued an MS4 Phase II permit in 2018.  

urbanized area

Map of QAC designated Urban Area

Under its Phase II MS4 designation, Queen Anne’s County is responsible for the implementation of six (6) Minimum Control Measures (MCM’s) prescribed by the General Permit to prevent the conveyance of harmful pollutants to the Chesapeake Bay and its tributaries:

  1. Public Education and Outreach
  2. Public Involvement/Participation
  3. Illicit Discharge Detection and Elimination (IDDE)
  4. Construction Site Runoff Control 
  5. Post-Construction Runoff Control
  6. Pollution Prevention/Good Housekeeping

Unmanaged Impervious Area and Restoration 

Queen Anne’s County has always managed stormwater associated with development to the highest State standards. Part of the MS4 program involves categorizing stormwater Best Management Practices (BMPs) by era to determine what is considered treated impervious area under the MS4 permit. BMPs are also required to be inspected every three years to demonstrate they are maintained in order for the impervious area that drains to them to be considered treated. In 2020 the County began an effort to map impervious areas within the urban area of the County that are both considered treated and untreated. Untreated acreage needs to be mitigated at 20%. Per the Accounting Guidance associated with the permit, the County is able to meet this 20% acreage restoration requirement through on-going environmental projects to include septic upgrades and the Kent Island Sanitary Sewer Project. To see the map of the urban area and find out if you have BMPs located in your community click here.

Illicit Discharge Detection and Elimination 

MS4 owners and operators covered under the general permit must manage, implement, and enforce management programs for controlling all stormwater discharges in accordance with the CWA (Clean Water Act of 1972) and corresponding stormwater NPDES regulations, 40 CFR § 122, to effectively prohibit pollutants in stormwater discharges or other unauthorized discharges into the MS4 as necessary to comply with Maryland’s receiving water quality standards. Illicit discharges are further defined in the County’s IDDE Ordinance. The permit requires the County to screen 20% of it's outfalls or up to 100 outfalls per year for pollutants during dry weather conditions. In a rural flat county like QAC, this usually involves low areas of roadside ditches that ultimately discharge into a water of the State but also includes some closed storm systems. 

Outreach and Education Partnerships 

CB Trust:  Queen Anne’s County and the Chesapeake Bay Trust partner in the Outreach and Restoration Grant Program (ORGP). This grant program encourages outreach, community engagement activities, and on-the-ground restoration projects that increase knowledge, change behavior, and accelerate stewardship of natural resources that involve residents in restoring local green spaces, waterways, and natural resources

Envision Choptank: Envision the Choptank is a collaborative effort, operating since 2015, that brings together nonprofits, government agencies, scientists, and community groups to identify solutions that will restore swimmable, fishable waters to the Choptank River. 

Corsica River Day: Every year QAC partners with the Corsica River Conservancy for a day of environmental education and celebration of the Corsica River. This free annual community festival brings together family fun, food vendors, live music, and environmental education on the riverfront of the Corsica River.

Shore Rivers: If you have an idea for an outreach and education or environmental steward project in your community feel free to reach out to County staff or your local riverkeeper. The County regularly takes advantage of riverkeepers’ efforts to conduct education, restoration, tree plantings, river grass plantings and more. Find out who your local riverkeeper is here:

MS4 Yearly Progress Reports

Water Quality Complaints 

The Department is working on a system to collect drainage and water quality complaints. For now please call our office ro report water quality complaints: 410-758-0925