MS4 Training & Consulting Solutions

Municipal Separate Storm Sewer Systems (MS4s)




The MS4 NPDES permitting program and other water-quality related programs look at reducing pollutants in stormwater discharges from municipalities. Stormwater quality is an economic hardship and is no longer considered just an environmental or ecological concern.  Among other issues, sediment in stormwater reduces the ability of a stream to convey stormwater, increasing flooding.  Other pollutants in streams that supply drinking water to communities increase the cost of treatment, and the higher cost is passed along to residents and businesses. As the United States grows in population, most of the growth is occurring in urbanized areas. You may wonder what is a Municipal Separate Storm Sewer System (MS4)? A MS4 is a conveyance or a system of conveyances that is owned by a state, city, town, village, military base, or other public entity that discharges stormwater to waters of the United States.  A MS4 collects or conveys stormwater (including storm drains, pipes, ditches, etc.).   It’s not a combined sewer system and is not part of a publically owned treatment works (POTW).


The challenge with urbanized areas is the resultant water pollution that occurs when rain water hits the ground and picks up pollutants that enter our waterways. Polluted stormwater runoff is commonly transported through Municipal Separate Storm Sewer Systems (MS4s), from which it is often discharged untreated into local waterbodies. To prevent harmful pollutants from being washed or dumped into a MS4, operators must obtain a NPDES permit, develop a stormwater management program and provide an annual report as to the condition of their MS4 system.  MS4 Permit Manager Software  provides small and large MS4 municipalities a financially feasible and easy to use solution for US EPAs requirement for NPDES MS4 General Permit compliance.  CLICK HERE to watch a brief online video demonstration.

There are presently 2 different types of MS4s. They are:

1. 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.

2. Phase II, issued in 1999, requires regulated small MS4s in urbanized areas, as well as small MS4s outside the urbanized areas that are designated by the permitting authority, to obtain NPDES permit coverage for their stormwater discharges.

Most of the time, Phase I MS4s are covered by individual permits and Phase II MS4s are covered by a general permit. Each regulated MS4 is required to develop and implement a stormwater management program (SWMP) to reduce the contamination of stormwater runoff and prohibit illicit discharges. That’s where the NPDES Training Institute comes in.  We offer MS4 Compliance & Enforcement Inspection Training and MS4 Permit compliance services and MS4 Software solutions to Phase I and Phase II municipalities throughout Alabama, Georgia, Louisiana, and Mississippi.

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