MS4. Unless you are a civil engineer or a municipal public works director charged with dealing with discharge permits, you may not know that “MS4” stands for municipal separate storm sewer systems (called MS4 because “s” is repeated four times). An MS4 is a system of storm drains, pipes, or ditches that collect and carry stormwater, untreated, into our waterways (not to a sewage treatment facility).
To reduce stormwater pollution, the Clean Water Act requires larger cities and towns to develop an MS4 plan that includes six Minimum Control Measures: public education, public involvement and participation, illicit discharge
detection and elimination (finding and eliminating sources of contamination that improperly enter the pipes), construction measures designed to reduce stormwater pollution, post construction inspections to ensure compliance, and municipal pollution prevention practices.
MS4 permits for these plans must be renewed every five years. Casco Baykeeper Ivy Frignoca is participating in the stakeholder process initiated by Maine’s Department of Environmental Protection, as it drafts the next MS4 permit.
You may have noticed that storms are more intesne, and the pollutants that rainstorms are flushing into the Bay are increasing dramatically. After one heavy rainstorm, we found a wedge of polluted stormwater 18 feet deep floating on top of seawater in Portland Harbor. Ivy worries,“Imagine what it would be like for a fish trying to navigate through that toxic mix of oil and gas from city streets, pesticides, bacteria, and nitrogen pollution from sewage and fertilizers!”
Ivy says, “The goal is to improve water quality and reduce nitrogen inputs and other pollutants. Reviewing and commenting on drafts of the next MS4 permit gives us an opportunity to help reduce the impacts of the largest source of pollution into Casco Bay.”