Municipal Separate Storm Sewer System (MS4)

I am part of the Stormwater team at ALLARM. One of my tasks is to educate the public about what Municipal Separate Storm Sewer Systems (MS4) are and how to manage stormwater through different plans (Stormwater Management Plans). Every plan focuses on six Minimum Control Measures (MCM). ALLARM helps the Borough of Carlisle meet two of the minimum control measures:

MCM #1: Public Education and Outreach on Stormwater Impacts.

ALLARM helps the Borough achieve this MCM by reaching out to the public to inform them about the impacts of stormwater runoff on the water quality of the LeTort Spring Run, which flows into the Conodoguinet Creek, then the Susquehanna River, then the Chesapeake Bay, and finally the Atlantic Ocean.

MCM #2: Public Involvement/Participation

ALLARM provides an interactive opportunity for the public to participate in development and implementation of the program.

Through PennState Extension’s website, I learned more information about Municipal Separate Storm Sewer Systems. The term “municipal” in the context refers to a unit of local government like the Borough of Carlisle. The 4 Ss are a collection of structures such as storm drains and ditches that gather stormwater and discharge it without treatment into the local streams and rivers. For instance, the stormwater from a storm drain at Dickinson College will go to LeTort Spring Run, the Conodoguinet Creek, Susquehanna River, Chesapeake Bay, and finally the Atlantic Ocean.

One of our Stormwater Steering Committee meetings happened recently, which was led by one of my fellow Watershed Coordinators. We discussed how we are trying to fulfill the two MCMs. There a variety of ways to fulfill the two MCMs, but we narrowed in on these strategies:


For more information regarding MS4, visit Information on this website is provided by Andy Yencha, Penn State Extension Educator, Renewable Natural Resources.

Storm drain markers that ALLARM installed on Carlisle storm drains that say “Don’t Dump: Drains to LeTort.”