Overview

Combined sewer systems are sewers that are designed to collect rainwater runoff, household sewage, and industrial wastewater in the same pipe. During periods of heavy rainfall, the amount of wastewater in a combined sewer system can go beyond the amount the system can take, causing overflows of dirty, untreated wastewater into nearby water bodies.

MM CSO Gallons

Million (MM) Gallons of CSO Discharge

Million gallons of discharge from combined sewer system overflows (CSO) entering water bodies.

Our Data
  • 41.568 MM Gallons

     

    2013

  • 50.834 MM Gallons

     

    2014

  • 5.518 MM Gallons

     

    2015

  • 9.786 MM Gallons

     

    2016

  • 9.614 MM Gallons

     

    2017

Our Data
2013

41.568MM Gallons

 
2014

50.834MM Gallons

 
2015

5.518MM Gallons

 
2016

9.786MM Gallons

 
2017

9.614MM Gallons

 
Charts & Graphs

What Does This Chart Show Us?

More intense rainfall events are one of the reasons the 2018 discharge amounts are so high. The September 18, 2018 rain event provided 4 inches of rain overall, at times rain falling at 1 inch per hour; more than the pipes can handle. That’s when CSOs happen. Because of the new screening and disinfection facility, nearly half of the City’s CSO output was screened to remove trash and treated in a disinfection process to remove bacterial pollutants before being discharged to the Merrimack River.

View Our Sources Here

  • From 2014 to 2015 the City of Nashua reduced sewer discharge into the Nashua and Merrimack Rivers by more than 89% or the gallon equivalent of 68.6 olympic size swimming pools

  • Did you know that the City of Nashua has more than 100 miles of combined sewers and has 8 drains that flow directly into the Nashua or Merrimack Rivers?

  • The City of Nashua has implemented three specific projects to address the sewage discharge issue, reducing the total gallons released by more than 45 million.

How You Can Help

  • Reduce the Amount of Water that Runs off your Property

    During a heavy rain event the more green space on your property, the less water that will runoff into the street and overload the drain pipes. You can keep water on your property by replacing asphalt driveways and walkways with gravel, grass, or permeable pavers, which allow water to flow through them into the ground rather than running off the driveway.

    More Information
Recent Updates for Nashua
Be a Part of Our Resilient Nashua Initiative!

Nashua will be working with community stakeholders throughout 2018 to develop a comprehensive resilience initiative with the main purpose being to identify acute shocks and chronic stressors impacting our City, now and in the future. We encourage everyone in our community to take part.

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Improved Water Quality in Lyle Reed Brook

For over a decade, Lyle Reed Brook, a tributary to the Nashua River had been listed as a water body with impaired water quality by the State of New Hampshire.  After being tested again in 2016, Lyle Reed Brook is now delisted and found to be fully supporting of aquatic life for both dissolved oxygen and pH.

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