Wastewater Treatment Plant Improvements


Rehabilitate the Mystic Wastewater Treatment Plant to present day standards that include provisions for nitrogen removal while retaining treatment capacity that will accommodate projected sewage flows for more than 20 years into the future. Unique to this renovation is inclusion of a new process called BioMag™ that is capable of improving performance within the footprint of the existing structures. The project includes lesser enhancements at the Pawcatuck and Stonington Borough plants such as  replacing chlorination with UV for disinfection and improving nitrogen removal capability.


Stonington operates and is responsible for three separate sanitary sewer systems each with its own treatment plant. A draft “Wastewater Facilities Plan” for collection, treatment, and disposal for the next 20 years was completed in 2007 and filed with The Connecticut DEP (now DEEP). The DEP gave conceptual approval in January 2009.The Facilities Plan recommends upgrading and maintaining operation of all three treatment plants. Each is to be upgraded to achieve a high degree of nitrogen removal. The Mystic plant is the oldest and in the most immediate need of upgrading. It has been in service for more than 35 years and has not undergone a significant upgrade or renovation since its commissioning. Due to lower flows and loads at the Pawcatuck and Stonington Borough plants, the timing of these upgrades can be phased later to optimize funding opportunities and minimize cost impacts.

Project Budget:        $ 18,325,000

Funding Source:        

General Obligation Bonds issued by the Town

  • authorized by special referendum on November 16, 2010