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Infiltration/Inflow and Biological Nutrient Removal Plan of Study

Salisbury, Connecticut

Services: Water & Wastewater
Clients Served: Government

Loureiro was retained by the Town of Salisbury, Connecticut to assist in the assessment of the town’s infiltration and inflow generated throughout the collection system and to evaluate the options for reduction of nutrients, specifically nitrogen and phosphorous at the water pollution control facility (WPCF). The project will be funded as a planning study by the Connecticut Department of Energy & Environmental Protection (DEEP) through the Clean Water Fund.

The town currently has approximately about 11 miles of gravity sanitary sewer located throughout the town with four sewage pump stations. Recent WPCF data indicates significant infiltration and inflow is generated even during moderate rainfall events with average daily flows elevating by over 300% during moderate events. The town’s population growth has been limited since the 1960s and as such, the existing treatment facility is adequate for the current hydraulic loads provided the excessive infiltration and inflow is addressed.

Consistent with all publicly owned treatment works in Connecticut, the Salisbury WPCF has realized receding limits for nitrogen and forthcoming phosphorus written into their National Pollutant Discharge Elimination System permit. The study assesses the compliance alternatives and includes a cost-benefit analysis to assess the validity of implementing costly WPCF improvements.


  • Plan of Study meets the Connecticut DEEP requirements for Clean Water Funding
  • The town has older vitrified clay tile sewers within the Lakeville section
  • One particular user in town comprises approximately 30% of the sewage flow during the school year.
  • The existing WPCF has sand filter beds for polish prior to discharge into the receiving watercourse