Infiltration/Inflow Source Removal Program

  1. Project Overview
  2. Frequently Asked Questions
  3. Project Update

Project Overview

The Infiltration/Inflow/ (I/I) Source Removal Program is a multi-year/multi-phase project that will investigate sources of I/I throughout the City of Framingham.

The City is required by the Massachusetts Department of Environmental Protection (MassDEP) to identify and remove sources of rainwater runoff and groundwater that enter the sanitary sewer system. 

Inflow is rainwater or groundwater that enters the sewer system through a direct, piped connection or leaking manhole covers. It is clean water that does not need to be treated as wastewater.

Infiltration is groundwater that enters the sewer system through broken or leaking pipes or leaking sewer manholes. It is clean water that does not need to be treated as wastewater. 

The City’s Wastewater Master Plan identified areas where flow data suggests inflow issues (i.e., flow increases in response to a rainfall event). The 2019 Private Source Inflow Removal Concept Report conducted investigations in those areas and identified over 100 specific potential sources that are suspected of discharging clean water into the sewer system.

The City and hired consultants are working to systematically identify, prioritize and address potential I/I sources.

How does the City detect Inflow and Infiltration?


Detect Infiltration:

  • Closed Circuit Television Video (CCTV) - Placing a camera into sewer pipes and recording their condition. 
  • Sewer Manhole Inspections - Remove the cover of the manhole and inspect for visible cracks or leaks.
  • Flow Metering - Install a meter in the sewer pipe to measure the flow (sewerage and infiltration that travels through the pipe. 
  • Smoke Testing - Crews use specialized candles to create a non-toxic, non-staining smoke that is blown by a large fan into sewer manholes located on the road. By blowing the smoke into manholes, it enters the City’s sewer pipe system.  Crews will monitor where the smoke escapes and record their findings.

Detect Inflow:

  • Dye Testing - Pouring a non-staining dye into a suspected source (roof downspouts, sump pumps, and floor drains). A source is confirmed if the colored dye is observed in the sewer system. 
  • Building Inspections - City personnel will enter a building to verify if a sump pump is improperly connected to the sewer system. 
  • Smoke Testing - Crews use specialized candles to create a non-toxic, non-staining smoke that is blown by a large fan into sewer manholes located on the road. By blowing the smoke into manholes, it enters the City’s sewer pipe system.  Crews will monitor where the smoke escapes and record their findings.

Depending on where the confirmed source is detected from, appropriate action is taken to eliminate the source from discharging into the sewer system.

Smoke testing was conducted in September 2021 to investigate the sources of I/I. Testing occurred in western Framingham, bounded by Pleasant Street, the Massachusetts Turnpike (I-90), Route 9 (Worcester Road), Temple Street, and the Southborough town line.

Image of a residential home's roof stacks smoking

Dye shown in a sewer manhole

The City conducted Dye Testing in October 2019.  This type of testing involves pouring a non-staining dye into the suspected drain or downspout. A source is confirmed if the colored dye is observed in the sewer system (as pictured to the left).



Infiltration DETECTED via CCTV inspection

[Closed Circuit Television Video (CCTV) footage that depicts a cracked sewer lateral connection at the sewer main. This crack is allowing groundwater to infiltrate into the sewer system. This footage was recorded by the Framingham Wastewater Department. ]