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Infiltration/Inflow Source Removal Program
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. | |
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. ]
FREQUENTLY ASKED QUESTIons
WHAT IS INFLOW?
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.
What is Infiltration?
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.
What are the typical sources of inflow?
Typical inflow sources include roof downspouts, sump pumps, and driveway drains that are connected to the sewer system. Leaking sewer manhole structures or covers located in low or wet areas are also sources of inflow.
Why is it important to remove infiltration & inflow (I/I) sources?
The City is required by the Massachusetts Department of Environmental Protection (MassDEP) to identify sources of rainwater runoff and groundwater that enter the sewer system. The City pays the Massachusetts Water Resource Authority (MWRA) for every gallon of water that enters the sewer system regardless of its source. Removal of inflow to the sewer system will reduce sewer capacity and overflow issues, protect surface water quality, and decrease the City’s sewer costs.
What work was previously done to identify I/I and why?
The City’s Wastewater Master Plan identified areas where flow metering data suggests inflow issues (i.e., flow increases in response to a rainfall event). The City is currently in a multi-phase, long-term plan to identify and remove sources of I/I in the sewer system. Previous efforts have included identification of potential inflow sources, dye testing, smoke testing, and closed-circuit television (CCTV) of sewer pipes.
How is I/I identified?
Both infiltration and inflow can be estimated by installing flow meters in sewer manholes. Flow meter data is correlated to rainfall and groundwater levels.
Infiltration is identified through the inspection of sewer manholes and CCTV of sewer pipes. CCTV involves placing a TV camera into the pipe and recording the condition of the pipe. Flow isolation is also used to identify infiltration by measuring the flow during off-peak hours.
Inflow is typically identified by conducting smoke testing, dye testing, or building inspections. Smoke testing involves introducing non-toxic smoke into the sewer pipe and noting if smoke protrudes comes out at roof leaders, catch basins, yard drains, or other potential inflow sources. Dye testing involves pouring a non-toxic, non-staining dye into the potential source and seeing if it appears in the downstream sewer manhole. Building inspections are when City personnel enters a building to verify whether a sump pump is improperly connected to the sewer system.
How is I/I removed?
Infiltration caused by broken or cracked pipes or manholes can be removed by either replacing or rehabilitating the infrastructure. Inflow caused by leaking manhole covers can be removed by replacing the cover, or installing waterproof covers in low, wet areas. Inflow caused by improper drain or sump pump connections can be removed by re-piping the discharge of the source.
Spring 2022
Smoke testing was conducted in September 2021.
Design work continues to remove sump pump discharge inflow sources from the sanitary sewer system.