Inflow and infiltration (I/I) happens when water from the environment enters the sewage system for treatment. Inflow is when there is a rapid flow of storm water in the sanitary sewer system. Infiltration is the gradual downward flow of water from the surface of the earth into the soil and into the wastewater collection system.
Inflow and Infiltration occurs through through
cracks or holes in the pipe network or through inappropriate connections
such as catch basins or roof downspouts. I/I increases the flow and volume in
the sanitary sewer and reduces the capacity of the pipe and the treatment plant.
The result is a higher risk of overloading the pipe network leading to potential
basement flooding, and increased flows and volumes that must be treated at the
The sanitary sewer system is an underground pipe network that collects
wastewater produced by houses, businesses, and institutions. The purpose of
the pipe network is to direct the wastewater to a treatment plant where the water
is treated before being discharged into Lake Ontario.
The storm sewer system is an underground pipe network that collects rainwater
runoff. During storm events, rainwater infiltrates into pervious areas, such as
grassed lawns and gardens. Any rainwater that does not infiltrate will turn into
runoff that will flow down impervious areas, such as roads and parking lots.
Catch basins and other inlets are designed to collect the rainwater runoff and
convey the water through a storm sewer system. Rainwater, unlike wastewater,
does not need to be treated by a plant and can be treated by on-site controls
such as a stormwater management pond or an oil and grit separator. Therefore
the purpose of having a storm and sanitary sewer system is to separate these
flows prior to treatment and discharge to the environment.
The Town of Newmarket is currently working with Civica Intrastructure on a Inflow and Infiltration reduction study.
Inflow and Infiltration (I/I) Reduction Study
The Town of Newmarket is working with Civica Infrastructure Inc. on an Inflow
and Infiltration (I/I) reduction study. The study’s objectives are to identify
sources of I/I entering the sanitary sewers and to develop a plan to reduce these
“extraneous” flows. A flow monitoring program with field testing is being
conducted to identify sources of I/I entering sanitary sewers. The flow
monitoring program will identify general areas within the Town of
Newmarket that have increased I/I. Additional field testing will then be
conducted in these areas to identify the specific sources of I/I.