Infiltration and Inflow is often referred to as I/I and is the occurrence of storm water or ground water entering into municipal wastewater systems.
This extraneous water enters the sanitary sewer system through cracked pipes, leaking manholes as well as downspouts and sump pumps from homes that are connected directly to the sanitary sewer system.
Once this storm water enters the sanitary sewer it adds to the daily volume of wastewater that must be collected, pumped and treated by municipal wastewater facilities. |
|
|
| Why is Infiltration and Inflow a Problem? |
Once it enters the sanitary sewer system, infiltration and inflow must be moved and treated in the same manner as sewage.
When too much excess water enters our sewers as Infiltration or Inflow the following problems may occur:
- Sewage may backup into residents homes creating a health hazard and an expensive cleanup of their property;
- Sewage may overflow from manholes or bypass treatment facilities contaminating properties as well as rivers, lakes and our harbour;
- Sewer systems will require upgrades sooner than designed resulting in increased utility bills to residents;
- Infiltration and inflow will use up existing hydraulic capacity in our sewers which will restrict the opportunity for growth;
- Excessive water in our sewers will decrease the efficiency of wastewater treatment plants and will result in higher operating costs of these plants as well as increased utility bills to residents.
During a rainstorm, the average home in our area may produce as much as 1600 gallons of water exiting from rooftops, driveways or groundwater from around your home. If your downspout is connected to the sanitary sewer or if your sump pump is connected to the sanitary sewer then this water may enter the sewer system and be the cause of these problems.
|
| What can Property Owners Do to Help? |
|
Disconnect downspouts:
Downspouts that are connected to the sewer system should, when possible be disconnected and the rainwater water allowed to discharge onto lawns or gardens. This should only be done when care and consideration is given to understanding where the water will go. Downspouts should be extended away from your foundation wall to insure no basement moisture problems occur.
Sump pump disconnect:
Many homes that have sump pumps connected to the sanitary sewer could easily disconnect them and discharge this clean water onto lawns and gardens. Again consideration should be given to insure there is adequate surface area on the lawn to permit this discharge without creating drainage related problems for your property or your neighbours’ property.
Uncapped cleanouts:
All cleanout pipes that are uncapped, have a loose cover or are below the ground surface can allow a large amount of storm water to enter the sewer system. A sealed cover is easy to install by the homeowner and will make a positive difference.
Redirecting storm water away from the sewer system and onto your lawn and other pervious areas is good for your lawn and gardens as well as providing for groundwater recharge and assists in maintaining surface water levels in our rivers and lakes.
|
| What is Halifax Regional Municipality Doing to Control I/I? |
HRM currently maintains over 11,000 sanitary manholes, over 990km of sanitary sewer lines, 690km of storm sewers, 300km of combined sewers and 174 pumping stations. Based on the age, historical construction practices, number of connections as well as other factors there is significant opportunity for I/I to enter the municipal sanitary sewer system.
Problem areas are identified through preliminary field investigations by staff of Public Works Operations (PWO) and information from wastewater treatment plant operations. Priorities are established based on the findings of these investigations. Studies and remedial works are carried out through HRM’s normal tendering process.
Infiltration and Inflow studies have been completed for a number of sewersheds and facilities within the areas that are serviced by municipal sewers and wastewater treatment plants.
Remedial measures that have been implemented to date based on recommendations in these studies focus on reducing I/I conditions at the source. Some of the measures that we have undertaken to includes the grouting and injection of cracks and holes in manholes, sanitary sewer line replacements, inflow bins, plugs in manhole covers, placement of sealed manhole covers in low lying areas and on private property, the disconnection of downspouts and foundation drains.
|
| Other I/I Program Components |
|
In addition to the above, staff have prepared sewershed mapping for sewersheds within the serviced areas of HRM for use in management and tracking of the I/I Reduction Program as well as to support the Regional Planning Process. This mapping will continue to be improved as new information becomes available.
Another component of the I/I program is collection of survey data, where necessary, for input into HRM’s corporate Stormwater and Wastewater Infrastructure Data. Accurately surveyed location and elevation information is collected for both storm and sanitary system components within the various sewersheds concurrently with observations on inflow and infiltration. The collection of survey information during an I/I study avoids future duplication of effort in traffic control and removal of manhole covers. |
|
