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Sanitary Sewer Inflow & Infiltration
The Batavia Sewer Division is committed to ongoing sewer collection system maintenance activities. A primary goal of the sewer division is to eliminate sources of water inflow and infiltration that enters the sanitary sewers. The sanitary sewer lines are designed for sanitary sewage only in most Batavia neighborhoods. In older parts of the west side of Batavia there are still some combination sewers in service. The combination sewers are designed to handle both sanitary sewage and storm water. At some point, the city may be required to separate all of the combination sewers and install new storm sewers to handle the rainwater flows.
Definition of Inflow & Infiltration
Inflow and infiltration, is clean storm and/or groundwater that enters the sewer system through cracked pipes, leaky manholes, or improperly connected storm drains, down spouts and sump pumps. Most inflow comes from storm water and most infiltration comes from groundwater.
Inflow occurs when rainwater is misdirected into the sanitary sewer system instead of storm sewers. Examples are roof downspouts, yard and area drains, manhole covers, and cross connections from storm drains. The remedy for inflow is to remove improper connections to the sanitary sewer system.
Infiltration occurs when ground water seeps into the sanitary sewer system through cracks or leaks in sewer pipes. The cracks or leaks may be caused by age related deterioration, loose joints, damage or root infiltration. The remedy for infiltration is repairing or replacing the leaking infrastructure.
Maintenance techniques used by the Batavia Sewer Division to identify inflow and infiltration entering the sanitary sewers include the following.
Sump Pump Inspections
The city is actively pursuing sump pump inspections to identify homes that may be illegally connected to the sanitary sewers. All sump pump water is ground water and must be pumped to the yard, or to a storm sewer. Over the past several years the city has performed more than 500 inspections and identified more than 50 illegal sump pumps tied into the sanitary sewer system. The city inspects homes by neighborhoods. Homeowners are advised that letters are mailed and appointments are made for the inspection of the sump pump lines.
As illegally connected sump pump lines are identified, homeowners are provided with 30 day notices for removal and redirection of the pump discharge lines.
The city is instigating a smoke testing program to help identify inflow and infiltration into the sanitary sewers. Smoke testing is a relatively simple process that consists of blowing smoke mixed with large volumes of air into the sanitary sewer line, usually induced through the manhole. The smoke travels the path of least resistance and quickly shows up at sites that allow surface water inflow. Smoke will identify broken manholes, illegal connections including roof drains, yard drains, uncapped lines and cracked mains and laterals, providing there is a passageway for the smoke to travel to the surface.
Although video inspection and other techniques certainly are important components of an inflow and infiltration survey, research has shown that approximately 65% of all extraneous storm-water inflow enters the system from somewhere other than the main line (private sector lateral service lines). Smoke testing is a method of inspecting both the main lines and laterals. Smoke travels throughout the system, identifying problems in all connected lines, even sections of line that were not known to exist or thought to be independent or unconnected. Best results are obtained during dry weather, which allows smoke a better opportunity to travel to the surface.
The city periodically inspects all of the sanitary sewer manholes for leaking joints and deteriorating conditions. As the leaks in manholes are identified, the city schedules grouting, or sealing of the leaking joints. This task is similar to basement walls that have cracks and must be grouted to eliminate seepage. The city owns and operates equipment for grouting the cracks and also hires contractors to perform this duty.
Cleaning & Televising
The city cleans and televises sanitary sewer lines on a regular basis. The cleaning and televising program identifies breaks, cracks, root intrusion, etc. in the sanitary sewer lines. Although somewhat labor intensive, cleaning and televising is a common maintenance technique. The city owns and operates special trucks and sewer televising equipment for this purpose.
Questions or comments concerning the City of Batavia's Infiltration and Inflow Maintenance Program can be directed to the city's Water and Sewer Division at 630-454-2450.