Sewer System

The Sanitary Sewer Collection System

Each day, an average of 7 million gallons of wastewater flows through the sanitary sewers under DeKalb. During heavy rainfall, the volume can be as much as 10 times that.

Most of the public sewer mains are 8 inches in diameter. They feed into larger sewer mains that can be up to 18 inches. These drain into large interceptor sewers that can be up to 36 inches in diameter. The interceptors carry the sewage to the headworks of the treatment plant. 

Sewer Tests

KWRD routinely monitors and evaluates the condition of our more than 150 miles of sanitary sewer mains. The average DeKalb sewer main is 50 years old, and while some of it is in excellent condition, much of it is not.

To identify places where mains need repairs, the District uses a combination of monitoring and evaluation tools. We use flow monitors to record how much water is flowing through a particular main. If the volume or speed dramatically increases after a rainfall, we know surface water is somehow leaking into the sanitary sewer.

Other ways we evaluate sewer conditions include inserting cameras into sewer lines to inspect them, introducing dye into adjacent storm sewers to look for cross-flooding, blowing nontoxic smoke into the main as a visual tracer, and manually inspecting manholes for signs they need repair.

Why We Test

The sanitary sewer was not designed to handle the volume of water that comes with rainfall. When surface water or groundwater leaks into the sanitary sewer, the main can quickly fill. Waste flowing into the main from private service laterals has no place to go, and a mixture of rainwater and sewage begins backing up through the drains of the lowest house in the neighborhood.

How It Impacts You

Residents should see little to no impact from KWRD testing. We do not need to access your home, and you can flush toilets and use water normally. When we are making repairs, you may notice barricades and digging around manhole covers or temporary traffic detours. Plantings over sewer easements may be disturbed.

Occasionally, the nontoxic dye we use to check for flooding from storm sewers can be visible in the Kishwaukee River when the stormwater is released. This dye is harmless to aquatic life, but it has been known to turn the river green.

Lift Stations - When Gravity Is Not An Option

Sometimes, the position of buildings relative to the nearest sewer main means the pipes can’t be slanted to the correct angle. That’s where the KWRD’s seven lift stations come into play.

Sewers drain wastewater into wells at the lift stations, just like they do at the headworks. The lift station wells are just much smaller. Pumps then lift the wastewater high enough for it to drain into the next level of sewer pipes, and gravity again takes over.

Lift stations require constant supervision to keep them operating and prevent overflow. Each station has a backup generator. The stations continuously send data about their operating status to the main plant through a computer system, so plant operators can respond quickly if something goes wrong.