SSES - Sewer System Evaluation Survey
The sanitary mains and the treatment plant weren't constructed to handle the vast amounts of water carried by the City of DeKalb storm sewer system when it rains. During any normal day, the District sewer water usage is under 7 million gallons. During one 2.25-inch rainfall, plant flow reached 40 million gallons as the rain water leaking into the system from the storm sewers and improperly connected house laterals reached the plant.
Where Does 40 Million Gallons of Rain Water Go?
Ground water leaking from the storm sewers into the sanitary mains creates an even worse problem when rainfall amounts are greater or when the ground is already saturated. The sewage treatment plant process takes time and the capacity is limited. When the plant fills up and can hold no more water, the collection system itself becomes a holding tank for the excess rain water and sewer backups occur.
Doing Sewer System Evaluation Survey testing helps the City of DeKalb and the DeKalb Sanitary District find the leaks and fix them to keep storm water where it belongs when it rains.
Cross-Flooding
Cross-flooding is done by introducing dye into the storm sewers. Then closed-circuit television is used to observe any impact on adjacent sanitary sewers. This simulates what happens during rain events.
Is That Antifreeze?
When the storm water is released, the dyed water can be visible in the Kishwaukee. The dye utilized is not harmful to aquatic life, but has turned the river green during past tests.
Some Traffic Disruption During Testing
The District adheres to City of DeKalb requirements for signage and blockades at cross-flooding sites. District personnel do block off areas of the streets for short periods of time while actively testing. Crews do not need access to homes, and no change in water usage patterns is required.
Manhole Inspections
There are over 3400 manholes in the DeKalb Sanitary District collection system. Manholes can collapse due to age, geological processes, or traffic. Manholes are inspected to identify those in need of repair and to assure that they are not blocked by debris of any kind.
Little Impact on Residents
- Areas around manhole covers will be barricaded.
- There may be temporary traffic diversions.
- Some digging may be done to access manhole covers.
- Plantings over sewer easements may be disturbed.
- Crews do not need access to homes.
- No change in water usage patterns is required.
Smoke Testing
Smoke Testing is a process in which non-toxic "smoke" is blown into the sanitary sewer mains and used as a visual tracer to help determine the condition of the sewer pipes. If, for example, smoke came out of a storm sewer catch basin, it would indicate a connection to the sanitary sewer, which is something we would want to correct.
No Smoke Enters Properly Connected Buildings
If home plumbing connections are in good condition, no smoke should enter any building. Smoke testing crews do not need access to homes, and no change in water usage patterns is required.
Act to Prevent Problems
If any fixtures or drains have not been used in a while, the water in the water seal traps may have evaporated. This condition would allow smoke to enter the home or business. To avoid annoyance and irritation, it is recommended that water be added to any such drains to avoid the possibility of trap malfunction.