Combined Sewer Overflows

Sewers have existed in Columbus since the latter part of the 19th Century. When they were first constructed they had a simple task, to transport water from inhabited areas to the river where it would go away. No classifications were placed on these waters as to whether they were polluted or not since the science of the time made no distinction on how these waters were handled.

By the 1940's it became clear to most that the rivers and streams in Indiana had to be protected from pollution by community sewage. Columbus joined most Indiana communities and constructed a wastewater treatment plant to improve polluted waters and prevent harm to the waterways. From that point on, sanitary flows have been handled separately from rainwater flows.

However it was considered cost prohibitive and unnecessary then to reconstruct the old 'single pipe' sewers and overflow weirs were built to direct the heavy flows that occur during rains and that the treatment plant couldn't handle to the rivers. This is the system that has served the community until recently.

In order to comply with Federal and State regulations and to be good stewards of the environment, Columbus has constructed a system of large diameter sewers, screens, pumps and holding basins to control these storm related flows and prevent untreated wastes from entering our nearby rivers. For more information regarding these efforts "click here".

In order to provide background information, following are answers to some frequently asked questions regarding combined sewer system overflows and the associated programs.

What is a combined sewer system?

When households dispose of wastewater from toilets, sinks, clothes washers, or dishwashers, it travels through underground pipes to a Wastewater Treatment Plant (WWTP). The WWTP treats the wastewater to State standards before discharging it to a local stream or river. In some cities, however, older sewer systems were designed to also accept stormwater run-off from the city during rain events. A Combined Sewer System (CSS) is then a system of pipes that carry both wastewater as well as stormwater during rain events.

What is a (CSO)?

During dry weather, combined sewers carry wastewater to the WWTP. However, during a heavy rain event, a combined sewer pipe can get too full. These combined pipes were designed with “safety valves” that allow the combined wastewater and stormwater to overflow into a stream or river during rain events. If combined pipes did not have overflows, untreated wastewater could back-up into homes and businesses, and cause flooding in the streets. When the untreated wastewater and stormwater do overflow into a stream, this is called a Combined Sewer Overflow or CSO. The point where the overflow enters a stream is a CSO outfall.

Why are combined sewer overflows a problem?

The combined sewage that overflows into a stream contains various water pollutants. This combination of raw sewage and stormwater can carry a variety of human disease-causing bacteria and viruses, oils, chemicals, or other wastes and debris. There are also pollutants that can take oxygen from the river, making it difficult for fish and other organisms to survive. Overall, an overflow event poses a threat to water quality, aquatic life, human health, and aesthetic property values. How long should I avoid contact with the stream or river after a CSO event?

There are several factors that affect the length of time a stream or river is impacted, such as the size of the stream, the volume of the overflow, the amount of pollutants introduced during the overflow, and the overall area that drains into the stream. Most public health officials generally advise that these areas be avoided for at least 48 hours after a heavy rain event.

How can I be notified of overflow events?

The CCU has an automated system that can notify interested parties when combined sewer overflows occur. If you wish to be notified of overflow events, please fill out the form at the following link. [CSO NOTIFICATION LIST].

What can I do now to help keep the Flatrock and East Fork White Rivers cleaner?

Every citizen of a combined sewer community can help minimize the impacts of overflows to local streams and rivers. If you live in a part of the City that has combined sewers, remember that everything that goes down the drain in your home, or washes into storm grates along the streets, has a potential of ending up in local streams and rivers. Try to avoid dumping strong chemicals, solvents, or paints down household or business drains. Also be aware of outdoor contaminating activities near storm drains. This could include such activities as storing, oils, herbicides, pesticides, general garbage and even grass clippings in places where they could wash into the storm drains.