CSO General Information

Combined Sewer Overflow System

The Mississinewa River is a beautiful waterway and a wonderful resource for the citizens of Marion. The river provides a place to enjoy a wide range of recreational activities including fishing, canoeing, and observing wildlife. We must all work together to protect and enhance this resource for Marion's citizens and future generations.

Protecting water quality and natural habitat in the Mississinewa River and its tributaries starts with looking at the sources of stream pollution. Marion's combined sewer overflows (CSOs) are one of many sources of pollution contributing to the water quality of the Mississinewa River. Please take a few minutes to review this information to better understand how Marion's CSOs affect the water quality of the Mississinewa River.

To view a map of the locations of the Marion's Active CSO Discharge Points click here.
What is a combined sewer overflow (CSO)?

To understand combined sewer overflows it is important to understand what a combined sewer system is. Over 100 years ago cities recognized the need to construct sewers to carry sewage away from homes and businesses to protect public health. Originally sewers were designed to carry both sewage and storm water directly to streams and rivers. The natural biological processes in streams and rivers broke down the organic waste from the sewage. This system was adequate until the growing population created too much waste for the river to clean up naturally. Today scientists understand that the bacteria and viruses contained within combined sewage can create a potential health hazard when discharged to our waterways.

Currently the combined sewer system carries sewage from our homes and businesses to the Marion wastewater treatment plant instead of the river. However, when it rains or there is a large amount of snow melt, excess water that enters the combined sewer system through catch basins and other drainage structures can exceed the capacity of combined sewer system and the wastewater treatment plant. When this occurs the excess water is discharged to the Mississinewa River through CSO outfall structures.

Many older cities in the Great Lakes, Middle Atlantic and Northeast regions have combined sewer systems. There are approximately 950 communities in the U.S. with combined sewer overflows. In Indiana, the Indiana Department of Environmental Management has identified 105 CSO communities.

What impacts do CSOs have on water quality?

Sewage, household, automobile, and other waste flowing into rivers and streams can cause:

A health hazard for people - combined sewage may contain harmful bacteria and viruses such as E. coli that can make people sick. A few things you can do to project yourself and your family are:

  • People should avoid contact with all urban streams in the Marion area during and for at least 72 hours after a rain event or a period of rapid snowmelt.
  • Parents should teach children to never play in or near a stream or river without adult supervision.
  • Everyone should thoroughly wash their hands and face after contact with any stream, river or lake.
  • If you wade in or fall into a waterway you should take a bath or shower when you return home.
  • Damage to habitat and aquatic life - Organic waste, like sewage, can contribute to impaired water quality by causing dissolved oxygen levels in our streams to fall. Other chemicals that build up on streets and rooftops can damage the habitat of different kinds of aquatic life.
  • * A nuisance to people near the river - sewage and trash from CSOs can look and smell bad, driving people away from the area and lowering the quality of life for all of Marion's citizens.

What is being done about Marion's CSOs?

The City of Marion is working to solve the problems caused by CSOs. The City's sewer system maintenance program now virtually eliminates all dry-weather overflow. Existing sewer systems and wastewater treatment facilities are being used more efficiently and effectively to reduce overflows.

The City of Marion is developing a long-term plan that will include goals for CSOs, control measure options, and their corresponding costs and effectiveness. Addressing CSOs can be expensive, so we must consider our options carefully and find the most cost-effective use for available resources.

You can be part of the solution. By understanding our systems, and by keeping informed along the way, you can help your government make the best decisions on this serious and complex issue. Your participation is vital to ensure future generations will be able to enjoy clean waterways.

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