Combined Sewer Overflow

At the Town of Brownsburg, we've committed to reducing the amount of untreated overflows from combined sanitary and stormwater sewers that reach White Lick Creek. It's important for residents to have a greater understanding of these sewers and why this work is important.

Combined Sewers

Combined sewers include both sewage (sanitary and industrial waste) and stormwater. When residents dispose of household wastewater, the flow generated travels through sanitary sewer pipes that carry it to the wastewater treatment plant. In some parts of Town, stormwater runoff from roofs, parking lots, and streets empty into the same system that carries sanitary wastes to the wastewater treatment plant. These systems are referred to as combined sewers.

Combined Sewer Overflows

During heavy rainstorms and rapid snowmelt, extra flow from stormwater runoff goes into these combined sewers which can overwhelm the main pumping station to the wastewater treatment plant. As the pump station becomes overwhelmed, the combined sewage and stormwater flows into a 1 million gallon storage tank. For extreme weather events, the tank does fill up and overflows to White Lick creek to prevent flooded basements and streets. These Combined Sewer Overflows are referred to as CSOs. Brownsburg has one discharge point which is the overflow from the tank.

When CSOs occur, they discharge untreated sanitary/industrial wastewater and runoff from rainfall and snowmelt into White Lick Creek. The combination of raw sewage and stormwater can carry a variety of human bacteria and viruses. In addition, combined sewer overflows contain a variety of chemicals, oils and other wastes. Although the untreated overflow is typically diluted by rain and river water, it still poses a potential health and environmental hazard.

CSO Reduction Efforts

In the 1990s, the Town of Brownsburg Brownsburg installed process units called swirl concentrators to partially treat the overflows.

The Environmental Protection Agency (EPA) and Indiana Department of Environmental Management (IDEM) require communities to develop Long Term Control Plans for either treating discharges to a higher level of standards or totally eliminating the discharges. A million-gallon tank designed to meet the requirements as established by IDEM has been constructed to catch the overflow discharges.

Combined Sewer Overflow

Once a rain event is over, the tank is emptied by pumps and the flows are treated at the existing wastewater treatment plant. Brownsburg personnel collects data including flow monitoring, daily rainfall totals, and visual observations to verify the tank is operating as required by IDEM.

The CSO tank is designed to allow overflows to the creek in the event of intense heavy rain or snowmelt events. During these overflows, additional monitoring, sampling, and testing are required to determine the level of treatment the tank provides and whether or not additional control measures will be required in the future. With continued stormwater pipe and sanitary sewer pipe separations planned for the future, flows to the tank should continue to be reduced.

Combined Sewer Overflow Sluice

CSO Public Notification

The Town of Brownsburg, as part of their combined sewer overflow notification program, hereby states that the potential for a combined overflow into White Lick Creek during and immediately following any rain event or snowmelt throughout the year. People who swim in, wade in, or ingest the water contained in White Lick Creek may become ill.

Wastewater Treatment Plant discharges are disinfected from April 1 through October 31 of each year; therefore, all individuals should remain clear of White Lick Creek during the winter months regardless of the weather. Those individuals with property along White Lick Creek between the Town of Brownsburg and the Town of Plainfield may request a warning sign along the creek bank of their property.

Individuals needing to know whether a combined sewer overflow event has occurred, or may potentially occur, may contact the Wastewater Treatment Plant Superintendent. The contact number to request additional information, warning signs, or to obtain whether or not the potential for an overflow event exists during the next 48 hours is 317-852-1114.