Combined Sewer Overflows (CSO)

Combined sewers are sanitary wastewater and stormwater runoff that are collected in the same sewer. The combined flow is then transported to the Wastewater Treatment Plant.  Sometimes when it rains, combined sewers do not have enough capacity to carry all the flow to the Wastewater Treatment Plant.  In these situations, a portion of the untreated wastewater discharges into the Maumee or Auglaize River, creating a combined sewer overflow (CSO). These overflows help to minimize backups in homeowner basements during heavy rainfalls.

Long Term Control Plan:
The City is currently working with OEPA on a Long Term Control Plan (LTCP) to reduce the amount of CSO’s discharged during heavy rainfalls.  Over the last 10 years, the City has removed 16 CSO’s but still has 28 that remain active.  Although 28 remain, the City has done several projects to reduce the amount of overflows.

How to make a difference:
Remove downspouts from discharging into the sanitary sewer allowing storm water to “splash” on the ground.
Avoid using excess water during rain events. For example: avoid doing laundry.

Do not discard your grease into the drain. Scrape the grease into a can and dispose of it in the trash. Grease will build up in sewer lines restricting the flows.

Do not dispose of any wipes or feminine products in the toilet. These do not breakdown and can build up causing an obstruction.Back to Water Pollution Control

For more information:

City of Defiance, WPC 419.782.0841