Combined Sewer Overflows (CSO)

The Combined Sewer Overflow Map on this page gives the approximate locations of the Defiance combined sewer overflow outfall sites. The triangles represent sites with real-time monitored data and the circles represent sites with real-time modeled data. If the site icon is red, an overflow has been detected or modeled to occur and will remain red for 24 hours after the discharge event has ended. The icons are updated every 5 minutes.

If any icon is red the following areas may be affected:

  • Auglaize River
  • Maumee River
  • Ditch to Auglaize River
  • Preston Run
  • Riverside Park, Pontiac Park, Library/Fort Grounds, and Kingsbury Park.

If you hover over an icon with the cursor, the outfall name, water body the discharge affects, and date/time discharge started will appear. If you click on an icon a dropdown screen will appear that allows you to download a file with overflow event durations and volumes for a chosen time period based on the system model.

If you have any questions
please contact:

Water Pollution Control
Superintendent – Mark Lehnert

419.782.0841

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.
  • Visit landtolake.com/make-a-difference for information on landscaping projects that help control stormwater.