This website serves as a notification system to alert the public of the occurrence of combined sewer overflow (CSO) events and as a prediction of elevated bacteria levels in Onondaga Lake and its’ tributaries.
Background – What are combined sewer overflows (CSO)?
During dry weather, the combined sewer system (a combination of sanitary and storm sewers) and wastewater treatment plants have the capacity to transport and treat all the sanitary sewage entering the treatment system. However, when the flow into the sewer increases as a result of rainfall and/or snowmelt, the capacity of the system may be exceeded. When system capacity is surpassed, the combined sewer system will discharge into nearby water bodies through combined sewer outfalls designed to prevent and protect neighborhoods from flooding. When a CSO is occurring, and for a time period following the rainfall event, bacteria levels increase and water quality in the lake and its tributaries is impacted. The map provided on this website depicts the CSO outfall conditions and locations.
The information on the map is updated using a model to anticipate the quantity of rainfall that will trigger each CSO. The model was developed using U.S. EPA’s Storm Water Management Model (SWMM). Real time rainfall data are taken from the weather station at the Metropolitan Wastewater Treatment Plant (Metro) and these values are compared to the trigger values in the model to estimate where and when overflows are likely occurring.
Weather station information is transmitted hourly. Should the hourly rainfall meet or surpass the CSO trigger, the outfall will be represented as discharging. On this website, pins on the map appear at each of the existing CSO outfall locations.
Please be advised that this is a predictive system based on a mathematical model, not actual water sample results. The Department has been conservative in estimating the probability of combined sewer overflow events occurring. The Onondaga County Department of Water Environment Protection will also use this site to alert the public of sanitary sewer overflows, sewer maintenance operations, or other conditions that may impact water quality.
Efforts to Reduce the Occurrence of Combined Sewer Overflow (CSO) Events
Onondaga County is working to reduce CSO events through the implementation of the Save the Rain program – a comprehensive stormwater management plan employing a combination of innovative green and gray infrastructure projects. The County will capture 95% of the CSO volume, greatly reducing the pollution to Onondaga Lake and its tributaries. For more information on our mitigation efforts and further details on all of our green and gray project implementation, please visit the Save the Rain website.
Where are the CSO Outfalls?
Currently there are 46 active CSO locations and includes an area of 6547 acres or approximately 10 miles.��Onondaga County has posted signs like the one below at the CSO outfall locations. The pins on the map signify the outfall locations. Each outfall has a sign with a specific number that references its associated overflow location along the water body such as the one below: