CSO/SSO Info

What is a Combined Sewer System (CSS)?
A combined sewer system is a wastewater collection system that is specifically designed to collect and convey sanitary wastewater (domestic sewage from homes as well as industrial and commercial wastewater) and storm water through a single pipe. During normal dry weather conditions, sanitary wastes collected in the combined sewer system are conveyed to a wastewater treatment plant. During rain events or snowmelt, the systems are designed to overflow when the collection system capacity is exceeded, resulting in a combined sewer overflow (CSO) that discharges directly to surface waters such as rivers, streams, estuaries, and costal waters.

History of CSOs
Combined sewer systems were among the earliest sewer systems constructed in the United States and were built until the first part of the 20th century. Hundreds of communities built combined sewers because they were a cost-effective way to provide sewer service and improve drainage. The overflow points were designed to act as relief points for the excess flow in the sewers, thereby reducing the potential for sewer backups and flooding during rain events. When these sewer systems were first constructed, these overflows were considered an acceptable way to manage excess water.

What is an Separate Sanitary Sewer System (SSS)?
A separate sanitary sewer system is a wastewater collection system, owned by a state or municipality that is specifically designed to collect and convey only sanitary wastewater (domestic sewage from homes as well as industrial and commercial wastewater). In such systems, storm water is conveyed through a separate set of pipes. These systems are not designed to collect large amounts of storm water runoff from precipitation events. A sanitary sewer overflow (SSO) can occur when collection system capacity is exceeded due to wet weather, when normal dry weather flow is blocked for any of several reasons, or when mechanical failures prevent the system from proper operation.

For the last 40 years, the sewers constructed in Northern Kentucky have been separate sewer systems. SSOs have a variety of causes including:

• Blockages from fats, oils, and grease
  
  
• Blockages from roots
  
  
• Blockages from vandalism
  
  
• Line breaks in aging and deteriorating systems
  
  
• Public and private storm water connections that allow excess rain water to enter directly into separate sanitary sewer lines
  
  

Are Overflows Common?
Overflows are complex and costly issues that affect not only Northern Kentucky, but also many other communities throughout the U.S.

Today, there are 746 communities with combined sewer systems with a total of 9,348 CSO outfalls that are regulated by federal permits (NPDES). EPA estimates that about 850 billion gallons of untreated wastewater and storm water are released through CSOs each year in the U.S.

Unfortunately, SSOs are a chronic and growing problem in many parts of the country. EPA estimates that between 23,000 and 75,000 SSOs occur each year throughout the United States, resulting in the releases of between 3 billion and 10 billion gallons of untreated wastewater.

When do sewer overflows occur?
Overflows should only occur during wet weather. Whether an overflow occurs and what the magnitude is depends on many factors, including volume, rainfall intensity, if the ground is saturated or dry, and on the natural variability of rainfall.

If you observe an overflow, especially during dry weather, please contact SD1 at 859-331-6674.

What will it cost to control overflows?
The EPA estimates that $88 billion and $50.6 billion is needed over the next 20 years to control SSOs and CSOs respectively throughout the nation.

What impacts do CSOs and SSOs have?
Because CSOs contain raw sewage and large volumes of storm water, as well as contribute pathogens, solids, debris, and toxic pollutants to receiving waters, they can create public health and water quality concerns. SSOs can also create public health and environmental concerns because they contain raw sewage and can occur on land and in public spaces.

Pollutant concentrations in CSOs and SSOs vary substantially, not only from community to community and event to event, but also within a given event. It is important to note that waterbodies also receive pollutants of the types found in CSOs and SSOs from other sources such as storm water runoff.

How to protect yourself from overflows
To protect yourself and family members from health concerns associated with sewer overflows, SD1 recommends avoiding contact with water near discharges both during and following rain events for at least 72 hours. This includes activities such as boating, wading, fishing and swimming. In addition, when Ohio River levels reach 38 feet, officials warn against coming in contact with the water. Before you recreate near local waterways, be sure to check the water quality data – even if it is not immediately following a rain event. Click here to view water quality data.

What actions should be taken to reduce the impacts of overflows?
The watershed approach is central to water quality assessments, and the identification of control strategies must include all sources of pollution affecting water quality. Better integration of programs and activities at the watershed level will provide economies of scale with respect to monitoring and reporting, protecting water quality and reducing the impacts of CSOs and SSOs.

Sanitation District No. 1 is developing an Adaptive Watershed Management Plan to address sewer overflows in Northern Kentucky. This approach will also aid in taking a holistic approach to addressing issues such as pollution in storm water runoff, non-point source pollution and sanitary sewer needs. To learn more about Watershed Management, click here.

What can you do to help?

• Notify SD1 of overflow events in your neighborhood by calling 331-6674. This can assist in efforts to prioritize improvement projects for the region
  
  
• Don’t pour household products such as cleansers, beauty products, medicine, and paint down the drain or into storm drains
  
  
• Don’t pour auto fluids such as motor oil and antifreeze down the drain or into storm drains
  
  
• Fix leaks from vehicles
  
  
• Don’t discard lawn care products into the drain or into storm drains
  
  
• For information on proper disposal of hazardous wastes, call the Household Hazardous Waste Hotline 859-341-4151
  
  
• Take cars to a commercial car wash where the water is treated before being returned to the environment
  
  
• If you wash your own car, use biodegradable soap over grass or gravel
  
  
• Keep sidewalks and streets free of litter and debris and never sweep leaves or grass clippings into street storm drains
  
  
• Volunteer for SD1’s storm drain marking program, Save-a-Stream, Block-by-Block. To learn more about this educational program, click here.
  
  

Where can I get more information regarding overflows?

• Call SD1's Information Hotline at 859-547-1316
  
  
• EPA’s Report to Congress on Impacts and Control of Combined Sewer Overflows and Sanitary Sewer Overflows
  
  
• The EPA’s CSO Information Site
  
  
• The CSO Partnership
  
  
• Kentucky Division of Water’s CSO Information Site
  
  
• The Ohio River Valley Water Sanitation Commission (ORSANCO)
  
  
• The Water Environment Federation (WEF)
  
  
• National Association of Clean Water Agencies (NACWA)