Water Quality - Health & Environment

CSOs contain raw sewage which can carry a variety of human bacteria and viruses with the potential to cause illness. Stormwater also contains pollutants that can cause health concerns, including a variety of chemicals, oils, animal wastes, and other wastes picked up by stormwater as it flows across parking lots, roads, lawns, and other surfaces.

All of the CSOs in Omaha occur during wet weather events, so the sewage, chemicals, and pollutants in the overflow are diluted by rain and river water. Still, the potential for health and environmental hazards is present. People most likely to be affected are water skiers, swimmers and others involved in direct water contact activities during wet weather.

The combined sewer system allows millions of gallons of untreated sewage and stormwater to enter the waterways in a typical year. Concerns associated with these discharges include:
• The possibility of human contact. Overflows from combined sewers contain raw sewage, which can carry disease-causing organisms.
• Impacts on aquatic life, such as fish
• Sewers may overflow near community parks and adversely affect recreational areas
• Overflows may cause offensive odors and leave unsanitary debris along the banks of rivers and streams
• Many area streams may not meet the state’s water quality standards for recreational activities, such as wading

The extent of the health concern from a CSO discharge is influenced by:
• The size of receiving stream (which affects the dilution level)
• The duration of the precipitation event (also affects the dilution level)
• The time of day that the CSO discharge occurs (there is heavy use of the sanitary sewer system during AM or PM peaks)

Regulations, Permit Requirements and Compliance

Leahy Mall park - Downtown

The City’s requirement to address CSOs is based in the federal regulations of the Clean Water Act of 1972, the CSO Control Policy of 1994, the subsequent Wet Weather Water Quality Act of 2002, and the City’s permit from the Nebraska Department of Environmental Quality (NDEQ). The permit is in effect while the plan is being developed and implemented. Since the issuance of the permit, the City and NDEQ have agreed that the final LTCP will be developed by October 2009. The LTCP will lay out a path for the City to implement and construct the solutions that will be described in the plan.

The NPDES permit for CSOs also required the City to review their procedures to determine if there were ways that they could reduce the number of the CSOs, or reduce the load of pollutants from the discharges. These procedures range from the operational procedures at the treatment plants to the review of maintenance procedures for the combined sewer system. This review, and the resulting changes, are included in (what is referred to as) the Nine Minimum Controls.

The City has made significant progress toward accomplishing these controls. The City:

• Reviewed and standardized all of its procedures to more effectively operate and maintain the sewer system
• Instituted a permit system for industries discharging stormwater to the combined sewer system
• Is working with a consultant, developing and refining a computer model of the combined sewer system to help evaluate CSO control alternatives
• Identified areas where separation of the sewer system will have the greatest impact on minimizing overflows. In addition to the regulated CSO items, the City continues to move forward with projects to address sewer back-ups within the system.
• Continues to with meet regularly with the NDEQ and the Environmental Protection Agency (EPA), providing progress updates on permit requirement compliance, and on the overall CSO Control Program.

Resources

CSO Monitoring Plan Portal
http://ne.water.usgs.gov/projects/cso.html

Missouri River Water Information Portal
http://ne.water.usgs.gov/missouririverwq/index.html