| Nebraska Department of Environmental Quality | Winter 2010 |
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Omaha Submits Comprehensive Plan To
Deal With Combined Sewer Overflow Problems
On, Sept. 25, 2009, the City of Omaha submitted its final combined sewer overflow (CSO) plan to the Nebraska Department of Environmental Quality. This comprehensive plan provides the schedule of completion of a series of projects which will reduce overflows from its combined sewer system.
A consent order with the state had established an October 1st deadline for the city to submit this plan to meet requirements of the federal Clean Water Act.
“The submission of this final plan is an important step by the City of Omaha to decrease discharges from their combined system and to protect the quality of our water,” said Steve Goans, supervisor of NDEQ’s Wastewater Section. “This is a significant milestone in a project that could transform the city’s water infrastructure.”
What are combined sewer systems and CSOs?
Combined sewer systems are an older design (many were built over 100 years ago), that allow wastewater from homes and businesses to be combined with stormwater. In more modern sewer systems, these two aspects are built as separate systems – that is, the wastewater system conveys homes’ and businesses’ sewage to treatment facilities, while the separate storm water drainage systems transport rainfall directly into rivers and streams.
The environmental concern with the older combined sewer systems is that, during wet weather, sewage overflow can bypass the communities’ wastewater system, combining with the stormwater to discharge directly into our rivers without proper treatment. When this happens, it is called a combined sewer overflow (CSO). In Omaha, CSOs are discharged into tributaries of Papillion Creek or the Missouri River.
Currently, these overflows can occur even during relatively small precipitation events in Omaha. A rainfall as small as one-tenth of an inch can cause the system to overflow and directly discharge sewage into Nebraska’s rivers.
Omaha is not unique in this regard; the federal government estimates that over 770 communities across the nation have combined systems.
The City of Omaha has been making efforts to reduce CSOs in recent years. Since the 1960s, newly constructed sewer systems include separate pipes for wastewater and stormwater, and many projects have been initiated by the city to separate parts of the existing combined systems. However, the city still has most of the old combined sewer system in use.
The city, the state and the federal government are all in agreement that comprehensive action must be taken in Omaha to address this CSO problem. In fact, the city could face severe penalties if it did not develop and implement a comprehensive plan to correct the situation.
“The City of Omaha has recognized that extensive wastewater renovations are needed, and they have accomplished a great deal already,” NDEQ Director Mike Linder said. “This plan formalizes efforts that are already under way, and presents a clear and effective road map to resolving CSO issues in the future.
“The City is to be commended for taking a comprehensive approach to address these issues.”
NDEQ will be reviewing these plans in great detail in coming months to ensure the city’s plans will conform with all relevant water quality regulations.
How Will CSOs be addressed?
Omaha’s final plan focuses on three main components to address combined sewer overflows. They are:
- Targeted Sewer Separation – In several of the areas in Omaha that still have a combined system, targeted sewer separation will be the primary control used. The existing single-pipe combined sewer systems will be separated to carry its two components, storm water and sewage. This will ensure that storm water is transported to rivers, and sewage will go directly to wastewater treatment.
- High Rate Treatment Facilities – Three high rate treatment facilities will be built at outflow locations to treat overflows before reaching the Missouri River, Papillion Creek or Cole Creek. These facilities are designed to temporarily hold sewage overflows during rain events, until it can be treated and released at a manageable rate.
- Deep Conveyance Tunnel – The plan proposes a 5.8 mile cross-basin tunnel which will carry combined sewage and storm water runoff to one high-rate treatment plant adjacent to the current Missouri River Waste Water Treatment facility.
The final plan and related detailed information are available for review at http://www.omahacso.com.
Nebraska Department of Environmental Quality
1200 "N" Street, Suite 400
P.O. Box 98922
Lincoln, Nebraska 68509
(402) 471-2186