Abating combined sewer overflow
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Installing new sewer lines on Tallman Street (2005)
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Some areas of Syracuse have sewers that carry both
sanitary sewage—from homes and businesses—and also
stormwater from the streets. During dry weather these
sewers carry all the sanitary sewage to the Metropolitan Syracuse Wastewater Treatment Plant for
treatment.
During times of heavy rain or melting snow, however,
the amount of water is far greater than the capacity
of the sewers. At these times, the sewers overflow and
discharge the excess—a combination of runoff and
sanitary sewage—into Onondaga Creek and Harbor Brook and
eventually gets to Onondaga Lake. This is
combined sewer overflow (CSO).
The sewer system was designed to overflow in this way
to prevent sewage from backing up into streets and
basements.
CSOs create human health risks because they add
bacteria, floating trash, organic material, heavy
solids, and grit to city streams and Onondaga Lake. Material
from CSOs collects on vegetation along and in streams.
It looks bad and smells bad, and it can also transmit
disease to humans who may come in contract with the
water. Material from CSOs also depletes the dissolved
oxygen in the water that is necessary for aquatic
life.
Overflows from combined sewers are being abated
Before about 48 years ago, Syracuse had ninety
points where sewage could overflow and reach Onondaga Creek,
Harbor Brook, or Ley Creek. The City of Syracuse owned
and maintained the sewerage system. The City did not
eliminate any of the overflows of the combined sewers.
Onondaga County began to take ownership of the combined
trunk sewers and two interceptor sewer lines in the
1960s and ’70s. It immediately began making
improvements. By 1985, it had closed permanently about
forty overflow points.
Brief history of local sewerage facilities.
Today
we have just 49 overflow
points, and that number will diminish further as
additional projects are completed.
By abating CSOs, Onondaga County will meet or exceed federal and state water
quality
requirements,
reduce human health risks associated with the discharge of
untreated sewage to Onondaga Creek and Harbor Brook and Onondaga Lake, and eliminate
odors caused by discharging overflows.
The County will also make improvements to the area
affected by construction of the abatement work.
Progress on sewer separation in Syracuse
CSOs are being addressed with several types of projects:
Regional treatment facilities
remove and/or store solids and floating material. They
are also equipped to disinfect effluent to receiving
streams if storage capacity is exceeded.
Sewer separation
divides combined sewer systems into individual
sanitary sewers and storm sewers.
Floatables control facilities
remove floating debris with net bags, screens, or
skimmer boats.
Learn more about the benefits of the floatables control facilities.
Increased storage and transport capacity
optimize storage volumes in existing combined sewers
and provide increased storage with new large
conveyance pipes and underground tanks.
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Midland CSO Abatement Facility
Susan Miller, Project Deputy Director
Onondaga County Dept of Water Environment Protection