Combined sewers systems were constructed mostly in the
1920s and 1930s in what is now old Columbus, a
rectangular region bounded by Hudson Street on the
north, Alum Creek on the east, Refugee Road to the
south, and the Olentangy/Scioto Rivers to the west.
These sewer pipes, which conduct both sanitary sewage
and storm water, represent an old technology found
mostly in the Midwest and also in some northeastern
Although the Columbus Division of Sewerage and
Drainage (DOSD) reports that only 5-10% of its total
system is combined sewers, newer sewers upstream drain
into the combined sewer area. As explained on page 4 of
this issue, combined sewers have a divider that
separates the lower part of the pipe, with surface storm
water on one side and sanitary sewage on the other. At
low flow, all water is treated at the wastewater plant.
At high flow, storm water and sewage mix and are
discharged untreated into the river.
You may have noticed huge concrete pipes along the
Scioto with prominent signs warning of sewer discharge:
an 11-foot diameter pipe in Bicentennial Park, an 8-foot
pipe west of Deshler and Front Streets, a 6-foot pipe
near Dodge Park, an 11-foot pipe near the federal
building, a pipe near the civic center, large pipes near
Greenlawn Dam, and others. The Olentangy receives
diluted sewage near Hudson from a 7-foot pipe near
Tuttle Park, a 9-foot pipe beneath Neil Avenue below the
Fifth Avenue dam, and other pipes. Alum Creek receives
diluted sewage from a 12-foot high pipe discharging near
the Alum Creek tanks.
Such large pipes can carry big volumes of
wastewater. One location last year reported discharging
72 million gallons in a single overflow event. DOSD
figures show peak combined sewer overflow (CSO)
discharge rates of 300 million gallons per day.
DOSD and Ohio EPA are concerned about the problem of
wet weather discharges of combined sewer overflows.
There are 31 CSO points where diluted sewage can be
released. Columbus and OEPA entered into a Consent
Order with steps the city must take to address combined
sewer issues. (See the article Ohio EPA Asks
Columbus to Fix Combined Sewers in this issue.)
Under this legal document, the city must write a Long
Term Control Plan by July 2005, laying out steps they
will take to reduce and treat combined sewer
discharges. The plan requires data on the waste water
stream and from the rivers. The city has already begun
collecting information and modeling the system.
Unfortunately, the federal government permits CSOs,
which discharge diluted sewage. The Bush Administration
has proposed allowing “blending”, that is, legalizing
the discharge of diluted raw or partially treated
sewage. This regulation, like many others, has been put
on hold until after the November election. The Sierra
Club supports treatment of all sewage and is strongly
opposed to a loosening of regulations allowing “blended”
sewage to be discharged to the rivers.
The first part of the CSO consent order process was
the recent Technology Initial Alternatives report.
Because of Sierra Club requests, the whole report is now
available on the
DOSD website in pdf
The report tries to draw initial sizing estimates of
what is needed to handle the combined sewer system. The
report then lays out alternatives and qualitatively
evaluates them. It is long and technical but some
conclusions can be drawn.
Eleven technology alternatives are presented, ten are
examined in detail, and several are closely related to
each other. The resulting alternatives grouped
according to closely related technologies by the city’s
consultants are: 1) building new sanitary sewers in the
combined sewer area, 2) redirecting upstream separated
sanitary sewage away from the combined system, 3)
storage of combined sewage to hold peak flows, 4)
consolidation or relocation of CSO discharge points, 5)
different basic treatment methods for combined sewage
(screening, primary, advanced primary), and 6)
biological treatment of peak flow at the waste water
plants. Note that alternatives 2) through 6) leave the
present system with CSO discharges largely in place.
The consultant’s evaluation reflects the city’s
preferences in the scoring. The city clearly prefers
leaving the present combined system in place and
building storage through underground pipes and
aboveground tanks in order to redirect upstream sanitary
sewage away from the combined sewer system, consolidate
outfalls, or “move them to less sensitive areas of the
streams”. But these alternatives will constrain options
for the future. Expanding treatment at the two
wastewater treatment plants is ignored.
The Sierra Club supports complete separation of storm
water and sanitary sewage and storm water policies which
protect streams. We advocate for treatment of all
sewage released into the environment. Information on
sewage discharges should be posted on the internet,
along with other data on water quality and technical
planning reports. The public has a right to know how
their municipal dollars are being spent and to have a
say in the planning process.
The Bush Administration has proposed allowing
“blending”, that is, legalizing the discharge of
diluted raw or partially treated sewage.