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 format.  

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.