Water Luncheon Seminar

Green-Gray Decentralized Detention Infrastructure to Control Combined Sewer Overflows

Nestor Alonso Mancipe-Munoz, University of Cincinnati, Department of Biomedical, Chemical and Environmental Engineering.

WHEN: January 21, 2014 – 11:30am-1:00pm
WHERE: Wilma H. Schiermeier Olentangy River Wetland Research Park, Heffner Building, Columbus, OH (map)

Register online here or download abstract and registration form.

Combined sewer overflows (CSO) are uncontrolled and untreated discharges of wastewater into urban streams that occur when the capacity of the collection system or the treatment facility are exceeded during heavy rainfall or snowmelt events.  Resilient and affordable solutions are needed to control CSOs and help manage urban flooding and improve water quality.  Typically, Gray infrastructure (i.e. sewers and treatment facilities) are proposed to mitigate CSO impacts.  A more environmentally friendly approach called Green  infrastructure (i.e. bio-infiltration, green roofs, rain gardens, etc) is being considered to solve this problem.  Interest has grown in using a combination of “green” and “gray” infrastructure because it not only mitigates CSOs, but also maximizes social, economic, and environmental benefits.  A unique framework that combines state-of-the-art mathematical modeling complemented with Geographical Information Systems (GIS) was developed to assess a non-conventional “green” and “gray” infrastructure alternative, composed of short storm sewers (gray) that  convey stormwater runoff into small decentralized detention ponds (green).  The detention ponds release the captured runoff back into the existing sewer at a constant rate controlled to  prevent the occurrence of a  downstream CSO.  The proposed framework includes methods to calibrate a high resolution rainfall-runoff model, identify potential sites for small detention ponds, and produce control-operation policies.  Results show that the green-gray infrastructure alternative is feasible and provides a higher CSO reduction at a lower cost than a conventional “gray only” alternative for a typical rainfall year.  The framework provides a useful promising tool for evaluating effectiveness, feasibility, and operation-control of this alternative in urban areas to reduce CSOs.

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