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EVALUATION OF PROCEDURES TO PREVENT BACKFLOWS TO
LAKE MICHIGAN FROM THE CHICAGO WATERWAY SYSTEM Primary Investigator: Dr. Charles S. Melching Sponsor: Metropolitan Water Reclamation District of Greater Chicago Duration: February-December 2007 Funding Level: $52,000 The Chicago Waterway System (CWS) is a 76.3 mi branching network of navigable waterways controlled by hydraulic structures in which the majority of flow is treated sewage effluent. The CWS was created to drain combined sewer overflows (CSOs), stormwater runoff, and treated wastewater from the Chicago area away from Lake Michigan and for commercial and recreational navigation. During larger storms it may become necessary to allow flow to go to Lake Michigan through the lakefront sluice gates and locks. Such backflows can potentially affect the water supply of the City of Chicago, the accessibility of beaches to the public, and the general environment of Lake Michigan. Thus, it is a high priority for the Metropolitan Water Reclamation District of Greater Chicago (MWRDGC) to avoid such backflows. Since the O’Brien Lock and Dam was completed in 1965, forty-eight storms have caused the MWRDGC to open the sluice gates or locks at the lakefront and allow water to flow to Lake Michigan. Between 1990 and the present thirteen backflow events have occurred. The decrease in frequency of backflow events from 35 in 25 years (1965-1989) to 13 in 18 years (1990-2008), i.e. from 1.4/yr to 0.7/yr, reflects the effectiveness of the Tunnel and Reservoir Plan (TARP) in reducing flood flows. However, the volumes of the backflows since 1990 has been very large with 6 of the 10 largest (post O’Brien Lock and Dam) backflow volumes occurring since 1990. Thus, changes in operation procedures at the Lockport Powerhouse and Controlling Works were evaluated to see if the volume of backflows to Lake Michigan could be reduced. A detailed study of seven historic backflow events (including the 2nd and 4th largest since 1965) was done to evaluate changes in operation procedures to determine if backflows could be avoided or reduced in volume. The study applied a dynamic-wave simulation model to the CWS at a 15-minute time step combining measured inflows for the major tributaries, CSO pump stations, and water reclamation plants with simulated gravity CSO flows computed by the U.S. Army Corps of Engineers. Publications: ·
TR#19 – Evaluation
of Procedures to Prevent Flow Reversals to Lake Michigan from the Chicago Waterway
System ·
Paper from World Environmental and Water
Resources Congress, Kansas City, MO, May 17-21, 2009 Evaluation of Methods to Reduce Backflows from the Chicago Waterway System
to Lake Michigan
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Institute for Urban Environmental Risk Management ©2001 Marquette University -- Last Update: February 26, 2005 |
