Corps Seeks Comments On Chicago Flood-Prevention Plan
The Chicago Engineer District is seeking public comments on a plan to lower the level of portions of Chicago waterways before storms to better prevent flooding.
The Chicago Area Waterway System Updates to the Water Control Manual For Chicago Lock and T.J. O’Brien Lock and Dam draft Environmental Assessment is available online, and the comment period runs through December 22.
The project is not expected to have any impact on navigation, according to the Corps of Engineers. It affects the north branch of the Chicago River extending north to the Wilmette Pumping Station, the south branch and the Chicago Sanitary & Ship Canal extending southwest to the Lockport Lock and Dam.
The recommended plan for implementation would allow water in the Chicago Area Waterway System (CAWS) to be lowered to -4 Chicago City Datum (CCD) for short periods when precipitation is expected and tunnels and reservoirs are already at or near capacity to provide additional flood storage. The waterway level could also be dropped to facilitate maintenance vessel access.
The current plan allows the waterway level to drop to -3 CCD for short periods, so this proposal would decrease the water level by 1 additional foot.
High Lake Levels
The changes would compensate for reduced ability to backflow into Lake Michigan at the Chicago River Controlling Works (CRCW), Wilmette Pumping Station and the T.J. O’Brien Lock and Dam during periods of high lake levels, according to the draft assessment. Backflow cannot occur until the CAWS is at a higher level than Lake Michigan. With current protocols, under certain conditions, flooding begins to occur at several adjacent river facilities before the Corps can initiate a backflow.
The drawdown would also give overhead clearance to Corps maintenance fleet vessels.
It would result in an additional 10,000 acre-feet of flood storage capacity in the CAWS.
The draft is available at the Chicago District’s Project webpage: www.lrc.usace.army.mil/Missions/Water-Management/Chicago-Area-Waterway/. Comments should be emailed to Ryan Johnson at ryan.a.johnson@usace.army.mil. Questions should be directed to Johnson at 312-846-5559 or through email.
