The Metropolitan Water Reclamation District of Greater Chicago (MWRD) has been working to provide flood protection for Cook County after a rain event that began at 7 p.m. on June 30 and ended at 1:35 a.m. the next morning. All systems are running at full capacity as an average of 1.83 in. fell across Cook County: 3.08 in. in the north, 1.45 in. central and 1.63 in. in the south.
When the Chicago area waterway levels are higher than Lake Michigan and certain elevations are reached, the MWRD opens control structures to move as much water as possible out of the system. This provides overbank flooding protection as well as more capacity for storm water. The gates at Wilmette were opened at 11:23 p.m. and closed at 5:50 a.m. The gates on the Chicago River Controlling Works downtown were opened at 12:58 a.m. and closed at 7:10 a.m. The amount of water released to Lake Michigan will be estimated in the weeks following this storm event, after operational issues have been addressed.
The Tunnel and Reservoir Plan (TARP) system is operational and working as designed. TARP is comprised of 109 miles of tunnel and two reservoirs. The Mainstream Tunnel, which is 40.5 miles long and can hold 1.2 billion gal, was full at 11 p.m. The Calumet Tunnel, which is 36.7 miles long and can hold 630 million gal, was full at 2:30 a.m. The Des Plaines Tunnel, which is 25.6 miles long and can hold 405 million gal, is currently full. The Kirie Tunnel is 6.6 miles long, can hold 70 million gal and was filled by 1 a.m. The entire tunnel system holds 2.3 billion gal. The Majewski Reservoir, which can hold 350 million gal, is in operation and receiving flow.
MWRD encourages the public to minimize their use of water in their homes to reduce the amount of water flowing into the sewer system during extraordinary rain events such as what is occurring. This will provide maximum capacity for combined storm water flows.
Source: MWRD
