From midnight until 8:00 a.m. on Thursday, April 18, 3.94 inches of rain was recorded at the Evanston Water Plant. During this time, there were several short-duration, high-intensity rainfalls. With so much water falling in such a short time frame, the sewers have become overwhelmed. In some cases, this has resulted in sewage backing-up into basements. In other locations, such as on areas along Central Street, the pressure of the water in the sewers has dislodged manhole covers and resulted in water flowing onto the street.
This situation is not just in Evanston – all of the surrounding communities are experiencing the same problem. The combined sewer systems from all of these communities flow to the Metropolitan Water Reclamation District’s sewer system, which includes large diameter interceptors that carry the sewage to the treatment plant. When the District’s interceptors are filled to capacity, they then discharge to the deep tunnel, which stores storm water. However, when the deep tunnel is full, as it is currently, the excess storm water flows to the North Shore Channel. When the Channel level rises, valves are opened at the Wilmette Harbor, allowing water in the Channel to flow into Lake Michigan. The water level in the Channel rose quickly last night, and the valves at the Wilmette Harbor were opened at 1:20 a.m. this morning.
The District’s sewer system was already running near full capacity due to the rain events that occurred prior to today. During the week of April 8, a total of 1.6 inches of rainfall was recorded and another 1.6 inches of rain had occurred earlier this week.
As of 9:30 a.m., the Utilities Department has received 50 basement flooding complaints and 45 street/alley flooding complaints from all areas in the city. Basement flooding concerns are considered a priority and are being responded to in the order that the calls are received. Street/alley flooding concerns are being addressed as time allows.
Two power outages have occurred in Evanston as a result of the storm. In southwest Evanston, in the area bordered by Oakton, Asbury, Howard and Hartrey, 384 accounts were without power for approximately 3 hours, between 4:00 and 7:00 a.m.
Approximately 98 accounts are still without power in the area bordered by Washington, Sherman, Monroe and Elmwood. The power went out at approximately 5:00 a.m. ComEd crews are currently on site to correct the problem and power is estimated to be restored in this area by 10:00 a.m.