Slowing the Flow
Chicago initiated its inlet control valve system (called the “Rainblocker” program) as one facet of a multi-dimension concept.
DWM workers installed close to 200,000 inlet restrictor valves into Chicago’s street catch basins, at a rate of 90 to 120 per day. When the restrictor valve is installed in the storm water catch basin in the street, the device, in essence, shrinks the pipe to funnel and regulate the water from the street to the main sewer line. During a heavy rain event, the smaller opening allows less water into the sewer system. The streets act as a temporary holding area for the rainfall. Surplus water in the system will not be forcing contaminated water back through homeowners’ private lines and into the home’s lowest spot – the basement. The street ponding buys time for the system to catch up.
A Work in Progress
The city is the first to recognize flooding problems still exist. Flooded streets, a problem deemed preferable to flooded basements, are an acknowledged byproduct of the valve system because of the restricted flow of water into the sewers. In the recent rains, some residents reported only a couple of inches of water where in previous storms their basements had held over a foot of water. In some instances, however, homes that had never been flooded before were flooded in this last event due to ponded runoff entering basement windows and doors.
When Mother Nature decides to dump four inches of rain in little over an hour, it’s difficult for any man-made system to handle such a rain event. Private lines may be blocked or damaged. Downspouts add millions of gallons of clean water to the sewers. Streets fill up and water flows overland, sometimes causing flooding.
The “Rainblocker” program is clearly a work in progress, but if basement backup has been minimized each time it rains, then it appears the city is headed in the right direction. This system requires combined efforts from city officials and all impacted citizens. In the next phase of resolving bottlenecks in the system, we are working with the Chicago Sewer Department to identify over-the-curb flooding of homes and to evaluate areas that continue to experience basement flooding. Please let us know if you are having an issue with flooding or sewer backups.