Wilmette is part of the Metropolitan Water Reclamation District (MWRD) of Greater Chicago. And, I’ve realized, things get complicated when you share a sewer system with 9.5 million people!
Just to add to the complexity, the whole system ultimately flows into the Chicago River. And that river, which should drain northeast into Lake Michigan, has been re-engineered through a system of locks and pumping stations, reversing its direction, to carry treated waste water south, away from the lake.
With this as the backdrop, here’s my “shaggy dog” story for the last week of a rainy spring season in Wilmette…
Sunday: Fun On the Beach
During a break from the rain on Sunday, we headed to the Wilmette beach. The water was beautiful, flat, and clear–a little cold for us, but great for our dog Ellie:
Sunday, June 14, at the Gillson Park Dog Beach.
Monday: Rainy Day
On Monday, the day of the big Blackhawks game, it poured rain. June had started off pretty wet, so I double-checked the basement and sump pump. (All good!) Then I went online to find out: istheresewageinthechicagoriver.com
The answer from the Open City app was “Yes.” Data supplied by the MWRD indicated that sewage had already started overflowing into the Chicago River, even before Monday’s rain.
Overflows from Old Combined Sewers
Digging a little deeper, I found an MWRD report for the previous 24 hours:
Combined Sewer Overflow (CSO) Map (Source: MWRD June 14, 2015)
Red lines on the map mark areas affected by combined sewer overflows (CSOs), which are as bad as they sound.
Old style combined sewers, including the system that serves Wilmette’s east side, are designed to drain both runoff (from storms) and domestic sewage (from toilets, sinks, etc.), and transport it all to Water Reclamation Plants (WRPs) for treatment.
During heavy rainfall, combined sewers are inundated by storm runoff. Eventually, MWRD treatment plants can’t keep up, and the tunnel and reservoir storage becomes full. Then sewage can back up into basements of homes and businesses connected to the combined sewers (that is, east of Ridge Road, in Wilmette).
To relieve pressure and prevent sewage backups, the combined sewers in Greater Chicago are allowed to overflow into local rivers, at a number of outfalls that the MWRD monitors. Based on the map, it appeared that Wilmette’s own combined sewer system had overflowed into the North Shore Channel (top right).
Monday Night: Wilmette Locks Open
While running errands later in the day Monday, I listened to tornado alerts on the radio, watched the downpour, and decided to check out the Wilmette locks, located just west of the dog beach in the first photo:
Wilmette Locks and Pumping Station, June 15, 2015.
The locks and pumping station separate the North Shore Channel from the lake, and force the channel to flow south into the main Chicago River. But to my untrained eye, the water level looked high. As the level rises, there’s a risk of flooding along the banks. And if the channel rises above the combined sewer outfalls, sewage could back up into the basements of homes connected to the combined sewers.
Shortly before the Blackhawks game started, I checked the MWRD Facebook page and found the announcement: “Gates opened at Lake Michigan.” When the MWRD opened the Wilmette locks, rainwater and sewage flowed into Wilmette harbor and Lake Michigan.
Tuesday: Beach Closed Due to High Bacteria
The morning after the locks were opened, the beach was closed:
Gillson Beach closed due to high bacteria levels, June 16, 2015.
For the moment, our shaggy dog would have to stay on high ground.
So far this year, there have been 10 days of CSOs. Last year had a total of 41 CSO days.
Links:
Combined sewers are likely to overflow because they’re designed to clear away stormwater, but the aging systems also take in extra stormwater due to infiltration and inflow.
More About Wilmette’s Combined Sewer Overflows
MWRD Tunnel and Reservoir Plan (TARP) to Prevent Combined Sewer Overflows
Still confused by the modern use of these controlling works. During regular weather operations – which is most of the year – the channel is kept well below the level of the lake. To my mind, this would mean that you’d only need gravity to flush the channel during regular operations. On the other end of things, during rare storm events that fill the channel, you’d only need gravity to backflow it into the lake, right? So, it’d seem to me that this structure operates more as a controlling works – like the Chicago & O’Brien locks – than as a pumping station.
In fact, the only kind of scenario I can imagine where you’d need to pump water would the rare times when the lake falls below the level of the water in the channel AND the channel’s water is for some reason deemed to be too low (though still higher than the lake). Am I not understanding something, here?
Watched a short video on the changes to the structure done over a decade ago, but didn’t really understand what they changed or why. Apparently, two of the pumps were taken out of commission, but the tunnel left open? Why? The only part I understood was the reconstruction of the lock to make emergency backflow operations easier. But the changes to the pump tunnels went completely over my head so that I still have no idea how this structure is regularly used.
I’m not an expert on the Wilmette locks. Your first paragraph, I believe, describes the typical scenario. Right next to the locks is the shaft down to the Tunnel and Reservoir Plan (TARP) system, which the Metropolitan Water Reclamation District (MWRD) built to handle combined sewer overflows during storms. So if the eastside of Wilmette gets a severe storm and the old combined stormwater/sewage system overflows, then it can flow into the TARP shaft to await processing. If there is still too much overflow into the channel, the MWRD can open the locks, draining the channel into Lake Michigan, so residential areas along the channel are not flooded. As you point out, there are probably cases where the MWRD has to use pumps instead of gravity to handle water exchange at the locks, but I’m not really an expert on this. You could try to get more information at the MWRD facebook page: https://www.facebook.com/MetropolitanWaterReclamationDistrict
Disgusting,Is what they do to lake Michigan,
The sewer will always be in the lake.
It should be a crime.