sewage overflow and permeable surfaces

Permeable Surfaces Protect Chicago’s River and Lake from Sewage Overflow


Two things happened last night that no one living in Chicago could have missed: the Blackhawks win and a deluge level rain storm. The Blackhawks: If you weren’t watching the game, you couldn’t have missed your neighbors whooping with joy and shooting off fireworks.  Everyone was happy.  The Rainstorm: you might have been walking home from work (like I was) or biking (like Chris) and drenched to the skin … or you might have had your street or basement flooded.  Maybe the rain was a fun adventure for you or maybe it was a big inconvenience.  But, that’s not all it was.

So … There’s a Sewage Overflow into the Lake, Again

Unfortunately the consequences of this kind of downpour on Chicago are more pervasive than the annoyance of a flooded street or basement.  Chicago has a Combined Sewer System, which means that the same pipes under the street carry the stormwater collected by street drains and the (human and chemical) waste that gets flushed down our indoor drains every day.  Normally all that water goes to several sewage treatment plants around the city and is cleaned and filtered before it goes back into the waterways.  When there’s too much rain, however, the treatment plants can’t handle it and extra water is released into the Chicago River.

combined sewer

This is known as as Combined Sewer Overflow and it is Gross!

And when even more rain falls (as it did last night) the engineers at the Metropolitan Water Reclamation District have to let the water overflow into Lake Michigan, flooding the lakefront beaches … and our drinking water intake pipes, with sewage.  Even the $3 Billion “Deep Tunnel” project, meant to catch and hold fast floods of water isn’t enough to hold as much rain as we’ve just gotten.

Rain, Rain, (won’t) Go Away

We can’t stop the rain from falling.  In fact, scientists think that heavy downpours (the kind that cause major flooding) will be more common in the future – another unfortunate side effect of climate change – so we need.  Check out this map of deluge level downpours around the US over time, courtesy of Climate Central.

So What Do We Do?

Buckminster Fuller once proposed putting a full weather controlled dome over Midtown Manhattan, which would have been an incredible feat of engineering (and undeniably cool) but is actually a terrible response to the elements.  Just imagine the amount of runoff that would have generated!

Instead we need to think about more holistic ways to handle the water that is going to fall.  Mostly, we need to make sure that as much water as possible stays where it lands – by soaking back into the soil and down to the water table, without getting mixed in with sewage and needing treatment in the first place, let alone overflowing into the river and lake.  The less hard surface there is in the City, the less water that hits the ground will end up in the sewers.

In the short term, try hard not to flush nasty things down the toilet or drain during a rainstorm (skip the laundry, make sure to use biodegradable soap, etc).  To plan for future rainstorms, we need more green roofs, permeable driveways and alleys, and to cut down on hard surface and paved roadways … all of these things can measurably reduce our danger of sewage overflow into the River and Lake.  As a bonus, those features also reduce Chicago’s Heat Island Effect, and keep the city cooler all summer.  Its win, win!