Recent rain events in Chicago and its suburbs have overwhelmed the region's combined sewer system, sending sewage flowing into area waterways five different times since May 1, according to an alert system managed by the Metropolitan Water Reclamation District (MWRD).
While an MWRD spokesperson said combined sewer overflow (CSO) records show the region is slightly below average for this time of year, the pollution events do raise concerns with critics who said the massive project aimed at decreasing CSOs is taking too long to implement.
"The Tunnel and Reservoir project is not scheduled to be completed for another 15 years," said attorney Jessica Dexter of the Environmental Law and Policy Center. "Meanwhile, there will be unlimited amounts of raw sewage being dumped into our river every time it rains."
MWRD data also showed 330 CSO events have occurred in Chicago waterways since 2009.
MWRD said its Tunnel and Reservoir Plan (TARP), commonly referred to as Deep Tunnel and due to be completed in 2029, is already providing benefits. According to MWRD, the number of CSO events has been reduced by half since the TARP tunnels and Majewski Reservoir went online, preventing an estimated 85 percent of CSO pollution.
MWRD further expects CSOs to dramatically decrease when the Thornton Reservoir goes into service in 2015.
"So that's billions of gallons of water that would have gone into the Chicago waterways that instead will be temporarily stored," said MWRD principal civil engineer John Lemon.
To put it into perspective, MWRD said one billion gallons is equivalent to .6 inches of water covering the entire Thornton service area, which is 90.8 square miles.
Thornton will serve Chicago's south side and south suburbs and will ultimately join two other TARP reservoirs and more than one hundred miles of tunnels designed to limit floods and keep water out of basements.
Preventing floods and polluting events have been continuing concerns in greater Chicago since the late 1800s. Like many other regions of the time, the area was built with a single sewer system that handles waste water and storm water. During heavy storms the combined sewers can get overwhelmed, sending raw sewage into waterways like the Chicago River.
While the existing TARP infrastructure is helping, the problem persists.
"We paved almost everything and so storm water that used to land on the ground and be infiltrated now ends up in the sewer system which just doesn't have the capacity for it," said Margaret Frisbie of Friends of the Chicago River.
Meantime, MWRD is under increasing pressure to disinfect more of the water pumped into the waterways by the end of 2015. MWRD said current additions to its treatment plants will better clean and disinfect the water.
The ultimate goal is to make the Chicago River a destination for recreation.
Frisbie said she is confident that will happen soon.
"As long as you know after a potential rain storm that there could be a combined sewer overflow, the rest of the time the river, you know, basically keeping general protection, washing your hands, and such and so forth is pretty good, and once disinfection occurs it's going to be really good," Frisbie said.