"You have a whole system that carries water to TARP, and you can't logistically enlarge every pipe," St. Pierre said in a recent interview. "So you really have to think about different ways to manage water, including developing a kind of hybrid where we keep water out of the [sewers] and modulate it, so the system can handle flows gradually over time."
Such a system is under construction at sites south of downtown Chicago, where MWRD and the Army Corps of Engineers are building two of the largest catch basins ever conceived. The basins, essentially deep quarries hollowed out by dynamite and earth excavators, will be able to hold an estimated 15 billion gallons of stormwater, which engineers believe should contain runoff from virtually any storm event.
When completed in 2029, the two new reservoirs, known as Thornton and McCook, will join an existing 350-million-gallon catch basin near O'Hare International Airport that since 1998 has helped avoid $250 million in flood damage, according to MWRD officials.
Last year, the Obama administration solidified that plan under a consent decree among the Justice Department, U.S. EPA, the Illinois EPA and MWRD. The agreement, which is awaiting court approval, came years after U.S. EPA first notified Chicago authorities of MWRD's massive Clean Water Act violations and imposed a new timetable for completing the reservoirs.
According to MWRD, most of the reservoir capacity -- roughly 11 billion gallons -- will be in place by 2017, including the 7.9-billion-gallon Thornton reservoir, which will trap sewer overflows from the highly industrialized Calumet-Saganashkee Channel, which links the Port of Chicago to the Chicago Sanitary and Ship Canal.
Reservoirs added, but construction moves slowly
But environmental groups, some of which have fought for decades to force MWRD to eliminate combined sewer overflows, remain dissatisfied with the settlement as drafted. They want a federal judge to require more of MWRD, including that the Thornton and McCook reservoirs be finished on a much shorter timetable than the consent decree currently allows.
Jessica Dexter, a staff attorney with the Chicago-based Environmental Law & Policy Center, said TARP, which was conceived in 1972 -- the same year the Clean Water Act became law -- has become an administrative dead weight that MWRD has been unable or unwilling to carry through to completion.
"Over the course of years, the deadlines keep slipping back and back and back," Dexter said of the plan. "We think they can be more ambitious with it."
The Deep Tunnel portion of TARP, for example, came online in 2006, after decades of start-and-stop excavation work that was subject to changing political and budgetary priorities.
Among their complaints, outlined in a March 21 letter to the Justice Department, is that federal regulators simply endorsed MWRD's "status quo" planning schedule for completing the reservoirs by 2029, which would make TARP a 57-year project.
By comparison, the nation's largest public works project, Boston's Central Artery/Tunnel, or "Big Dig," was conceived around the same time as TARP and completed in 2007 at a cost of roughly $15 billion.
Dexter and other critics say there's no reason to spend another 17 years digging reservoirs when Chicago's stormwater management challenges are growing more daunting by the year. If TARP is to be the first line of defense against sewer overflows, the argument goes, it should be deployed much faster.
"We need to finish what we started in 1972, and do it as quickly as we can," Dexter said.
Part of the problem, according to critics like the Environmental Law & Policy Center and the Natural Resources Defense Council, is that the reservoir construction schedule is tied to a vendor contract that allows excavation to speed up or slow down based on how quickly the limestone being mined from Thornton and McCook sites can be sold.