Under-river pipeline needed to stop sewage going into the Des Plaines
Karen Sorensen | 7/16/2014, 4:24 p.m.
The city of Joliet is seeking a state loan of more than $31 million to prevent millions of gallons of raw sewage from being dumped in the river or coming up in manholes during heavy rainstorms.
Known as the Combined Sewer Overflow Elimination Program, the project calls for construction of an 8-foot to 10-foot tunnel below the Des Plaines River so sewage does not mix with storm water runoff when the city’s water treatment system is overwhelmed during big rainfalls.
On the west side of the river, a new interceptor pipeline and screening facility will grab large items – tree branches, discarded belongings and the like – before they go into the tunnel, Public Utilities Director Jim Eggen said. On the east, a new wastewater treatment plant/pump station will replace the East Side Wastewater Treatment Plant near River and Davis streets, which was built in the 1950s, Eggen said.
It’s a massive undertaking, and what’s proposed is just phase two of what could end up being a $70 million project, he said.
Beyond that, it’s not optional. The city has known for many years that the project would have to be undertaken and has some reserves with which to repay the loan it’s seeking, Eggen said. If the city did not act, the IEPA would and the result could be a court order in which a judge would mandate that water and sewer rates be increased to pay for the work immediately.
Instead, the city will obtain a 2.25 percent interest loan from the state to allow the work to be funded over 20 years, Eggen said.
Joliet’s not alone
More than 770 towns in the United States, most of which are older communities that built their sewer systems before 1950, still have combined storm and sanitary sewer pipelines that must be replaced.
When it was built, Joliet was a much smaller city and regulations on sewage overflow not as regimented. The 36-inch pipeline under the river – and its capacity of 8 million gallons a day – was deemed sufficient to handle storm water and waste coming from the west side to the east side treatment plant, and there was no requirement the two waste sources be kept apart.
And on most days, there is no problem, Eggen said. That’s not true during a period of heavy rainfall, however, when the pipeline gets overwhelmed by rain water and as much as 85 million gallons gets pushed into the system, he said. The relief valve is the waste water being dumped into the river either at the treatment plant or manholes on both sides of the river, he said.
Historically, overflows have occurred 34 times, with 17 occurrences taking place between 2009 and April 24, 2014.
How it will work
Construction of the interceptor/screening facility south of the Interstate 80 bridge will begin first, followed by the underground tunnel, which will be undertaken in 2015 and could take anywhere from 18 to 24 months to complete, Eggen said. It will be located 20 to 25 feet below the bottom of Des Plaines to ensure it does impact the river.