NACWA was pleased to honor the Metropolitan Water Reclamation District of Greater Chicago (MWRDGC) this month with a National Environmental Achievement Award for Operations & Environmental Performance with its McCook Reservoir Stage 1.

Within the service boundaries of MWRDGC lies a combined sewer area of 375 square miles. The biggest challenge of managing combined sewers are storms that can cause combined sewer overflows (CSO) that contaminate waterways and cause flooding. Two of the main missions of the MWRDGC are to improve the quality of water in watercourses in its service area and to protect businesses and homes from flood damages.

On December 4, 2017, Stage 1 of the McCook Reservoir was completed and placed into operation.  The reservoir passed its first significant test when more than 2.5 inches of rain fell on the Chicagoland area on February 19, 2018, and approximately 3 billion gallons of CSO were diverted to the newly completed McCook Reservoir Stage 1, preventing this polluted water from discharging to area waterways and/or surcharging the sewer system and flooding some of the 3.1 million people within the service area.

TARP is the Chicago area’s CSO long term control plan for cost-effectively complying with Federal and State water quality standards. TARP’s main goals are to protect Lake Michigan – the region’s drinking water supply – from raw sewage pollution; improve water quality of area rivers and streams; and provide an outlet for floodwaters to reduce street and basement sewage backup flooding.

Stage 1 of the McCook Reservoir can hold 3.5 billion gallons of storage capacity and will protect residents of Chicago and 36 suburban communities from flooding. It can provide an estimated $114 million per year in flood reduction benefits, while also capturing untreated water that formerly overflowed into waterways in rainy weather. After the storm subsides, the polluted water is pumped from the reservoir to the MWRDGC owned Stickney Water Reclamation Plant to be treated and safely discharged to the environment.

From December 2017 through September 2018, MWRDGC witnessed a total of 28 storm events within the Chicagoland area, bringing 22 inches of rainfall. Due to those storm events, the McCook Reservoir Stage 1 has successfully captured approximately 20 billion gallons of combined sewage. All that combined sewage was then pumped out of the reservoir, treated at the Stickney Water Reclamation Plant, and safely discharged to the waterways.

As a result of this project and other water quality enhancements, Chicago area residents now see the river system as a major asset. Marinas, riverfront trails and riverside restaurants abound; river recreation and tourism are on the rise; and game fish have returned to the Chicago Area Waterway System.