Overview
- The Metropolitan Water Reclamation District said Monday that Thornton was about 94 percent full and McCook was at or near capacity, together holding nearly 11 billion gallons of stormwater and sewage.
- McCook has reached full capacity multiple times this year, counting six fills so far compared with five fills from 2021–2025, which shows a recent increase in strain on the system.
- If reservoirs top out, the MWRD warned that south suburban communities could see river flooding and Chicago could face combined-sewer overflows into the Chicago River because the system must release or pump stored water for treatment.
- The pressure on the reservoirs follows repeated heavy storms and soaked soils, and NOAA data show Illinois annual precipitation has increased over decades, making even moderate rain more likely to produce floods.
- Longer-term fixes include a McCook expansion that will add about 6.5 billion gallons but is not expected to finish until about 2032, prompting officials and advocates to push for more green stormwater storage and other near-term measures to protect homes and neighborhoods.