The deep tunnel system is filling up once again, especially the stormwater reservoir in McCook. The system's second largest reservoir, McCook, is 95% full after heavy storms swept through the area Sunday night. The McCook Reservoir reached capacity five times between 2021 and 2025. Riverside is one of the communities that relies on the McCook Reservoir. In addition to people using less water when heavy storms hit, Berkelhammer said more green infrastructure could help ease the burden on the system.