Hours before heavy rains swamped Chicago and Cook County suburbs on July 2, the region’s $3.8 billion flood-control project appeared ready as can be to bottle up storm runoff.

       The Deep Tunnel’s massive sewers, capable of holding 2.3 billion gallons, were almost empty, according to Metropolitan Water Reclamation District records.

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       At the end of tunnels hundreds of feet below the Chicago River, Des Plaines River and North Shore Channel, the McCook Reservoir — more than 20 times larger than Soldier Field — was just 17% full of raw sewage and runoff being stored until it could be safely treated.