The New York City Department of Environmental Protection is installing monitoring sensors under manhole covers to alert it of elevated flow levels in sewer pipes.
It's part of a pilot program to improve performance and reliability of sewer infrastructure citywide.
Twenty-one manholes will get the new technology; 11 in Queens, five in Brooklyn and five on Staten Island.
Another 20 will be installed by spring 2013.
DEP Commissioner Carter Strickland said when elevated flow levels are detected below the roadway, crews can be dispatched to inspect and perform maintenance to stop a problem before it gets worse.
He said preventative maintenance can prevent the system from being overwhelmed during heavy rain.
The city has 7,400 miles of sewer lines.