Neighborhood News: The World's Largest Plumbing Repair - New York City's principal water-supply aqueduct gets a bypass operation.

The Delaware aqueduct, 85 miles end to end, is the longest tunnel in the world. It invisibly brings about half of New York City’s water, just over 500 million gallons per day, down from the Catskills to a holding basin in Yonkers. It’s about as old as Joe Biden, and it has not been drained for repairs since he was in high school. The stretch where it crosses under the Hudson (from Newburgh to Wappinger) passes through crumbly limestone, and it has been leaking for decades, now losing up to 35 million gallons of water daily. The best solution has been, as with many aging circulatory systems, bypass surgery. Getting down there required digging a pair of holes, 900 and 700 feet deep, then boring two and a half miles across to connect them. Two billion dollars and a decade later, that new tunnel is ready to connect to the old, and that means shutting the aqueduct off for eight months. Even just draining it so work can begin is a huge job. This summer, there were practice “dewatering events,” as the Department of Environmental Protection calls them. It’s a winter project because we use less water then.

- By Christopher Bonanos