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 river (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........