One of the few mistakes that were made when the Delaware Aqueduct was built in the late 1940's had to do with lining the concrete tunnel. The pipe, 85 miles long, runs mainly through shale, a rock that supports tunneling. But in two places the aqueduct runs through limestone, which, according to Department of Environmental Protection spokesman Adam Bosch, "is crumbly and not supportive of tunneling." In fact, limestone absorbs water, which is why the engineers at the time decided to line these sections with steel.
But, they didn't line them all the way through the limestone sections. Cracks and small holes in the concrete have since developed. What this means is that up to 35 million gallons of water are being lost each day.
The DEP is now working to correct this mistake. The holes in the pipe are in Warwarsing, a town in Ulster County, and will be filled with grout. But the main leaks are in Roseton and are much more serious. The cracks cannot be easily sealed. A major construction project has been undertaken by the DEP that will take 7 years and cost and approximately $1.5 billion. A 2.5 mile bypass pipe will be connected to the original tunnel, run under the Hudson River and reconnect with the aqueduct lower down.
To complete the job, the Delaware Aqueduct will have to be turned off for six months, meaning that the city will have to draw more water from other sources, and take conservation measures.
For more details, listen to the story and go to the companion article, "Your Role in Fixing a Leak in the World's Longest Tunnel," at CityLimits.org.