N.Y. DEP begins study of new method to seal cracks in Delaware Aqueduct

NEW YORK — New York City Environmental Protection (DEP) Commissioner Carter Strickland announced the start of a year-long pilot study to evaluate a new method of sealing cracks in concrete water pipes that could eventually help stop leaks and maintain the Delaware Aqueduct — an 85-mile water tunnel that conveys approximately half of the drinking water from four upstate reservoirs to more than eight million people in New York City, and 1 million people in Ulster, Orange, Putnam, and Westchester counties.

A Syracuse University lab test, funded in part by DEP, demonstrated that introducing lime and other chemicals into water flowing through concrete pipes can effectively seal hairline cracks and reduce leaks. In August, DEP began a $4 million proof of concept experiment at the Rondout Reservoir that will simulate actual conditions in the Delaware Aqueduct and determine if this new leak sealing technique can be applied on a larger scale.

“The Delaware Aqueduct is a critical link between our reservoirs and the 9 million New Yorkers who rely on the water it supplies,” said Strickland. “This study is one of many investments we are making to ensure future generations have access to this precious resource, and a demonstration of our commitment to exploring every option to stop leaks in the aqueduct.”

The lime study experiment is taking place in a temporary structure on the southeast side of the Rondout Reservoir. Inside, water from the reservoir is being pumped through three 2,400-foot sections of 1.5-inch diameter pipe. Scientists are testing different flow rates to determine if the lime and other chemicals introduced into the pipes will seal cracks under conditions similar to those inside the Delaware Aqueduct. A high flow setting simulates the actual velocity of water inside the aqueduct and will help determine if lime is deposited in cracks at that speed. A lower flow setting will help scientists learn if enough lime remains in the pipe to seal cracks after it travels for approximately 80 minutes — the time it takes water to travel from the reservoir to the leaking sections of aqueduct in Wawarsing. The experiment will also help researchers assess the extent to which lime deposits build on the walls of the pipe, which can reduce capacity in the aqueduct.

As water flows through the test pipes, modules spaced in 800-foot intervals simulate different-sized cracks, and monitor changes in pressure that allow researchers to determine if those cracks are being filled. The experiment will also help calculate appropriate lime dosage and which chemical combinations are most effective at sealing cracks. Chemical combinations being examined include: lime, lime with carbon dioxide, “liquid lime” which uses calcium chloride, sodium hydroxide, and carbon dioxide.

Water exiting the experiment site will be treated and then discharged back into the reservoir. All water reintroduced to the reservoir will be permitted by the New York State Department of Environmental Conservation and will not have any adverse effects on the New York City drinking water supply.

The pilot project is part of Water for the Future, a comprehensive $2.1 billion plan to fix the leaking Delaware Aqueduct. The plan includes construction of a three-mile bypass tunnel around a portion of the aqueduct that is leaking in Roseton in Orange County, and repair work to sections that are leaking in Wawarsing in Ulster County. DEP plans to break ground on the bypass tunnel in 2013, and expects to complete the connection to the Delaware Aqueduct in 2021.