NEWBURGH, N.Y. - All along the East Coast, persistent drought has shriveled streams like never before. But tucked in the woods 70 miles north of New York City, a circular pool of fresh, clear water spills into a sparkling brook that runs downhill to the Hudson River.
No matter how dry the weather, gauges measure a flow of between 4 million and 6 million gallons a day.
No one is thrilled, however.
The sinkhole and half a dozen other springs and wet spots nearby are fed by leaks 600 feet underground in one of the most important water tunnels in the world, the 85-mile Delaware Aqueduct.
This 55-year-old tunnel carries, on average, half of New York City's daily supply of a billion-plus gallons of water from reservoirs along the Delaware River where it rises in the Catskill Mountains. It also supplies this town and dozens of others along its route to the city.
At certain times of the year, the tunnel carries 90 percent of the water for the 9 million people served by the sprawling 19-reservoir water system, which is considered an engineering marvel of the industrial era.
When the tunnel is at full capacity, about 36 million gallons a day escape through uncharted breaks in the cement and steel lining, engineers for the city say. That might not seem much in a billion-gallon-a-day system, but the leak equals the total water usage of the city of Rochester, N.Y.
A new urgency
And, with New York City and surrounding communities preparing to enact drought emergencies in coming weeks requiring strict water conservation, fixing the leak has taken on new urgency, even though city officials acknowledge that inspections and repairs could take several years.
"It's particularly true in a drought, but you hate to see that kind of water lost at any time, given what went into building that aqueduct and the reservoirs," said Diane Galusha, who chronicles the deaths of 79 workers during construction of the Delaware tunnel in her book Liquid Assets: A History of New York City's Water System (Purple Mountain Press, 1999).
The leaks have grown substantially since they were first noted by city engineers and consultants in 1991. In 1995 and 1996 alone, the leakage rate when the tunnel was running full bore grew from 25 million gallons a day to 34 million gallons a day, engineers reported.
After 10 years of analysis and preparations - a period environmental groups and some city elected officials say took far too long - the repair effort is proceeding rapidly.
It is risky and elaborate, and includes roles for deep-sea divers, robots and pilots flying with heat-sensing cameras that can detect chill tunnel waters as they seep to the surface.
The project began in the fall of 2000, when city water officials started developing a contingency plan "in case of tunnel failure," according to one city memo - on the theory that the leakage might be weakening overlying rock sufficiently to close the 13-foot- diameter tunnel entirely.
This plan would include requiring upstate communities that tap 125 million gallons a day from the city system to shift to local sources, sharp restrictions in the city and temporarily using other supplies that are not as clean as the water from the distant Catskills.
No 'imminent danger'
But recent engineering studies show no signs that such a calamity looms, said John McCarthy, a senior engineer at Malcolm Pirnie Inc., the engineering company hired by the city to conduct the investigation and make the repairs. The first stages of the project could cost more than $27 million.
"There is no evidence in all the investigative work we've done that the tunnel is in any imminent danger," McCarthy said.
The potential for problems was evident even in the years before World War II, as armies of "sand hogs," the underground workers who specialize in tunnel digging, cut their way deep into the limestone that leads from New York's forested mountains to its concrete canyons.
The Delaware branch of the three-pronged city water supply was the last to be built, with final elements finished in 1967. It captures the water from the upper reaches of the branches of the Delaware River and stores them in four reservoirs west of the Hudson.
At the Rondout Reservoir, the water plunges 1,000 feet and enters a 45-mile stretch of the tunnel, which cuts east beneath scrubby rock ridges, fast-spreading exurbs and hillside apple orchards before it crosses far below the Hudson.
On the east side of the river, the Delaware water rises through shafts and fills another storage reservoir before it flows south through more tunnels and holding basins to city taps.
The system is a hydrological triumph, allowing most of the city - even buildings up to 12 stories high - to be supplied by gravity alone. But right from the start, geologists noted two spots where the landscape dipped along the initial 45-mile route, identifying weakened areas of faults and cracks deep below. One was in Wawarsing, a rural community east of the mountains, and the other on the northern edge of Newburgh, an old river town on the west bank of the Hudson.
The most worrisome spot, by far, was the one on the riverbank. Two separate faults intersect there precisely where the tunnel diggers drove under the river. In the understated argot of engineering, reports cited the area's "unfavorable geology."
As the diggers proceeded, they had to inject cementlike grout into the rock ahead of them, trying to glue the fractured spots together before moving ahead with the excavation.
To prevent leaks, engineers added heavy steel liners, nests of reinforcing steel bars and extra layers of concrete.
The Delaware water began to flow in 1945 and all was well. In 1958, the last time the aqueduct was drained, inspectors drove the entire length of the tunnel in a modified jeep and found some small leaks, but nothing significant.
They did, however, notice some problems in the long stretch far beneath the Hudson. "The concrete lining in this area which is directly under the Hudson River has numerous cracks in addition to those that are contributing to the inward leakage," the inspection report noted.
By the 1990s, concerns were growing rapidly, but quietly. The city never publicly discussed the problem until lawyers for Riverkeeper, a private environmental group, spent 18 months wresting documents under the Freedom of Information Act.
Among them were reports by Victor Feigelman, a longtime engineer for the city and later a consultant, who noted starting in 1991 that significant leakage had developed.
The city conducted tests introducing harmless dye into the tunnel and timing how long it took to surface in the Newburgh sinkhole and other spots. Consistently, it took the dye less than an hour to migrate from the tunnel up through 600 feet of rock to the pool.
A new problem
Even as the extent of the leaks became clear, the city identified a new problem that might prevent repairs. A shaft east of the Hudson, which is used in the rare instances when the tunnel is drained, had a leak somewhere in the bronze gates and valves where it joined the tunnel 700 feet underground.
In December 2000, a repair operation began that was as dangerous and hair-raising as a spacewalk. Deep-sea divers, far out of their usual element, descended 70 stories into the 13-foot-wide shaft in a 12-foot-wide diving bell. Alternating teams spent five days inspecting and finally repairing a half-inch hole where a metal plug had popped out of a fitting.
More analysis led to a plan to use a self-propelled craft to inspect all 45 miles of the tunnel where the leaks are suspected. Oceanographic engineers are building a 400-pound mini-submersible, which they plan this fall to lower 1,000 feet into the vertical shaft leading to the tunnel's upstream end.
The torpedo-shaped device, programmed to stay dead center in the tunnel, will use five digital cameras to record every foot of the lining as it heads downstream and, 45 miles later, is plucked out through another shaft by a tethered submersible robot.