- As Shaft 6B in Wappinger is excavated, blasted rock is loaded into buckets and hauled to the top.
A few yellow hardhats bob amid the gray sheen of the shale that has yet to be coated in concrete. It took two years of methodical blasting to delve this far. The big, gaping hole in the ground, some 34 feet in diameter, is called Shaft 6. It's 675 feet deep, 600 of those feet below sea level, just north of the Newburgh-Beacon Bridge, on the eastern bank of the Hudson River in the Town of Wappinger. This will be the end point of the new Rondout-West Branch Tunnel, where a bypass is being built to circumvent a section of the Delaware Aqueduct that has been leaking for over 25 years.
This massive pipeline carries 1.1 billion gallons of water daily from the Cannonsville, Pepacton, Neversink, and Rondout Reservoirs to the Croton Watershed and into New York City. At 85 miles, it is the world's longest tunnel, beating out recently constructed water pipelines in Finland and China. It supplies 8.4 million people in the five boroughs and another million north of the city, where dozens of towns tap into the line along the way.
Since opening in 1948, the tunnel has done its job admirably—except for two sections. One is beneath Wawarsing in Ulster County, the other below the Town of Newburgh, where the tunnel slips under the river. The aqueduct mostly cuts through shale, except for two places where it passes through more porous and permeable limestone. In those two spots, cracks have emerged, leaking up to 4 percent of the total flow—–15 to 18 million gallons a day, or 360,000 filled bathtubs—or almost double that, depending on volume. "It's not an insignificant loss," says Adam Bosch of New York City's Department of Environmental Protection (DEP), which manages the water supply. "You're putting all that work into collecting the water and protecting the water, and you don't want to be losing it through leaks."
Now a vast project more than 20 years in the making is being undertaken. It's a public works project of a rare scale, although almost nobody will notice or feel any effects: a DEP repair job that will take until 2023 to complete and cost $1.5 billion, paid for entirely by water bill revenues. It's the largest, most complex fix made to New York City's labyrinthine water system of aqueducts since its 1842 origin—a project that calls to mind the ancient Romans, who pioneered the gravity-powered methods the Delaware Aqueduct relies on. "It's the largest water supply system in the country," says deputy DEP commissioner Paul Rush. "This project impacts the place where the city gets half of its water. It's a massive project that's going on silently."
On the construction site, the scene looks even more archaic, positively Flintstonian. A giant bucket lifts the rubble from the pit through a pulley system, tipping it over the edge and into a horseshoe-shaped receptacle. The construction is padded to lessen the noise for residents nearby.
All that shale existed in the ground undisturbed for hundreds of millions of years until someone decided to name the buildings above it the Town of Wappinger and, shortly afterwards, blast the rock out. A round of explosions unloosed 10 feet of rock at a time, to be hauled up and donated to public works like Beacon's Long Dock Park or sold commercially. Once 100 fresh feet were excavated, the walls were coated by a two-story tall, spider-like machine, which rotated and spewed concrete to form a neat cylinder.
- The work platform at the bottom of the shaft, showing the excavator that is used to scoop up blasted rock.
The shaft is so deep it's several dozen degrees warmer down there than at its edge, thanks to the machinery, the lack of wind chill, and it's being over 600 feet closer to the earth's core. Around the gaping hole, the size and physics of the equipment beggar belief. Rods of rebar, the size of skateboard ramps, have been welded into pre-assembled sheets, bent to fit neatly along the new walls to fortify the concrete. The nuts and bolts being used are as big as dumbbells. Across the river, along Route 9W in the Town of Newburgh, near Marlborough, the same thing has happened, except that shaft goes 850 feet down, because it's being excavated from a bluff. It will have a large chamber at the bottom for a horizontal boring machine and sump pumps. Horizontal drilling will begin sometime in 2017, tunneling 600 feet below the river's deepest point.
The problem all this will address was first spotted in the early 1990s. A Central Hudson employee noticed bubbles along the Hudson's western bank at low tide. Water was shooting into the river from somewhere below, but it could only be seen from nearby, from a narrow strip of land cut off by train tracks. The water there was found to contain copper sulfate. Only the DEP's pipeline had used that chemical in that area to clear it of algae, but it hadn't been used since, so it could only have come from the Delaware Aqueduct. However, in the 1990s, technology hadn't yet advanced enough to pinpoint the leak's source, let alone plug a crack while it gushed vital tap water, as deep below ground as skyscrapers are tall. It would take another 20 years to figure out how to get it done.