Roger Witherspoon
Dec 21, 20035 min
By Roger Witherspoon
The Journal News (Westerchester County, NY)
The Journal News
December 21, 2003 Sunday
Delaware Aqueduct leaks prompt state to study alternatives
The Department of Environmental Protection has begun a $50 million, 10-year effort
to increase water storage capacity and conservation programs for the massive
system that serves more than 9 million people in Westchester and Putnam counties
and New York City.
The project was spurred by the deteriorating condition of the Delaware Aqueduct, the
largest of three major underground water tunnels bringing fresh water from the
three watersheds serving the New York City water system. Of the 1.4 billion gallons
of water used daily, the Delaware provides 50 percent to 70 percent from reservoirs
about 100 miles north of Putnam. The remainder is provided by the Catskill
watershed upstate and the smaller Croton watershed in Westchester and Putnam.
Yet the Delaware Aqueduct is leaking up to 1.2 billion gallons per month, more than
the combined daily water usage of 13 central and southern Westchester
communities.
In June, engineers from the Woods Hole Oceanographic Institution in Massachusetts
lowered a $2.4 million autonomous sub down a 1,000-foot access shaft into the
aqueduct at Wawarsing, letting it float through the West Branch Reservoir and taking
36,000 digital photographs of the water tunnel to try to pinpoint the leaks.
"There is not a single catastrophic failure point or hole in the tunnel," DEP
Commissioner Christopher Ward said. "But it did find a whole long range of spider-
pattern cracks and liner cracks stretching about 3,200 feet. There is no single failure.
It looks like the lines of the face of an aged person, and perhaps this is just what a
tunnel this old looks like."
A departmental study of the water system estimates that with existing conservation
and alternative methods of obtaining drinking water, primarily from the Hudson
River, a shutdown of the Delaware Aqueduct could trigger a shortage of more than
400 million gallons of water daily. Meeting that need would be difficult, DEP officials
said, if the cracked section of the Delaware water tunnel either collapsed or was
closed for replacement or repairs.
The Woods Hole analysis found cracks ranging from one-tenth of an inch to 2 inches
wide in the tunnel's steel and concrete lining. Most are on the western side of the
Hudson River, but the deterioration continues under the riverbed. Tests of the rock
structure immediately surrounding the tunnel on the western side found most of it to
be intact.
"The notion of tunnel pressure blowing out a large portion of the wall is considered
geologically impossible," Ward said. But the aqueduct's wall will not last indefinitely,
he added. The DEP is gearing toward the possible need to shut down the aqueduct's
Rondout-West Branch section in 2012 and replace it with a tunnel bypass from the
West Branch Reservoir in Kent, under the Hudson River to the Roseton area in
Orange County.
"Building a tunnel bypass would be such an expensive undertaking," Ward said. "It
would cost $4 billion to $5 billion easily. It is definitely something we have to
consider, but I'm just sort of choking on having to say it, given the price."
To get a better idea of how badly the tunnel has deteriorated, the department plans
to develop a remote-controlled submarine with a 13-mile tether to perform close-up
studies of the cracked wall.
"Nobody has ever built a tether that has to be as long as this tether," Ward said.
"People have asked why we didn't do this sooner, and the answer was the
technology just wasn't there. But I'm told such technology now exists, and we hope
to have it fabricated in about a year."
The tethered sub would be able to hover next to the cracks, despite the fast-moving
water, and provide more detailed photographic and sonar information about the
breaks in the wall and, possibly, the health of the rock behind it. Ward said the new
submarine could cost about $4 million.
Ward's statements that the Delaware Aqueduct cannot be depended on to meet
long-term regional needs mark a departure from the DEP's position during the
administration of former Mayor Rudolph Giuliani that the leaks posed no long-term
risk.
"We certainly commend Commissioner Ward for recognizing the seriousness of the
infrastructure repair issues and committing the resources to developing solutions,"
said Mark Yaggi of the environmental group Riverkeeper, which frequently clashed
with the DEP in court over its watershed policies. "No one will know if or when the
Delaware Aqueduct may collapse. The only thing we know for sure is that it isn't
going to fix itself, and a collapse will be catastrophic. These steps are reassuring in
terms of securing the city's long-term drinking water needs."
Every component in the city's water system, which used hollowed-out tree trunks for
pipes until the mid-1800s, has to remain in perfect condition during the years it
takes for repairs, or the region would face even more serious water problems.
Yet, according to DEP documents, "many of these components are approaching 100
years of service without proper inspection, rehabilitation, or repair."
"The existing water supply system cannot meet system demands for the time during
which the tunnel must be taken out of service for its repair," the documents said.
To meet those needs, Ward has ordered two "dependability studies" of conservation
measures that may be taken to improve the region's water capacity. The $50 million
cost would be included in the department's capital budgets.
The issues to be studied range from giving residents rebates to purchase water-
efficient home appliances to finding ways to capture excess water.
"Right now we are losing about 10 billion gallons of water daily out of the reservoirs
because there is so much overcapacity," Ward said. "We could manage that water
better. If we could capture it in times of plenty, we could let it out when times are
lean."
During last year's drought, Ward said, residents saved 50 million to 100 million
gallons of water daily with voluntary conservation. Conservation of as little as 5
percent, he said, represents a water savings of more than 50 million gallons a day.
"When you talk of dependability, you have to look at everywhere the water might
be," Ward said. "We are trying to think more regionally than we have before."
Reach Roger Witherspoon at rwithers@thejournalnews.com or 914-696-8566.
Proposed conservation measures
* Pump up to 50 million gallons of water daily into Lloyd's Aquifer, which extends
from Long Island Sound to central New Jersey's Pine Barrens. Because of heavy rains
during the past year, the watershed's 18 reservoirs and three lakes are all
overflowing.
* An $8 million study will determine if deep wells can be sunk throughout Brooklyn,
Queens and Staten Island to tap into the aquifer and pump excess water into it. In
five years, there would be enough water stored to allow New York City to draw 200
million gallons daily for two years, if needed. The state Department of Environmental
Conservation has banned use of the aquifer for the past 18 years, and the city would
need permission to use it.
* A bypass tunnel and possible routes to take water from the Rondout Reservoir to
the West Branch Reservoir.
* Raise the height of two dams in the reservoir system, including the Croton Dam,
by 3 to 5 feet.
* Rebates to residents who purchase water-efficient dishwashers and washing
machines.
* Build desalinization plants on Long Island and along the Hudson River to convert
seawater to drinking water. The Hudson is a saltwater tidal estuary that runs more
than 150 miles from Manhattan to Troy.
* Convert the Chelsea pumping station in Manhattan into a water filtration plant that
could take water from the Hudson and add it to the Delaware Aqueduct's system.
The station would have to be capable of removing chemical contaminants such as
polychlorinated biphenyls, or PCBs, from the Hudson as well as zebra mussels and
other invasive organisms.
* Connect to water systems in Connecticut and New Jersey to augment shortfalls in
the New York City system.