It is an amazing project with a prosaic name. City Water Tunnel No. 3 will run from Yonkers to all five boroughs of New York City. Along its 60-mile route, it will deliver more than 1 billion gallons of drinking water per day to the city’s 7.3 million inhabitants.

The New York City Department of Environmental Protection is leading this massive and complex project. NYCDEP started construction on the tunnel in 1970 and expects to complete the project by 2020 at a cost of $5.5 to $6 billion.

NYCDEP is constructing the project in four stages.  It has completed stage 1, which runs about 13 miles and went into service in 1998. During that year, it began construction on the 8.5-mile Manhattan section of Stage 2, which runs from Central Park to Lower Manhattan. (Distances and estimates are from NYCDEP Fact Sheet City Water Tunnel No. 3)

NYCDEP would construct stage 2 by using a 450-ton tunnel boring machine that would chip through Manhattan’s crystalline bedrock, creating the 19-foot-diameter tunnel. The machine could grind away at a rate of at least 50 feet per day. Work would proceed more than 500 feet below street level, leaving those above undisturbed and largely unaware of the subterranean activities.

But the project was causing safety concerns. With twenty-four fatalities during stage one and the first sections of stage two, the tunnel was taking one life per mile. And operating such a massive cutting machine would demand new precautions.

Creative Science

To help address these issues and get the job done on time, USGS scientist Frederick Stumm began working on the project.  In cooperation with NYCDEP, Stumm began his efforts to help define the ground conditions along the planned path for the tunnel-boring machine. That path had to avoid the major fractures and faults that riddle Manhattan’s 500-million-year-old bedrock. Fractures pose a hazard because they sometimes contain clay, which could bind up the machine and cause a ceiling collapse. Boring into a major fracture could also unleash a torrent of groundwater into the tunnel, delaying the project, destroying electrical equipment, and possibly costing lives.  

From street level, Stumm and his team would drill boreholes 600 feet to 700 feet deep. They would apply a dozen different borehole-geophysical techniques to locate and characterize what was ahead of the tunnel-boring machine in the bedrock.  

Using borehole radar and other borehole methods to determine the 3-D orientation of fractures, they could see 60 feet to 90 feet through the bedrock. They could determine whether a fracture ahead could release enough water to cause a hazard. Elevated gamma radiation could indicate clay, and optical scans of the borehole bedrock could show the position of those fractures and the layering of the bedrock (foliation) in 3-D. Stumm and his team combined techniques and used them in novel ways.

Public Interaction

New Yorkers are not known for being easily distracted while on the street.  But drilling boreholes and using equipment that most people have never seen before garnered dozens of inquiries from passers-by each day.  Stumm describes the experience as “like working in a fishbowl.”

“Interest from the public has been considerable,” Stumm said.  “People approach with curiosity and, these days, some suspicion. The overwhelming majority walk away with new knowledge and a great appreciation for the geology below their feet and what it takes to bring water to the city. This has been a wonderful opportunity to interact with the public.”

But those interactions were not the only experiences that Stumm and his team shared with New Yorkers.  They were working on the project during the morning of Sept. 11, 2001.

“We were five blocks away from the World Trade Center — our closest boreholes to the site — on that day.  We saw the first plane coming in.  We couldn’t see the impact, but we heard the explosion, then the sirens.  We didn’t know what was happening and were concerned that we might be in the way.  When the towers fell, we had to escape on foot. We managed to retrieve our truck a couple of hours later and drove out of Manhattan.”

A Success Story

NYCDEP completed the Manhattan section of the tunnel earlier this year, ahead of schedule and with no fatalities or serious injuries during 10 years of construction. In recognition of Stumm’s work, the Federal Executive Board, which represents 150 agencies in New York, presented him with its Distinguished Scientific Achievement award. Stumm’s efforts greatly assisted in finalizing the route and boring the water tunnel in Manhattan and Queens safely and ahead of schedule. Stumm received his award on May 16 at its Employees of the Year Award Ceremony on Ellis Island, N.Y.  

Stumm attributes much of the success to the cooperation of many people working together as a team. These include USGS employees Anthony Chu, John Lane, John Williams, Stephen Terracciano, and Peter Joesten, and NYCDEP employees Mike Greenberg, Masud Ahmed, Lou Huang, and Colin Johnson.