Like any other major city, underground infrastructure serves as the lifeline for New York – from the steam and gas pipelines for heating and cooking, to the subways and vehicular tunnels that efficiently move people and goods through the metropolis.
However, one infrastructure network stands above the others – water.
Fresh and clean drinking water is our most fundamental need, and assuring its availability is naturally at the forefront of city planners. It is no surprise then that New York City is investing in one of the largest capital improvement projects in its history to ensure a safe and reliable drinking water source.
When completed, City Tunnel No. 3 will provide New York City with an alternative source of water delivery; reduce peak flows; facilitate the repair and inspection of the City’s two existing tunnels; and increase its ability to deliver water to consumers. The project, which will eventually span 60 miles, is expected to be completed at a total cost of $5.5 billion to $6 billion.
To learn more about the project, TBM spoke with Burjor Kharivala, P.E., Chief Tunnel Engineer for the New York City Department of Environment Protection (DEP), which is designing and overseeing construction of the tunnel. Kharivala was with the Board of Water Supply when the project started in 1970 and has spent much of his career working on the monumental project. The Board of Water Supply was later merged with DEP.
Originally from India, Kharivala came to United States to study, earning a civil engineering degree at Marquette University in Milwaukee and a master’s degree in structural engineering at The City College of New York. He started working for the City within the Department of Public Works in 1963, and after a stint working for a consultant, he rejoined the City within the Board of Water Supply in 1968. Following a project in Staten Island, Kharivala was assigned to City Tunnel No. 3 as the project began ramping up.
Background of the New York Water Supply
New York City’s water originates as far as 125 miles north and west of the city in three watersheds. For most of the 20th century, water had been conveyed into the city by City Tunnels Nos. 1 and 2 — constructed in 1917 and 1936, respectively. As early as the 1950s, the City realized the need for a third tunnel to meet the growing demands on the water supply system.
City Tunnel No. 3 will not replace the existing two tunnels. The operation of the new tunnel will also allow inspection and repair to take place in the existing two tunnels for the first time since they were put into operation — ensuring that the reliability of the system will continue for years to come.
Broken up into four stages of construction, City Tunnel No. 3 travels 400 to 800 ft below the streets of New York City. The first stage, a 13-mile stretch of 24-ft diameter concrete-lined pressure tunnel (which steps down in diameter to 20 ft) was constructed through bedrock 250 to 800 ft below the bustling streets of New York City. Completed in 1998 and costing more than $1 billion to construct, this first stage now extends from Hillview Reservoir in Westchester, through the Bronx, northern Manhattan, Queens and across Central Park. Tunneling for Stage 1 was completed by drill-and-blast methods. Remaining stages are being completed with TBMs.
Stage 2 comprises two sections, a Brooklyn-Queens leg, and a Manhattan leg that was activated in 2013. Various shaft construction and tie-in work remains before final completion. With final completion of Stages 1 and 2, DEP will have the ability to bypass one or both of City Tunnels No. 1 and 2, which will allow for inspection and any needed repairs.
Stage 3 includes the Kensico-City Tunnel, which involves the construction of a 16-mile long section extending from the Kensico Reservoir to the Van Cortlandt Valve Chamber in the Bronx. Stage 4 involves a 14-mile section that runs from the valve chamber in the Bronx under the East River and into Queens.
Starts and Stops
When DEP (still known as the Board of Water Supply at the time) began building City Tunnel No. 3 in 1970, it issued a $225 million tunnel contract (about $1.4 billion in today’s dollars) to get the project underway. The drill-blast project had an expected duration on the order of five years. Problems began quickly, however, as the contractor was overshooting the rock, requiring additional concrete – and expense – to line the tunnel. When inflation began to spiral upward in the mid-1970s, the contract was doomed and work was halted.
As a result of the financial crisis at the time, New York City was nearly bankrupt and City Tunnel No. 3 contracts were put on hold. When the city began to get back on its feet in the early 1980s, work resumed, culminating with the issuance of 16 contracts to complete Stage 1.
“The City learned several lessons after issuing the first tunnel contract,” Kharivala said. “The City decided to issue smaller, shorter duration contracts when possible, and it introduced a clause into the contracts that would require the bonding company to get another contractor to finish the job in the event of a default.”
Beginning with Stage 2, sections of City Tunnel No. 3 were constructed using TBMs. Interestingly, the city had previous experience with a TBM in the 1960s for the Richmond Tunnel connecting Staten Island and Brooklyn. Unfortunately, TBMs were still an unproven technology at the time and the machine failed to perform as expected, Kharivala said. As a result, the contractor pulled the machine out and finished the contract by drill-and-blast.
DEP is unique in that it designs most of its projects using in-house staff. In fact, that was one of the reasons that when he returned to the City in the late 1960s, Kharivala chose the Board of Water Supply. “That was the only agency that did design work in-house,” he said. “Still today, we do most of the tunnel design work in-house. For us it works well. We don’t have many change orders, and the people who are designing the projects are still going to be there in 10 or 20 years, so they are very careful to check and re-check the designs. A consultant may be able to provide the designs quicker, but using in-house staff costs less and the quality is very high.”
Between Stages 1 and 2, city engineers have designed and overseen the construction of about 30 miles of tunnels with diameters ranging from 10 to 24 ft, along with more than 30 shafts 500 to 800 ft deep with a finished diameter of up to 33 ft and three control chambers – the largest being Van Cortlandt which measures approximately 600 ft long, 40 ft wide, 40 ft high and 250 ft below grade. “Not once did we have to pull back a contract,” Kharivala said. “When we issued a contract, it was built according to the contract.”
When you consider the complexity of the New York City water system, which spans miles of tunnels, reservoirs, valve chambers, connecting shafts and treatment facilities, often the hardest part doesn’t have anything to do with building projects – it is finding work sites in Manhattan. “I had to spend a great deal of time working with politicians and residents to find a piece of land to build the shaft,” Kharivala said. “Sometimes we would manage to get a parking lot, but sometimes he had to sink a shaft in the sidewalk. Naturally, nobody wants construction in their backyard, so getting land was very, very difficult.”
As the designer of record for many City Tunnel No. 3 projects, Kharivala is spending his time these days helping young engineers learn the tricks of the trade as DEP continues to design its own work. “I designed the shafts for the Delaware Aqueduct repair project (Rondout-West Branch Bypass Tunnel, which will allow DEP to repair a leaking section of the pipeline 60 miles north of the city) but now most of the new jobs are being designed by young engineers,” he said.