Using the Hudson to Cool the Trade Center

A critical lifeline to the new World Trade Center from the very old Hudson River — four water pipes large enough for workers to crawl through — is nearing completion along West Street.

The pipes now extend from the Battery Park City bulkhead to the foundation wall on the west side of the trade center site. They will deliver cool river water — up to 30,000 gallons a minute at the peak — to the center’s chiller plant and then discharge it back into the river.

The $200 million chiller plant will cool and dehumidify air in the exhibition halls of the National September 11 Memorial and Museum, in the Transportation Hub and its tentacled passageways, in the shopping concourses, at the vehicle security checkpoints and in the performing arts center, should one be built.

The construction of the pipeline is therefore a key element in the overall redevelopment of the site, since it will help make those public spaces habitable.

“We built it for a hundred years,” said Paul W. Johnke, senior program manager in the World Trade Center construction division of the Port Authority of New York and New Jersey, who is overseeing the chiller plant and river water project. He said this was a reasonable life expectancy, given the design of the new piping and the fact that much of the original pipeline survived 9/11.

The chiller plant should begin operating in late 2011 and expand in phases with the tenants. “As they come on line, we’ll be ready to handle it,” Mr. Johnke said.

Looking out river water pipe to World Trade Center.David W. Dunlap/The New York Times Looking out from a water pipe into ground zero.

As first envisioned, the chiller plant would have cooled the entire new trade center complex — office towers and all — as the earlier system did. Environmentalists objected because so many small fish and fish eggs would have been sucked into the system and so many larger fish would have been trapped against the intake screens.

The Port Authority ultimately chose to use more traditional rooftop cooling plants for the office towers. Consequently, the river water system will use a peak of 30,000 gallons a minute at most; 24 percent of the maximum flow of the original system.

“We are satisfied with the result,” said Reed W. Super, a lawyer for the Riverkeeper environmental group. “Ideally, no Hudson River water would be used for cooling purposes. But we got the drastic reduction we asked for.” He said that over the course of a year, the number of fish sucked into the system would drop more than 80 percent and the number trapped on the screens by more than 90 percent.

Water entering the pipeline may range in temperature from the low 40s to the high 70s. After passing through a heat exchanger that separates the river water from the chilled water used to absorb heat from the air, the river water is discharged into the North Cove of Battery Park City. By state permit, it cannot exceed 91 degrees.

There will be times in fall, winter and spring when the natural coolness of the river water will eliminate the need for further mechanical chilling, Mr. Johnke said, thereby conserving energy.

As the environmental controversy subsided, a logistical challenge emerged, since the most crucial length of pipeline that needed replacement was in the path of the state Department of Transportation’s reconstruction of West Street, which also serves as Route 9A.

Rather than bureaucratically obstruct the pipeline work under the highway, the transportation agency took over as the construction manager for the Port Authority. “That’s our bread and butter: utilities and roadways,” said Joseph T. Brown, the Route 9A project director, “and that would allow us to progress the work years ahead of schedule.”

A joint venture of the Tully Construction Company and E. E. Cruz & Company performed the work in six months. As recently as late January, the four 42-inch pipes were still visible at the edge of the trade center site. Now, the only way to see them is to crawl inside, as Mr. Johnke did the other day with Peter J. Mazza, the engineering counsel to the Tully/E. E. Cruz venture.

“It’s all encased in concrete, and there’s a fiberglass protective wrap around it,” Mr. Mazza said as he surveyed the claustrophobic steel cylinder. The fiberglass was tested to ensure it was uninterrupted, he said, adding: “Then we were allowed to pour the concrete, which goes over epoxy-coated rebar. So — this baby will be here a long time.”