Sandhogs, Fresh Air and the Holland Tunnel

An engineering marvel provided the first direct link for autos between New York and New Jersey

By Serusha Govender

The biggest challenge, it seemed, was figuring out how to breathe. Though there were many dangers in digging through solid bedrock 28 meters below the Hudson River, chief engineer Clifford Milburn Holland was most apprehensive about adequate ventilation. It would prove a justifiable concern.

The Holland Tunnel took seven years to complete. (New York Public Library Digital Collections)

The Holland Tunnel took seven years to complete. (New York Public Library Digital Collections)

Commissioned in 1906 to link New York to New Jersey at a time when travel between the two was restricted to ferries, the Holland Tunnel was an unfathomably bold project. Authorities decided a tunnel option was preferable to a bridge, and cheaper. The sheer scale of the underground venture was unprecedented: No ventilation systems existed for tunnels of such length—the northbound tube would be 8,558 feet, the southbound tube 8,371 feet. In addition, no tunnel had ever conveyed vehicles for such a great distance. Even Thomas Edison said it might be impossible to remove exhaust fumes from and provide clean air to such a long tunnel.

Holland Tunnel workers entering the Spring Street lock in 1921. (New York Public Library Digital Collections)

Holland Tunnel workers entering the Spring Street lock in 1921. (New York Public Library Digital Collections)

When construction began on March 31, 1922, Holland prevented the Hudson’s waters from seeping into the tunnel by constructing a series of airlocks, creating a high-pressure environment that would keep the excavated tunnel rigid while construction workers, called “sandhogs,” dug ahead. The workers would descend level by level through each airlock into the tunnel, where the pressure was held at 47.5 pounds per square inch (similar to the air pressure in a mountain bicycle tire). Because of the intense pressure, the sandhogs were eventually restricted to half-hour shifts, twice a day. Exiting demanded a controlled decompression to avoid the bends (during which nitrogen bubbles form in the blood, sometimes leading to lethal aneurism). Although 756,000 decompressions were performed during the seven years of construction, only 528 cases of decompression sickness were recorded—and no deaths occurred as a result.

Once the tunnel became fully functional, ventilation posed new challenges. Holland was not sure how to remove the fumes exuded by thousands of cars—particularly carbon monoxide, which could asphyxiate drivers if it built up. Earlier, shorter systems conventionally blew air from one end to another. But tunnels this length would require gale-force winds. And what if there was fire? The system would create an underground inferno, incinerating everyone inside the tunnel. Holland and his team began a parallel construction project on a pioneering system that could extract the car fumes safely and pump in fresh air.

Holland designed an innovative ventilation system to keep fresh air flowing through the tunnel tubes. (New York Public Library Digital Collections)

Holland designed an innovative ventilation system to keep fresh air flowing through the tunnel tubes. (New York Public Library Digital Collections)

The system was inspired by shorter versions Holland had observed in Germany, England and Scotland. But his system was far grander, with four ventilation buildings and 84 massive extractor fans, driven by powerful electric motors, that completely changed the air inside the tubes every 90 seconds. Holland designed two additional layers of tunnel to be built above and below the main traffic tunnel; exhaust fumes were funneled out through the upper layer, and fresh air was pumped in through the bottom via ducts constructed in the bedrock. Four ventilation towers, two on either side of the Hudson River, housed the fans.

Holland’s designs proved groundbreaking, but Holland himself did not see them come to fruition. He died of a heart attack on the operating table while undergoing a tonsillectomy in Battle Creek, Mich., a day before a demolition united the tunnel tubes, one stretching from New York, the other from New Jersey. The project was taken over by Milton Freeman, who died of pneumonia after only several months on the job. Finally, engineer Ole Singstad oversaw completion of the tunnel, refining Holland’s ventilation system, and opening the tunnel for business on Nov. 14,1927.

Today the Holland Tunnel is the second longest continuous underwater vehicular tunnel in North America. Although it is no longer known as the Eighth Wonder of the World, it was designated a National Historical Landmark, becoming the 92nd such landmark in New York City. Few architectural endeavors are named after the engineers that designed them, especially if those projects are nationally funded. But after a barrage of requests from his compatriots, the American Society of Civil Engineers conferred the honor, renaming the Hudson River Vehicular Tunnel the Holland Tunnel in 1924.

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