An Immense Task

Hawera Star, Volume L, 7 February 1931, Page 9

An Immense Task

BORINGS for a vehicular tunnel under the Narrows, connecting Brooklyn and ' Staten Island, have been started on the Brooklyn side of the channel, says the “New York Times. ’’ This work was begun soon after the War Department had granted the permit for which application was made several months ago by the city’s Board of Transportation and its Department of Plant Structures. The tunnel under the Narrows —the gateway through the major portion of trans-Atlantic shipping enters and leaves the harbour —will be the largest of its type in the world. Its tubes will me 32 feet in diameter, exceeding those of the Holland Tunnel by two feet. In length it will be 5000 feet between ventilation shafts and 11,000 feet between portals; corresponding measurements of the Holland tube are 3500 and 8000 feet. Present estimates are that the cost of construction will be 78,000,000 dollars. The weightiest problem confronting the engineers is that of ventilation, according to Colonel J. R. Slattery, Deputy Commissioner of the Board of Transportation, which will be in charge of construction. The tremendous stretch of the tubes, which will lie 100 feet beneath the waters of the channel, will require the forcing of powerful streams of air through them to keep the atmosphere purged of gases left by automobiles. Twelve million cubic feet of air will be pumped through the tubes every minute, making necessary tubes larger in girth than those of the Holland Tunnel. The precise location of the terminal plazas has not been established in either borough. The Board of Transportation has prepared and submitted plans of entrance and exit plazas to the presidents of both boroughs. As yet the plans have not been approved. The tunnel’s chief service will be to by-pass much of the traffic between Jersey on the one side and Long Island and New England on the other, which at present is obliged to push its way through crowded city thoroughfares. Now that the War Department has approved the project, the Board of Transportation will proceed with the plans of construction, which will be presented to the Board of Estimate. Colonel Slattery expresses the opinion that work on the tunnel will begin by next July. Because of the immensity of the

New York Tunnel

To Cost Fifteen Million Pounds

task, its completion will take four years, a year more than the customary time allotment for such an undertaking. The time limit proposed by the War Department for its completion is Ist January, 1937. Colonel Slattery says it has not yet been determined whether shield construction or trench evacuation will he employed building the tunnel. Bids figured on both methods will be considered by the Board of Transportation. The two methods, Colonel Slattery believes, are equally well adapted to the construction of the, Narrows tunnel, and the choice between them will depend upon expediency and cost..

Shield construction was' used in the building of the Holland tubes, the Fifty-third and Fulton street tunnels (built by the Board of Transportation) and the Rutgers street tunnel, on which work is now proceeding.

“Although no criticism can be made of the Holland tubes, there are a few improvements which it may be possible for the Board of Transportation to make in the Narrows tunnel,” Colonel Slattery said. “We hope to introduce better lighting and to find a means of subduing the glare by using tiles of a slightly different tone. We are now looking for another type oi pavement as a substitute for the granite blocks laid in the Holland Tunnel. The ventilating system, while it will be similar, will be larger because of the greater length of the tubes. There will be vent towers near each bulkhead line and two more inland, one on each side of the Narrows. Fresh air will be forced in beneath the road and sucked out by exhaust fans in the roof of the tubes.

‘ ‘ The question of ventilation is the most important in the planning of tunnels. The first step is to find the tentative location of the tun nel and its exits. The next is to determine how much ventilation will be necessary for a given length. Then the size of the duets must be fixed so that the diameter of the tubes can be calculated. Plans must be made for the approach to the tunnels; ample plazas must be figured on. These decisions having been reached, the rest of the work is easy. While the general project of the Narrows tubes has been settled upon, the details have yet to be worked out. ’ ’