THE HOLLAND TUNNEI. GRAY AND HAGEN 585 



smooth, resilient, and lon^-wearinf; surface that will help to deaden 

 the sounds due to trallic, and he more quickly repaired than concrete. 



Each side of the roadway is lined with a j^aanite curh, the roadway 

 havin*; a transverse slope from one side to the other, with a de- 

 pressed concrete gutter hehind the curbstone on the low side with 

 side inlet openin<;:s at frequent intervals. The drain connects witli 

 a sump at the low point of the tunnel, from which a dischari^e pipe 

 is carried umler the roadway of each tunnel to the New York River 

 shaft. Intercepting sumps with pumping equipment are provided 

 in all the river and land shafts. 



The tunnel is lighted by electric lamps located in the side walls of 

 the tunnel immediately below the ceiling slabs. A continuous water 

 main is provided throughout the entire length of each tube, with hose 

 connections for fire protection and flushing at frequent intervals. 



The walls are lined with white tile, care being taken to eliminate 

 all tile containing blue, green, or red tints, upon advice of a " color 

 psychologist,'' on account of its " depressing effects." The color of 

 the borders is a light orange. The ceiling is painted white. 



The tunnel, with its twin tubes, 29 feet 6 inches in diameter, is the 

 largest subaqueous tunnel in America, exceeding by G feet G inches the 

 Pennsylvania Railroad tubes. On the New Jersey side, the diameter 

 of one of the tubes is increased to 30 feet 4 inches to meet ventilation 

 requirements. This exceeds by 4 inches the diameter of the Rother- 

 hithe Tunnel under the river Thames, London, England, which has 

 boon the largest subaqueous tunnel in the world. 



The shield method of construction was adopted for the Holland 

 Tunnel after careful consideration of other schemes, notably the 

 trench method. By the trench method, the work is conducted from 

 a plant floating in the river, and the tunnel is constructed either 

 under a protecting roof or floated into position and sunk in sections 

 in a dredged trench. The longest subaqueous tunnel built by this 

 method is the Detroit River tunnel of the Michigan Central Rail- 

 road. 



It was recognized that in the excavation of a trench under the 

 Hudson River, there would be an unavoidable interference with a 

 great volume of river traffic. Fifteen hundred boats cross the line of 

 the tunnel daily. Such congested river conditions would make every 

 dredge or other machine working in the tunnel an obstruction to 

 traffic. Collisions would be frequent, increasing the time and cost of 

 the work, with danger both to shipping and to the equipment of con- 

 struction. Storms, fog, and ice would cause a discontinuance of sur- 

 face work for at least two months of each 3"ear. At the New York 

 end, a large mass of ledge rock, involving blasting and removal at 

 great depth, would be a serious obstacle to open-trench excavation 

 under water. 



