Lining Towers

There were many problems connected with the construction of the Hoosac Tunnel. One that this page will discuss is the problem of projecting a straight line through Hoosac Mountain. When teams of tunnelers start blasting away on opposite sides of the mountain almost five miles apart, it is expected that they should meet somewhere in the middle. It was totally conceivable that both teams could miss each other and wind up in total failure. This is especially true when you are working six faces at the same time.

(East and west portal, central shaft and west shaft.)

Enter: Thomas Doane civil engineer. Tom Doane started by re surveying the mountain and building survey-lining towers that were built exactly on the line of the tunnel. In 1866 the first tower was built across the valley on the east side on Rowe’s Neck on the side of the mountain. From this vantage point the surveyor could see the tower at east portal and the top of Whitcomb Summit where the next tower was built. The next tower was built on the peak near Spruce Hill that could look directly across the valley over to Notch Mountain. From the Notch tower the surveyor could look directly back at the west portal. Each tower had a long iron pole protruding from the top and a surveyors transit inside to make exact measurements. Once the line was established over Hoosac the towers at each portal would site into the tunnel and shoot a line to a helper that would site a plumb bob hung from the ceiling. The line was carried on into the tunnel and it has been said that the error of closure was about 9/16ths of an inch in 4 ¾ miles of tunnel!

At this point we should not forget the efforts of Carl Wenderkinch civil engineer, who at central shaft hung small wires aligned with horizontal piano wires placed 1/8th of an inch apart down the shaft 1028 feet to the bottom to transfer the tunnel line to the work faces.

The measurements at west shaft would also prove to be a problem. Because the west shaft was smaller the double wire down to the bottom would not be precise enough so another shaft was dug 264 feet to the west and a wire was hung down both shafts for a more exact measurement.

Out of the six original towers only four remain. The towers at the east and west portals were removed after construction but the towers or what is left of them still remain.

This is a picture of what is left of the tower / range pole up on Rowe’s Neck just east of East Portal. There are four large steel spikes that mark the exact location. I do not know exactly what type of structure was built at this location but because there are no loose rocks at the site and the fact that you do not have to nail down a rock building, I think that the platform or survey hut was most likely made of wood.

A look from this location across the valley shows the East Portal parking area and the bridge across the Deerfield River. The view of East Portal however is blocked by vegetation.

Looking up on the hill reveals a line on the mountain. This is the old Western Union pole line that marked the exact tunnel centerline. This right of way was kept trimmed many years ago and is still visible from across the valley today.

This is one of the few photos that show the east portal lining tower as built
Note the survey pole on top of the tower.




Whitcomb Hill lining tower.





This is a picture of the men surveying the tunnel line at the Central Shaft. The transit is mounted on a stone monument that is on the centerline of the tunnel. The opening on the building marks the centerline that was used by Engineer Carl Wederkinch to transfer the line down the Central Shaft 1028 feet below.

Spruce Hill lining tower. There is not much left of this tower except the lowest level of stone. I believe that this tower was destroyed when the power line was installed over the west side of the mountain to feed the central shaft vent building.

This is a picture of the tower at West Portal. It was made from wood as it was a temporary structure. It would not make sense to build a rock building because the earth underneath would soon be excavated to provide the approach to the tunnel from North Adams.

Notch Mountain lining tower. This tower is by far in the best shape. There is still mortar well struck into the rock joints. On close examination one can see the tool marks left by the masons over 130 years ago.