Increasing the Clearances
The GUILFORD XPRESS has presented previously the need to increase clearances on our route from Ayer, Massachusetts to Mechanicville, New York in order to accommodate so-called “double stack” container shipments, which have become a prominent part of today’s rail traffic potential. Some of the work has been accomplished by digging out part of the sub-grade under the track in order to lower the track under bridges or in tunnels and achieve the larger clearance. The last issue of the XPRESS described the undercutting process and showed pictorially some of the details of the work.
The project required increasing the overhead clearance at two highway overpasses in Fitchburg, Massachusetts without closing the line to traffic. At the Putnam Street bridge, the vertical clearance had to be increased by 4 inches, and the increase at the Water Street bridge was one foot! It took the lowering of 2600 feet of the #2 track, with train service continuing over the #1 track. Track #2 was back in service in only 5 weeks!
Many aspects of this work have involved lots of ingenuity and some techniques new to the railroad. Two bridges in this section carry the track over the Nashua River. However, U. S. Army Corps of Engineers flood control requirements prevented the lowering of the bridges, which would have afforded the lowest cost method. Therefore, in order to reduce the depth of the supporting structure for the rail (that is, crossties and ballast), new steel fabrications covering at least 60% of the length of each bridge were applied, with either steel crossties or steel blocks of varying thickness welded to deck plates, which were equipped with Pandrol clips to secure the rail. The remaining portion of each bridge had conventional timber crossties which had been dapped, or notched out, to provide the needed seat for the rail. Further, there were three water mains to be lowered, with new valves installed, a Bell Atlantic cable relocated, and several abandoned gas and steam mains to be removed. With track realignment and additional drainage, the desired clearances were accomplished.
At another location, near Schaghticoke, New York, known on the railroad as “Snyder’s”, the track was realigned from its present location over to the location of the former second main track which had been long since removed. This roadbed was excavated significantly, down to the depth which, when topped by an appropriate layer of ballast, would support the existing main track at the desired clearance dimension. A lot of work to clear one obstruction!
Finally, the work continues in the Hoosac Tunnel. The tunnel bore, as built, was actually a tube constructed of brick where the rock itself could not be trusted and required lining. Over the years, some of the brick would shift or break, and a steel liner fabricated to the correct diameter was installed as needed. In the early part of the 20th century, electric locomotives were used to haul trains through the tunnel to eliminate the problems created by steam locomotive smoke. The electric locomotives received their power through an overhead wire system which was anchored to the ceiling of the tunnel with extremely hard bolts. When the diesel locomotives took over, the wires were taken down, but the bolts were not entirely removed and protruded into the bore. The steel lining sections were installed to clear these bolts as there was ample vertical clearance, particularly as the tunnel was now single track rather than double.
Now, the need to increase vertical clearance within the tunnel has brought the focus back to the old catenary (overhead wire) mounting bolts. It has been necessary to cut the bolts off, using a special welding electrode designed for burning the hardened material used in the manufacturing of these bolts. The steel lining is then jacked upward into contact with the tunnel ceiling to get maximum clearance, and the lining is anchored in this new location.
The actual undercutting beneath the track in the tunnel has just been completed. A track laying machine, which straddled the track, was used to lift and remove 156 foot long segments of track so that an excavator could dig out the ballast underneath. An abandoned 15 inch reinforced concrete drainage pipe, which had been filled with concrete, was found under the track. This had to be removed since it would have prevented the lowering of the track to the desired depth. Each day, the track was reconnected and reballasted to the lower elevation, thus achieving the vertical clearance needed with a minimal disruption of train service. It is also expected that drainage will have been improved by the conclusion of this project.
The project of increasing the clearances has been challenging, but the people of the Engineering Department have met the challenge with ingenuity, skill and persistence. The future of Guilford Rail will be much stronger as a result of these efforts as the traffic base is enlarged by the ability to move double stack containers.
