Labourers work inside tunnel number 7 at Mahur in Dima Hasao district. Telegraph picture

Lumding (Nagaon), Sept. 1: Light can now pass through tunnel 7, while man and machine move inexorably to complete tunnel 10.

The two tunnels on the Lumding-Silchar broad gauge track posed the greatest challenge for the Northeast Frontier Railway on account of the geophysical conditions of the Barail range that the two pierce.

But all that is now safely in the past as the NF Railway exudes confidence about the broad gauge line becoming functional by March 2015 — over 18 years since work began.

While tunnel 7 at Mahur, which measures 1,675 metres, is complete, 4 per cent work is still left for its counterpart, 10, at Haflong, which is 3,095 metres long.

The 210km route will pass through 17 tunnels and nearly 500 bridges to give a huge boost to the communication of Barak valley by reducing travelling time between the two places by four to five hours.

According to N. Brahma, deputy chief engineer, NF Railway (construction), laying of tracks through tunnel 7 would be completed this month while those through 10 would be in place by January next year.

A major stretch of the project is located in hilly terrain for which the existing metre gauge alignment (MG) has large number of sharp curves and steep gradients. As such sharp curves and steep gradients are not permitted on the BG it is not following the MG alignment.

“The existing MG alignment and the one proposed for the BG intersect at different levels for stretches of six to ten metre which will necessitate earthwork of about 12 lakh cubic metres,” Brahma said,” Brahma said.

“Work in those locations cannot be done without dismantling the existing MG track by taking a mega block (period of suspension of train services till resumption of BG train services). For which we are taking the mega block (suspension of train services) for six months, from October 1 to March 2015,” Brahma said.

The Lumding-Silchar gauge conversion is part of a national project that covers 420.26km at a cost of Rs 5,185.44 crore. The progress of the project is 90.59 per cent and expenditure till July is Rs 4,306.42 crore.

Besides Lumding-Silchar, the other parts of the project are Badarpur-Kumarghat (118km), Kumarghat-Agartala (109km), Arunachal-Jiribam (50km), Baraigram-Dullabcherra (29.40km), and Karimganj-Maishasan (13.50km).

Brahma said the law and order situation in Dima Hasao district was very unfavourable and there were frequent strikes and agitation causing serious disruption of work.

In a meeting with Assam chief secretary in July, the NF Railway highlighted the security requirement. It also held a meeting with the Assam home commissioner to review security.

During the mega block, a large number of men and machines will be working day and night. Because of shortage of skilled labour in the area, the NF Railway will bring 3,000 labourers from other places. The railway has set target of completing nine stations before the mega block and commissioning 29 others during the period.

Once completed, the maximum permissible speed of train will be 70km per hour in hill sections and 100km per hour in the plains.

The NF Railway has also completed another challenge of constructing of 54 metres tall and 705 metres long bridge over the Dayang.