Banyumas, ANTARA JATENG - Construction of Kalirajut railway tunnel in the regency of Banyumas, Central Java, would start early next month, the contractor PT Pembangunan Perumahan said.

The plan is drilling would begins from the inlet in the village of Notog in the first week of April, Project Manager of the company Apri Setiawan said here Monday night.

The drilling in the outlet would start in May, delayed for slow process of land clearing in the area of the village of Tambaknegara, Setiawan said.

However, the problem over land clearing would soon be settled, he said, adding, "hopefully the process would be wrapped up this week."

He said the distance between the new and old tunnels is 345 meters that the work would not hamper the train schedule.

He said construction of the 555 meters long tunnel with diameter of 11 meters would take 11 months with only 1 meter each from the inlet and outlet per day.

Protection would be made for every meter drilled as the rocks easily crumbled, he said, adding the rocks would crumble if drilling is too long up to four meters or more without protection.

Therefore, drilling is made with Twin Header instead of explosive as explosion would likely cause the rock to collapse, he said.

The walls of the tunnel are 30 to 100 centimeters thick but the diameters of the tunnel averages 11 meters, he said.

He said there should be no problem in the drilling as surveys had been made three times involving a number of experts.

"The only problem is frequent rainfall. The environment would be muddy causing difficulty in disposing of the material from the drilling," he said.

Two new tunnels - the Kalirajut and Kebasen tunnels - would be built for the Purwokerto-Kroya double track to replace the existing ones. The Kebasen tunnel is to be built by other contractor.

The new tunnel in Kalirajut is located south of the existing tunnel. The old tunnel is only 260 meters long.

Meanwhile, in Kebasen, the plan is to build two new tunnels close to each respectively 109 metrs and 183 meters long located north of the existing tunnels. The two new tunnels would replace a 79 meter long one used until now.

The tunnels would reduce the distance between Purwokerto and Kroya to 27 kilometer from now 36 kilometers by rail track.