General Mining Division-2 Runs its First Underground Mining Project

Site Faraz

PT Dahana (Persero)’s 2nd General Mining Division recently succeeded in expanding its business to Sumatra.

This time, the division of which most of its operations are located in the island of Kalimantan ran an explosives purchase and blasting supervision at PT Faras Pratama. The copper mining project was located in the village of Pakan Salak, Koto Pari, Solok, West Sumatra.

Located in the depth of Sumatra’s tropical rainforest, the access road towards the project could be considered rather difficult. It took 7 hours of land trip from Padang to reach the location. Lush forest of the Barisan Mountains became a distinct characteristic of Solok site project which was also completed with a copper smelter facility. “There is almost no communication access available here, the forest is still very virgin and sometimes we encounter Sumatran tiger or honey bear at the forest,” said Yuyun Agus Riyanto, Solok’s Site Coordinator.

Solok site project had a different character compared to other site projects currently run by General Mining Division-2. The project which first started to run on July 13, 2013 was an underground copper mining, unlike other of the division’s coal mining projects which were of an open pit type.

The blasting used tunneling method which became General Mining Division-2’s first experience in this type of explosives service. “Although the drilling and blasting service is currently not carried out by Dahana, we still get to learn a lot from the tunneling mining process. The rock at the mining location is of hard andesite, therefore blasting (using explosives) is needed since it would be impossible to extract the rock solely using drilling equipment. This is our division’s first experience in running a tunneling project,” Yuyun said.

Yuyun further explained that the hole in each tunnel reached a depth of 200-300 meters from the surface, the tunnel diameter being approximately 2x2 m2. “We have already completed blasting 2 holes at 3 different locations in 1 month,” he revealed. The blasting technique itself must be done specifically and used very small amount of explosives. Each blasting activity which was carried out once a week only used 20 blast holes with an average depth of merely 1.5 meters, resulting at least 7.6 BCM of overburden.

According to Yuyun, other than the safety risks which were higher than that of open pit mining, there was also a high risk in the success rate of finding copper reserves in the ground. “Once we already extracted rocks until 40 meters of depth, but was forced to put the work into halt since no galena (copper ores) were found in the ground,” told Yuyun. (IDR)

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