25 July 2016
If you look in the direction of the cliffs above the MP 72 CIP complex, you will see a grayish strip stretching from north to south. Many of you may well have observed this strip – some would be curious, and perhaps many could care less. But this is something you should be informed about.
The grayish strip in the distance that you may have spotted constitutes the CIP Rock Fence Barriers, a long-term mitigation program to reduce the risk of falling rocks in the CIP area.
The PTFI contract of work area straddles a beautiful and rich, but challenging landscape. The PTFI operations area in Papua is long known to be filled with natural challenges, indeed from the time this company first ventured into the area more than 40 years ago.
The CIP area is more particularly prone to real rock-falls. According to PTFI’s accidents records, in December 2009 there was a fatality resulting from falling rocks in the cliffs above the CIP area.
The CIP area is a hectic place, where permanent activities are located - the OB 3 & 4 offices, underground mining support facilities (batch plants, crushers, etc), warehouses and shops, the AP Portal main access – and there is almost always a significant concentration of workers and equipment.
In order to minimize the risk of casualties and damages in this crucial area, GeoEngineering Division by way of the Hydrology Regional & Civil Geotech Department undertook the Rock Fence Barrier project aimed at containing rock-falls from the CIP cliffs and precluding associated threats in the MP 72 CIP complex.
The Rock Fall Protection Team (RPT) – a contractor team of slope construction specialists – was appointed by a Hydrology Regional & Civil Geotech Department team to work on the CIP Rock Fence Barrier project from 2013 until completion in 2014 (not a simple task given the rough terrain, and entailing a considerable budget). Completion time was a priority given the urgency of the project. It was also an indication of PTFI’s real commitment to workers safety in carrying out operations.
The rock fence barrier in the CIP area was built in 2 places: on the northern cliff and south of the CIP area. The construction method entailed putting up a combination flexible structure consisting of steel posts and reinforced steel mesh designed for efficiency and effectiveness in absorbing impacts from falling rocks.
Selection of the two rock fence barrier locations was preceded by special and highly thorough research through simulation and analyses of rock falls. The study indicated these two locations provided the best options for setting up rock fence barriers.
In addition to rock fence barriers, towards minimizing risks from falling rocks the Hydrology Regional & Civil Geotech team also recommended building a deflection wall on the northern side of CIP and a cable fence on the southern side. Further, Hydrology Regional & Civil Geotech prepared a hazard zone map for the MP 72 CIP complex, to provide protection against foreseeable rock falls from the retention walls built. Detailed and exhaustive calculations and planning went into the measures taken to minimize risks.
Since the time the rock fence barriers along with all engineering devices were installed, there has been no report of incidents associated with rock falls in the area. The fact that we can now work confidently and safely merits recognition, appreciation, and thankfulness. (Sularso)