Impact of a Panguna Mine Pit Lake

By Leonard Fong Roka

The Panguna Mine pit is about half a kilometre deep and two kilometres wide. Today it sleeps idle a scar of suffering in the heartland of Bougainville. Kilometres of gravel stretches and slopes surrounds the pit to the west and to the east, stands the imposing Pen hill (organic rock) brae that was butter-cut to the side of the central regions of the Crown Prince Range by the BCL; added on, is the rock spree and slip that slides to settle into the pit.

Panguna mine pit

In the early days of the BCL operations (1970s), the naturally occurring crust water systems that sprouted from the numerous sections of the pit, was drained by a pumping station mounted at the lowest section of the pit through a network of steel pipes to the surface. This was a costly exercise.

To minimise the cost of operations, BCL engaged a foreign specialized company to open a drainage tunnel network. A location right at my family’s piece of land was selected (in 2004, I erected my house right at the entrance and lived there ever since).

Pit Drainage tunnel entrance

From the entrance, the Panguna pit is around 6 kilometres to the north-east, but the company cut the tunnel straight east towards the Kongara area more than a hundred kilometres away but cut it short from continuing and redirected it towards the pit.

After mapping out their position some 3-400 metres below the pit, the company punched from the bottom of the pit, 1.5 metre in diameter steel pipes piece by piece through the crust to the tunnel below. After reaching it, the punched in 3 more and the job was done. The strategy was, every time the pit expanded down, a piece of the steel was cut. The pit experienced from JULY 1985 no nightmare of water built-up.

My concern today is the concentration of wash-out from the sides of the pit at the bottom. It threatens the intake vaults (of course, two were already permanently shut off). The remaining two, are near from their fate. And when they are shut, the Panguna pit will turn into a huge lake of water.   

The only lowest point that the reservoir can drain is through the main pit entry wing and out into the Kavarong River firstly, through the public vehicles pit-area entry tunnels. This water, however, washes away with it, tonnes of gravel that hosts the pit workshop section to the secondary crusher (a distance of half a kilometre).

Public vehicle pit area access tunnels

The flow of this washout from the Panguna Pit Lake shall further energize the naturally running Kavarong River along the ‘V-shape concrete Kavarong waterway that is already in a state of a long pond system after blocked by a huge landslide from the direction of the BCL Concentrator Zone (beyond this point, right below new Dapera village, the V-shaped water system is in better condition).

V-Shape Kavarong water way. Workable area beyond Dapera

Landslide affected zone of the Kavarong waterway near the BCL concentrator

Water filled sections of the water way near the former BCL light vehicle workshop

These combine forces of nature, will block the V-shape water way, around new Dapera and divert the water, through the lower section stretching from the secondary crusher to the B-40 workshop, into the more lower belt (5-10 metres lower) hosting the conveyor belt system that former supplied the spreaders kilometres away to the south-west that poured gravel into the Tumpusiong Valley (my home).

Spreader area

All these areas just mentioned, of course, before the mine came into existence, were the sky or tree tops enjoyed by the winged animals. The waste gravel from the pit area filled in the valley and today made it possible for human occupation.  Some dozens or hundreds of metres below is the pre-mining river bed of the Kavarong River.

Gravel brae above Pirurari village

Once the genesis is done, we face the catastrophic action of nature that is the Kavarong River trying to relocate its old bed as it washes with it billion tonnes of waste gravel down into the Tumpusiong Valley.

The washout will first consume the Pirurari village and move on into my section, where the Kavarong River is still searching for its apical bed.

Pirurari Village below

The Panguna-Jaba section of the highway into South Bougainville will be off once and for all. Affecting the economically vibrant South by cutting off the access to the Bougainville east coast areas like Arawa and Buka, for Bana district, this is the access not too costly from driving through Siwai to Buin and to Arawa.

For the Tumpusiong valley where many of us are now settled near the highway to the Southern districts and close to the banks of the polluted Kavarong River, this will cause us to resettle to the higher altitudes with some costs.

Tumpusiong Valley

This is a disaster soon to be unfolded for the Panguna District and the Bana District in South Bougainville.