Opal Mining Threatens Roads in Lightning Ridge
Bill Kotru, a seasoned opal miner in Lightning Ridge, fears that a large underground cavity, known as a "ballroom," could soon cause the collapse of a local road. This concern arises after authorities partially closed two roads due to dips appearing in the bitumen, indicating potential instability beneath the surface.
Kotru, who has witnessed numerous mine collapses during his 43 years of opal mining, expressed surprise when he saw roadworks being conducted in an area he had previously mined. He estimates that the ballroom under the roadworks is approximately nine meters high and 50 meters wide, with several other similar cavities scattered in the vicinity.
His primary concern lies with a specific cavity located only 2-3 meters below the road surface. He worries that heavy vehicles or adverse weather conditions could trigger a collapse, endangering the road and its users.
Initial investigations by the Walgett Shire Council revealed two cavities, one measuring a staggering 350 cubic meters and the other 150 cubic meters, located approximately 15 meters underground. Council officials attribute the dips to vibrations from heavy vehicles causing the cavity roofs to give way.
The increased traffic on Lorne Road, which had become a popular shortcut to the Castlereagh Highway after being sealed last year, prompted the council to close the intersection and implement detours.
The extent of the legacy mining cavities remains unclear, as historical maps provide an incomplete picture. These cavities also posed challenges during the construction of a multi-million dollar opal center in another part of town, requiring additional work to reinforce the foundation.
Currently, the responsibility for investigating and reinforcing the cavities remains a point of contention between the council and the state government. While a geotechnical engineering assessment is planned to determine the risks and potential solutions, the funding for these actions remains unresolved.