Due to significant recent demand and increased output this stone quarry was nearing its end of life. Previous studies had demonstrated further expansion to be unprofitable. Current quarry operations were reducing access and creating safety concerns for continuing production. Access was becoming difficult for haul trucks.
The previous mine expansion studies had been undertaken in-house more than 8 years previously and were based on drill hole test results that were over 15 years old. Economics were completely different with different outputs, equipment, labour rates, etc.
The local market was still buoyant and demand was increasing. Little competition existed in the local area.
Cycle times were increasing due to longer haul times. LOM was estimated in months so no additional equipment could be justified. Loaders were standing for long periods waiting for haulers that would arrive in groups.
Test hole results showed significant overburden stripping would be required to expand the quarry. Management could not conceive a workable plan for the quarry’s expansion.
A detailed analysis showed a discrepancy between existing visually observable overburden depths and drill results. Also, previously completed localised stripping depths did not agree with the existing development plan projections.
Senior management were keen to extend the LOM to capitalise on the current high demand, projected to continue for several years. Capital was available for development provided economics justified the investment.
New test holes were drilled in strategic locations to develop a revised overburden profile.
In conjunction with consulting engineers, a 3D mine development model and simulation was developed.
Revised economics were developed based on various scenarios for overburden stripping costs, improved access, increased productivity, reduced cycle times, etc.
A full revised LOM plan was developed with multi-stage overburden stripping and mine development phases.
The crusher location was revised for improved cycle time.
Contactors were sourced and the overburden contract bid with the resulting contract was awarded at 30% below initial planned estimates. Removal was completed 3 months ahead of schedule and production commenced earlier than originally anticipated.
LOM was extended by over 35 years at full production. A new capital equipment plan was implemented and additional haul trucks were added for increased production efficiencies.
