RPS was commissioned by Cadia Valley Operations to provide regular hydrogeological reviews of the performance of open pit dewatering and depressurisation and to provide input to the design and implementation and management of ongoing dewatering and depressurisation schemes, advice on overall mine water management and the investigation and design of dewatering systems for planned future open pit and underground mines.
As part of annual site visits/reviews, the performance of existing depressurisation schemes were reviewed and future depressurisation and monitoring plans and designs confirmed. Surface water management (control of water at and behind pit crests) is a key factor in reducing recharge of pit wall structures and was an important component of the annual review process. A concept design for a life of mine pit sump pumping system was also developed.
In addition, the water management protocols and “water rush” contingency plans for the Ridgeway underground mine (Sub-Level Cave operation) were reviewed and a dewatering strategy developed for the Cadia East underground mine. The latter included the design of an underground dewatering bore to advance dewater/ depressurise a known wet structure along the path of the decline. A large diameter vertical bore was drilled from a drill cuddy at a higher level and allowed to free flow to depressurise the target structure. It is planned to pump from the hole, when the hydrostatic head has (as a result of free flow) declined below the bore collar.