From concept to feasibility design to environmental and social impact assessment
The Tampakan project is a proposed open pit copper and gold mine located in south-central Mindanao, Philippines. KCB was commissioned to assist with the conceptual and feasibility studies for mine waste and water management facilities, and to develop a conceptual mine closure plan for part of the owner’s Environment and Social Impact Assessment submission.
Tailings Dam Design
The proposed cyclone sand tailings dam is in an earthquake-prone region with over 2 m of annual rainfall. The design of the tailings dam included:
- site investigations for determining the geological, hydrogeological and geotechnical properties of the dam foundation;
- slope stability analyses of the dam, during subsequent raises, under static and post-earthquake conditions during mine operations and post-closure;
- seepage analyses to estimate the amount of seepage and determine the phreatic surface within the dam;
- simplified dynamic deformation analyses of the dam, using the 2D-plane strain finite difference software FLAC (Fast Lagrangian Analysis of Continua);
- embankment dam zoning and filter design;
- construction material specifications and a preliminary construction schedule; and
- a robust closure configuration for long-term stability.
Water and Waste Management Facilities
Water management facilities at the proposed Tampakan mine are designed to collect and treat process-affected water. The design included:
- surface water diversion facilities as part of a long-term water management strategy;
- geochemical assessment and modelling of tailings and waste rock for the potential for acid rock drainage and metalliferous leaching;
- groundwater assessment to determine the hydrogeological model of the site, and engineering design to control seepage particularly through the dam abutments;
- innovative waste rock dump design, using interior dams, to mitigate the potential impact of acid rock drainage; and
- development of site-wide water balance model using updated climate data and mine plans in GoldSim to confirm and improve the water management plan.
Environmental and Social Impact Assessment (ESIA)
As part of the ESIA, KCB developed conceptual closure plans for the tailings storage facility, fresh water dam and waste rock storage facility. Our ESIA activities included:
- development of a site-wide water balance model using updated climate data and mine plans in a new GoldSim model to simulate rainfall, evaporation and surface run-off;
- assessment of water quality post-closure, given that some mine waste may be potentially acid forming;
- waste storage facility design to mitigate the environmental impacts of potentially acid forming material on downstream users;
- design of erosion and sediment control systems; and
- development of a long-term care and maintenance plan for mine waste facilities.