Lac de Gras Development Area - EKATI Diamond Mine

Northwest Territories, Canada

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Years of Service

1995 to 1996

Project Description

In 1996, BHP Diamonds was seeking approval to develop several open pits in the Lac de Gras Area, Northwest Territories, to mine kimberlite pipes at depth in the bedrock. During the EIS process, concerns were raised as to the potential impact of this mine development on the regional hydrogeology in general and the surrounding lakes in particular.

BHP retained Robertson GeoConsultants Inc. (RGC) to study the effects of the proposed mining development on groundwater flow in the study area. Three specific tasks were completed. First, the transient groundwater flow to one of the proposed open pits were simulated using a representative 2D cross-section in order to estimate the time required to reach steady-state conditions and to estimate the volumes of groundwater released from storage during maximum pit development. Second, a regional 3D groundwater model (steady-state) was developed in order to study the impact of one proposed pit on the regional groundwater flow system and to estimate seepage from the various surrounding lakes into the pit. Finally, the results of the 2D approach were compared to those obtained with the detailed 3D groundwater model in order to assess whether the 2D model approach is sufficient for estimating total seepage into a given pit.

Following comprehensive feasibility studies, extensive community consultation and environmental assessment, in November 1996, the Minister of the Department of Indian Affairs and Northern Development and the Premier of the NWT announced that BHP's Lac de Gras project had received final Cabinet approval and had the full support of the government. Construction began in 1997 and the Ekati mine opened officially on 14 October, 1998, becoming Canada's first diamond mine. Since then, over US$1 billion of rough diamonds have been produced and sold.

Services Provided

  • Development of 3-D groundwater flow model to evaluate the impact of open pit mining on regional groundwater regime at depth in fractured bedrock
  • Management of a team of 3 modelers
  • Liaison with client during model development and review process

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