Abstract:
Agnico Eagle Mines owns and operates the Whale Tail Project located approximately 160 km by road north of Baker Lake in the Kivalliq District, Nunavut. The upper 285 m of the Amaruq gold deposit is to be mined by open pit, and the remainder by underground mining methods. The open pit (to the north) is separated from Whale Tail Lake (to the south) by an 850 m long, secant wall core, rockfill dike – the Whale Tail Dike. Construction of the dike was carried out during Q3-Q4 of 2018. Curtain grouting of the secant wall-to-bedrock interface and fractured, near surface bedrock was carried out in artic winter conditions from November 2018 to February 2019, and dewatering commenced in March 2019. In August 2019, a higher than anticipated seepage rate in the downstream area of the structure was observed. Installed vibrating wire piezometers and thermistor strings indicated that water was potentially seeping beneath the secant pile wall and through bedrock. Seepage measurements obtained by monitoring the daily dewatering rates as well as weirs along the downstream toe indicated that approximately 500 to 600 m3 /h was flowing into the northern catchment. This paper describes the efforts realized and successful rehabilitation grouting works carried out in artic winter conditions, against a head of water, to reduce the noted seepage to a more manageable 200 to 300 m3 /h. Keywords: Whale Tail Dike, rehabilitation, seepage reduction, curtain grouting, arctic conditions