Whale Tail Dike Rehabilitation Grouting Success-Paper

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The Whale Tail Dike in Nunavut is an 835 m-long water-retention structure with a cement-bentonite secant-pile cutoff wall. After dewatering began in March 2019, seepage into the North Basin reached approximately 500–600 m³/h—five to six times the expected rate—creating a risk to the mine’s water-management capacity.<br /><br />Investigations, including geophysical profiling and monitoring of piezometers and thermistors, suggested that water was bypassing the cutoff wall through fractured bedrock. A remedial grouting program began in late 2019 under Arctic winter conditions. The work focused mainly on a downstream blanket of bedrock holes, using staged drilling, split-spaced hole patterns, repeated grouting, and stable cementitious mixes. Thixotropic additives and calcium chloride helped grout set despite flowing groundwater and low temperatures. The planned upstream work was largely unnecessary as results from the downstream treatment became apparent.<br /><br />By March 2020, inferred seepage had fallen to about 230 m³/h, and the program was stopped after approximately 35% of the planned Phase I work. Measurements in spring and summer 2020 indicated total seepage of roughly 150–270 m³/h, compared with 500–600 m³/h in 2019. Seepage collected at the dike toe also declined substantially, and fewer seepage channels were visible.<br /><br />The authors conclude that rehabilitation grouting achieved its immediate water-management objective, reducing seepage by about 50% overall. The completed Phase I work contributed an estimated 25–30% of the total reduction, without requiring the planned deeper upstream curtain.

Keywords

Whale Tail Dike

Nunavut

seepage reduction

rehabilitation grouting

cutoff wall

water-retention structure

fracked bedrock

Arctic winter conditions

piezometers

cementitious grout