Closure north of 66°

Closure north of 66°

It’s another bitterly cold morning. Mine reclamation work has continued with the use of mobile light towers since the sun set for the season. A call comes in over the radio; the boom on an excavator has cracked. Minus 52°C has won the battle. The soil remediation activities will cease until spring. Closing a mine in the Arctic is no less a challenge than building one.

Permafrost engineering and the traditional knowledge of northern residents will benefit the remediation effort. Permafrost can be used to control the migration of contaminated groundwater. Berms of fine-grained material constructed down gradient of an impacted site build up the level of the permafrost below the berms and thus create a subsurface barrier that inhibits the water’s migration. In the high Arctic, permafrost can also be used to encapsulate contaminated soil within mine workings, even under the warmest climate change scenarios.

To direct the day-to-day excavation of contaminated soil, soil samples need to be tested but the cost and time of shipping samples from remote sites can be prohibitive. Field screening tools, such as gas detectors and portable analysers, must be relied upon along with professional judgment. A portable X-Ray Fluorescence (XRF) analyzer is a valuable tool for assessing metal concentrations. Depending on the grain size and heterogeneity of the soil, the samples may need to be screened to -2mm to get results that are comparable to those of a laboratory. A program to examine the relationship between the field results using various sample preparation techniques and laboratory results must be completed before using the XRF to guide soil remediation. An XRF analyzer, coupled with a GIS database to manage and communicate the sample results, was utilised during the successful reclamation of both the Polaris Mine (75°N latitude) and Nanisivik Mine (73°N latitude).

North of 66°, SRK’s expertise can help clients manage their mine closures.

Arlene Laudrum: alaudrum@srk.com

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