Area K Pilot Mine Mitigation, Glenrock, WY

To mitigate the subsidence risk by mines inundated with water under high artesian conditions, and to eliminate communication between water in the mine and groundwater aquifer above and below the mine, a special design approach was developed for such conditions. To assess the risk associated with subsidence mitigation in artesian conditions and because of the lack of any precedent, a Pilot Program was conducted. The purpose of pilot program was to prove the viability of the newly developed design approach and to determine the feasibility of injecting high-mobility grout beneath a highly developed residential area in Glenrock, Wyoming with minimal impact on the groundwater regime. Throughout this program, Brierley was successful in adopting means and methods to control artesian flow within the mined interval by installing a series of strategically located discharge wells. This allowed to maintain an optimal equilibrium between induced pressure increments developed by grout injection and the pre-existing pressure regimes in the affected aquifers.. In addition, surveying of monuments proved that no ground heave or settlement were observed as a result of the mitigations activities.