Predicted Post-Closure Aqueous Geochemistry at the Cortez Hills Underground Mine, Nevada, USA

Autor: Nathan Sims, Andrew K. Davis, Jerritt Collord, M. Lengke
Rok vydání: 2021
Předmět:
Zdroj: Mine Water and the Environment. 40:639-656
ISSN: 1616-1068
1025-9112
DOI: 10.1007/s10230-021-00771-5
Popis: An investigation was undertaken to predict the post-closure water chemistry of the Cortez Hills Underground Deep South Extension where the mine workings will be backfilled with cemented waste rock. The objective was to determine the potential effects of the tunnel water on adjacent groundwater once the groundwater table recovers, hydraulic conditions stabilize, and ambient groundwater flow is reestablished. The average background groundwater chemistry from three wells representing discharge to the tunnel area during closure, and the worst-case groundwater dissolution chemistry of tunnel floor/unconsolidated backfill, shotcrete (sprayed concrete), cemented backfill and country wallrock/cemented backfill reactions were used to calculate their contribution to the total mass loading during tunnel flooding. The volume of groundwater flow through the tunnel area was coupled with these releases to calculate a total tunnel water quality. All analytes met NV Division of Environmental Protection Profile I standards, except for As, Sb, and Pb, due to their naturally-elevated background groundwater levels (0.08, 0.014, and 0.03 mg/L, respectively). The PHREEQC geochemical code was used to determine the post-closure dissolved phase solutes that could migrate to adjacent groundwater. The dissolved tunnel water chemistry was predicted to be pH = 8.2, with an alkalinity of 124 mg/L CaCO3 and with all solutes meeting Profile I except for As (0.07 mg/L) and Sb (0.01 mg/L). The predicted water chemistry was dominated by the influent groundwater, which comprised ≈97% of the mass loading and was similar to two existing underground seeps.
Databáze: OpenAIRE
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