Field-scale prediction of seepage fluxes for assessment of environment impacts

对矿物资源开发项目进行环境风险评估的一个主要挑战是，对有可能将污染物带到矿区以外的接收环境的地下水流作出可靠的估计。这项研究涉及旨在改进预测这些渗透通量的方法的项目;一个项目涉及预测断裂基岩中的渗透通量，另一个项目涉及在废物接触采矿前地面的矿山废物储存基地的水流分配。 第一个项目的目标是确定战略，对从单个钻孔试验中得出的破碎岩石水力特性的局部尺度测量值进行平均，以估计岩体的整体或大尺度水力传导率，该传导率控制着，例如，在没有自然水力遏制的情况下，尾矿蓄水池的渗漏量。 对于位于以断裂基岩为主的地质环境中的矿场，目前还没有严格的依据来指导这种平均过程。第二个项目的目标是建立一个定量基础，以确定在矿山废物储存基地确定水通道的过程的特征。废石储存如果具有地球化学反应性，往往是接收环境面临的最大单一风险。 虽然近年来已作出相当大的努力来了解渗入废石堆的情况，但很少有人注意了解可溶性污染物一旦到达采矿前的地形表面，然后在堆与前地面之间的界面处被地表水流动转移，或进入地下水系统并被带到堆底之外，如何进行分配。 这项研究是基于现场数据集和数值模拟的分析，以指导控制过程的解释，并制定程序，以改善污染物释放到环境中的风险评估。

One of the key challenges in conducting environmental risk assessments for mineral resource development projects is formulating reliable estimates of subsurface water flows that have the potential to carry contaminants beyond the mine site to the receiving environment. This study involves projects designed to advance methodologies for prediction of these seepage fluxes; one project addresses prediction of seepage fluxes in fractured bedrock, the other the partitioning of water flow at the base of a mine waste stockpile where the waste contacts the pre-mining ground surface. The objective of the first project is to identify strategies for averaging local-scale measurements of the hydraulic properties of fractured rock derived from tests in individual boreholes, to estimate the bulk or large-scale hydraulic conductivity of the rock mass which controls, for example, the amount of seepage leaving a tailings impoundment in the absence of natural hydrodynamic containment. The currently exists no rigorous basis to guide this averaging process for mine sites located in a geologic setting dominated by fractured bedrock. The objective of the second project is to develop a quantitative basis for characterizing the processes that determine water pathways at the base of a mine waste stockpile. Waste rock stockpiles, if geochemically reactive, often represent the greatest single risk to the receiving environment. While considerable effort has been directed in recent year to understand infiltration into waste rock stockpiles, little attention has been directed to understanding the partitioning of soluble contaminants once they reach the pre-mining topographic surface, and are then either transported by surface water flow at the interface between the stockpile and the former ground surface, or enter the groundwater system and are carried beyond the toe of the stockpile. The study is based on an analysis of field data sets and numerical simulations to guide the interpretation of controlling processes, and development of procedures for improved assessment of the risk of contaminant release to the environment.