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

对矿产资源开发项目进行环境风险评估的主要挑战之一是，对有可能将污染物从矿场带到接收环境的地下水流量进行可靠的估计。这项研究涉及旨在改进这些渗漏通量预测方法的项目；一个项目涉及裂隙基岩中渗漏通量的预测，另一个项目涉及废物接触采矿前地表的矿山废物堆积物底部的水流分配。第一个项目的目标是确定根据个别钻孔试验得出的裂隙岩石水力性质的局部尺度测量值的平均化战略，以估计控制例如在没有天然水动力围挡的情况下离开尾矿库的渗漏量的岩体的整体或大规模水力传导性。目前，对于以裂隙基岩为主的地质环境中的矿场，没有严格的基础来指导这一平均过程。第二个项目的目标是建立一个量化的基础，以确定确定矿山废物储存底部水路的过程的特征。废石储存如果具有化学反应，往往会对接收环境构成最大的单一风险。虽然近年来已作出相当大的努力来了解废石储存的渗入情况，但很少有人注意了解可溶污染物一旦到达开采前的地形表面，然后在储存和以前的地面之间通过地表水流动输送，或进入地下水系统并带到储存的脚趾之外。这项研究的基础是对现场数据集和数值模拟的分析，以指导对控制过程的解释，并制定程序，以改进对污染物向环境释放的风险的评估。

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.