Environmental Impact Assessment of Leachate from Waste Rock Piles on Groundwater Using Numerical Model, Case Study Anhui, China

This study evaluates the transport of leaching water infiltration from waste rock piles on the surrounding groundwater, using Anhui, China, as an example. Based on a detailed analysis of hydrogeological conditions in the study area, a numerical groundwater model was established to simulate the transport of a specific pollutant (manganese). The distribution and levels of manganese pollution in the groundwater environment caused by the infiltration of leachate were assessed for different operating conditions using MODFLOW and MT3D module. The results show that without anti-seepage measures in place in the waste rock piles, the concentration of manganese in the center point of the rock pile reaches the maximum allowable value of 0.1mg/l by the second year. The maximum horizontal diffusion distance was 188 m. The concentration of manganese in the center point reached 0.45 mg/l by the tenth year, which is 4.5 times more than the allowable value, and the diffusion area was approximately 0.06 km2. As a result of leachate infiltration, bedrock aquifers in the study area will be polluted. However, if anti-seepage measures are in place with an impermeable layer with a vertical permeability coefficient of 1×10−7cm/s, then the maximum concentration of manganese in the center of the waste rock piles is reduced to 0.08 mg/l by the tenth year. This is within the allowable limits. Therefore, we concluded that leachate from the waste rock piles will lead to high levels of manganese in the underlying aquifers, and that anti-seepage measures must be taken to prevent this.