Spatial distributions of lignite mine spoil properties for simulating 2-D variably saturated flow and transport

In open-cast brown coal mine spoils, the effect of heterogeneity on water h ow and solute transport is largely unknown. The objective of this study is to analyze tile effects of differently generated hydraulic property distrib utions on transport processes in mine spoil heaps originating from open-cas t lignite mining. Spatial distributions of hydraulic properties are generat ed with two different approaches. A deterministic approach is based on the description of mixing, segregation, and compaction during dumping. Using in formation on the mining and dumping technology along with geological proper ties of overburden sediments, we generate spatial distributions of the spoi l bulk density and texture for a representative 2-D-vertical cross-section of 22 m depth and 29 m width. Water retention is calculated with the Arya a nd Paris approach and hydraulic conductivity with the Kozeny-Carman equatio n. The second approach uses direct geostatistical simulation of relative hy draulic conductivity. Water flow and solute transport is simulated with the numerical finite element code SWMS_2 D. The deterministic approach leads t o a two-peaked concentration front with tailing. A significant fraction of the solutes is transported faster as compared with a homogeneous profile. B oth approaches induce a spreading of the concentration front. Utilizing ava ilable information on the dumping technology and on the overburden geology may help to improve predictions of water flow and solute transport in spoil heaps. (C) 2001 Elsevier Science B.V. All rights reserved.