EFFLUENTS FROM A WASTE ROCK DEPOSIT OF A FORMER URANIUM MINE SN SAXONY/GERMANY — MASS FLOW BALANCE OF WATER AND DISSOLVED SOLIDSD. BIEHLERColenco Power Engineering AG,Liestal. Switzerland
Abstract. Soon after uranium mining had ceased in eastern Germany in 1990. work lor remediation of several mining sites began. The Wismul GmbH, owner of the Mine of Dresden-Gittersee's waste rock dump, introduced the concept of reducing the impact to the environment via water and air paths by implementing a multi-layer soil cover. The deposit consists mainly of waste rock (clastic sediments of Dohlener Becken. deep melamorphic rocks) but also of low-grade ore (U-rich coal) and tailing materials. At the time when remediation started, the effluents completely infiltrated the underground. Because of previous surface exilltration activities, they were already known to be very rich in dissolved solids, especially in sulphate and uranium. As demanded by the state authorities, the owner funded a vast hydrogeological study of the site. In testing the efficiency of surface sealing.
The study indicated a mass flow balance of water and dissolved solids for the current situation, and predicted emissions into the water path which would occur after realisation of the proposed soil cover. The Held investigation program consisted of:
— measurements of flow, of concentrations of dissolved solids (e.sp. U and Ra-226) and of contents of environmental isotopes in precipitation, surface runoff, seepage water and groundwater in the current condition of the dump
— the study of waste rock material (geochemistry, mineralogy) waste rock material elution tests
— underground investigation by drilling boreholes up to 270 in in depth
The resulting data allowed for:
— a hydrogeological conceptual model of the site
— a consistent mass flow balance for the current condition of the dump
— a prediction of concentrations in groundwater resulting after the realisation of a soil cover
The predictions show that the concentrations of dissolved solids in the contaminated groundwater would be significantly decreased. Furthermore it would be possible to reach the standards for drinking water with respect to uranium content. Based on the presented stud} the realisation of the proposed surface cover can be recommended.