Abstract: At the former uranium mining site of Ronneburg, large scale underground and open pit mining for nearly 40 years resulted in a production of about 113 000 tonnes of uranium and about 200 million cubic metres of mine waste. In their present state, these materials cause risks to human health and strong environmental impacts and therefore demand remedial action. The remediation options available are relocation of mine spoil into the open pit and on site remediation by landscaping/contouring, placement of a cover and revegetation. A suitable vegetated cover system combined with a surface water drainage system provides long-term stability against erosion and reduces acid generation thereby meeting the main remediation objectives which are long-term reduction of radiological exposure and contaminant emissions and recultivation. The design of the cover system includes the evaluation of geotechnical, radiological, hydrological, geochemical and ecological criteria and models. The optimized overall model for the cover system has to comply with general conditions as, e.g. economic efficiency, public acceptance and sustainability. Most critical elements for the long-term performance of the cover system designed for the Beerwalde dump are the barrier system and its long-term integrity and a largely self-sustainable vegetation. (C) 2001 Elsevier Science Ltd. All rights reserved.

Abstract: Treatment of radioactively-contaminated and metal-laden mine waters and of seepage fiom tailings ponds and waste rock piles is among the key issues facing WISMUT GmbH in their task to remediate the legacy of uranium mining and processing in the Free States of saxony and rhuringia, Federal Republic of Germany. Generally, contaminant loads of feed waters wn aimnisn over time. At a certain level of costs for the removal of one contaminant unit, continued operation of conventional water treatment plants can hardly be justified any longer. As treatment is still required for water protection, there is an urgent need for-the development and implementation of more cost efficient technologies. WISMUT GmbH and BioPlanta GmbH have studied the suitability of helophye species for contaminant removal from mine waters. In a fust step, original waters were used for an in vitro bioassay. The test results allowed for the determination of the effects of biotic and abiotic factors on helophy'tes'tolerancer ange, growth, and uptake capability of radionuclides and metals. Test series were carried out using Phiagmites australis, Carex disticha, Typha latifolia, and Juncus effusus. Relevant cont-aminant components of the mine waters under investigation included uraniunl iron, arsenic, manganese, nickel, and copper. Investigations led to a number of recommendations conceming plant selection for specific water treatment needs. In a second step, based on these results, a constructed wetland was built in l99g as a pilot plant for the treatment of flood waters liom the pöhla-Tellerhäuser mine and went on-line. Relevant constituents of the neutral flood waters include radium, iron, and arsenic. This wetland specifically uses both physico-chemical and microbiological processes as well as contaminant accumulation by helophytes to achieve the treatment objectives. with the pilot plant in operation for three years now, average removal rates achieved are 95 Yo for kon, 86 yo for arsenic, and 75 % for raäium. WISMUT GmbH intends to put a number of other projects of passive/biological mine water treatment into operation before the end of 2001_