In its present condition, the dam of the tailings pond is less stable than is recommended by international practice. A surveillance system has been established to observe both vertical and horizontal soil movement and the buildup of stresses in the soil. The stability of the dam depends primarily on erosion by shore processes and the consequent reduction of the counterbalance, as well as the reduction in strength of the Cambrian clay underlying the dam caused by creep and by water percolating to the bottom of the pond. The most critical need is to enlarge the counterbalance and to stop erosion. The surveillance system should be supplemented with a system of inclinometers. Monitoring of coastal processes should be continued. At present, the hydrodynamic stress on the dam is minimal because the pebble layer allows drainage of water out of the tailings pond and into the sea. The regulatory requirement to end emissions into the Baltic Sea must be met without causing undesirable hydrodynamic stresses on the dam. This could be done by covering the pond and diverting precipitation water. 9. References I. Report on Topographic-Geodetic Studies at the Tailings Pond. 1965, No. A-4-01187 (in Russian). 2. Report on Geotechnical Studies at the Tailings Pond of Plant PO Box 22. 1965, No. 64691 (in Russian). 3. Report on Topographic-Geodetic and Geotechnical Studies at the Thennal Power Plant's Ash Impoundment. 1976, No. 15740 (in Russian). 4. Technical Report on Topographic Planning of the Thennal Power Plant's Ash Impoundment. 1979, No.

Zusammenfassung
Proceedings of the NATO Advanced Research Workshop, held in Tallinn, Estonia, 5-9 October 1998

Inhalt
Introductory Material: The Situation At Sillamäe.- Industrial Complex in Northeast Estonia: Technical, Economic and Environmental Aspects.- Uranium Processing at Sillamäe and Decommissioning of the Tailings.- SillamäeA Common Baltic Concern.- Master Plan for Remediation of the Sillamäe Tailings Pond and Technical Design Project.- Site Monitoring.- Stability of the Dam at the Sillamäe Tailings Pond.- Process Flow Sheet.- Rare Earth Production at the Sillamäe Plant,1969-1991 and the Possibility of Scandium Extraction from Loparite.- Indoor Occupational Exposure to Radiation at the Silmet Plant in Estonia: A Preliminary Assessment.- Experience with Uranium Tailings in Other Countries.- Remediation of the Former Uranium Mine Ranstad.- Remediation of Tailings Dams.- Remediation Concepts for Uranium Mining Operations in CEEC:A Phare Multi-Country Environmental Sector Programma.- WISMUT Experience in Remediation of Uranium Mill Tailings Ponds.- Post-Remediation Monitoring and Maintenance Experience at Uranium Mill Tailings Sites, United States.- Current State of Remediation of Tailings Ponds and Their Surroundings in Hungary.- The Environmental Impact of Former Uranium Mining Activities at the Novoveska Huta Site, Slovakia.- A Heritage from Uranium Mining in Poland.- A Field Study of Capillary and Hydraulic Barriers in Landfill Covers Varying in Slope at Los Alamos, New Mexico, USA.- Regulatory and Legal Issues.- Estonian Radiation Protection Requirements and the Sillamäe Site.- Legal Responsibility and Liability for the Sillamäe Site.- Regulations and RequirementsSwedish Approach.- Nordic Experience with Environmental Regulations.- Assessment of Options.- Outline of a Multiattribute Utility Approach to Development of a Waste Management Strategy atSillamäe.- The Potential for Economic Recovery of Metals from the Sillamäe Site.- Applicable Technologies.- Oil Shale Ash: Its Characterization and Possible Use in Remediation at the Sillamäe Site.- Types of Oil Shale Ash and Methods for Increasing Their Reactivity.- Utilization of Semi-Coke for Energy Production.- Magnetic Separation for Rare Earth Oxide Recovery at Sillamäe, Estonia.- Purification and Utilization of Waste Waters from Silmet Plant Containing Ammonium Salts.- New Approaches for the Treatment of Naturally Occurring Radioactive Materials.- Ash Cements Stabilized by Supercritical CO2Carbonation for Tailings Pond Overlayer.- A Novel Chemical Nitrate Destruction Process.