[en] Properly selected and oversized local sources of riprap may provide superior erosion protection compared with revegetation at a number of uranium mill tailings sites in arid regions of the United States. Whereas highly durable rock is appropriate for protecting diversion channels to the height of the 5-year flood, marginal quality rock may be adequate for protecting infrequently flooded side slopes of diversion channels, tailings embankments and caps. Marginal quality rock may require oversizing to guarantee that design size specifications are met at the end of the performance period (200 to 1000 years). This paper discusses a methodology for oversizing marginal quality rock. Results of cyclic freezing and thawing tests are used to determine oversizing requirements as functions of the performance period and environment. Test results show that marginal quality rock may be used in frequently saturated areas but in some cases oversizing will be substantial and in other cases marginal quality rock may be disqualified. Oversizing of marginal quality rock appears to be a practical reality in occasionally saturated areas (between the 5-year and 100-year floods). Furthermore, oversizing will not generally be required on slopes from the 100-year flood. 6 refs., 4 tabs

[en] The state-of-the-art regarding methods for the in-place dewatering of uranium mill tailings is described. Since large amounts of water in tailing impoundments can cause long-term seepage problems, drainage of the tailings both during operations and during the reclamation stage is highly desirable. Dewatering of tailings also provides for settlement prior to the placement of the cover and increases the pile's stability for earth-moving equipment during site reclamation and cover placement. The application of various drainage techniques is discussed with regard to their effectiveness in minimizing the amount of water remaining in an impoundment during long-term reclamation. Drainage techniques that are reviewed include underdrain gravity-flow systems, single wells and well-points, electro-osmosis, vertical drains, and evapotranspiration. It has been shown that the underdrain gravity systems provide an effective and reliable means of dewatering tailings. If feasible, they will probably prove to be the best option for the in situ dewatering of tailings because of their practicality and relatively low cost. The other methods would be recommended only as backup systems or in existing impoundments that do not have underdrain systems

[en] The integrity of cover systems placed on tailings impoundments will be affected by the potential for differential settlement of the tailings surface. Settlement of the sand fraction will occur relatively rapidly. The slimes will take longer time for consolidation and will produce greater settlement. This report reviews the phenomenon of consolidation for saturated and unsaturated tailings. The effect of load application by cover placement and the extent to which dewatering of tailings will cause consolidation are considered. In addition, the feasibility of inducing consolidation by alternative means and the potential applicability of these methods to tailings impoundments reclamation are discussed. Differential settlement of the tailings will cause tensile strain to be developed in covers. This strain could be large enough to cause cracking within a relatively brittle compacted clay. Dewatering of tailings by drainage can cause settlement even greater than that by placement of a cover material. Dewatering of the tailings would also increase the stability of the tailings surface, thereby enhancing reclamation operations. Consequently, in view of the enhanced surface stability and the fact that a portion of the differential settlement can be accomplished prior to cover placement, dewatering of tailings impoundments during operations may have benefical effects

[en] This books collects paper from a symposium on engineering aspects of waste management. Topics include: risk assessment of uranium mill tailings; stabilization of petroleum refining wastes; leaching of hazardous and radioactive materials from solid waste; excursion control at uranium mines; permeability of landfill soil liners, groundwater monitoring systems, and subsurface fuel release monitoring

[en] Geotechnical and geohydrological aspects of waste management are engineering parameters in the design and operation of waste disposal facilities. The 24 chapters in this volume are from the proceedings of the Ninth Annual Symposium on Geo-Aspects of Waste Management held at Fort Collins, Colorado, February 2-6, 1987. Some topics were (1) the design and operation of surface impoundments and hazardous waste landfills, (2) leaching hazardous and radioactive materials from solidified waste, (3) measurements of water infiltration and nuclide releases from laboratory models, (4) liability of hazardous waste management, and (5) investigation of subsurface fuel emission. It has been estimated that about 300 million tons of toxic waste per year are produced in the US. As industries in the US confront the growing problem of how to manage toxic wastes, they are using many new methodologies

[en] Erosion from many mining and construction sites can lead to serious environmental pollution problems. Therefore, erosion management plans must be developed in order that the engineer may implement measures to control or eliminate excessive soil losses. To properly implement a management program, it is necessary to estimate potential soil losses from the time the project begins to beyond project completion. Three methodologies are presented which project the estimated soil losses due to sheet or rill erosion of water and are applicable to mining and construction areas. Furthermore, the three methods described are intended as indicators of the state-of-the-art in water erosion prediction. The procedures herein do not account for gully erosion, snowmelt erosion, wind erosion, freeze-thaw erosion or extensive flooding

[en] Properly selected and oversized local sources of riprap may provide superior erosion protection compared with revegetation at a number of uranium mill tailings sites in arid regions of the United States. Whereas highly durable rock is appropriate for protecting diversion channels to the height of the 5-year flood, marginal quality rock may be adequate for protecting infrequently flooded side slopes of diversion channels, tailings embankments and caps. Marginal quality rock may require oversizing to guarantee that design size specifications are met at the end of the performance period (200 to 1000 years). This paper discusses a methodology for oversizing marginal quality rock. Results of cyclic freezing and thawing tests are used to determine oversizing requirements as functions of the performance period and environment

[en] Uranium mill tailings impoundments require long-term (200 to 1000 years) stabilization. This report reviews currently available methodologies for evaluating factors that can have a significant influence on tailings stabilization and develops methodologies in technical areas where none presently exist. Mill operators can use these methodologies to assist with (1) the selection of sites for mill tailings impoundments, (2) the design of stable impoundments, and (3) the development of reclamation plans for existing impoundments. These methodologies would also be useful for regulatory agency evaluations of proposals in permit or license applications. Methodologies were reviewed or developed in the following technical areas: (1) prediction of the Probable Maximum Precipitation (PMP) and an accompanying Probable Maximum Flood (PMF); (2) prediction of the stability of local and regional fluvial systems; (3) design of impoundment surfaces resistant to gully erosion; (4) evaluation of the potential for surface sheet erosion; (5) design of riprap for protecting embankments from channel flood flow and overland flow; (6) selection of riprap with appropriate durability for its intended use; and (7) evaluation of oversizing required for marginal quality riprap

[en] Flume studies were conducted in which riprap embankments were subjected to overtopping flows. Embankment slopes of 1, 2, 8, 10 and 20% were protected with riprap layers with median stone sizes of 1, 2, 4, 5 and/or 6 inches. Riprap design criteria for overtopping flows were developed in terms of unit discharge at failure, interstitial velocities and discharges through the riprap layer, resistance to flow over the riprap surface, potential impacts of the filter blanket on the riprap layer stability, and the effects of flow concentrations on the riprap stability. The resulting riprap design criteria were compared to the Stephenson, the US Army Corps of Engineers, the US Bureau of Reclamation, and the Safety Factors methods for riprap stone design; the Leps relation for interstitial velocities through riprap; and the Anderson et al. and Corps of Engineers relationships for estimating Manning's n values for resistance to flow. 16 refs., 24 figs., 18 tabs

[en] Flume studies were conducted in which riprap embankments were subjected to overtopping flows. Embankments slopes of 1, 2, 8, 10, and 20% were protected with riprap containing median stone sizes of 1, 2, 4, 5, and/or 6 in. Riprap layer thickness ranged from 1.5 D₅₀ to 4 D₅₀. Riprap design criteria for overtopping flows were developed in terms of unit discharge at failure, interstitial velocities and discharges through the riprap layer thickness and gradation on riprap stability, and potential impacts of integrating soil into the riprap layer for riprap stabilization. A riprap design procedure is presented for overtopping flow conditions