DESIGN OF SLURRY IMPOUNDMENTS AND OTHER MINE WASTE DISPOSAL FACILITIES


The mining of metals and minerals typically results in the production of substantial amounts of fine particulate materials known as tailings. These tailings are often in the form of an aqueous slurry that must be contained in an impoundment. Tailings impoundments can reach several hundred feet in height, and the stability and environmental performance of these structures is a major concern. The most common type of slurry impoundment is the valley fill, which utilizes the sides of the valley for containment and requires an embankment (generally of on-site materials) to dam the valley. For economic and operational reasons, the valley fill embankment is normally raised in several stages with coarse mine waste, as dictated by disposal demands. We have engineered numerous staged slurry impoundments and areexperienced with the various types of staged construction (upstream, centerline, and downstream). We routinely design impoundment embankments, discharge structures, liners, erosion and sedimentation control structures, haul roads, and other engineering features associated with slurry impoundments. D’Appolonia performs all aspects of engineering analysis, design, preparation of plans and specifications, and permitting, and we provide construction monitoring services for all of the structures that we design. Our expertise in mine waste disposal also encompasses the design of surface disposal cells and the development of plans for underground injection of slurry.



Mine complex for which D'Appolonia has provided engineering services.



Some descriptions of D'Appolonia projects related to coal refuse facility design and construction are provided in the following:


EXAMPLE PROJECTS


Coal Refuse Impoundment Design and Expansion

D'Appolonia has been responsible for planning, design and permitting services for a 160-acre coal refuse impoundment. The initial design was for a 60-foot-high diked impoundment constructed from coarse coal refuse, but the facility was expanded to 100 feet in height to accommodate co-disposal of coal refuse with combusiton ash. D'Appolonia's responsibilities have also included support in obtaining permits and performing breach analyses related to preparation of an Emergency Action Plan. D'Appolonia also provides periodic review of construcion and refuse material parameters.


Upstream Expansion of Coal Refuse Disposal Facility

D'Appolonia provided engineering and permitting services for the upstream expansion of the slurry impounding coal refuse disposal facility at Emerald Mine No. 1 in Greene County, PA. The final disposal facility configuration included two dams totaling more than 2000 feet in length, with the main dam exceeding 370 feet in height.


Design/Construction Monitoring of Coal Refuse Disposal Facility

D’Appolonia provided engineering and construction monitoring services for development of a slurry impounding coal refuse disposal facility. The facility was designed for 15.9 million tons of disposal capacity and a 19-year service life. Upstream construction was employed for the staged raising of the impounding embankment. The coarse coal refuse embankment stages were designed with internal drains for seepage control and sized for projected refuse generation rates.


Seismic Piezocone and Dilatometer Testing of Coal Refuse

D’Appolonia performed an in-situ testing program at the coal refuse disposal impoundment at a western Pennsylvania mine to confirm the applicability of shear strength properties for fine coal refuse (FCR) used in slope stability analyses of the pond embankment and to evaluate potential liquefaction susceptibility of the FCR.


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