2019-09-30_REVISION - M1988108 - Laserfiche WebLink

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ARCOSA Water Management and Runoff Control A comprehensive description of the local and regional surface water hydrology and groundwater hydrologoy are presented in Exhibit G. Precipitation runoff and water that originates from seeps at the alluvial material and shale interface will be intercepted by a ditch (to be installed) and will be channeled around the quarry to catchment ponds on the quarry floor. The ditch will be installed to prevent seepage down the sides of the quarry and the location of the ditch may be adjusted as necessary based on mining operational needs. The location of these ponds will be shifted from time to time to permit uniform deepening of the quarry floor. Up to approximately 30,000 gallons per day of water may be pumped from the quarry to the processing plant for various purposes including dust suppression and scrubber water. The right to this water is provided through formal lease agreement with the Hogan Family who owns the decreed water rights for the area. More information about water rights and water management may be found in Exhibit G. Off-spec Materials Management and Disposal Off-spec material is generated during the process operations and includes three primary types of materials. 1) Shale fines 2) Baghouse dust 3) Lime scrubber sludge mixed with shale fines These materials are stockpiled at the processing facility in advance of being placed into the mined-out portions of the quarry or will be used for reclamation during backfilling of the quarry. The baghouse dust and shale fines are essentially comprised of native material that is too fine for use as a final product. This material is placed back into the quarry as backfill material. The lime flue gas scrubbing system generates a lime sludge that is mixed with shale fines and is generally composed of the following: • 50% Raw Shale Fines • 38% Gypsum (CaSO4.2H2O) • 10% Flyash • 2% Unreacted Lime The addition of lime to fine-grained soils (e.g., shale fines and clays) may provide lime fixation and stabilization benefits through chemical reactions with the mineral structure of the soil. A multitude of scholarly studies and engineering practices consider the addition and mixing of lime to fine-grained soil to improve physical properties of the soil allowing for improved strength and stiffness, and allows one to render unsuitable materials workable for bulk fill and other earthwork applications2. Generally, with tme (i.e., curing of the mixed soil) the physical properties improve for fine-grained soil mixed with lime. Though the lime interaction with shale fines has not been specifically evaluated for this Site; the mixing of the lime sludge with soil is anticipated to have at least a marginally positive effect on soil physical properties. 2 Boardman et al.,(2001).Development of stabilisation and solidification in lime-clay mixes.Geotechnique 50,No.6,pp.533-543.