b'WASH SYSTEMSClosed loop aggregate wash systems By Craig LegerThe importance of recirculating water onsite to allow for material processingT here has been an increasing demand for aggregate products Primary Settling Pond: will accept silt-laden discharge from the that require washing during their processing to removewash plant.fines (silt- and clay-sized particles) from coarse aggregate in an effort to meet production or market specifications forSettling Ponds: from the primary settling pond, water will move hydraulic separation of fine aggregate material.through additional settling ponds to further polish or clarify the water.Simply stated, the purpose of a closed loop wash plant systemFresh Water Intake / Clear Pond:fresh water from the settling is to allow for material processing onsite in which water is recircu- ponds will be stored in the freshwater intake pond for re-use in lated between the wash plant/processing equipment and a seriesthe wash plant.of weir-separated ponds. Normally,inawell-designedsystem,nooff-sitesurfacewater A typical aggregate wash plant will include the wash plant anddischarge is required as part of the wash plant operations as water processingequipment,aclear/freshwaterpondandaseriesofiscontinuallycirculatedbetweentheprocessingplantandthe settling ponds and polishing ponds as described in the column toponds. Some water, however, is lost from the wash system due to the right. This type of wash system is common at many aggregatevarious factors:sites throughoutOntario.In unlined ponds, standing water will percolate from the base of the pond and re-infiltrate the groundwater system. The rate of leakage is greatly dependent on the type of liner and quality of the installation.Washing plant at the Thomas Water sorbed to the washed aggregate that is stockpiled: A portionCavanagh Almonte Quarry of the sorbed water will drain from stockpiles and re-infiltrate the groundwater system.Evaporation.Some water adheres to the settled fines when the ponds are even-tually excavated to maintain pond capacity.30 AVENUESWINTER 2020'