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Water Handling and Quality Considerations <br />• Given that the Thickener Sump is designed and utilized in overflow, emergency, or unplanned maintenance <br />situations, to contain the partial or full conterns of the Thickener Tank, the water and other materials in the sump <br />would not nomtally be suitable for direct discharge, due to high suspended solids concentrations. The current float <br />pump installation on the Thickener Sump is designed to route any discharge from the sump back to either the <br />Thickener Tank or the Coal Preparation Plain make-up water inlet, avoiding the need for discharge to either <br />sedimentation ponds or surface drainages. It is anticipazed that some coal solids will settle-out and accumulate in <br />the sump. The sump is designed so that small mobile equipmern can access the sump basin to clean-out any <br />significant accumulations of solids. Sump clean-out will be conduced on an as-needed basis, following removal of <br />any water and slurred coal (pumped back to the Thickener Tanl~, and the sediments will be loaded into trucks and <br />hauled to the existing coal refuse disposal facility. <br />Incident Precipitation and Run-On -The surface azea of the Thickener Sump is only approximately 0.086 acres, <br />so water contributions from normal incident precipitation aze negligible (0.013 ac-fr fora 10-yeaz, 24-hr event or <br />2.9 percent of pond capacity). A drainage collection ditch (Ditch D-2) irnercepts any surface runoff from the south <br />and routes it around the Thickener Sump to Pond D and other surrounding areas are graded to drain away from the <br />sump, so water contributions from run-on are similarlynegligible. For design dewatering purposes, the contnbution <br />from incident precipitation for the Probable Maximum Precipitation (I'MP) event (132 inches over 24hours) is 0.09 <br />acre-feet, or approximately 21.5 percent of pond capacity and slightly over 1-foot of depth with the pond near its <br />maxirnum design wazer ]eveL With a capacity of 250 gpm, the Thickener Sump float pump installation can discharge <br />the accumulated precipitation from the PMP over a period of about 2.0 hours. <br />Water ~v is -Because arty water, other than the negligrble incidern precipitation, discharged to the sump is process <br />water that will be recycled back irno the Preparation Plant system, all such weer is covered by existing water rights <br />associated with the process water supply. <br />• <br />TR OS-48 Ex8W-3 Revised - Mazch 2005 <br />