Laserfiche WebLink
designed to shut off sump pumps during such an event had been <br />temporarily disabled due to construction and re-routing of trenches, <br />piping and electrical conduit. <br />Corrective Actions: Groundwater collection pumps and intake valves were immediately shut <br />off upon discovery. Water in the building was pumped to the concrete <br />Barrens Ponds. The cone filter was cleaned and the surge tank was <br />flushed to the concrete Barrens Ponds to remove sediment. Water <br />treatment operations were successfully restored. Temporary run- <br />permissive systems for sump pumps were installed within a few days <br />acid no similar or related problems have occurred since. <br />Two large parallel sand filters were subsequently obtained and installed <br />within the water treatment plant facilities in the event that future <br />construction, remediation or water management/treatment issues may <br />involve introduction of significant amounts of sediment into water to be <br />treated in the plant. It has not been necessary to use the sand filters to <br />date, but they are currently functional. A closed system backwash <br />design (a solids separation tank) for backwashing the sand filters is <br />currently in development. <br />Quantity: An estimated 50,000 gallons of raw alluvial groundwater went to the <br />building floor and sump containment systems. An estimated 27,000 <br />gallons of overflow went to the open piping winterization trench being <br />constructed adjacent to water treatment plant. The overflow was <br />contained in the building, sump and trench, and did not flow overland <br />into Ralston Creek. Water reaching the trench re-infiltrated into the <br />alluvium. Based on known groundwater flow patterns in the alluvium, <br />the water released to the trench is believed to have ultimately migrated <br />to areas where water collection sumps return captured water to the water <br />treatment plant for treatment. <br />Material: Alluvial groundwater (approximately 7 mg/L dissolved uranium). <br />South Concrete Barren Pond Leak <br />Date/Time: October 2-15, 2010 <br />Description: Water pumped into the south concrete Barrens Pond during the <br />exploration core hole location and plugging effort was subsequently <br />determined to be leaking from the pond into the alluvium. (There is no <br />evidence that the north Barren Pond leaks.) At low water storage levels <br />(approximately 6-10 inches), the south Barren Pond shows no evidence <br />of leakage but, at higher storage levels, leakage is evident. Based on <br />known groundwater flow patterns in the alluvium, water released from <br />the leaking south concrete pond is believed to have ultimately migrated