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-19- I: Recommendations Mining activities and construction on the mine site limits the _ locations where pollutants may be transmitted to the ground water. Ditches and sedimentation ponds encompassing the mine area prevent potentially contaminated surface flocv from leav- ' ing the general vicinity; localizing the potential problem areas. Potential places for pollutants to enter the ground water sys- ("' tem on the Colowyo site are limited to: '1) t`~e tops of filled areas and overburden stockpiles where the soil cover has been removed; 2) the mine water collected at the base of the pit; ~-~ ~ " ~3)~the sedimentation ponds where contaminated water may per- colate into the system; and 4) he alluvium of the train load- out area where coal is stockpiled briefly, before shipment. ~.. ~rEntrance of pollutants into the ground vrater system through ~` s oil and fill is the most robable source of p p pollution to the `ystem: T4ater from snowmelt or rainfall can easily enter the `• spoils pile, percolate by gravity to the bottom of Streeter Gulch, and enter to shallow alluvial rtround crater system. T::e f_ fresh, broken overburden can be a source of pollutants, thus • increasing the TDS of the crater. Depending on the permeability L of the top of the Streeter Gulch alluvium, small springs may or may not develop at the base of the spoils pile. The volume of water collected at the base of the pit has histor- L ically been small. The ground water that enters the mine through springs upon the pit sides rarely reaches the base of the pit. Evaporation or percolation into the next aquifer only to be re- l.. moved by the next mining phase accounts for this small volume. The volume of water in the pit will be large only after rain- l storms, or during the snowmelt season. At these times, the eater could be pumped out of the pit, stored and used to settle dust later in the season to keep the hydraulic head of water in . the pit low to decrease infiltration. Also, the pit contains ( a natural lining that prevents infiltration in the sense that L "' Leonard Rice Consulting Water Engineers. Inc.