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4 <br /> <br />2 <br />4. All springs and seeps in the area should be identified in baseline studies. I would <br />recommend descriptions of any flows greater than one gallon per minute including <br />location, estimated flow, and field parameters (temperature, pH, electrical <br />conductivity). <br />5. Colowyo did not describe how flows in monitored drainages will be estimated. Some <br />type of peak flow measurement in ephemeral channels would be adequate. <br />Continuous flow recorders would be more appropriate for any streams that flow most <br />of the year. <br />6. The Division cannot make any final recommendations regarding monitoring plans <br />during the life of mine before the hydrologic environment has been characterized. <br />7. If plans to develop an underground mine beneath the Colowyo Mine are pursued, <br />please be aware that, <br />a. the stability of excess spoil fills and associated drainage structures would need <br />to be assured before those structures could be affected by subsidence, <br />b. the potential for any spoil aquifers to communicate with underground mine <br />workings via faults or subsidence features would need to be addressed, <br />c. potential subsidence impacts to impoundments, wells, and oil or gas pipelines <br />would need to be adequately addressed. <br />8. An additional aspect of hydrology baseline information Colowyo needs to address is <br />the location of wells, irrigation structures, and water uses within one mile of any <br />potentially affected area. <br />Please feel free to contact me or our staff if we can be of any further assistance as you plans <br />evolve. <br />Sincerely, <br />~~~ ~~ <br />L~Z P. Routten <br />rrY <br />Senior Environmental Protection Specialist <br />cc: Erica Crosby <br />~:~~si~oiw~ <br />