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Rob Laird <br />From: Rob Laird <br />Sent: Wednesday, February 17, 2010 8:33 AM <br />To: 'Bird, David' <br />Cc: Dan Hunt; Mark Johnson <br />Subject: RE: AM -04 approval <br />Tracking: Recipient Delivery Read <br />'Bird, David' Delivered: 2/17/2010 8:33 AM <br />Dan Hunt Delivered: 2/17/2010 8:33 AM Read: 2/17/2010 9:08 AM <br />Mark Johnson Delivered: 2/17/2010 8:33 AM <br />re =M] <br />Thanks for the concurrence. Our low point within the pit is in the west central portion and that is where we pump <br />to the river from as you have seen. We have trenched to that location for the temp drain within the pit. We can <br />then also fill from either the north or the south until such a time that we desire to shut the pumps off and /or build <br />the permanent drain. This is another scenario in conjunction with what you have described below. We will keep <br />you posted. As I have written, we will not know the outcome of the Adams County approval /disapproval for some <br />time to come. Rob <br />From: Bird, David [mailto:David.Bird @state.co.us] <br />Sent: Wednesday, February 17, 2010 8:15 AM <br />To: Rob Laird <br />Cc: Waldron, Tony <br />Subject: RE: AM -04 approval <br />More, <br />I agree that committing to a solid date for the permanent drain installation would be premature. The critical <br />milestone will be when the pit backfill starts to approach the elevation of the temporary drain outflow and <br />potentially obstruct its flow. That is when we will have to start paying close attention. Or if for some reason the <br />temporary drain fails to convey the ground water adequately, but so far it seems to be doing quite well. <br />I don't think it makes any sense to start installing the permanent drain until the backfill gains considerable <br />elevation, because it seems to me that the existence of a pit face nearby could potentially destabilize the drain. <br />So as long as the temporary drain is doing its job, and as long as the backfill is below the level of the temporary <br />drain outflow, then the situation is stable and we can cross the bridge to the permanent drain at a later time. <br />David Bird <br />Division of Reclamation, Mining 8s Safety <br />Department of Natural Resources <br />1313 Sherman Street, Rm 215 <br />Denver, CO 80203 <br />Tel: 303-866-3567 x8108 <br />Fax: 303 -832 -8106 <br />2/18/2010 <br />