2007-07-30_PERMIT FILE - C1981008A (25)

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3. WATER LEVELS AND CONFIGURATION No pit pumping has occurred in Pond 008, so the water levels that have been experienced in the pond in the past few years (2004-2006) are reflective of the post-mine condition. The drainage area of 102.9 acres is large enough that the pond will hold water for at least 30-45 days longer per year than the intermittent Calamity Draw which is located immediately to the south of Pond 008. Also, there is no other stock pond within a reasonable vicinity to this pond. Pond 007 is to the east but it is on anotherlandowners property. Attachment 2.05.3(3)-4 shows the as built calculations for Pond 008. These calculations assume that most of the land has been restored to irrigated pasture in developing the runoff volumes. For a 10 year event, the runoff is 3.27 acre-feet. For events that occur each year on the average, it can be assumed that 2.0-2.5 acre feet will be delivered to the pond. A volume of 2.5 acre feet would entail a surface area of approximately 0.6 acres, as shown on the Elevation-Capacity-Discharge Table in the Sedcad run of Attachment 2.05.3(3)-4. This elevation corresponds to a water depth • of 5.5 feet. It is normal for the pond to contain at least 2.0 feet of water depth for at least 45 days more than Calamity Draw to the south. At this depth, the pond will contain a volume of 0.69 acre feet. The principal spillway is an 18" CMP pipe with an 8' riser on it at elevation 5659.1' and two 6" sections at elevation 5652.0' which have two 6" valves to regulate the elevation in the pond. This detail is shown on Map 2.05.3(3)-4-3. As explained previously, The two 6" pipes will be lowered slightly to the bottom of the 18" barrel so that at no time could there be more than 2.0 acre feet of water detained in the pond. This will be done when the pond is turned over to the landowner as part of the bond release. (Revised August 2006 Attachment 2.05.3{3)-19-7