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XBOW <br />Sanborn Creek Mine <br /> <br />East Yard Sediment Pond <br />Recertification <br />In accordance with Rule 4.05.6(10), each sediment pond will be inspected during constmction under <br />the supervision of, and certified after construction by, a qualified registered professional engineer. <br />Certification of the constructed pond shall be forwarded to the Division immediately following <br />construction <br />The East Yard Pond is located in the Elk Creek Facilities Area Details of the pond are shown on <br />drawing E8-3404. Technical Revision Number 26 required minor modification to the spillway of the <br />pond with the installation of a 12-inch-diameter pipe as the emergency spillway, at an elevation 1- <br />foot higher than the 6-inch~iameter-pipe primary spillway. <br />As can be seen on drawing ES-3404, the 10-yr, 24-hr storm event and the 3-yr sediment storage <br />capacity can be contained below the primary spillway, and the 25-yr, 24-hr storm evert and the 3-yr <br />sediment storage capacity can be contained below the emergency spillway. During over 15 years of <br />operational experience since the East Yard Pond was initially constructed, there has never been a <br />recorded discharge from the pond, and during over 3 years of my personal experience on the mine <br />site, water levels have never reached more than about a foot of water in the bottom of the pond. <br />The 12-inch-diameter-pipe emergency spillway was installed shortly after Technical Revision <br />Number 26 was approved in April 1996. Since the new spillway pipe was required to be 1-foot <br />higher than the previously existing 6-inch pipe, additional road base material was required to be <br />placed on the mad south of the pond to meet the requirement of 1-foot of freeboard above the <br />emergency spillway. <br />Since the pond capacity is sufficient to totally contain the 25-yr, 24-hr storm event, road base was <br />added occasionally to the road, and thoroughly compacted by daily traffic on this access road to the <br />Sanborn Creek Mine portals. Final grade on the road was reached this summer, and constnrction <br />was completed with my final inspection, as part of my regular quarterly pond inspections, today. <br />P O Box 5 3 5 Somerset C o l o r a d o 8 1 4 3 a U S A <br />TEL (9 7 0) 9 2 9- 5 1 2 2 FAX (9 7 0) 9 2 9- 5 1 7 7 <br />