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.. <br />_ 1l1l-ll --III-I <br />I~I ~II~~~~~~IIII~II <br />PowDERHORN coAL co. <br />NORTH DECLINE <br />EAST SIIMP <br />As a temporary drainage control measure during the reclamation <br />phase of the North Decline area, Powderhorn designed and <br />installed a below grade catchment basin or sump for a portion of <br />the areas east of the reclaimed channel. The design is included <br />in Powderhorn's Mining and Reclamation Permit application on page <br />AAA-7, appendix AAA, Volume 8, revised 10-7-92. The sump was <br />designed to contain a 25 year 24 hour storm event without <br />discharge and was designed below grade to eliminate compaction <br />requirements on the embankments. <br />The sump was started in the spring of 1992 but was not completed <br />to its final design size until October 22, 1992. Material <br />excavated from the sump was piled around the edges of the sump <br />for ease in backfilling in the future but was not compacted to <br />form an embankment. The attached diagram shows the below grade <br />capacity of the sump as surveyed October 27, 1992. <br />Considering the design, observations during construction and <br />measured installation capacity of this sump, I hereby certify <br />that, to the best of my knowledge and belief, this east sump <br />meets the impoundment requirements of rule 4.05.09 of the <br />Regulations of the Colorado Mined Land Reclamation Board for Coal <br />Mining. Note: This sump is not classified as an impoundment by <br />MSHA. <br />i2- <br />~^.,-,,, <br />RE~E~A~~. <br />DEC 2 81992 <br />n r.~ <br />