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iiiiiiiiiiiniuiii <br />999 <br />ADDENDUM TO: HYDROLOGIC AND HYDRAULIC DESIGN OF SEDIMENTATION <br />PONDS AND OTHER DRAINAGE FEATURES FOR NATIONAL KING <br />COAL MINE. JANUARY 1998. <br />REVISON TYPE: This revision reports on changes/additions.to two pipes within the mine <br />yard drainage system. ''°°'"~`='~~~':• <br />.;~ ~ r;. <br />REVISIONS BY: Don R. May, P.E. <br />v ~4. ~• iO~ <br />REVISION DATE: August 1998 ~ 4~, 23c5 `•:,} <br />Revision 1. ~;s;~~`;""'~y~ .:~' <br />The 24" CMP listed as reach 9 in the above mentioned drainage report was replaced <br />and rerouted. The former pipe collected flow from the ditch, reach 6, and discharged it into the <br />ditch, reach 11. With the construction of the new scales in this area the drainage system was <br />changed so that the reach 11 ditch was replaced with a pipe. Because of this the reach 9 pipe <br />was rerouted. It begins at the same location, end of reach 6 ditch, and now flow towards the <br />northwest to discharge directly into the reach 8 ditch which subsequently drains directly into the <br />west pond. <br />The required discharge capacity reported in the Drainage Report remains the same at <br />0.9 cfs. The pipe slope was reported by mine personnel as an 8' drop in 150' or S=0.053. <br />Analysis showed that a 12" CMP provides a flow capacity of 4.47-cfs greatly exceeding the <br />required capacity. The new 12" CMP will henceforth be referred to as reach 9. <br />Revision 2. <br />A culvert was installed under the service road which runs from the shop on the upper <br />terrace to the main lower yard. The culvert is under the portion of the service road that is located <br />directly under the conveyor belt. This culvert collects runoff from the yard area near the base of <br />the waste rock pile, at the toe of the slope below the shop and water flowing down the service <br />road. The culvert is strictly for convenience and could (has historically at times) been replaced <br />with flow over the road. It discharges into a drain that feeds the main yard pipe (reach 4). <br />The CMP culvert has dimensions of diameter 18", length 40' and a slope of 2.5' drop in <br />40' (data provide by mine personrel). This results in a flowing full discharge capacity of over 14 <br />cfs. The required discharge capacity for all inflow to the West Pond (of which this is only one <br />contributing poriton) is only 6 cfs. Therefore the constructed 18" culvert is more that adequate. <br />