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CERTIFICATION OF CONSTRUCTION <br />PONDS P-1, P-2, P-4, P-5, P-6, P-7 and P-8 <br />These ponds were installed in 1980 while the mine access <br />road was being upgraded and surfaced. The as-built design in- <br />formation is given on maps D-4-5 and D-4-6 and associated write- <br />up in the Snowmass Coal Company Permit No. C-025-81. The location <br />of these ponds is shown on map D-4-8. These ponds were build as <br />energy discipators for the diversion ditches along the mine access <br />road. A disucssion on the use of these ponds is given on pages <br />4-17 and 4-18 in the permit. <br />These ponds were excavated below natural ground level for the <br />volumes shown on map D-4-5. No compaction data was taken because <br />no embankments were made. During the construction of these ponds, <br />topsoil was.salvaged and stockpiled on the refuse disposal area. <br />The revegetation work on these ponds was done in the fall of 1980. <br />On site inspection of these installations February 2, 1984, <br />revealed the discharge structure from P-4 to be an 18" culvert <br />rather than 24" as designed. The following calculation was done <br />to determine the effect: <br />Mannings Equation Q = 1.486 AR2/35~ <br />n <br />n = roughness coefficient, for 18" helical unpaved CMP = 0.019 <br />S = slope, measured 0.09 ft/ft <br />A = area, <br />R = area/wetted perimeter <br />(Formula and n taken from Handbook of Steel Drainage and <br />Highway Construction Products, 1971) <br />The calculated Q for the installed pipe is 29.3 CFS which <br />is 2.3$ under the design requirement of 30 CFS. Considering the <br />freeboard above the culvert this culvert should handle the designed <br />flow. <br />Information considered in the certification of these ponds is: <br />Approved design done by Dravo, consultation with Hank Artaz, super- <br />visor of construction, and personal observations February 2, 1984. <br />To the best of my knowledge and understanding, these ponds have <br />been installed to meet the requirements of the Regulations of the <br />Colorado Mined Land Reclamation Board for Coal Mining, 1980. <br />Larry M. Reschke ~,~ <br />P.E.~No. 19691 rv~~V`^"'cg~o <br />LMR:mgc ti ig ~~~ <br />