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F off from the 020 0.0 148 0.07 <br />ope and into <br />ope from the <br />k and pad i <br />(Attachment 3) <br />Runoff from the 0.20 0.0 148 0.07 <br />tank and pad away <br />from the slope <br />(Attachment 4) <br />Description `; Depth (with Freeboard) j Velocity <br />Interceptor Ditch i 0.47 feet 1.37 feet per second (fps) <br />(Attachment 5) <br />Point Discharge I 0.04 feet 0.57 fps <br />(Attachment 6) I <br />7. CONCLUSIONS <br />Best management practices of utilizing an upper cleanwater diversion ditch and graveling the tank pad at the <br />water tank result in discharge from the site meeting effluent standards of 0.5 ml/I following a 10 -year 24 -hour <br />storm event. <br />Best management practices of ditch feather distribution and hay bales for point discharge energy dissipatiW (- _. <br />• are highly recommended as part of the facility. <br />A small area exemption is warranted. <br />CERTIFICATION <br />This certification is limited to office design, based on physical descriptions and site conditions <br />information provided by Kathy Welt, Environmental and Engineering Supervisor, West Elk <br />Mine, Mountain Coal Company. The analysis is good engineering practice, and conclusions <br />reached, based on the information provided, are valid to the best of my knowledge. A Small <br />Area Exemption is warranted under current rules. <br />� Lr/� <br />Svfo . alker, P.E. <br />Colorado Registration Number 18378 <br />Date: f 9 <br />