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• <br />Runoff from the I 0.20 0.0 143 0.07 <br />cutslope and into ' <br />the slope from the <br />tank and pad I <br />(Attachment 3) I <br />Runoff from the 0.20 ~ 0.0 148 0.07 <br />tank and pad away <br />from the slope ; i <br />(Attachment ~) ~ <br />Descrip[ion ~ Depth (with Freeboard) Velocity <br />interceptor Ditch 0.47 feet 1.37 feet per second (fps) <br />(Attachment 5) ~ <br />Point Discharge 0.04 feet 0.57 fps <br />(Attachment 6) <br />7. CONCLUSIONS <br />Best management practices of utilizing an upper cleanwater diversion ditch and graveling the tank pad a[ [he <br />water tank result in discharge from the site meeting effluent standards of 0.5 ml/1 following a 10-year 24-hour <br />storm event. <br />• Best management practices of ditch feather dis[ribu[ion and hay bales for poin[ discharge energy dissipation <br />are highly recommended as part of the facili[y. <br />A small area exemp[ion 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 />~~~ ~ r,~/~l~ <br />. ~~ B"yfor ,~. ' alker, P.E. <br />c Colorad'o~tegistration Number 13378 <br />Q <br />°~ <br />...,,. ~ - <br />\J <br />