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2.05.3 (3) (c) (i) has been installed along the road to comply with this requirement and to convey surface water from the af.fecte3 area into a sedimentation pond. Refer to r"ap 2.05.3(2)(1)-1 for details of the road as constructed. Two culverts have been installed under the roadway to convey runoff ' from undisturbed areas, via natural drainages. directly to the river. The revised Land Use Map, 7_.04.3(2)(a)-1, shows the locations ' of the two culverts. An 18" CtdP drains the natural draws under the road, while a 9" Ct•IP drains the west portal area. Both are ' sized adequately. Calculations and peak flows for these culverts are shown on Figure 2.05.3(3)(c)(i). ' Grading and maintenance of the roads and drainage structures will be accomplished by mine employees and yard equipment. (ii) Geotechnical analysis. Not Applicable (iii) Alteration of a natural drainage way. P]ot applicable.. ' The diversion to the main drainage north of ARCO'S test revegetation site is in reality a ditch, approximately 150 feet= long, 1 foot wide, and 0.5 feet deep. The purpose of this ditch is to divert any runoff from the draw at the inlet end, around ' ARCO'S 56 foot by 220 foot fenced, revegetation test plot. The ditch was installed when ARCO installed the test plot and wi1:L not be removed by Bear Coal Company during the reclamation. 'Che ' spoils pile north of the revegetation test plot will be covered by six-inches of topsoil, and revegetated. The Land Use Map, 2.04.3(2)(a)-1, has been revised deleting the "permanent runoff diversion". ~.~ 7'h;, r~~fti 7z ? For runoff to .occur in this watershed, 3.71"~f rainfal St occur (see Culvert Calculations, Figure 2.05.3(3)(c)(i)). A,100 year, 24 hour event will ~.+~•> nr~~uce 2 9" of rainfall in atin tha runoff for this area will occur infrequently. ' RE~72SED May 15, 1981 62 .~