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4 <br />MESA COUNTY <br />STORM DRAINAGE CRITER(AL MANUAL TABLE 402 <br />RAT2ONAL. METHOD <br />RECOMMENDED AVERAGE RUNOFF <br />CO EF F = C Z ENTS <br />AND PERCENT 2MPERV= OUS <br />^C^ FREQUENCY <br />LAND USE OR SURFACE PERCENT 10 100 <br />CHARACTERISTICS IMPERVIOUS A&B CAD A&B C6D <br />Business <br />Commercial Areas 95 .90 .90 .90 .90 <br />Neighborhood Areas 70 .75 .75 .80 .80 <br />Residential <br />1/8 Acre or less 65 .55 .65 .65 .75 <br />1/4 Acre 40 .50 .60 .60 .70 <br />1/3 Acre 30 .40 .50 .55 .60 <br />1/2 Acre 25 .35 .45 .45 .55 <br />1 Acre 20 .30 .40 . .40 .50 <br />Industrial <br />Light Areas 80 .70 .70 .80 .80 <br />Heavy Areas 90 .80 .80 .90 .90 <br />Parks and Cemeteries 7 .30 .35 .55 .60 <br />Playgrounds 13 .30 .35 .60 .65 <br />Schools 50 .45 .50 .60 .70 <br />Railroad Yard Areas 40 .50 .55 .60 .65 <br />Undeveloped Areas <br />Historic Flow Analysis 2 .15 .25 .20 .30 <br />Greenbelts, Agricultural <br />Pasture/Meadow 0 .25 .30 .35 .45 <br />Forest 0 .10 .15 .15 .20 <br />Exposed Rock 100 ~.90 .90 .95 .95 <br />Offsita Flow Analysis 45 .55 .60 .65 .70 <br />(when land use is <br />not defined) <br />Streets <br />Paved 100 .90 .90 .95 .95 <br />Gravel 90 .80 .80 .85 ,85 <br />Drive and Walks 100 .90 .90 .95 ,95 <br />Roofs 90 .90 .90 .95 .95 <br />Lawns 0 .25 .30 .35 ,45 <br />NOTE: The Rational Method Formula coefficients do not apply fo r <br />larger basins where the time of concentration exceeds 60 <br />minutes. <br />