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<br />BOULDER COUNfy"- -. <br />STORM DRAINAGE CRITERIA. MANUAL <br /> <br />, <br />RUNOFF COEFFICIENTS AND I)ERCENT IMPERVIOUS <br /> <br />l~-: TABLE 801 <br /> <br /> RUNOFF COEFFICIENTS <br /> LAND USE OR PERCENT FREQUENCY <br /> SURFACE CHARACTERISTICS IMPERVIOUS 2 5 10 100 <br /> Business: <br /> Commercial Areas 95 .87 .87 .88 .89 <br /> Neighborhood Areas 70 .60 .65 .70 .80 <br /> Residential: <br /> Slngle-Family Figure-603 .40 .45 .50 .60 <br /> Multi-Unit (detached) SO .45 .50 .60 .70 <br /> Multi-Unit (attached) 70 .60 .65 .70 .80 <br /> 1/2 Acre Lot or Larger Figure-603 .30 .35 .40 .60 <br /> Apartments 70 .65 .70 .70 .80 <br /> Industrial: <br /> 11 9 ht Areas 80 .71 .72 .76 .82 <br /> Heavy Areas 90 .80 .80 .85 .90 <br /> Parks, Cemetaries 7 .10 .10 .35 .60 <br /> P1 aygrounds 13 .15 .25 .35 .65 <br />J School s uo-~70 <br />J 50 .45 .50 .'60 - <br />-'-,.- . . . ~. . --. . "___......__....o..__~-_~'-""'~~-~~~~~,__ <br /> ~ai1 road Yard Areas --- 40 .40 .45 .50 .60 <br /> Undeve10eed Areas: (see "Lawns") <br /> Historlc Flow Analysis 2 <br /> Greenbelts, Agricultural <br /> Offsite Flow Analysis 45 .43 .47 .55 .65 <br /> (when land use not defined) <br /> Streets: <br /> Paved 100 .87 .88 .90 .93 <br /> Gravel 13 .15 .25 .35 .65 <br /> Drives and Walks 96 .87 .87 .88 .89 <br /> Roofs 90 .80 .85 .90 .90 <br /> Lawns, Sandy Soil 0 .00 .01 .05 .20 <br /> Lawns, Clayey Soil 0 .05 .10 .20 .40 <br /> NOTE: The Rational Formula coefficients do not apply for larger basins where <br /> the time-of-concentration exceeds 60 minutes. <br /> --- -- <br /> WRC EN~ REFERENCE: USDCM DRCOG Rev. May 1, 1984 <br /> _1':37_ <br />