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<br /> DRAINAGE CRITERIA MANUAL RUNOFF <br />. TABLE 3-1 (42) <br /> RECOMMENDED RUNOFF COEFFICIENTS AND PERCENT IMPERVIOUS <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 /> Single-Family * .40 .45 .50 .60 <br /> Multi-Unit (detached) 50 .45 .50 .60 .70 <br /> Multi-Unit (attached) 70 .60 .65 .70 .80 <br /> 1/2 Acre Lot or Larger * .30 .35 .40 .60 <br /> Apartments 70 .65 .70 .70 .80 <br /> Industri a 1 : <br /> Light Areas 80 .71 .72 .76 .82 <br /> Heavy Acres 90 .80 .80 .85 .90 <br />. Parks, Cemetaries: 7 .10 .10 .35 .60 <br />Pl aygrounds: 13 .15 .25 .35 .65 <br /> Schools: 50 .45 .50 .60 .70 <br /> Railroad Yard Areas 40 .40 .45 .50 .60 <br /> Undeveloped Areas: <br /> Historic Flow Analysis- 2 (See "Lawns") <br /> Greenbelts, Agricultural <br /> Offsite Flow Analysis 45 .43 .47 .55 .65 <br /> (when land use not defined) <br /> Streets: <br /> Pa ved 100 .87 .88 .90 .93 <br /> Gravel 13 .15 .25 .35 .65 <br /> Drive 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, Cl ayey Soil 0 .05 .10 .20 .40 <br /> NOTE: These Rational Formula coefficients may not be valid for large basins. <br />. *See Figure 2-1 for percent impervious. <br /> 5-1-84 <br />