R-1999-31 - Laserfiche WebLink

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Zone R-1 R-2 R-3 MH NC GC BI LI m PUD e e Runoff coefficients, as shown in Table I, shall be the minimum used, based on total development under existing land zoning regulations. Where land uses other than those listed in Table I are planned, a coefficient shall be developed utilizing values comparable to those shown. Larger coefficients may be used if considered appropriate to the project by the City Engineer. The time of concentration is defined as the longest time, without unreasonable delay, that will be required for a drop of water to flow from the upper limit of a drainage area to the point of concentration. The time of concentration to any point in a storm drainage system is a combination of the "inlet time" and the time of flow in the drain. The inlet time is the time for water to flow over the surface of the ground to the storm drain inlet. Because the area tributary to most storm sewer inlets is relatively small, it is customary in practice to determine the inlet time on the basis of experience under similar conditions. Inlet time decreases as the slope and the imperviousness of the surface increase, and it increases as the distance over which the water has to travel and retention by the contact surfaces. Time of concentration shall be computed from Figure 2, and in no case shall the inlet time be more than the time shown in Table I. Table I Zoning District Name Low Density Residential Mid Density Residential High Density Residential Manufactured Housing District Neighborhood Commercial District General Commercial District Business Industrial Park District Light Industrial Heavy Industrial Planned Unit Development District Runoff Coefficient "C" 0.50 0.60 0.80 0.55 0.80 0.85 0.85 0.85 0.85 variable Maximum Inlet Time in Minutes IS IS 10 IS 10 10 10 10 10 10 to 15 Miscellaneous Land Uses Land Use Runoff Coefficient "C" Church School Park 0.70 to 0.90 0.50 to 0.90 0.30 to 0.70 Stormwater Criteria 4 of 12