Laserfiche WebLink
Group D - Includes clayey gravels, clayey sandy gravels, clayey <br />sands, clayey gravelly sands, low plasticity clays, sandy <br />or silty clays, organic silts and clays of low plasticity, <br />highly plastic clays and silty sands, organic silts and clays <br />of high plasticity. <br />Curve numbers that were assumed in the development of the model were based <br />on the hydrologic soil group for each watershed based on the information <br />contained in the County Soil Survey. Development plans shall consider post - <br />development site soil conditions when choosing runoff curve numbers for final <br />design. <br />Curve numbers (CN) are given in SCS TR-55. Average CN values for each land <br />use type are used in the design of the storm drainage facilities in undeveloped <br />areas. For the modeling of existing facilities, CN values were determined for <br />each type of development and current zoned land use in each subwatershed. In <br />general, the unpaved, non -wetland areas were modeled with curve numbers that <br />most closely represent the Anoka Sand Plain. The curve numbers were then <br />adjusted to reflect the percentage of impervious surfacing. <br />It should be noted that if land use changes to more or less impervious surfacing <br />than the model, it will affect the model and updates may be needed. <br />Section IV <br />October 21, 2015 Page 38 <br />