Laserfiche WebLink
Storm Water calculations <br /> For : Wilderness Point Resort <br /> Prepared by: Gregory R. Halling, PE <br /> Date: October 29, 2010 <br /> The entire property has a sandy subgrade with a sandy loam topsoil. Hydraulic conductivity rates of the <br /> sands were field verified and range from 6.86 to 118 feet per day. The slowest rates were in the soils that <br /> were low and close to the wetland. Upland areas all had rates that were greater than 24 feet per day which <br /> equates to a rate of 12 inches per hour. However, a sandy loam topsoil typical rate is 4 to 10 inches per <br /> hour. The HydroCad calculations have used a rate of 3 inches per hour in the lowest infiltration basins and 6 <br /> inches per hour in the basins that are more than 6 feet above the lake. Several of these areas are natural low <br /> areas and no grading is required. All of the infiltration basins will accommodate a 2 year storm without any <br /> infiltration. All of the basins typically hold the 100 year storm with the assumption that infiltration will be <br /> taking place at the assumed rates. However,if the ground is frozen when the larger storms take place then <br /> the basins will over flow. However, then if the ground is frozen there should be little potential for erosion to <br /> take place. All of the basin locations noted in the model are described based on the proposed unit type or <br /> number. There are several depressions that we have left land locked due to the sandy nature of the soils. <br /> None of these areas are a threat to the structures that are to be constructed. With the sands in the area there is <br /> no danger of these infiltration basins impacting the footings of the structures as long as bottom of the basins <br /> are at least 10' away from the structures. See attached HydroCad results for the 2 and 100 year storms. <br />