Grading/Drainage

The grading and drainage plan is important in determining where the water will drain to during storms. The grading plan was determined in order to have the water drain to the desired culverts. Sub-basin 5 was made to be the upper portion of the RDC. All of the runoff from this sub-basin is drained into the 18 in. culvert that is also located in this sub-basin. With an impervious area added in the sub-basin, all of the water that drained into sub-basin 5 would drain out through that 18 in culvert. The other area that received impervious area within it was sub-basin 4. This was a much large subbasin which is designed to completely drain into the 18 inch culvert located within this subbasin. An open channel was created to make the water flow from that 18 in. culvert to the large 48 in. culvert. From this culvert it will flow into the retention basin located on the other side of the main offices. The grading plan for the lower asphalt region is not as drastic as the upper region, but it still will make the water drain to the desired culvert. All of the grades that were used for these subbasins is shown in the Construction Plan, sheet 7.