2022 08 Drainage Report

Table 21-1 Non-Erosive V. ies for Point Discharges Maximem Stable Slope for Point Discharges for Various Soils Soil Type Perennial, Natural Vegetation Maximum Slope (%) Sands 18 Sandy loam 2.0 Silt loam, loam 25 Sandy clay loam 3.5 Clay loam. 5.0 Graded loam to gravel 5.0 Discharge from each proposed stormwater basin will disperse over a broad area. It should be noted that existing downstream surface is vegetated an no sandy surface conditions were observed. The existing vegetation will not substantially concentrate flows. Stability Criteria (in conjunction with table 21-1) i The maximum discharge rate shall be 10 cfs or less for the twenty-five (25) year storm. The discharge rate for the proposed outfall does not exceed 10 cfs for the 25-year storm. ti, Multiple outlets may be utilized to reduce individual outlet flow rates to levels below the thresholds noted above. Outlets should be spaced no closer than 50 ft horizontally to avoid re-mixing of flows. Not applicable as the outlets are below the threshold noted above. iii, Flow over the outlet area shall be less than 0.5 cfs/ft. Designers shall not design excessive widths which will cause flows to concentrate. The proposed flows do not exceed 0.5 cfs/ft. As noted above, the peak 25-year peak flow from any of the four (4) proposed basins is 0.68 CFS. As such, the flow over the outlet area is 0.18 cfs/ft. SHI Builders August 2022 DEC# 4266-99-001 -9-