• Detention, retarding, and retention basins will be constructed as close to the Master Plan facilities as possible so that they can be eliminated in the future upon completion of the ultimate facilities.
  • Freeboard will not be required in detention, retention, or retarding basins. However, an emergency spillway which can convey 125% of peak postdevelopment 25-year flow in a safe manner and preclude upstream flooding will be required.
  • Basin side slopes shall be 2:1 or flatter, subject to slope stability analysis. Side slopes of 4:1 or flatter will be required if slope is planned to be mowed.
  • Retention, retarding, and detention basin designs will incorporate a 15 ft. wide all weather drive access road to the basin floor to facilitate maintenance. The maximum slope of the access road shall be limited to 15 percent. Proper turning radius or a hammerhead shall be provided. The paved section shall be 12 feet wide and shall have a structural section of 3" AC over 4" aggregate base compacted to 95% or 5" PCC over proper base prepared as recommended by the soils engineer.
  • For flow-by detention basins, a reinforced concrete low flow channel shall be provided from basin inlet(s) to basin outlet.
  • For retention basins and retarding basins, an approved energy dissipater shall be provided at the basin's inlet to preclude erosion. In addition, those basins which incorporate retention storage, shall have a bypass flow device to carry nuisance water around and out of the basins should upstream drywells fail.
  • All basins shall be fenced with a 6-foot high fence or wall approved by the City. Access to the basins shall be gated (15 ft. minimum) and locked.

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