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<br />9) Construct with an impermeable liner when the system has less than three (3) feet of <br />separation between seasonally saturated soils or bedrock; <br />10) Designed with a maintenance access, typically eight(8) feet wide. <br />iii. Wet Sedimentation Basin <br />1) Permanent volume of 1,800 cubic feet of storage below the outlet pipe for each acre <br />that drains to the basin; <br />2) Permanent volume must reach a minimum depth of at least three (3) feet and must have <br />no depth greater than 10 feet; <br />3) Must be configured to minimize scour or resuspension of solids; <br />4) In addition to the permanent volume, the basin must provide the water quality volume <br />as live storage. Water quality volume is described in Section b.iii, b.iv, and b.v; <br />5) Water quality volume discharges at no more than 5.66 cubic feet per second (cfs) per <br />acre of surface area of the basin; <br />6) Designed to prevent short-circuiting and the discharge of floating debris; <br />7) Basin outlets must have energy dissipation; <br />8) Must include a stabilized emergency overflow to accommodate storm events in excess <br />of the basin's hydraulic design; <br />9) Must have a maintenance access, typically eight (8) feet wide, for the basin; <br />10) Must be located outside of surface waters and any buffer zones identified in <br />Construction Stormwater General permit. <br />11) Permittees must design basins using an impermeable liner if located within active <br />karst terrain. <br />iv. Regional Wet Sedimentation Basins <br />1) When the entire water quality volume cannot be treated by volume reduction practices <br />onsite, regional wet sedimentation basins can be used or created, provided they are <br />constructed basins, not a natural wetland or water body. <br />2) The regional basin conforms to all requirements for a wet sedimentation basin as <br />described in Part d.iii. (Wet Sedimentation Basin) <br />3) Must be large enough to account for the entire area that drains to the basin. <br />4) Waterways between the project and the regional basin must not be significantly <br />degraded. <br />5) Written authorization from the City of Arden Hills or private entity that owns and <br />maintains the regional basin.