8.1. SR 11-04-2013 - Laserfiche WebLink

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SECTION 5 to a maximum extent reasonable, but allows for the implementation of the City's goal to have defined outlets and overflows available for all City stormwater retention areas. 5.5.8.Storm Sewer Policies 1. Trunk storm sewer system shall be designed to accommodate a 100-year critical duration rainfall event. A trunk system shall be defined as the main channel of the stormwater system connecting stormwater storage facilities or serving as an outlet and downstream conveyance system for a stormwater storage facility. 2. Minor drainage facilities shall carry the 10-year recurrence runoff flows. Minor facilities include street gutter capacity, cross-culverts, storm sewers, and swales to the limits of easement and/or right-of-way. 3. The minimum storm sewer size shall be 15 inches in diameter. Twelve-inch diameter storm sewer may be used for catch basin leads. 4. The minimum culvert size shall be 15 inches in diameter. 5. Driveway culverts shall have adequate length to allow 4 horizontal to 1 vertical side slopes for the driveway. 6. Culverts shall be placed at or up to 0.2 feet below the ditch flowline. 7. Culverts located within County or State right-of-way shall be provided with safety aprons and grates with a maximum slope of 6 to 1. Marking posts shall be installed in accordance with the County or Mn/DOT permit. 8. Minimum full flow velocities for storm sewers shall be 2.5 fps. 9. Storm sewer and culvert outlets shall be designed to prevent erosion. Rip-rap and aprons shall be placed to/below normal water level of the receiving body of water. 10. The 100-year high water level shall be labeled on Plans for all wetland and ponding areas. 11. Rear yard inlets shall be reviewed by the City Engineer on a case-by-case basis. 12. Drainage swales shall have a minimum slope of 1.00%. Surface Water Management Plan City of Elk River Section 5 WSB Project No.1992-030 Page-6