A complete and adequate drainage system design in compliance with local and regional drainage plans, title 9, chapter 7 of this Code, and Otsego Engineering Manual shall be required for the subdivision and may include a storm sewer system or system of open ditches, culverts, pipes, catch basins and ponding areas, or a combination thereof.
A. Stormwater drainage facilities shall be provided and designed to meet all Minnesota Pollution Control Agency National Pollutant Discharge Elimination System (NPDES) and Municipal Stormwater (MS4) requirements.
B. Stormwater drainage facilities, where required, shall be designed to convey the flow of surface waters without damage to persons or property. The system shall ensure drainage at all points along streets, and provide positive drainage away from buildings and on site waste disposal to accommodate frequent floods. The facilities shall be designed to protect against surface erosion and siltation of surface water and to prevent the discharge of excess runoff onto adjacent properties.
C. All developments are responsible for control of surface or stormwater to equal or improve predevelopment conditions:
1. Developmental drainage systems shall be provided that accept flow from upstream areas, that control, convey, and pond developmental runoff, that limit outflow to the natural predevelopment rate, and that do not have detrimental impacts on downstream properties.
2. All pipe conveyance shall be to 10-year design return frequency.
3. Flood protection shall be provided for 100-year design return frequency. Flood protection for public and personal property shall be one and one-half feet (1.5') plus any encroachment above the floodplain.
4. All ponding, detention or retention shall be designed for 100-year frequency storm condition with a positive outlet. All storm runoff shall be calculated by the Soil Conservation Service Method TR55 using Atlas 14 storm events. (Ord. 2019-06, 2-25-2019)