(A) Waterways.
(1) Natural drainage systems shall be used if feasible for storage and flow of runoff. Storm water drainage may be discharged to marshlands, swamps, retention basins or other treatment facilities. Diversion of storm water to marshlands or swamps shall be considered for existing or planned surface drainage. Marshlands and swamps used for storm water shall provide for natural or artificial water level control. Temporary storage areas or retention basins scattered throughout developed areas shall be encouraged in order to reduce peak flow, erosion damage and construction cost.
(2) The widths of a constructed waterway shall be sufficiently large to channel runoff from a ten-year storm. Adequacy shall be determined by the expected runoff when full development of the drainage area is reached.
(3) No fences or structures shall be constructed across the waterway that will reduce or restrict the flow of water.
(4) The banks of the waterway shall be protected with permanent vegetation.
(5) The banks of the waterway shall not exceed five feet horizontal to one-foot vertical.
(6) The gradient of the waterway bed shall not exceed a grade that will result in a velocity that will cause erosion of the banks of the waterway.
(7) The bed of the waterway shall be protected with turf, sod or concrete. If turf or sod will not function properly, rip-rap may be used. Rip-rap shall consist of quarried limestone, field stone (if random rip-rap is used) or construction materials and concrete. The rip-rap shall be no smaller than two inches square nor larger than two feet square. Construction materials shall be used only in those areas where the waterway is not used as part of a recreational trail system.
(8) If the flow velocity in the waterway is such that erosion of the turf sidewall will occur and the velocity cannot be decreased via velocity control structures, then other materials may replace turf on the sidewalls. Either gravel or rip-rap would be allowed to prevent erosion at these points.
(9) Development of housing and other structures shall be restricted from the area on either side of the waterway.
(B) Sediment control of waterways.
(1) To prevent sedimentation of waterways, pervious and impervious sediment traps, and other sediment control structures, shall be incorporated throughout the watershed.
(2) Temporary pervious sediment traps may consist of bales of hay with a low spillway embankment section of sand and gravel that permits a slow movement of water while filtering sediment. The structures would serve as temporary sediment control features during the construction phase of development.
(3) Permanent impervious sediment control structures shall consist of sediment basins (debris, desilting basins or silt traps) and shall be utilized to remove sediment from runoff prior to its disposal in any permanent body of water.
(C) Wetlands.
(1) Delineation report. Any person seeking to conduct wetland disturbing activities shall submit a wetland delineation report to the City Engineer. No permit to allow wetland disturbing activities shall be issued until approval of the wetland replacement plan application or a certificate of exemption has been obtained in strict conformance with the provisions of this chapter and the Minnesota Wetland Conservation Act.
(2) Impacts. Utilization and development impacts to wetlands shall be consistent with the storm water management policies of the city.
(3) Impacts to wetlands.
(a) Storm water discharge into wetlands shall be consistent with the requirements of this chapter.
(b) A building setback of 20 feet shall exist from the delineated edge of all wetlands at the time of development within areas developed or redeveloped after the effective date of this chapter, unless otherwise stated within the zoning district. If a wetland buffer strip is required around the wetland, no structures shall be placed within this strip.
(c) Wetlands shall not be drained or filled, wholly or partially, unless replaced by restoring or creating wetland areas of at least equal public value in accordance with the Minnesota Wetland Conservation Act.
(Ord. 583, passed 8-26-2019)