No development shall adversely affect the flow of surface waters to or from neighboring properties.
(A) Existing systems. Stormwater systems shall properly incorporate and be compatible with existing subsurface and surface drainage systems including agricultural systems. All existing drain tiles shall be incorporated into the new storm sewer system.
(B) Drainage easements. No obstructions shall be placed in any drainage easement that may block or divert the flow of surface drainage. All fences built in or across a drainage easement shall be either:
(1) Open to allow the flow of surface water; or
(2) Have the bottom of the fence at least six inches above grade to allow the unobstructed flow of surface water.
(C) Stormwater depths.
(1) The maximum depth of stormwater or floodwaters on new streets, parking lots, and other paved areas shall be eight inches measured at the gutter.
(2) The maximum depth of stormwater in other areas that are not designated drainage ways or water bodies shall be one foot.
(D) Best management practices. Developments shall incorporate all best management practices as may be required pursuant to the United States Clean Water Act, as amended.
(E) Diversions. Transfers of waters between watersheds shall be prohibited except when such transfers will not violate the provisions of this chapter.
(F) Runoff volume reduction.
(1) The applicant shall submit a strategy to meet the release rate requirements that minimizes the increase in runoff volumes and rates from the development and improves water quality.
(2) The applicant shall prepare a drainage plan using appropriate best management practices such as:
(a) Preservation of natural resource features of the development site (e.g. floodplains, wetlands, prairies, and woodlands);
(b) Preservation of the existing natural streams, channels, and drainage ways;
(c) Minimizing impervious surfaces created at the site (e.g. narrowing road width, minimizing driveway length and width, clustering homes, and shared driveways);
(d) Design of open vegetated channels to convey stormwater runoff;
(e) Preservation of natural infiltration and storage characteristics of the site (e.g. interspersing grass filter strips in areas with impervious cover and installing on-lot bio-retention facilities);
(f) Implementation of structural measures that provide water quality and quantity control, such as constructing wet bottom versus dry bottom basins; and
(g) Implementation of structural measures that provide only quantity control and conveyance.
(G) Design methods. Design methods shall be in accordance with the most current edition of the MWRDGC.
(H) Design rainfall. Design rainfall shall be in accordance with the most current edition of the MWRDGC.
(Ord. O-14-03, passed 2-18-03)