(A) General requirements. Every major subdivision request shall be accompanied by a drainage plan. The Planning Commission shall not recommend for approval any preliminary plat for a major subdivision which does not make adequate provision for storm or flood water runoff channels or basins. The storm water drainage systems shall be separate and independent of any sanitary sewer system. Storm sewers, where required, shall be designated by the Rational Method, or other methods if approved by the Planning Commission, and a copy of the design computations shall be submitted along with the plan. Inlets shall be provided so that surface water is not carried across or around any intersection, nor for a distance of more than 600 feet in a gutter.
(B) Location. The subdivider/developer may be required by the Planning Commission to carry away by pipe or open ditch any spring or surface water that may exist either previously to, or as a result of the subdivision. The drainage facilities shall be located in the road right-of-way where feasible, or in perpetual unobstructed easements of appropriate width, and shall be constructed in accordance with the construction standards and specifications.
(C) Accessibility to public storm sewers. Where a public storm sewer is accessible, the subdivider/ developer shall install storm sewer facilities, or if outlets are within a reasonable distance, adequate provision shall be made for the disposal of storm waters, subject to the specifications of the Engineer. However, in subdivisions containing lots less than 15,000 square feet in area are in business and industrial districts, underground storm sewer systems shall be constructed to an approved outfall. Inspection of the facilities may be conducted by the Engineer.
(D) Accommodation of upstream drainage areas. A culvert or other drainage facility shall in each case be large enough to accommodate potential runoff from its entire upstream drainage area, whether inside or outside the subdivision. The Engineer shall determine the necessary size of the facility, based on the provisions of construction standards and specifications.
(E) Effect on downstream drainage areas. The Engineer shall also study the effect of each subdivision on existing downstream drainage facilities outside the area of the subdivision. Local government drainage studies, together with other studies as shall be appropriate, shall serve as a guide to needed improvements. Where it is anticipated that the additional runoff incident to the development of the subdivision will overload an existing downstream drainage facility, the Planning Commission may withhold approval of the subdivision until provision has been made for the improvement of the potential condition in a sum as the Planning Commission shall determine. No subdivision shall be approved unless adequate drainage will be provided to an adequate drainage watercourse or facility.
(F) Areas of poor drainage. Whenever a plat is submitted for an area which is subject to flooding, the Planning Commission may approve the subdivision; provided that, the subdivider/developer fills the affected area of the subdivision to an elevation sufficient to place the elevation sufficient to place the elevation of streets and lots at a minimum of 12 inches above the elevation of the average probable flood, as determined by the Engineer. The plat of the subdivision shall provide for a floodway along the bank of any stream or watercourse, in a width which shall be sufficient in times of high water to contain or move the water, and no fill shall be placed in the floodway nor shall any structure be erected or placed there. The boundaries of the floodway shall be subject to approval by the Engineer. Areas of extremely poor drainage should be discouraged.
(G) Floodplain areas. The City Council may when it deems it necessary for the health, safety or welfare of the present and future population of the area and necessary to the conservation of water, drainage and sanitary facilities, prohibit the subdivision of any portion of the property which lies within the floodplain of any stream or drainage course. These areas shall be preserved from any and all destruction or damage resulting from clearing, grading or dumping of earth, waste material or stumps and in accord with county shorelands zoning. The land or lands subject to periodic flooding may be used in computing the number of lots to result from approval of the final plat, and in computing the area requirement of any lot; provided, the lot size meets the requirements of Ch. 154 of this code of ordinances and the subdivider/developer can prove to the satisfaction of the Planning Commission that each lot has a suitable building site and sufficient area for septic systems.
(2001 Code, § 12.07) Penalty, see § 10.99