Storm drainage ponds shall be required stormwater mitigation, unless the City Engineer deems an alternative method can be utilized to achieve the same mitigation result. Storm drainage ponds shall be constructed and designed as directed by the City Engineer and in accordance with the following criteria:
(A) The volume of the pond shall equal one inch of water multiplied by the entire contributing area, calculated in feet, that flows to the pond;
(B) The pond outlet shall be designed to drain the entire pond in not more than 72 hours;
(C) The sides of the pond shall have a maximum slope of three feet horizontal to one foot vertical (3:1), although a 4:1 slope is preferred and may be required at the direction of the City Engineer if deemed necessary. Pond slopes shall be stabilized with either landscaping, plantings, or rock. Details shall be provided in the approved landscaping plans, that are submitted to the Engineer for review prior to commencement of the landscaping;
(D) Pond inlets shall have a properly designed energy dissipater that eliminates erosion. If riprap is utilized as the energy dissipater, a concrete alley curb shall be poured around the riprap to facilitate a mowing edge. Pond inlets shall be constructed so that they are accessible for maintenance purposes;
(E) Pond outlets shall be located the greatest distance possible from the inlet;
(F) Topsoil shall be minimally compacted over the top surface area, to a minimum depth of six inches;
(G) The bottom of the pond shall be sloped to a drain manhole as recommended by the City Engineer. The manhole shall be located adjacent to the outlet of the pond or if there is no outlet the manhole shall be the greatest distance from the inlet to the pond that is possible;
(H) In the event a lift station is required, ponds shall have a minimum 15-foot wide asphalt access road and a minimum asphalt/concrete area of 20 feet by 20 feet at any lift station. The lift station and appurtenances shall be placed to allow clear access to the pond with trucks, mowers, etc.
(Ord. 906, passed 5-12-2016)