(A) Where water quality during dry weather periods in a small basin would be a potential problem due to lack of adequate dry weather flow, direct pollution from surface water runoff, or high nutrients in the flow, the basin should be designed to remain dry except when in flood use.
(B) Dry detention basins shall be designed to minimize the wetness of the bottom so that water does not remain standing in the bottom, thereby harboring insects and limiting the potential use of the basin. This shall be accomplished by means of a concrete low flow channel between inlet and outlet structures. Minimum slope shall be no less than 0.5%. An acceptable alternative to a concrete low flow channel will be an underdrain. In this case, a minimum of 1% slope shall exist between inlet and outlet structures, and the surface above the underdrain shall be grass sod.
(C) The detention basin should be designed to have a multipurpose function. Recreational facilities, aesthetic qualities, and the like, as well as floodwater storage, should be considered in planning the basin.
(D) Side slopes shall be three to one or flatter.
(E) There shall be a minimum of a three-foot berm at 2% between the right-of-way and the top basin slopes.
(F) A 20-foot-wide municipal easement shall be provided for access to allow stormwater storage ponds.
(G) When conduits are used for the outlet of the reservoir, they shall be protected by bar screens or other suitable provisions so that debris, or similar trash, will not interfere with the operation of the basin. Safety screens should also be provided for any pipe or opening in order to prevent children or large animals from crawling into the structures. For safety, a suggested maximum opening size is six inches.
(H) Grass or other suitable vegetative cover should be maintained throughout the entire reservoir area. Grass should be cut regularly no less than five times a year. Debris and trash removal, and other necessary maintenance, should be performed after each storm to assure continued operation in conformance to the design.
(Ord. 817, passed 8-2-1999)