Acceptable types of detention or retention facilities:
A. Dry Detention Facilities: Such facilities must be provided with underground drainage or a concrete trickle channel to eliminate standing water after storm periods. This type of facility may be used for recreational purposes and other approved uses to the maximum extent possible when not functioning as a detention facility.
B. Wet Detention Facilities: Such facilities will be used on a limited basis and will be approved only when the pond inflow is sufficient to maintain pond water surface levels and to preclude the water from stagnating.
C. Underground Detention Facilities: This type of facility may consist of basins, tanks, and/or oversized storm sewers.
D. Parking Lot Detention: This type of facility may be used provided the maximum one percent (1%) chance storm ponding depth is twelve inches (12") or less. Any repaving of the parking lot shall be evaluated for impact on volume and release rates and are subject to approval by the city manager. All parking lot detention areas shall have a minimum of two (2) signs posted identifying the detention pond area. The signs shall have a minimum of one and one-half (1.5) square feet and contain the following message:
WARNING
This area is a stormwater detention facility and is subject to periodic flooding to a depth of (provide one percent chance storm design depth).
Any suitable materials and geometry of the sign is permissible, subject to approval by the city manager.
E. Retention Facilities: Such facilities may be used when the existing conditions' runoff from a watershed would exceed the capacities of downstream facilities. The retention facility shall contain the one percent (1%) chance stormwater runoff and release shall be by evaporation, infiltration or slow release at outflow rates less than existing levels. (Ord. 1969, 2011)