A. The stormwater collection system shall be designed either:
1. To pass a minimum of the runoff from a ten percent (10%) chance storm in a pipe network together with an overland flow path with capacities so that the combination of the two will pass the runoff from a one percent (1%) chance storm under ultimate urbanized conditions, or
2. To pass the entire runoff from a one percent (1%) chance storm in the pipe network. Should the entire runoff from a one percent (1%) chance storm be conveyed in an enclosed drainage network, grading shall be designed to convey the runoff from the one percent (1%) chance storm overland in the event of inlet or storm sewer blockage or bypass.
3. In either case, an overland drainage easement shall be required for overland flows. No overland flows shall be allowed to adversely affect structures.
4. In areas where overland flows may cause problems, the city manager may require that the entire runoff from the one percent (1%) chance storm shall be conveyed through an enclosed drainage network.
5. In areas where ultimate urbanized flows are not planned for conveyance to a regional detention facility, the city manager may reduce the capacity requirement to the existing condition flows.
B. The overland flow portion of the collection system shall be confined to dedicated rights of way, or drainage easements to assure the stormwater can pass through the development without inundating the lowest level of any building, dwelling, or structure. All drainage easements shall be shown on the plat.
C. The detention or retention facilities which have been dedicated to and accepted by the city of Okmulgee, and which receive stormwaters from or discharge stormwaters to the collection system described in subsection A of this section. (Ord. 1968, 2011)