All subdivisions and sites are required to install Detention/Retention ponds if the post-construction 100-year design flow leaving the subdivision or site at any concentrated point is increased more than 10 cfs from the predesigned condition. Outlet structures shall be staged to prevent more than 10 cfs difference at the 5, 10, 25, 50 and 100 year flow levels. Outflow structures should be well maintained and unobstructed. Provisions for maintenance shall be included with plat or deed covenants. Except by special consideration, all detention and retention ponds shall remain the property of the subdivider/developer/homeowners association, and shall not be the direct responsibility of the City. Retention ponds shall be protected to prevent drowning and water stagnation (mosquitoes).