Inlets or drainage structures shall be utilized to collect surface water through grated openings and convey it to storm sewers, channels or culverts. Inlet design and spacing shall be in accordance with Section 7-400 of the Indiana Department of Highways’ Road Design Manual Volume 1 or other approved design procedure. The inlet grate openings provided must be adequate to pass the design 10-year flow with 50 percent of the sag inlet areas clogged. An overload channel from sag inlets to the overflow channel or basin shall be provided at sag inlets, so that the maximum depth of water that might be ponded in the street sag shall not exceed six inches. [Ord. 12-1-97C § 11(F).]