A. A drainage plan and report for the site in question and all pertinent off-site areas shall be prepared by a registered engineer. The report shall examine one-hundred-year storm flows (Q 100's), the one-hundred-year high water mark of any river, creek, arroyo, gully, diversion ditch, spillway, reservoir, etc., that may in any way affect the project area, along with the depth of flow for one-hundred-year runoff. The watershed in all off-site areas shall be considered fully developed. Intensities shall be for this area's one hour one-hundred-year storm based upon two and thirty-nine one-hundredths (2.39) inches per hour. A certificate shall be provided, signed, and sealed by a registered professional engineer that all drainage facilities, utilizing gutters and streets, are designed and sized to handle one hundred percent of the Q 100 runoff. The report shall comply with the requirements and standards of the city storm drainage master plan and drainage policy.
B. Every effort shall be made to utilize the natural slope of the land for the stormwater collection system. Subsurface drainage systems shall be discouraged, but where necessary shall be a minimum of twenty-four inches in diameter. Wherever possible, runoff shall be collected in depressed open areas throughout the proposed land development project. The plan shall include but not be limited to, the following:
1. Method of collection (surface and/or subsurface);
2. Depth, side slopes and area of retention;
3. Calculations of volume held and required;
4. High water elevation;
5. Method of disposal of water within thirty-six hours;
6. Any other data to form a complete plan.
C. The point or points in which natural drainage flows onto and from a property prior to development shall remain the same after the property has been altered for the development.
(Ord. 1179 § 3.3(B)(part), 1987)