All minor tributaries and surface drainage located within or immediately adjacent to and serving the subdivision shall be improved by the developer, as follows:
(A) All minor tributary channels shall be improved in accordance with the standards set forth in images adopted by reference, or other equivalent standards, as determined by the City or County Engineer. All channels shall be designed to carry a 100-year maximum flood, shall be designed for self- cleaning and ease of maintenance, shall have sufficient hard surface along the flow line to prevent ponding of water, and shall have design characteristics of alignment, materials of construction and cross- sectioned elements that will be hydraulically efficient and visually harmonious with the adjacent landscape.
(B) Enclosed storm sewers may be required by the City or County Engineer where special or unusual conditions make open channels hazardous or otherwise unfeasible.
(C) Site grading shall be carried out in a manner that surface water from each lot shall flow directly to a storm sewer, improved channel or paved street without crossing more than two adjacent lots.
(D) Surface water collected on streets shall be diverted to storm drains at satisfactory intervals to prevent overflow of six-inch high curbs during a 50-year frequency rain for the area and grades involved. In no case shall the drainage area served by one street exceed ten acres, regardless of the amount of flow.
(E) Drainage easements of satisfactory width to provide working room for construction and maintenance shall be provided for all storm sewers. In no case shall the easement be less than 20 feet.
(F) Bridges and culverts:
(1) Bridges or culverts shall be provided where water courses cross continuous streets or alleys.
(2) Bridges and culverts shall be sized to accommodate a 100-year frequency rain, based on the drainage area involved.
(3) Design of bridges and culverts shall conform to city or county construction specifications.
(G) Closed storm sewers:
(1) Closed storm sewers shall be constructed of pre-cast or prefabricated pipe or built in place of closed box design to conform with city or county specifications.
(2) Side slopes above the paved section shall be shaped and sodded on a slope of four horizontal to one vertical or flatter.
(3) Fences shall be outside of the 100-year frequency flooding line, shall not be erected below the shoulder of the sodded section, and in no case shall fences be closer than six feet (measured horizontally) to the edge of the paved section, except as specifically set out otherwise.
(4) Hand-laid rip rap may be substituted for sodded shoulders where desired for landscape purposed.
(`90 Code, § 16-17) (Ord. 2570, passed - -)