A drainage system shall be designed and constructed by the subdivider to provide for the proper drainage of the surface water of the subdivision and the drainage area of which it is a part. The following requirements and methods shall be followed:
(A) Storm drainage. A subdivision plat shall not be considered for final approval until the subdivider shall submit to the Planning Commission, or its duly authorized representative, a report by a registered civil engineer, as to the ability of existing watercourse channels, storm sewers, culverts, and other improvements pertaining to drainage or flood control within the subdivision, to handle the additional run-off which would be generated by the development of the land within the subdivision. Additional information shall be submitted to adequately indicate that provision has been made for disposal of surface water without any damage to the developed or undeveloped land downstream or below the proposed subdivision. This report shall also include:
(1) Estimate of the quantity of storm water entering the subdivision naturally from areas outside the subdivision.
(2) Quantities of flow at each pick-up point (inlet).
(3) Location, sizes, and grades of required culverts, storm drainage sewers, and other required appurtenances.
(B) Drainage requirements (grading).
(1) No final grading or sidewalk or pavement construction or installation of utilities shall be permitted in any proposed street until the final plat has been approved or conditionally approved by the Planning Commission, or its duly authorized representative.
(2) The subdivider shall grade each subdivision in order to establish street, block, and lot grades in proper relation to each other and to topography and further, a grading plan shall be prepared for the streets along with street improvement details. The grading of the roadway shall extend the full width of the right-of-way. Planting strips shall be graded at a gradient of not less than 2% upward from the curb to the sidewalk or property line.
(C) Drainage system requirements.
(1) The design criteria for storm drainage systems shall be based on information from the "Manual for Instruction for Drainage Design" prepared by the Department of Highways, Commonwealth of Kentucky, or any other acceptable drainage manual.
(2) Culverts and storm sewers in all streets shall be designed for at least a five-year storm frequency.
(3) For curbs and gutters, curb and gutter inlets and open channels an intensity of four inches per hour shall be used in all computations.
(D) Road drainage system.
(1) All roadways shall be provided with an adequate storm drainage system.
(2) The road storm sewer system shall serve as the primary drainage system and shall be designed to carry roadway, adjacent land, and building storm water drainage. No storm sewer shall be permitted to be run into the sanitary sewer system within the proposed subdivision.
(3) Curb drainage inlets and catch basins shall be provided at intervals along roadways. Inlet spacing shall be adequate to limit the spread of water to two feet into the roadway. Storm drainage inlets will be placed so that crosswalks will not be flooded during the design storm intensity of four inches per hour.
(E) Off-road drainage systems. The design of the off-road drainage system shall include the watershed affecting the subdivision and shall be extended to a watercourse or ditch adequate to receive the storm drainage.
(1) When the drainage system is outside of the road right-of-way, the subdivider shall make provisions for dedicating of an easement to the city to provide for the future maintenance of said system.
(2) The size and location of all off-street watercourses or ditches running through the subdivision shall be enclosed or left open subject to the approval of the Planning Commission, or its duly authorized representative. If a watercourse or ditch is left open it may be required to be protected by a fence as determined by the Planning Commission, or its duly authorized representative. The watercourse or ditch easement shall be wide enough to contain ample clearance for the operation of maintenance equipment.
(F) Drainage easement. Easements for drainage purposes shall be a minimum of ten feet in width. Where the watercourse is large, easement widths shall be increased as determined by the Planning Commission, or its duly authorized representative. Where watercourses cross platted lots diagonally, the subdivider should straighten such courses where practicable and should substantially follow sublot lines. Easements shall be shown on the record plat and shall cover all existing or reconstructed watercourses.
(G) Protection of drainage systems.
(1) The subdivider shall adequately protect all ditches to the satisfaction of the Planning Commission, or its duly authorized representative. Ditches and open channels shall be seeded, sodded, or paved depending on grades (slopes) and types of soils.
(2) As a general rule, ditches and channels with grades up to 1% shall be seeded, with grades from 1% to 4% shall be sodded, and with grades over 4% shall be paved. Seeding, sodding and paving operations shall be in compliance with the "Commonwealth of Kentucky, Department of Highways, Division of Design, Guidance Manual" issued by the Kentucky Department of Highways.
(H) Material specifications. Material and construction specifications for all drainage projects (i.e., pipe, tile, seed, sod) shall be in compliance with the "Standard Specifications for Road and Bridge Construction" issued by the Kentucky Department of Highways.
(Ord. 1971-2, passed 4-6-71)