(a) Hydrologic Design. Those waterways set forth in an adopted master plan for drainage for Stark County shall be designed and constructed for the quantities of water indicated in such master plan. All other drainageways shall be designed in accordance with the following frequencies:
(1) Major Waterways. Major waterways are defined as those with a tributary area in excess of six square miles. Such major waterways shall be designed for an average recurrence interval of fifty years.
(2) Secondary Waterways. Secondary waterways are defined as those with a tributary area of between one-half and six square miles. Such secondary waterways shall be designed for an average recurrence interval of ten to twenty-five years.
(3) Minor Waterways. Minor waterways are defined as those with 320 acres or less of tributary area. Such minor waterways shall be designed for an average recurrence interval of five to ten years.
Design quantities of flow for major waterways and waterways included in an adopted master plan for drainage will be provided the subdivider by the county. Design flows for secondary water ways shall follow the procedures outlined in Circular No. 4 of the Hydraulics Branch of the Bureau of Public Roads or Bulletin 43, Ohio Department of Natural Resources. Design flows for minor drainage facilities shall be computed by the use of the Rational formula:
Q = C i A
Wherein: Q = Cubic feet per second
C = Run-off coefficient
i = Intensity of rain fall, inches per hour
A = Tributary area
Note: C = O.4 for typical subdivisions. C shall vary from 0.4 to 0.6 or higher for high density allotments and special conditions such as large per cent of paved area, steep slopes and impervious soils. Intensity (i) to be determined using ten year frequency curve.
(b) Hydraulic Design.
(1) The hydraulic design of the subdivision shall be such that, after accumulating all energy losses through the various drainage transmission systems within the subdivision, depth of flow in the streets shall not exceed curb heights for ten year average recurrence intervals and for more remote events depth of flow or ponding shall not exceed a level which would cause inundation of foundations or basements in residences constructed within the subdivision. Within the subdivision, catch basins shall be so placed along the streets that the width of flow in the gutter will not exceed two feet for a one year average recurrence interval and will not exceed top of curb for a ten year average recurrence interval.
(2) Site grading within the subdivision shall be such that all lots will readily drain.
(c) Structural Design. All bridges, culverts, catch basins, manholes, inlet structures, etc., placed within the subdivision shall conform to standard plans on file with the City. Structural design of all drainage facilities shall be subject to the approval of the City Engineer.
(1) Open Channels. Minimum centerline radius of constructed channels shall be a minimum of five times the top width of the channel. Minimum bottom width of constructed channels shall be three feet.
A. Earth channels constructed within the subdivision shall have side slopes of 2:1 or flatter. Revetment, bank stabilization and stream bed stabilization, along constructed or natural channels, will be required if the channel velocities are sufficient to cause bank or invert erosion.
B. The top of bank shall be so graded that side drainage will enter channels only at points where structures are provided to prevent bank erosion. The design of open channels shall be in accordance with the Bureau of Public Roads publication, "Design of Roadside Drainage Channels," Hydraulic Design Series No. 4. Earth channels constructed within the subdivision, in those areas not revetted, shall be seeded over the prepared area (fertilized and limed) with a mixture of 55 pounds of Kentucky Bluegrass (poa Pratensis) and 75 pounds of Creeping Red Fescue (Restuca rubra) per acre to establish a vegetative cover.
(2) Closed Conduits. Excepting for adequate natural waterways, as hereinafter defined and except for allowable gutter flows, all storm drainage within the subdivision which is capable of being transmitted in a reinforced concrete pipe thirty inches or less in diameter, shall be carried in a closed conduit. Minimal conduit size shall be twelve inches diameter RCP or twelve inches diameter CMP. Minimum clearance between top of pipe and ground shall be fifteen inches.
A. The alignment of closed conduits shall be as nearly straight as practicable without undue bends and angle points; manholes or catch basins shall be provided at all angle points and at intervals not to exceed 300 feet for thirty inches and under 500 feet for over thirty inches. Inverted siphons shall not be permitted except for temporary structures.
B. Plain concrete pipe or equivalent may be used outside of road rights-of- way provided the strength of such pipe is sufficient to withstand loads imposed on it. In areas having run-off water with acid content or other corrosive effects, all pipe shall be provided with additional lining to assure a project life of fifty years. The above-stated pipe policy and the pipe policy used by the State of Ohio Department of Transportation (ODOT) shall be used in designing storm sewer systems.
(3) Bridges. All drainage structures having a span of ten feet or greater and all pipes having a diameter or span of ten feet or greater shall be defined as bridges. All calculations and plans pertaining to bridges shall require both preliminary and final approval from the Stark County Bridge Engineer.
(4) Culvert.
A. Minor Culvert. All culverts having a diameter of thirty-six inches or less shall be designated as minor culverts and shall be subject to the same requirements as part 2, "Closed Conduits". Minor culverts should extend from right of way to right of way.
B. Major Culvert. All culverts having a diameter greater than thirty-six inches shall be designated as major culverts. All major culverts shall be designed in accordance with the requirements of Circular No. 4 of the Hydraulics Branch of the Bureau of Public Roads or Bulletin 43 published by the Ohio Department of Natural Resources and shall be subject to the approval of the City Engineer. Major culverts should extend from right of way to right of way.
(Ord. 25-1980. Passed 9-2-80.)