(a) The design of the subdivision shall provide the necessary means to assure complete drainage in and adjacent to the property to be developed or subdivided. The subdivider or his engineer shall submit all drainage calculations along with the improvement plans. A ten year storm is to be used for storm sewers and ditches along with suitable runoff factors for the completed development both within the subdivider’s property and all lands upstream from the subdivider’s property. Culverts shall be designed on a 25 year storm frequency.
(b) If the design storm flow is calculated in an amount which can be conducted adequately by a 48-inch conduit or less, then the developer shall install a conduit of sufficient capacity up to 48 inches in size to conduct this drainage on and through the subdivider's property. If the design flow is calculated in an amount in excess of the capacity of a 48-inch conduit, then the subdivider must provide either a conduit or an open drainage channel treatment designed as provided herein. When necessary, outlet ditches or closed storm sewers of an approved type and size shall be required as part of the construction. If there is an easement or rights of way to be obtained by the subdivider for construction and future maintenance, these rights of way or easements shall be shown on final plat. Two copies of the easement shall be furnished to the Engineer.
(c) All storm sewer pipe shall be a minimum of twelve (12) inch diameter and have a minimum cover of two (2) feet. All storm drainage under pavement and to a point three (3) feet outside pavement shall be reinforced concrete tile or corrugated metal pipe and the trench shall be backfilled with an approved porous material (ODOT 603).
(d) Using an "n" factor of -.013, the following grades of pipe line shall be considered minimum:
Pipe Size (inches) | Minimum Grade (inches) |
12 | 0.33 |
15 | 0.23 |
18 | 0.18 |
21 | 0.14 |
24 | 0.12 |
For sizes larger than twenty-four (24) inches where an "n" factor other than 0.013 is used, the minimum grade shall be considered as that which produces a full flow velocity of not less than two and one half (2-1/2) feet per second. A maximum grade shall be one that produces velocities in excess of ten (10) feet per second.
(e) All storm sewer pipe shall be in accordance with the current State of Ohio Department of Transportation Construction and Material Specifications, Section 707.01, 707.02, 707.03 and 707.04 may be used upon approval by the City Engineer. The gauge of metal pipe shall be determined by the design engineer after proper consideration has been given to loads, cover and soil conditions. An "n" factor of 0.021 shall be used in all hydraulic calculations where aluminum, or galvanized metal, corrugated metal pipe is proposed.
(f) Manholes. Manholes, or inlets serving as manholes, shall be spaced at intervals of 400 feet or less for pipe twenty-four (24) inches or less in diameter, and at all grade, alignment and pipe size changes. Manholes shall be constructed of pre-cast concrete rings and domes. All work and materials shall be in accordance with Item 604 of the current State of Ohio Department of Transportation Construction and Material Specifications. Manholes shall be designed and constructed in accordance with the design shown in ODOT Standard Construction Drawing MH-3.
(g) Inlets. Inlets shall be designed to accept not less than one and one-half (1-1/2) cubic feet of storm water per second. Inlet time shall be computed by the design engineer. However, the maximum inlet time shall be as follows:
Distance of Travel to Inlet (feet) | Inlet Time (minutes) |
100 | 12 |
200 | 16 |
300 | 20 |
Inlets shall be designed and constructed in accordance with the design shown on ODOT Standard Construction Drawings CB-3, 3A, 6, 2-2A, and B, 2-3, 2-4, 2-5 and 2-6 or I-2A paved shoulder inlet. (Ord. 82-16. Passed 4-19-82.)