937.05 DEVELOPMENT OF DRAINAGE PLANS.
(a) This Chapter requires that a drainage plan be submitted and implemented for all Parcels that are being developed or redeveloped and that are subject to site plan or plat approval, unless specifically exempted in Section 937.02.
(b) The following information shall be submitted as part of an engineered site plan or construction drawing application.
(1) The design of storm sewer systems will be based upon the "Rational Method" using the equation Q=CiA and the "Manning Formula" (A is less than 100 acres). Areas greater than 100 acres use State of Ohio Bulletin Number 43 and compare with Bulletin Number 45 Floods in Ohio or Soil Conservation Service Technical Release #55, 2nd edition.
(2) Complete drainage calculations shall be submitted for pipe size determinations, 10 year hydraulic gradient checks and catch basin type and spacing designs. All culverts will be designed for a 10 year frequency storm with a hydraulic gradient check for a 25 year storm. The HGL shall be consistent with any data available at the City or County Engineer's office if established. Drainage calculations shall be prepared, organized, and submitted in a report format for review by the City engineer. The report shall include the designer and/or reviewer name(s) and the seal, signature, and date of the Professional Engineer responsible for the calculations in accordance with Section 4733.14 of the Ohio Revised Code.
(3) Storm sewers shall be designed to flow just full for the 5 year intensity-duration-frequency curve. The minimum velocity at just full shall be 2 feet per second. Minimum pavement gutter elevations shall be at or above the hydraulic grade line for a 10 year frequency storm. Use the 10 year intensity-duration-frequency curve for determining this hydraulic grade line.
(4) Detention/Retention facilities will be required. Existing conditions may limit the allowable out flow of the proposed site. The allowable outflow will be limited to the existing 5 year intensity storm for existing conditions of the proposed site and/or available capacity of the outlet, whichever is lesser. The detention facility shall store the proposed inflow from a 100 year intensity storm without overtopping a multi-stage outlet control structure.
(5) A flood route will be shown on the plan depicting the flow path of storm water in the event of a structure failure or storm that exceeds design capacity
(6) Grading plans will be required showing the proposed elevations at the right of way line, building lines and back lot lines. In areas where the site grading plan calls for the conveyance of surface storm water along or across rear property lines, a catch basin shall be provided. An absolute minimum grade of 0.3% shall be provided for rear lot swales. Flood routing shall be illustrated for the structures.
(7) Flood Hazard Boundary (if applicable) shall be shown along with a clear delineation and plan for work within the Flood Hazard Zone. Any FEMA permits required to accomplish grading and or construction objectives shall be identified. Reference also the City of Findlay Flood Damage Reduction Ordinance.
(c) FEMA regulations shall be strictly followed for all developments. Impacts on floodway and floodway fringe shall be addressed. Filling in floodplain requires a permit the City of Findlay. Flood boundaries shall be shown on plans along with 100 year storm elevations. All necessary CLOMRs, LOMRs, or LOMAs shall be secured from FEMA before construction of buildings can commence. FEMA studied streams and ditches require that new structures do not raise 100 year flood elevation unless public notification is performed and all parties affected by change are contacted and are agreeable to the raise in the 100 year flood elevation.
(d) The City of Findlay shall administer this regulation, and the City Engineer shall be responsible for determining the adequacy of the information submitted (b)(1)-(b)(6) of this Section and may request additional information.
(Ord. 2015-038. Passed 5-19-15.)