(a) Preliminary Drainage Plan Requirements. For subdivisions or as otherwise required by the City Engineer, a preliminary development plan shall include and shall have appended to it sufficient data for the City Engineer to check the feasibility of the drainage system as proposed by the owner/developer. A preliminary drainage plan for all developments shall be submitted to the City of Louisville for review and approval. It shall include a drawing showing the general runoff pattern of the area to be improved, as well as the runoff patterns of adjacent areas which may affect or be affected by the proposed improvement. Preliminary hydraulic design calculations (approximate flow rates and structure sizes) for all proposed basins, bridges over waterways, and culverts greater than 4 feet in span shall be provided. A copy of the preliminary plat, which is required by the Planning Commission, may serve as the preliminary drainage plan provided sufficient data has been supplied to check the feasibility of the drainage system as proposed by the developer. In conjunction with the minimum requirements listed in Section 1164.06(b), calculations shall be performed and submitted, at a minimum, for all critical points within the development. Critical points are locations such as confluences of streams and tributaries, junctions of proposed storm sewers with existing storm sewers (or vice versa), upstream site limits, downstream site limits, etc.
(b) Final Drainage Plan and Report Requirements. A final drainage plan shall include drawings of the entire drainage system and be submitted to the City of Louisville for review and approval. The plan shall conform to the guidelines herein and to any special conditions of the Planning Commission in approving the preliminary and final plans. The plan shall also include the engineering calculations used in determining the design of the drainage courses, drainage structures, and storm water runoff control structures.
All plans shall be sealed with the stamp of a Professional Engineer as required by the Ohio Revised Code. The drainage drawings must be approved by the City of Louisville prior to the construction of any portion of the drainage system.
Minimum requirements for drainage and engineering calculations for the drainage systems shall comply with all aspects of Section 1164.05 and also the following:
(1) A narrative summarizing points of analysis, methodology used, assumptions made, and other pertinent information necessary for review (as determined by the City Engineer) shall be prepared and submitted with the calculations.
(2) A drainage map showing the existing topography of the development area and adjacent land within three hundred (200) feet of its boundary. The topographic map shall use a contour interval appropriate to clearly portray the surface conformation and drainage pattern of the area.
(3) A vicinity map at a scale of not less than two thousand (2,000) feet to the inch showing the development area in relation to existing roads and nearest existing thoroughfares, streams, and other water areas.
(4) The drainage area for storm water management structures shall be outlined and have the acreage shown. To show the entire drainage area, additional sheets may be required. If additional sheets are needed, existing aerial mapping or USGS mapping shall be sufficient.
(5) The location of any adjacent existing drainage structures shall be shown. This information shall be based on field investigations, measurements, and mapping.
(6) The acreage of all tributary drainage areas and their sum.
(7) Hydrologic calculations including the following items:
A. Times of concentration, intensity, and runoff coefficients used in the Modified Rational Method to estimate the inflow hydrographs.
B. Overland slopes, curve numbers, hydraulic lengths, etc., used in the SCS Peak Discharge Method or the TR-55 Method.
C. For methods other than those above, enough information must be provided to the City to allow for an accurate review.
(8) Discharge in cubic feet per second (cfs), velocities in feet per second (fps), and any additional data needed to establish that the drainage system will convey the flow.
(9) Size and types of all drainage improvements including the detailed drawings of each component, typical sections, and easement widths.
(10) Routing calculations and their corresponding inflow and outflow hydrographs shall be provided for the critical storm and all less frequent storms up through the 100-year storm.
(11) Tabulated results including peak inflow, peak outflow, and maximum water surface elevations for all storm water management facilities.
(12) Calculations determining the elevation(s) and location(s) of the major flood path(s).
(13) The plan and profile of all drainageways shall be provided, including a cross section of open channels showing the depth of flow for the design year and 100-year frequencies.
(14) Supporting calculations for upstream and downstream channel capacities as they affect overflow or backwater within the development. Such calculations shall be substantiated by such additional survey information as is required to determine profile and cross section of the upstream and downstream channel reaches under consideration.