950.09 COMPREHENSIVE STORMWATER MANAGEMENT PLAN.
Comprehensive Stormwater Management Plan Required: The applicant shall develop a Comprehensive Stormwater Management Plan describing how the quantity and quality of stormwater will be managed after construction is completed for every discharge from the site and/or into a water resource or small municipal separate storm sewer system (MS4). Comprehensive Stormwater Management Plans must meet the requirements in the Construction General Permit and these regulations.
(a) Preparation by Professional Engineer: The Comprehensive Stormwater Management Plan shall be prepared by a registered Professional Engineer and include supporting calculations, plan sheets, and design details. To the extent necessary, as determined by the City of Youngstown Public Works Department, a site survey shall be performed by a registered Professional Surveyor to establish boundary lines, measurements, or land surfaces.
(b) Community Procedures: The City of Youngstown Public Works Department shall prepare and maintain procedures providing specific criteria and guidance to be followed when designing the stormwater management system for the site. These procedures may be updated from time to time, at the discretion of the City of Youngstown Public Works Department based on improvements in engineering, science, monitoring, and local maintenance experience. The City of Youngstown Public Works Department shall make the final determination of whether SCMs proposed in the Comprehensive Stormwater Management Plan meet the requirements of this regulation.
(c) Contents of Comprehensive Stormwater Management Plan: The Comprehensive Stormwater Management Plan must contain all elements and meet all requirements specified in the Construction General Permit. It shall also meet the following requirements.
(1) Location information: The application shall note the phase, if applicable, of the overall development plan and list sublot numbers if project is a subdivision.
(2) Site maps and SCM design plans: It is preferred that all SCMs and the entire site be shown on one plan sheet to allow a complete view of the site during plan review. If a smaller scale is used to accomplish this, separate sheets providing an enlarged view of areas on individual sheets should also be provided. Existing and proposed drainage patterns and any relevant offsite SCMs should be depicted. For each SCM, include the following:
A. An individual identification number
B. Location and size
C. Final site conditions and detail drawings of stormwater inlets and permanent SCMs. Details of SCMs shall be drawn to scale and shall show relevant volumes, elevations and sizes of contributing drainage areas.
D. A completed Ohio EPA WQv Calculator Spreadsheet and/or Runoff Reduction Spreadsheet or other equivalent compliance tools provided by Ohio EPA.
E. A completed review checklist demonstrating that all requirements for the SCM submittal have been met.
F. Any supplemental information requested by the City of Youngstown Public Works Department.
(3) Required Calculations: The applicant shall submit calculations for projected stormwater runoff flows, volumes, and timing into and through all SCMs for flood control, channel protection, water quality, and the condition of the habitat, stability, and incision of each water resource and its floodplain. These submittals shall be completed for both pre- and post-development land use conditions and shall include the underlying assumptions and hydrologic and hydraulic methods and parameters used for these calculations. The applicant shall also include critical storm determination and demonstrate that the runoff from offsite areas have been considered in the calculations. For each SCM, identify the drainage area and size in acres, percent impervious cover within the drainage area, volumetric runoff coefficient, peak discharge, and the time of concentration for each subwatershed. Pervious and impervious areas should be treated as separate subwatersheds unless allowed at the discretion of the community engineer. Identify the SCM surface area, discharge and dewatering time, outlet type and dimensions.
(4) Inspection and Maintenance Agreement. The Inspection and Maintenance Agreement required for SCMs under this regulation is a stand-alone document between the City of Youngstown and the applicant. This agreement shall be recorded with the County.
(5) Inspection and Maintenance Plan. This plan will meet the requirements of the Construction General Permit and will be developed by the applicant and reviewed by the City of Youngstown. Maintenance requirements of each SCM during and after construction should be included. Once the Inspection and Maintenance Plan is approved, a recorded copy of the Plan must be provided to the property owner or association that will be responsible for long-term operation and maintenance of the BMP and submitted to the City of Youngstown as part of the final inspection approval as described in Section 950.12.
(Ord. 22-344. Passed 9-21-22.)