§ 50-130. Minimum requirements.  


Latest version.
  • (a)

    The minimum stormwater control requirements shall provide management measures necessary to maintain or reduce the predevelopment peak discharges.

    (b)

    Stormwater concept and design plans, where applicable, shall be consistent with adopted and approved watershed management plans as approved by the board of commissioners.

    (c)

    Stormwater concept plan (optional). The stormwater concept plan (optional) shall include the following items:

    (1)

    Existing conditions/proposed site plans. Existing conditions and proposed site layout sketch plans, which illustrate at a minimum: existing and proposed topography; perennial and intermittent streams; mapping of predominant soils from soil surveys (when available); boundaries of existing predominant vegetation and proposed limits of clearing and grading, and location of existing and proposed roads, buildings, parking areas and other impervious surfaces.

    (2)

    Natural resources inventory. A written or graphic inventory of the natural resources at the site and surrounding area as it exists prior to the commencement of the project. This description should include a discussion of soil conditions, forest cover, topography, wetlands, and other native vegetative areas on the site, as well as the location and boundaries of other natural feature protection and conservation areas such as wetlands, lakes, ponds, floodplains, stream buffers and other setbacks (e.g., drinking water well setbacks, septic setbacks, etc.). Particular attention should be paid to environmentally sensitive features that provide particular opportunities or constraints for development.

    (3)

    Stormwater management system concept plan. A written or graphic concept plan of the proposed post-development stormwater management system including: preliminary selection and location of proposed structural stormwater controls; location of existing and proposed conveyance systems such as grass channels, swales, and storm drains; flow paths; location of floodplain/floodway limits; relationship of site to upstream and downstream properties and drainages; and preliminary location of proposed stream channel modifications, such as bridge or culvert crossings.

    (d)

    Final stormwater design/management plan (mandatory). The final stormwater design/management plan shall detail how post-development stormwater runoff will be controlled or managed and how the proposed project will meet the requirements of this article. This plan shall be in accordance with the criteria established in this section and must be submitted with the stamp and signature of a professional engineer (PE) licensed in the state, who must verify that the design of all stormwater management facilities and practices meet the submittal requirements outlined in the submittal checklist(s) found in the stormwater design manual. The plan shall include all of the information required in the stormwater management site plan review checklist maintained by the stormwater management division. This includes:

    (1)

    Common address and legal description of site.

    (2)

    Vicinity map.

    (3)

    Existing conditions hydrologic analysis. The existing condition hydrologic analysis for stormwater runoff rates, volumes, and velocities, which shall include: a topographic map of existing site conditions with the drainage basin boundaries indicated; acreage, soil types and land cover of areas for each subbasin affected by the project; all perennial and intermittent streams and other surface water features; all existing stormwater conveyances and structural control facilities; direction of flow and exits from the site; analysis of runoff provided by off-site areas upstream of the project site; and methodologies, assumptions, site parameters and supporting design calculations used in analyzing the existing conditions site hydrology. For redevelopment sites, predevelopment conditions shall be modeled using the established guidelines for the portion of the site undergoing land development activities.

    (4)

    Post-development hydrologic analysis. The post-development hydrologic analysis for stormwater runoff rates, volumes, and velocities, which shall include: a topographic map of developed site conditions with the post-development drainage basin boundaries indicated; total area of post-development impervious surfaces and other land cover areas for each subbasin affected by the project; calculations for determining, the runoff volumes that need to be addressed for each subbasin for the development project to meet the post-development stormwater management performance criteria in the Georgia Stormwater Management Manual; location and boundaries of proposed natural feature protection and conservation areas; documentation and calculations for any applicable site design credits that are being utilized; methodologies, assumptions, site parameters and supporting design calculations used in analyzing the existing conditions site hydrology. If the land development activity on a redevelopment site constitutes more than 50 percent of the site area for the entire site, then the performance criteria in the Georgia Stormwater Management Manual must be met for the stormwater runoff from the entire site.

    (5)

    Stormwater management system. The description, scaled drawings and design calculations for the proposed post-development stormwater management system, which shall include: A map and/or drawing or sketch of the stormwater management facilities, including the location of nonstructural site design features and the placement of existing and proposed structural stormwater controls, including design water surface elevations, storage volumes available from zero to maximum head, location of inlet and outlets, location of bypass and discharge systems, and all orifice restrictor sizes; a narrative describing how the selected structural stormwater controls will be appropriate and effective; cross-section and profile drawings and design details for each of the structural stormwater controls in the system, including supporting calculations to show that the facility is designed according to the applicable design criteria; a hydrologic and hydraulic analysis of the stormwater management system for all applicable design storms (including stage-storage or outlet rating curves, and inflow and outflow hydrographs); documentation and supporting calculations to show that the stormwater management system adequately meets the post-development stormwater management performance criteria in the manual; drawings, design calculations, elevations and hydraulic grade lines for all existing and proposed stormwater conveyance elements including stormwater drains, pipes, culverts, catch basins, channels, swales and areas of overland flow; and where applicable, a narrative describing how the stormwater management system corresponds with any watershed protection plans and/or local greenspace protection plan.

    (6)

    Post-development downstream analysis. A downstream peak flow analysis which includes the assumptions, results and supporting calculations to show safe passage of post-development design flows downstream. The analysis of downstream conditions in the report shall address each and every point or area along the project site's boundaries at which runoff will exit the property. The analysis shall focus on the portion of the drainage channel or watercourse immediately downstream from the project. This area shall extend downstream from the project to a point in the drainage basin where the project area is ten percent of the total basin area. In calculating runoff volumes and discharge rates, consideration may need to be given to any planned future upstream land use changes. The analysis shall be in accordance with the manual.

    (7)

    Construction—Phase erosion and sedimentation control plan. An erosion and sedimentation control plan in accordance with the Georgia Erosion and Sedimentation Control Act (or reference to the local erosion and sedimentation control ordinance) or NPDES permit for construction activities. The plan shall also include information on the sequence / phasing of construction and temporary stabilization measures and temporary structures that will be converted into permanent stormwater controls.

    (8)

    Landscaping and open space plan. A detailed landscaping and vegetation plan describing the woody and herbaceous vegetation that will be used within and adjacent to stormwater management facilities and practices. The landscaping plan must also include: the arrangement of planted areas, natural and greenspace areas and other landscaped features on the site plan; information necessary to construct the landscaping elements shown on the plan drawings; descriptions and standards for the methods, materials and vegetation that are to be used in the construction; density of plantings; descriptions of the stabilization and management techniques used to establish vegetation; and a description of who will be responsible for ongoing maintenance of vegetation for the stormwater management facility and what practices will be employed to ensure that adequate vegetative cover is preserved.

    (9)

    Operations and maintenance plan. Detailed description of ongoing operations and maintenance procedures for privately owned stormwater management facilities and practices to ensure their continued function as designed and constructed or preserved. These plans will identify the parts or components of a stormwater management facility or practice that need to be regularly or periodically inspected and maintained, and the equipment and skills or training necessary. The plan shall include an inspection and maintenance schedule, maintenance tasks, responsible parties for maintenance, funding, access and safety issues. Provisions for the periodic review and evaluation of the effectiveness of the maintenance program and the need for revisions or additional maintenance procedures shall be included in the plan.

    (10)

    Maintenance access easements. The applicant must ensure access from public right-of-way to stormwater management facilities and practices requiring regular maintenance at the site for the purpose of inspection and repair by securing all the maintenance access easements needed on a permanent basis. Such access shall be sufficient for all necessary equipment for maintenance activities. Upon final inspection and approval, a plat or document indicating that such easements exist shall be recorded and shall remain in effect even with the transfer of title of the property.

    (11)

    Inspection and maintenance agreements. Unless an on-site stormwater management facility or practice is dedicated to and accepted by the county as recorded on the final plat, the applicant must execute an easement and an inspection and maintenance agreement binding on all subsequent owners of land served by an on-site stormwater management facility or practice.

    (12)

    Evidence of acquisition of applicable local and nonlocal permits. The applicant shall certify and provide documentation to the county community development agency that all other applicable environmental permits have been acquired or applied for the site prior to approval of the stormwater management plan.

(Ord. of 9-28-93; Code 1977, § 3-22.5A-15; Ord. of 4-13-04; Ord. of 2-27-07)