§ 1145. Contents of the stormwater management plan.

The plan shall include all information required in the stormwater management site plan checklist found in the GSMM, including the following information:

(a)

General. Common address and legal description of the site, and a vicinity map;

(b)

Existing conditions hydrologic analysis. The existing condition hydrologic analysis for stormwater runoff rates, volumes and velocities, which shall include the following information:

1.

A topographic map of existing site conditions with the drainage basin boundaries indicated;

2.

Acreage, soil types and land cover of areas for each sub-basin affected by the project;

3.

All perennial and intermittent streams and other surface water features;

4.

All existing stormwater conveyances and structural control facilities;

5.

Direction of flow and exits from the site;

6.

Analysis of runoff provided by off-site areas upstream of the project site; and

7.

Methodologies, assumptions, site parameters and supporting design calculations used in analyzing the existing conditions site hydrology. For redevelopment sites, pre-development conditions shall be modeled using the guidelines established by the director of public works for the portion of the site undergoing land development activities.

(c)

Post-development hydrologic analysis. The post-development hydrologic analysis for stormwater runoff rates, volumes and velocities, which shall include the following information:

1.

A topographic map of developed site conditions with the post-development drainage basin boundaries indicated;

2.

Total area of post-development impervious surfaces and other land cover areas for each sub-basin affected by the project;

3.

Calculations for determining the runoff volumes that need to be addressed for each sub-basin for the development project to meet the post-development stormwater management performance criteria of this article;

4.

Location and boundaries of proposed natural feature protection and conservation areas;

5.

Documentation and calculations for any applicable site design credits that are being utilized; and

6.

Methodologies, assumptions, site parameters and supporting design calculations used in analyzing the existing conditions site hydrology. Redevelopment sites on which the land development activity constitutes more than 50 percent of the entire site shall meet the performance criteria of this article as concerns the stormwater runoff from the entire site.

(d)

Stormwater management system. The description, scaled drawings and design calculations for the proposed post-development stormwater management system, which shall include the following information:

1.

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;

2.

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;

3.

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);

4.

Documentation and supporting calculations to show that the stormwater management system adequately meets the post-development stormwater management performance criteria of this article;

5.

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;

6.

A narrative describing how the stormwater management system corresponds with any watershed protection plans and/or local greenspace protection plan, as applicable; and

7.

A narrative describing the extent to which non-structural stormwater controls, specifically including stormwater better site design practices, are implemented.

(e)

Post-development downstream analysis. A downstream peak flow analysis that 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 every point or area along the boundary of the project site 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 represents ten percent of the total basin area. In calculating runoff volumes and discharge rates, consideration may need to be given to any planned alteration in future, upstream land use. The analysis shall be in accordance with the GSMM.

(f)

Construction-phase erosion and sedimentation control plan. An erosion and sedimentation control plan in accordance with article 8 of this UDC and the NPDES permit for construction activities. The plan shall also include information on the sequence/phasing of construction and temporary stabilization measures and structures that will be converted into permanent stormwater controls.

(g)

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 following information:

1.

Arrangement of planted areas, natural and greenspace areas and other landscape features depicted on the plan drawings;

2.

Information necessary to install the landscape features shown on the plan drawings;

3.

Descriptions and standards for the methods, materials and vegetation to be used in the installation;

4.

Density of plantings;

5.

Descriptions of the stabilization and management techniques used to establish vegetation;

6.

Identification of the party responsible for ongoing maintenance of vegetation for the stormwater management facility and the practices to be employed to ensure that adequate vegetative cover is preserved; and

7.

The extent to which landscaping will implement stormwater better site design practices.

(h)

Operations and maintenance plan. Detailed description of ongoing operations and maintenance procedures for stormwater management facilities and practices to ensure their continued function as designed and built, or preserved. This plan will identify the components of a stormwater management facility or practice that must to be regularly inspected and maintained, and the equipment and skills necessary to the inspections and maintenance. 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 process for revisions or additional maintenance procedures shall be included in the plan.

(i)

Maintenance access easements. The applicant shall provide unfettered access to stormwater management facilities and practices requiring regular maintenance at the site from public right-of-way. Such access shall be sufficient to accommodate all necessary maintenance equipment. Such access shall also be for the purpose of inspection and repair and shall be guaranteed by the granting of a permanent, maintenance access easement. Upon final inspection and approval, a plat or document indicating that such easements exist shall be recorded and shall survive the transfer of title to the property.

(j)

Inspection and maintenance agreements. The applicant shall 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 in accordance with this article.

(k)

Evidence of acquisition of applicable local and non-local permits. The applicant shall certify and provide documentation to Jackson County that all other applicable environmental permits have been acquired for the site prior to approval of the stormwater management plan.

(l)

Additional requirements. Any additional requirements which may be specified in the GSMM, as applicable.

(Ord. No. 17-003 , § 1, 10-2-2017)