Snellville › Unified Development Ordinance

Chapter 400 — Land Development, Article 4 — Stormwater

current as of 2025-03-10re-check pendingOfficialVerify with City of Snellville ↗2 sections · full chapter

§ 404-1

Stormwater Conveyances

Chapter 400. Land Development Article 4. Stormwater Stormwater Conveyances Improvements Required Stormwater conveyance systems, which include but are not limited to culverts, storm drainage pipes, catch basins, drop inlets, junction boxes, headwalls, gutter, swales, channels, and ditches, shall be provided for the protection of public right-of-way and private properties adjoining project sites and/or public rights-of-way. Stormwater conveyance systems that are designed to carry runoff from more than one lot, existing or proposed, must meet the requirements of this UDO.

Design Criteria All stormwater conveyance systems design calculations must be certified by a Professional Engineer currently registered in the State of Georgia. (See Sec. 404-2.5)

Methods to calculate stormwater flows shall be in accordance with the Gwinnett County Stormwater Management Manual.

All portions of a stormwater conveyance system shall be analyzed using the same methodology.

Run-off coefficients used for the Rational Method and runoff Curve Numbers used for the SCS Method shall be consistent with those shown in the Gwinnett County Stormwater Management Manual.

Conveyance system design is to be in accordance with the methods contained in the Gwinnett County Stormwater Management Manual.

The 100-year ponding limits at and upstream of the culvert shall be shown on the Development Plans and on the Final Plat (if applicable).

Standard Specifications Unless otherwise specifically set forth herein all of the materials, methods of the construction, and workmanship for the work covered in reference to stormwater conveyances must conform to Gwinnett County’s most recent minimum requirements.

All piped stormwater conveyances dedicated to the City must be Reinforced Concrete Pipe (RCP).

Only Reinforced Concrete Pipe (RCP) shall be used for all dams 9 feet or more in height unless the Georgia Safe Dams Program requires another material.

Piped Outfall Location Piped Outfalls (such as headwalls) may not be located closer to the project site's property line with an adjoining property than the greater of the distance necessary to construct velocity protection or a flow distance equal to six pipe diameters. For non-circular conduits, this distance shall be six times the rise dimension of the conduit.

The invert elevation of a piped conveyance system outfall shall be no more than 2 feet above the elevation of the bottom of the receiving watercourse.

Concentrated Flows The maximum post-developed flow velocity at the project site's downstream property line with an adjoining tract may not exceed the maximum pre-developed flow velocity. Calculations are required to support this velocity standard.

The discharge of concentrated flows of stormwater into public roadways must be avoided as practicable. In no case shall such concentrated flows, including flows from swales, ditches, draws, driveways, or piped systems, exceed the allowable peak flow rates in the table below.

Street Classification Allowable Peak Flow Rate for a 2-Year Storm Local 2.0 cfs Minor Collector 1.0 cfs Other 0.5 cfs In residential subdivisions, the drainage area contributing to the peak flow along any property line between lots within 50 feet of the building setback line for either lot may not exceed 2 acres, unless contained within a piped drainage system or maintained in a natural watercourse. The stormwater conveyance shall be in a drainage easement.

Public Drainage Systems Public drainage systems include any stormwater drainage structure located within the public right-of-way (ROW) engineered and constructed to manage stormwater passing parallel to or crossing the public ROW. These structures include, but are not limited to: catch basins, drop inlets, curb and gutter, culverts under roadways, and channels within the right of way.

Piped drainage systems that originate and terminate on private property, or piped systems that depart the roadway right of way but are not in a dedicated drainage easement, will not be maintained by the City without the establishment of the appropriate easement that is dedicated to the City and recorded in accordance with City requirements. If a private piped system crosses roadway ROW, only that portion of the drainage system located within the right of way will be maintained by the City.

Drainage Easements Drainage Easement Requirements

1.Drainage easements are required for any part of the drainage system which is designed to carry stormwater runoff from more than one lot, existing or proposed.

2.Drainage easements for drainage conveyances must be provided according to the minimum requirements found in Easements for Storm Drain Pipes Table and must conform to City standards. The minimum easement width is based on the pipe diameter (span) plus 2 feet plus two times the pipe invert depth.

This value must be rounded to the nearest 5 feet. For pipes exceeding 16 feet in depth, a pre-submittal conference must be held with the Director to determine any potential, additional requirements.

Easements for Storm Drain Pipes Table Maximum Pipe Invert Depth (in feet)

Table or figure — shown as printedverify at source ↗

                Pipe Size (in inches)                         Minimum Easement       Width  (in  feet)

            4       5      6       7        8      9    10        11     12    13    14          15     16

15          20      20     20      20       20     25   25    30         30    30    35          35     40

18          20      20     20      20       20     25   25    30         30    30    35          35     40

24          20      20     20      20       20     25   25    30         30    30    35          35     40

30          20      20     20      20       25     25   25    30         30    35    35          35     40

36          20      20     20      20       25     25   25    30         30    35    35          35     40

42                  20     20      20       25     25   30    30         30    35    35          40     40

48                  20     20      20       25     25   30    30         30    35    35          40     40

54                  20     25      25       25     30   30    35         35    35    35          40     40

60                         20      25       25     25   30        30     35    35    35          40     40

66                                 25       25     30   30        30     35    35    40          40     40

72                                 25       25     30   30        30     35    35    40          40     40

Minimum Sanitary Sewer Easement Widths Permanent sanitary sewer easements may be no less than 20 feet in width when no other parallel utilities are located therein. When warranted, temporary construction easement widths shall be determined by the Gwinnett County Department of Water Resources.

See Chapter 200 Article 7 for other utility easement requirements.

Common Easement A common easement for sanitary sewer and drainage purposes is allowed if the pipes are parallel and at least 10 feet is provided between pipes (on center).

See stormwater easements for minimum widths of common easements.

Watercourse Drainage easements must be provided where a development is traversed by or contains a watercourse, impoundment, detention facility, improved channel, floodplain, natural stream or channel. It may conform substantially to the flooding limits of the 100-year storm based on fully developed conditions per the land use but may be no less than 20 feet in width.

Property owner responsibility Drainage easements off the street right-of-way must be clearly defined on the final plat. The property owner must keep the easement free of obstruction in such a way as to assure the maximum designed flow at all times. The property owner may not alter any drainage improvements without prior written approval from the City. No structure except driveways may be constructed or erected in an easement without the prior written approval from the City. Driveways must cross an easement as close to perpendicular as practical. Property owners may plant landscaping in an easement that is piped; however, the City is not responsible for replacing the landscape material located in the easement when it is removed to maintain the drainage system.

Stabilization Measures All easements which were required to be cleared must be fine graded and grassed within 10 days of completing construction work. The use of sediment control measures may be required to protect the area until a comprehensive vegetative cover is obtained.

§ 404-2

Stormwater Management

Stormwater Management Introduction It is hereby determined that:

Land development projects and other land use conversions, and their associated changes to land cover, permanently alter the hydrologic response of local watersheds and increase stormwater runoff rates and volumes, which in turn increase flooding, stream channel erosion, and sediment transport and deposition;

Land development projects and other land use conversions also contribute to increased nonpoint source pollution and degradation of receiving waters;

The impacts of post-development stormwater runoff quantity and quality can adversely affect public safety, public and private property, drinking water supplies, recreation, fish and other aquatic life, property values and other uses of lands and waters;

These adverse impacts can be controlled and minimized through the regulation of stormwater runoff quantity and quality from new development and redevelopment, by the use of both structural facilities as well as nonstructural measures, such as the conservation of open space and greenspace areas. The preservation and protection of natural area and greenspace for stormwater management benefits is encouraged through the use of incentives or “credits.”

The Georgia Greenspace Program provides a mechanism for the preservation and coordination of those greenspace areas which provide stormwater management quality and quantity benefits;

Localities in the State of Georgia are required to comply with a number of both State and federal laws, regulations, and permits which require a locality to address the impacts of post-development stormwater runoff quality and nonpoint source pollution;

Therefore, the City of Snellville has established this set of stormwater management policies to provide reasonable guidance for the regulation of post-development stormwater runoff to protect local water resources from degradation. It has determined that it is in the public interest to regulate post-development stormwater runoff discharges to control and minimize increases in stormwater runoff rates and volumes, post-construction soil erosion and sedimentation, stream channel erosion, and nonpoint source pollution associated with post-development stormwater runoff.

Purpose and Intent The purpose of this section is to protect, maintain and enhance the public health, safety, environment, and general welfare by establishing minimum requirements and procedures to control the adverse effects of increased post-development stormwater runoff and nonpoint source pollution associated with new development and redevelopment. It has been determined that proper management of post-development stormwater runoff will minimize damage to public and private property and infrastructure, safeguard the public health, safety, environment and general welfare of the public, and protect water and aquatic resources. Additionally, the City of Snellville must comply with several State and federal laws, regulations, permit, and the requirements of the Metropolitan North Georgia Water Planning District’s regional water plan related to managing the water quantity, velocity, and quality of stormwater post-development. This ordinance seeks to meet that purpose through the following objectives:

Establish decision-making processes surrounding land development activities that protect the integrity of the watershed and preserve the health of water resources;

Require that new development and redevelopment maintain the pre-development hydrologic response in their post-development state as nearly as practicable in order to reduce flooding, streambank erosion, nonpoint source pollution and increases in stream temperature, and maintain the integrity of stream channels and aquatic habitats;

Establish minimum post-development stormwater management standards and design criteria for the regulation and control of stormwater runoff quantity and quality;

Establish design and application criteria for the construction and use of structural stormwater control facilities that can be used to meet the minimum post-development stormwater management standards;

Encourage the use of nonstructural stormwater management and stormwater better site design practices, such as the preservation of greenspace and other conservation areas, to the maximum extent practicable. Coordinate site design plans, which include greenspace, with the County’s greenspace protection plan;

Establish provisions for the long-term responsibility for and maintenance of structural stormwater control facilities and nonstructural stormwater management practices to ensure that they continue to function as designed, are maintained, and pose no threat to public safety; and, Establish administrative procedures for the submission, review, approval, and disapproval of stormwater management plans, and for the inspection of approved active projects, and long-term follow up.

Applicability General This section applies to all land development, including, but not limited to, site plan applications, subdivision applications, and grading applications, unless exempt under Paragraph B immediately below. These standards apply to any new development or redevelopment site that meets one or more of the following criteria:

1.New development that involves the creation of 5,000 square feet or more of impervious cover, or that involves other land development activities of 1 acre or more;

2.Redevelopment that includes the creation, addition or replacement of 5,000 square feet or more of impervious cover, or that involves other land development activity of 1 acre or more;

3.Any new development or redevelopment, regardless of size, that is defined by the administrator to be a hotspot land use; or,

4.Land development activities that are smaller than the minimum applicability criteria set forth in clauses 1 and 2 above if such activities are part of a larger common plan of development, even though multiple, separate and distinct land development activities may take place at different times on different schedules.

Exemptions The following activities are exempt from this section:

1.Individual single-family or duplex residential lots that are not part of a subdivision or phased development project;

2.Additions or modifications to existing single-family or duplex residential structures;

3.Agricultural or silvicultural land management activities within areas zoned for these activities; and,

4.Repairs to any stormwater management facility or practice deemed necessary by the administrator.

Adoption of County Manual In implementing this section, the City must use and require compliance with all relevant design standards, calculations, formulas, methods, and other guidance from the Gwinnett County Stormwater Management Manual as well as all related appendices.

This section is not intended to modify or repeal any other article, ordinance, rule, regulation or other provision of law, including but not limited to any applicable stream buffers under State and local laws, and the Georgia Safe Dams Act and Rules for Dam Safety. In the event of any conflict or inconsistency between any provision in the City’s MS4 permit and this section, the provision from the MS4 permit will control. In the event of any conflict or inconsistency between any provision of this section and the Gwinnett County Stormwater Management Manual, the provisions from this section shall control. In the event of any other conflict or inconsistency between any provision of this section and any other ordinance, rule, regulation, or other provision of law, the provision that is more restrictive or imposes higher protection standard for human health or the environment shall control.

Permits Permit Application Requirements No owner or developer may perform any land development activities without first meeting the requirements of this section before commencing the proposed activity.

Unless specifically exempted by this section, any owner or developer proposing a land development activity shall submit to the City a permit application on a form provided by the City for that purpose.

Unless otherwise exempted by this section, a permit application must be accompanied by the following items in order to be considered:

1.Stormwater concept plan and consultation meeting certification in accordance with paragraph B below;

2.Stormwater management plan in accordance with Paragraph C below;

3.Inspection and maintenance agreement in accordance with Paragraph D below, if applicable;

4.Performance bond in accordance with Paragraph E below, if applicable; and,

5.Permit application and plan review fees in accordance with Paragraph F below.

Stormwater Concept Plan and Consultation Meeting Before any stormwater management permit application is submitted, it is recommended that the landowner or developer meet with the City for a consultation meeting on a concept plan for the post-development stormwater management system to be utilized in the proposed land development project. This consultation meeting should take place at the time of the preliminary plan of subdivision or another early step in the development process. The purpose of this meeting is to discuss the post-development stormwater management measures necessary for the proposed project, as well as to discuss and assess constraints, opportunities and potential ideas for stormwater management designs before the formal site design engineering is commenced.

To accomplish this goal the following information should be included in the concept plan which should be submitted in advance of the meeting

1.Existing Conditions / Proposed Site Plans. Existing conditions and proposed site layout sketch plans, which illustrate at a minimum:

a.Existing and proposed topography;

b.Perennial and intermittent streams;

c.Mapping of predominant soils from soil surveys (when available);

d.Boundaries of existing predominant vegetation and proposed limits of clearing and grading; and

e.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 before the commencement of the project, including:

a.Soil conditions, forest cover, topography, wetlands, and other native vegetative areas on the site

b.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.).

c.Identification of 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:

a.Preliminary selection and location of proposed structural stormwater controls;

b.Location of existing and proposed conveyance systems such as grass channels, swales, and storm drains; flow paths;

c.Location of floodplain/floodway limits;

d.Relationship of the site to upstream and downstream properties and drainages; and

e.Preliminary location of proposed stream channel modifications, such as bridge or culvert crossings.

4.Local watershed plans, the County greenspace projection plan (if applicable), and any relevant resource protection plans will be consulted in the discussion of the concept plan.

Management Plan Requirements The stormwater 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 section, including the performance criteria set forth in Sec.

404-2.6. This plan must be in accordance with the criteria established in this

section and be prepared under the direct supervisory control of either a registered Professional Engineer or a registered Landscape Architect licensed in the State of Georgia. Clauses 3, 4, 5, and 6 below must be prepared under the direct supervisory control of a registered Professional Engineer, who shall seal and sign the work. Portions of the overall plan may be prepared and stamped by a registered Land Surveyor licensed in the State of Georgia as appropriate, such as boundary surveys, contour maps, erosion, and sedimentation control plans.

The stormwater management plan must ensure that the requirements and criteria in this section are being complied with and that opportunities are being taken to minimize adverse post-development stormwater runoff impacts from the development.

The plan must consist of maps, narrative, and supporting design calculations (hydrologic and hydraulic) for the proposed stormwater management system. The plan shall include all of the information required in the Stormwater Management Site Plan checklist found in the stormwater design manual. This includes:

1.Common address and legal description of the site.

2.Vicinity Map.

3.Existing Conditions Hydrologic Analysis. The existing condition hydrologic analysis for stormwater runoff rates, volumes, and velocities, which must include:

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

b.Acreage, soil types and land cover of areas for each subbasin affected by the project;

c.All perennial and intermittent streams and other surface water features; all existing stormwater conveyances and structural control facilities;

d.Direction of flow and exits from the site; analysis of runoff provided by off-site areas upstream of the project site; and

e.Methodologies, assumptions, site parameters and supporting design calculations used in analyzing the existing conditions site hydrology.

f.Predevelopment conditions for the portion of the site undergoing land development activities shall be modeled assuming one of the following applicable conditions:

i.For new development, use the associated runoff curve number assuming land cover type to be wooded in good condition. All site areas, which are clearly defined on plans to remain undisturbed land throughout project development, can use curve number values associated with the actual land cover that exists.

ii.For redevelopment of land without existing stormwater management Facilities, use the curve number value associated with the current land cover condition of the site, which may not exceed the composite curve number associated with the land-use cover types indicated on the permitted development plan on record. Also, for land use cover types that are not clearly defined on permitted development plan on record, assume that all non-impervious areas are wooded in good condition.

iii.For the redevelopment of previously developed land with existing stormwater management facilities either:

a.Use the associated curve number, assuming the land cover type for the predevelopment condition is wooded in good condition; or

b.Use the curve numbers based on the existing land cover; however, predevelopment hydrologic conditions must consider routing stormwater runoff through existing stormwater management facilities. When routing, stage/storage and stage/discharge for these facilities/practices shall be based on original permitted stormwater management report and/or approved as-built on record. The existing non-wooded land cover types and associated areas must be similar to and not exceed the land cover types and associated areas indicated within the approved stormwater management report and/or as-built stormwater management report on record.

4.Post-Development Hydrologic Analysis. The post-development hydrologic analysis for stormwater runoff rates, volumes, and velocities, which must include:

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

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

c.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 Sec. 404-2.6;

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

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

f.Methodologies, assumptions, site parameters and supporting design calculations used in analyzing the existing conditions site hydrology.

g.If the land development activity on a redevelopment site constitutes more than 50% of the entire site area, then the performance criteria in Sec. 404-2.6 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 must include:

a.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;

b.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;

c.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);

d.Documentation and supporting calculations to show that the stormwater management system adequately meets the post-development stormwater management performance criteria in Sec. 404-2.6;

e.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

f.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 the safe passage of post-development design flows downstream.

a.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.

b.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 10% of the total basin area.

c.In calculating runoff volumes and discharge rates, consideration may need to be given to any planned future upstream land use changes.

d.The analysis shall be in accordance with the stormwater design manual.

e.The analysis must include all culverts, obstructions, existing and potential erosion problems, elevations of existing improvements, existing drainage complaints, and any other existing modifications to natural conditions.

f.The downstream watercourses and receiving conveyance must be analyzed to ensure that the channel velocities do not exceed values recommended in the stormwater design manual nor does the pipe system exceed the current design criteria of these regulations.

g.If the existing downstream conditions are overburdened by the pre-developed flows in the stream, then the developer shall work with the City to resolve the problem. The meaning of “overburdened” shall include but not be limited to situations where 25-year velocities exceed the non-erosive velocity of the stream and/or habitable structures are shown to be subject to flooding for any frequency up to an including the regulatory flood and stormwater facilities that cannot carry the design storm in accordance with the stormwater design manual or other applicable regulations.

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:

a.The arrangement of planted areas, natural and greenspace areas and other landscaped features on the site plan;

b.Clearly specify the type of trees, shrubs, and other vegetation within a stormwater management facility or practice and certify the survivability of the vegetation with the expected fluctuation of water ponding within the facility or practice. The stumps of all trees and shrubs within the stormwater management facility or practice, which are not indicated on the landscape plan, shall be cut flush with the ground or removed and associated debris removed, unless landscape plan modification is submitted and approved by the administrator.

c.Information necessary to construct the landscaping elements shown on the plan drawings;

d.Descriptions and standards for the methods, materials, and vegetation that are to be used in the construction;

e.Density of plantings;

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

g.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 stormwater management facilities and practices to ensure their continued function as designed and constructed or preserved.

a.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.

b.The plan must include an inspection and maintenance schedule, maintenance tasks, responsible parties for maintenance, funding, access and safety issues.

c.Provisions for the periodic review and evaluation of the effectiveness of the maintenance program and the need for revisions or additional maintenance procedures must be included in the plan.

10.Maintenance Access Easements. The applicant must ensure access from a 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.

a.Such access shall be sufficient for all necessary equipment for maintenance activities of the stormwater management facility, which shall include but not be limited to:

i.Clearing, grubbing, and grading access, so that it can be utilized by rubber-tired construction vehicles.

ii.Maintaining a minimum access drive width of 15 feet with a maximum slope of 20% (5H:1V).

iii.Requiring access drive to be grassed or paved.

b.For non-residential lots and subdivisions, the easement width from the right-of-way to the stormwater management facility/practice shall be a minimum of 20 feet.

c.For residential lots and subdivisions, the easement width from the right-of-way to the stormwater management facility/practice shall be a minimum of 30 feet.

d.Every structural stormwater management facility and practice shall be enclosed within an easement, extending a minimum of 10 feet beyond the perimeter of the practice or a minimum of 10 feet beyond the 100-year ponding limit, whichever is greater. The easement enclosing the facility shall be named “Best Management Practice (BMP) Easement.”

e.Non-structural practices implemented and/or better site design credits applied toward achieving stormwater management performance criteria, which require an area of land to remain natural and/or undisturbed, shall be identified within a conservation easement. These areas may include but not be limited to: natural conservation areas (such as stream buffers, wetlands, and floodplains), undisturbed upland areas, and reforestation/revegetation.

f.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 City as provided in Paragraph D below, 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 in accordance with Paragraph D below.

12.Evidence of Acquisition of Applicable Local and Non-local Permits. The applicant must certify and provide documentation to the City that all other applicable environmental permits have been acquired for the site before approval of the stormwater management plan.

Inspection and Maintenance Agreements Before the issuance of any permit for a land development activity requiring a stormwater management facility or practice hereunder and for which the City requires ongoing maintenance, the applicant or owner of the site must, unless an on-site stormwater management facility or practice is dedicated to and accepted by the City, execute an inspection and maintenance agreement, and/or a conservation easement, if applicable, that shall be binding on all subsequent owners of the site. If the development or redevelopment has a stormwater management facility and/or practice that was previously constructed during another phase of development and does not have a recorded inspection and maintenance agreement, an inspection and maintenance agreement must be established, approved, and recorded, following these same procedures.

The inspection and maintenance agreement, if applicable, must be approved by the City before plan approval, and recorded in the deed records upon final plat approval.

The inspection and maintenance agreement must identify by name or official title the person(s) responsible for carrying out the inspection and maintenance.

Responsibility for the operation and maintenance of the stormwater management facility or practice, unless assumed by a governmental agency, shall remain with the property owner and shall pass to any successor owner. If portions of the land are sold or otherwise transferred, legally binding arrangements shall be made to pass the inspection and maintenance responsibility to the appropriate successors in title. These arrangements must designate for each portion of the site, the person to be permanently responsible for its inspection and maintenance.

As part of the inspection and maintenance agreement, a schedule shall be developed for when and how often routine inspection and maintenance will occur to ensure proper function of the stormwater management facility or practice. The agreement shall also include plans for annual inspections to ensure proper performance of the facility between scheduled maintenance and shall also include remedies for the default thereof.

In addition to enforcing the terms of the inspection and maintenance agreement, the City may also enforce all of the provisions for ongoing inspection and maintenance in accordance with Sec. 404-2.8.

The City, in lieu of an inspection and maintenance agreement, may accept dedication of any existing or future stormwater management facility for maintenance, provided such facility meets all the requirements of Sec. 404-2.8 and includes adequate and perpetual access and sufficient area, by easement or otherwise, for inspection and regular maintenance.

Performance and Maintenance Bonds Before or concurrent with the recording of a final plat for a subdivision, or issuance of a certificate of occupancy for a non-subdivision project, the developer shall provide acceptable surety such as a bond or letter of credit providing for the maintenance of the facility for a period of not less than 24 months. The amount of the surety shall be the greater of 50% of construction costs of the facility or 100% of the cost to clean out the facility. At the end of 18 months, the City may require the surety to be renewed due to anticipated maintenance caused by such concerns as future construction activity in the basin draining to the facility. A renewed surety may be required up to a total maximum of 10 years. The surety for a facility shall be renewed during the 10 years until:

1.The surface water drainage area within the project has undergone final stabilization and all planned construction activity has been completed;

2.All stormwater runoff in the surface water drainage area within the project is coming from undisturbed or stabilized areas;

3.At least 90% of the lots in that surface water drainage area within the project have been sold to an unrelated party, permanent structures completed, and final stabilization achieved;

4.The accumulation of acreage of undeveloped lots, lots with no completed permanent structure and no final stabilization, within the surface water drainage area within the project is less than 5 acres or 10% of the total area of the common development draining to the facility, whichever is greater; and

1.Within 2 months of surety release, the facility shall be cleaned out, if necessary, and a new record survey, drawing and certification shall be submitted, showing that the volume of the facility is equal to or greater than the volume shown in the record survey, drawing and certification when the facility was approved. As an alternative, a new record survey, drawing and certification showing that the facility complies with these regulations per Sec.

Chapter 400.404-2.7.C404-2.7.C must be submitted.

Application Procedure

1.Applications for land development permits shall be filed with the City.

2.Permit applications must include the items set forth in paragraph A above (two copies of the stormwater management plan and the inspection maintenance agreement, if applicable, must be included).

3.The City must inform the applicant whether the application, stormwater management plan, and inspection and maintenance agreement are approved or disapproved.

4.If either the permit application, stormwater management plan or inspection and maintenance agreement are disapproved, the City shall notify the applicant of such fact in writing. The applicant may then revise any item not meeting the requirements hereof and resubmit the same, in which event clause 3 above and this clause shall apply to such resubmittal.

5.Upon a finding by the City that the permit application, stormwater management plan, and inspection and maintenance agreement, if applicable, meet the requirements of this section, the City may issue a permit for the land development project, provided all other legal requirements for the issuance of such permit have been met.

6.Notwithstanding the issuance of the permit, in conducting the land development project, the applicant or another responsible party will be subject to the following requirements:

a.The applicant must comply with all applicable requirements of the approved plan and this section and must certify that all land clearing, construction, land development, and drainage will be done according to the approved plan;

b.The land development project must be conducted only within the area specified in the approved plan;

c.The City is allowed to conduct periodic inspections of the project;

d.No changes may be made to an approved plan without review and written approval by the City; and,

e.Upon completion of the project, the applicant or another responsible party must submit the engineer’s report and certificate and as-built survey required by Sec. 404-2.7.C.

Application Review Fees The fee for review of any stormwater management application will be based on the fee structure established by the City and must be made before the issuance of any building permit for the development.

Modifications for Off-Site Facilities The stormwater management plan for each land development project shall provide for stormwater management measures located on the site of the project, unless provisions are made to manage stormwater by an off-site or regional facility. The off-site or regional facility must be located on property legally dedicated for the purpose, must be designed and adequately sized to provide a level of stormwater quantity and quality control that is equal to or greater than that which would be afforded by on-site practices and there must be a legally-obligated entity responsible for long-term operation and maintenance of the off-site or regional stormwater facility. In addition, on-site measures must be implemented, where necessary, to protect upstream and downstream properties and drainage channels from the site to the off-site facility.

A stormwater management plan must be submitted to the City which shows the adequacy of the off-site or regional facility.

To be eligible for a modification, the applicant must demonstrate to the satisfaction of the City that the use of an off-site or regional facility will not result in the following impacts to upstream or downstream areas:

1.Increased threat of flood damage to public health, life, and property;

2.Deterioration of existing culverts, bridges, dams, and other structures;

3.Accelerated streambank or streambed erosion or siltation;

4.Degradation of in-stream biological functions or habitat; or

5.Water quality impairment in violation of State water quality standards, and/or violation of any State or federal regulations.

Performance Criteria The following performance criteria apply to all stormwater management plans, unless otherwise provided for in this section:

Water Quality All stormwater runoff generated from a site must be adequately treated before discharge. It will be presumed that a stormwater management system complies with this requirement if:

1.It is sized to treat the prescribed water quality treatment volume from the site, as defined in the Georgia Stormwater Management Manual;

2.Appropriate structural stormwater controls or nonstructural practices are selected, designed, constructed or preserved, and maintained according to the specific criteria in the Georgia Stormwater Management Manual; and

3.Runoff from hotspot land uses and activities identified by the City are adequately treated and addressed through the use of appropriate structural stormwater controls, nonstructural practices, and pollution prevention practices.

Stream Channel Protection Protection of stream channels from bank and bed erosion and degradation must be provided by using all of the following three approaches:

1.Preservation, restoration and/or reforestation (with native vegetation) of the applicable stream buffer;

2.24-hour extended detention storage of the 1-year, 24-hour return frequency storm event; and

3.Erosion prevention measures such as energy dissipation and velocity control.

The 24-hour extended detention of the 1-year, 24-hour return frequency storm event may be waived by the administrator for sites that discharge either directly or through piped stormwater drainage systems, which discharge directly into larger rivers, wetlands, lakes, estuaries, tidal waters, or other situation where the reduction in the smaller flows will not have an impact of the stream bank or channel integrity.

Overbank Flooding Protection Downstream overbank flood and property protection must be provided by controlling (attenuating) the post-development peak discharge rate to the pre-development rate for the 25-year, 24-hour return frequency storm event. If control of the 1-year, 24-hour storm under paragraph B above is exempted, then peak discharge rate attenuation of the 2-year through the 25-year return frequency storm event must be provided.

Extreme Flooding Protection Extreme flood protection must be provided by controlling or safely conveying the 100-year, 24-hour storm event (denoted Qf) such that flooding is not exacerbated.

This must be accomplished either by:

1.Controlling Qf through the stormwater management system to maintain the existing 100-year floodplain; or

2.By sizing the onsite conveyance system to safely pass Qf and allowing it to discharge into a receiving water whose protected floodplain is sufficiently sized to account for extreme flow increases without causing damage.

If the option in clause 2 above is used, the extreme flood protection criterion may be waived by City in lieu of provisions for safe and effective conveyance to receiving waters that have the capacity to handle flow increases to maintain a 100-year level.

Structural Stormwater Controls All structural stormwater management facilities must be selected and designed using the appropriate criteria from the Georgia Stormwater Management Manual.

All structural stormwater controls must be designed appropriately to meet their intended function. For other structural stormwater controls not included in the Georgia Stormwater Management Manual, or for which pollutant removal rates have not been provided, the effectiveness and pollutant removal of the structural control must be documented through prior studies, literature reviews, or other means and receive approval from City before being included in the design of a stormwater management system. In addition, if hydrologic or topographic conditions, or land use activities warrant greater control than that provided by the minimum control requirements, the City may impose additional requirements deemed necessary to protect upstream and downstream properties and aquatic resources from damage due to increased volume, frequency, and rate of stormwater runoff or increased nonpoint source pollution loads created on the site in question.

Applicants must consult the Georgia Stormwater Management Manual for guidance on the factors that determine site design feasibility when selecting and locating a structural stormwater control.

The location of the structural stormwater management facilities may not disturb or encroach within:

1.Any required (as opposed to voluntary) buffer, landscape strip, or tree protection areas;

2.A public right-of-way, unless a written agreement is received granting permission from the authority having jurisdiction.

3.Utility easements and/or adjacent lots, unless a written agreement is received granting permission from the impacted lot/utility owner(s).

4.An individual lot of sale within a residential subdivision, unless the structural stormwater management facility is only intended for that lot (not providing stormwater management for more than one lot). If the facility provides stormwater management for more than one lot in a residential subdivision, the facility must be on a separate lot owned and maintained by a mandatory property owner’s association.

Credits for Nonstructural Measures The use of one or more site design measures by the applicant may allow for a reduction in the water quality treatment volume required under paragraph A above. The applicant may, if approved by the (local permitting authority), take credit for the use of stormwater better site design practices and reduce the water quality volume requirement. For each potential credit, there is a minimum set of criteria and requirements which identify the conditions or circumstances under which the credit may be applied. The site design practices that qualify for this credit and the criteria and procedures for applying and calculating the credits are included in the Georgia Stormwater Management Manual.

Drainage System Guidelines Stormwater conveyance facilities, which may include but are not limited to culverts, stormwater drainage pipes, catch basins, drop inlets, junction boxes, headwalls, gutter, swales, channels, ditches, and energy dissipaters must be provided when necessary for the protection of public right-of-way and private properties adjoining project sites and/or public right-of-way. Stormwater conveyance facilities that are designed to carry runoff from more than one lot, existing or proposed, must meet the following requirements:

1.Methods to calculate stormwater flows shall be in accordance with the stormwater design manual;

2.All culverts, pipe systems, and open channel flow systems shall be sized in accordance with the stormwater management plan using the methods included in the stormwater design manual; and,

3.Design and construction of stormwater conveyance facilities shall be in accordance with the criteria and specifications found in the stormwater design manual.

Dam Design Guidelines Any land disturbing activity that involves a site that proposes a dam must comply with the Georgia Safe Dams Act and Rules for Dam Safety as applicable.

Construction Inspections Compliance with Approved Stormwater Management Plan All development must be: (a) consistent with the approved stormwater management plan and all applicable land disturbance permit and building permit;

and (b) conducted only within the area specified in the approved stormwater management plan. No changes may be made to an approved stormwater management plan without review and advanced written approval by the administrator.

Inspections to Ensure Plan Compliance During construction periodic inspections of the stormwater management system construction shall be conducted by the staff of the City or conducted and certified by a professional engineer who has been approved by the City. Construction inspections shall utilize the approved stormwater management plan for establishing compliance.

All inspections must be documented with written reports that contain the following:

1.The date and location of the inspection;

2.Whether the construction is in compliance with the approved stormwater management plan;

3.Variations from the approved construction specifications; and,

4.Any other variations or violations of the conditions of the approved stormwater management plan. If any violations are found, the applicant must be notified in writing of the nature of the violation and the required corrective actions.

Final Inspection and As-Built Plans Upon completion of a project, and before a certificate of occupancy will be granted, the applicant is responsible for certifying that the completed project is in accordance with the approved stormwater management plan.

1.Newly Constructed or Modified Stormwater Management Facilities/Practices for Development/Redevelopment: All applicants are required to submit actual as-built surveys for any stormwater management facilities or practices after final construction is completed. The surveys must show the final design specifications for all stormwater management facilities and practices and must be certified by a Professional Engineer. The surveys must be submitted for review and approval by the City. A final inspection by the City is also required before the release of any performance securities can occur.

2.Non-Modified Stormwater Management Facilities That Existed Before Development/Redevelopment: All applicants are required to have a Professional Engineer certify that every non-modified existing stormwater management facility is operating as originally approved after construction is completed. The certification must be submitted to City for review and approval.

A final inspection by the City is also required before the release of any performance securities can occur.

3.The required certification for clauses 1 and 2 above must, at a minimum, include a certification of volume, or another performance test applicable to the type of stormwater management system component, to ensure each component is functioning as designed and built in accordance to the design specifications in the approved stormwater management plan. This certification and the required performance tests must be performed by a qualified person and submitted to the City with the request for a final inspection.

Ongoing Inspections Long-Term Maintenance Inspection of Stormwater Facilities and Practices Stormwater management facilities and practices included in a stormwater management plan which are subject to an inspection and maintenance agreement must undergo ongoing inspections to document maintenance and repair needs and ensure compliance with the requirements of the agreement, the plan and this section.

A stormwater management facility or practice shall be inspected on a periodic basis by the responsible party in accordance with the approved inspection and maintenance agreement. In the event that the stormwater management facility has not been maintained and/or becomes a danger to public safety or public health, the City shall notify the person responsible for carrying out the maintenance plan by registered or certified mail to the person specified in the inspection and maintenance agreement. The notice shall specify the measures needed to comply with the agreement and the plan and shall specify the time within which such measures shall be completed. If the responsible party fails or refuses to meet the requirements of the inspection and maintenance agreement, the City may correct the violation as provided in Sec. 404-2.9 (Violations, Enforcement, and Penalties).

Inspection programs by the City may be established on any reasonable basis, including but not limited to: routine inspections; random inspections; inspections based upon complaints or other notice of possible violations; and joint inspections with other agencies inspecting under environmental or safety laws. Inspections may include but are not limited to: reviewing maintenance and repair records;

sampling discharges, surface water, groundwater, and material or water in stormwater management facilities; and evaluating the condition of stormwater management facilities and practices.

Right-of-Entry for Inspection The terms of the inspection and maintenance agreement shall provide for the City to enter the property at reasonable times and in a reasonable manner for the purpose of inspection. This includes the right to enter a property when it has a reasonable basis to believe that a violation of this section is occurring or has occurred and to enter when necessary for abatement of a public nuisance or correction of a violation of this section.

Records of Maintenance Activities Parties responsible for the operation and maintenance of a stormwater management facility shall provide records of all maintenance and repairs to the City.

Failure to Maintain If a responsible party fails or refuses to meet the requirements of the inspection and maintenance agreement, the City, after 30 days written notice (except, that in the event the violation constitutes an immediate danger to public health or public safety, 24 hours’ notice shall be sufficient), may correct a violation of the design standards or maintenance requirements by performing the necessary work to place the facility or practice in proper working condition. The City may assess the owner(s) of the facility for the cost of repair work which shall be a lien on the property and may be placed on the ad valorem tax bill for such property and collected in the ordinary manner for such taxes.

Violations, Enforcement, and Penalties Any violation of the approved stormwater management plan during construction, failure to submit as-built surveys, or failure of the final inspection shall constitute and be addressed as violations of, or failures to comply with, the underlying land disturbance permit or building permit. To address a violation of section, the City shall have all the powers and remedies that are available to it for other violations of building and land disturbing permits, including without limitation the right to issue notices and orders to ensure compliance, stop work orders, and penalties as set forth in the applicable articles for such permits.