1 A SUBSTITUTE ORDINANCE BY CITY UTILITIES COMMITTEE 12-O-1761 AN ORDINANCE TO AMEND VARIOUS SECTIONS OF CHAPTER 74, ARTICLE X OF THE CITY OF ATLANTA CODE OF ORDINANCES FOR THE PURPOSE OF PROMOTING GREEN INFRASTRUCTURE AND RUNOFF REDUCTION PRACTICES; COMPLYING WITH THE METROPOLITAN NORTH GEORGIA WATER PLANNING DISTRICT S MODEL POST-DEVELOPMENT STORMWATER MANAGEMENT ORDINANCE; STREAMLINING THE PERMITTING PROCESS; PROMOTING MAINTENANCE OF STORMWATER MANAGEMENT FACILITIES; AND FOR OTHER PURPOSES. WHEREAS, Article X of Chapter 74 of the City of Atlanta Code of Ordinances sets out the requirements and procedures to control the adverse effects of post-development stormwater runoff and nonpoint source pollution associated with new development and redevelopment by focusing on the types of frequently occurring storm events that generate the most water quality impacts; and WHEREAS, the use of green infrastructure and runoff reduction practices improves water quality in our streams and reduces the magnitude and frequency of flooding and combined sewer overflow events through the infiltration, evapotranspiration, and reuse of stormwater runoff; and WHEREAS, the use of trees, shrubs and other vegetation associated with green infrastructure mitigates impacts of urban heat islands, reduces energy demand by decreasing the amount of energy used for heating and cooling, improves air quality, increases carbon sequestration, and improves aesthetics; and WHEREAS, implementing green infrastructure and runoff reduction practices will bring the City of Atlanta one step closer to becoming a Top 10 sustainable city, in accordance with Mayor Kasim Reed s goals; and WHEREAS, the City of Atlanta is required to remove barriers to green infrastructure in accordance with NPDES Municipal Separate Storm Sewer System (MS4) permit requirements; and WHEREAS, the Metropolitan North Georgia Water Planning District Act, O.C.G.A , et seq., requires that the City of Atlanta adopt and administer the Metropolitan North Georgia Water Planning District s ( District s ) Model Post-Development Stormwater Management for New Development and Redevelopment or equally effective; and WHEREAS, in an effort to streamline the permitting process in accordance with the goals of the Department of Planning and Community Development, a stormwater consultation
2 meeting early in the permitting process will ultimately speed up the time that it takes to acquire a permit; and WHEREAS, ongoing maintenance of stormwater management facilities is necessary to ensure proper functionality; and WHEREAS, the Commissioner of the Department of Watershed Management recommends that the following sections of the City s Code be amended in order to effectuate the changes outlined above. NOW THEREFORE, BE IT AND IT IS HEREBY ORDAINED BY THE CITY COUNCIL OF THE CITY OF ATLANTA, GEORGIA as follows: Section 1. Section of the City Code of Ordinances is hereby deleted and replaced in its Sec Introduction. It is hereby determined that: (a) (b) (c) (d) (e) (f) 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 can 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 projects by the use of structural and nonstructural measures, such as the conservation or restoration of open space and greenspace areas; 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; and Therefore, the City of Atlanta has established this set of regulations governing the management of post-development stormwater runoff and the ongoing maintenance of stormwater control systems for the purpose of protecting local water resources from degradation. It is in the public interest to regulate post-development stormwater runoff
3 discharges and control systems in order to reduce or 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. Section 2. Section of the City Code of Ordinances is hereby deleted and replaced in its Sec Purpose and intent. (a) (b) The purpose of this Article 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 post-development stormwater runoff and nonpoint source pollution associated with new development and redevelopment by focusing on the types of frequently occurring storm events that generate the most water quality impacts. 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. This ordinance seeks to meet those purposes through the following objectives: (1) Establish decision-making processes surrounding land development activities that protect the integrity of the watershed and preserve the health of water resources; (2) Establish post-construction stormwater management and site planning and design criteria to protect natural resources from the direct impacts of the land development process, and to preserve and/or restore natural hydrologic conditions on development sites; (3) Encourage the use of nonstructural stormwater management methodologies, stormwater better site design practices, peak rate and/or runoff reduction, and the preservation of greenspace and other conservation areas by establishing minimum post-development stormwater management standards and design criteria for the regulation and control of stormwater runoff quantity and quality; (4) Establish design and application criteria for the construction and use of structural stormwater control facilities that meet the minimum post-development stormwater management standards; (5) Coordinate site design plans with the City of Atlanta's greenspace protection plan; (6) Establish provisions for the long-term responsibility for operation, inspection, maintenance, and repair of private structural stormwater control facilities and private commitments for nonstructural stormwater management practices to
4 ensure that they continue to function as designed, are maintained, and pose no threat to public safety or the environment; (7) 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 compliance; and (8) Protect public health and safety by reducing the risk of localized flooding and reducing the amount of runoff entering public rights of way. Section 3. Section of the City Code of Ordinances is hereby deleted and replaced in its Sec Definitions. The following words, terms and phrases, when used in this Article, shall have the meanings ascribed to them in this section, except where the context clearly indicates a different meaning: Applicant means a person submitting a post-development stormwater management application and plan for approval. Channel means a natural or artificial watercourse with a definite bed and banks that conducts continuously or periodically flowing water. Commissioner means the Commissioner of the Department of Watershed Management or a designee. Conservation easement means an agreement between a land owner and the City of Atlanta, other government agency, or land trust that permanently protects open space or greenspace on the owner's land by limiting the amount and type of development that can take place, but continues to leave the remainder of the fee interest in private ownership. Demolition means removal of an existing building, structure, or other impervious surface. Detention means the temporary storage of stormwater runoff in a stormwater management facility for the purpose of controlling the peak discharge. Detention facility means a detention basin or structure designed for the detention of stormwater runoff and gradual release of stored water at controlled rates. Developer means a person who undertakes land development activities. Development means a land development or land development project.
5 Drainage easement means an easement appurtenant or attached to a tract or parcel of land allowing the owner of adjacent tracts or other persons to discharge stormwater runoff onto the tract or parcel of land subject to the drainage easement. Erosion and Sedimentation Control Plan means a plan that is designed to minimize the accelerated erosion and sediment runoff at a site during land disturbance activities. Extended detention means the detention of stormwater runoff for an extended period, typically 24 hours or greater. Extreme flood protection means measures taken to prevent adverse impacts from large lowfrequency storm events with a return frequency of 100 years or more. Flooding means a volume of water that is too great to be confined within the banks or walls of a conveyance or stream channel and overflows onto adjacent lands. Grading means altering ground surfaces to specified elevations, dimensions and slopes; this includes, but is not limited to, stripping, cutting, filling, stockpiling and shaping or any combination thereof and includes the land in its cut or filled condition. Greenfield means land in its natural condition. Greenspace means permanently protected areas of the site that are preserved in a vegetated state. Green Infrastructure means an interconnected natural system and/or engineered system that strengthens and mimics natural hydrologic functions and processes through the use of plants and soil to slow, filter, evapotranspire, and infiltrate stormwater runoff close to its source; or the capture and reuse of stormwater runoff. High Risk Operation means an area where the use of the land has the potential to generate highly contaminated runoff, with concentrations of pollutants in excess of those typically found in stormwater as consistent with facilities operating under a Standard Industrial Code (SIC) or requiring coverage under the Georgia General NPDES Stormwater Permit for Discharges from Industrial Activities or as identified as a highly visible pollutant source (HVPS) per the City of Atlanta s Stormwater Management Plan (SWMP) developed in accordance with the requirements of the City of Atlanta s NPDES Municipal Separate Storm Sewer System (MS4) permit. Hotspot means an area with, or having potential for a high level of pollution and/or contamination within a larger area of low adverse environmental impact or normal environmental quality. Hydrologic Soil Group (HSG) means a Natural Resource Conservation Service classification system in which soils are categorized into four runoff potential groups. The groups range from
6 group A soils, with high permeability and little runoff produced, to group D soils, which have low permeability rates and produce much more runoff. Impervious cover means a surface composed of any material that significantly impedes or prevents the natural percolation of water into soil, which includes, but is not limited to, rooftops, buildings, streets and roads, and standard concrete or asphalt surface. Industrial stormwater permit means a National Pollutant Discharge Elimination System (NPDES) permit issued to an entity which regulates the pollutant levels associated with industrial stormwater discharges or specifies on-site pollution control strategies. Inspection and maintenance agreement means a written agreement providing for the long-term inspection and maintenance of stormwater management facilities and practices on a site or with respect to a land development project, which, when properly recorded in the deed records of the Superior Court of Fulton or DeKalb County, whichever is applicable, constitutes a restriction on the title to a site or other land involved in a land development project. Jurisdictional wetland means an area that is inundated or saturated by surface water or groundwater at a frequency and duration sufficient to support a prevalence of vegetation typically adapted for life in saturated soil conditions, commonly known as hydrophytic vegetation, as determined by the U.S. Army Corps of Engineers. Land development means any land change, including, but not limited to, clearing, digging, grubbing, stripping, removal of vegetation, dredging, grading, excavating, transporting and filling of land, construction, paving, and any other installation of impervious cover. Land development activities means those actions or activities which comprise, facilitate or result in land development. Land development project means a discrete land development undertaking. National Pollutant Discharge Elimination System (NPDES) Permit means the applicable national pollutant discharge elimination system permit issued by the State Environmental Protection Division and in effect at the time of application for a post-development stormwater plan approval. New development means a land development activity on a previously undeveloped site. Nonpoint source pollution means a form of water pollution that does not originate from a discrete point such as a sewage treatment plant or industrial discharge, but involves the transport of pollutants such as sediment, fertilizers, pesticides, heavy metals, oil, grease, bacteria, organic materials and other contaminants from land to surface water and groundwater via mechanisms such as precipitation, stormwater runoff, and leaching. Nonpoint source pollution is a by-product of land use practices such as agricultural, silvicultural, mining, construction, subsurface disposal and urban runoff sources.
7 Nonstructural Stormwater Management Practice means any natural or planted vegetation or other nonstructural component of the stormwater management plan that provides for or enhances stormwater quantity and/or quality control or other stormwater management benefits and includes, but is not limited to, riparian buffers, open and greenspace areas, overland flow filtration areas, natural depressions, and vegetated channels. Off-site facility means a stormwater management facility located outside the boundaries of the site. On-site facility means a stormwater management facility located within the boundaries of the site. Overbank Flood Protection means measures taken to prevent an increase in the frequency and magnitude of out-of-bank flooding (i.e. flow events that exceed the capacity of the channel and enter the floodplain), and that are intended to protect downstream properties from flooding up to the 25-year frequency storm events. Owner means the legal or beneficial owner of a site, including but not limited to, a mortgage or vendee in possession, receiver, executor, trustee, lessee or other person, firm or corporation in control of the site. Percolation means the process of absorption of stormwater runoff into the subsoil. Permit means the permit issued by the City of Atlanta to the applicant which is required for undertaking any land development activity. Person means, except to the extent exempted from this ordinance, any individual, partnership, firm, association, joint venture, public or private corporation, trust, estate, commission, board, public or private institution, utility, cooperative, city, county or other political subdivision of the State, any interstate body or any other legal entity. Post-development refers to the time period, or the conditions that may reasonably be expected or anticipated to exist, after completion of the land development activity on a site as the context may require. Pre-development refers to the time period, or the conditions that exist, on a site prior to the commencement of a land development project and at the time that plans for the land development of a site are approved by the City of Atlanta. Where phased development or plan approval occurs, which includes but is not limited to demolition, preliminary grading, roads and utilities, the existing conditions at the time prior to issuance of the first project-related approval or permit shall represent pre-developed conditions, in accordance with Section (d). Project means the portion of the proposed development in terms of the area of land to be disturbed. Q means the peak rate of discharge.
8 Redevelopment means a land development project or addition on a previously developed site. Regional stormwater management facility means stormwater management facilities designed to control stormwater runoff from multiple properties, where the owners or developers of the individual properties may assist in the financing of the facility, and the requirement for sitespecific on-site controls may be either eliminated or reduced. Responsible party means the owner or owner s agent. Runoff means the flow of surface water resulting from precipitation. Runoff Reduction means the interception, evapotranspiration, infiltration or capture and reuse of stormwater runoff. Single Family Residential development means development or redevelopment of a lot containing a single one or two family dwelling as defined in Section (12) of the City of Atlanta s Zoning Ordinance. Site means the parcel of land being developed, or the portion thereof on which the land development project is located. Stormwater better site design means nonstructural site design approaches, practices and techniques that can reduce a site's impact on the watershed and can provide for nonstructural stormwater management. Stormwater better site design includes conserving and protecting natural areas and greenspace, reducing impervious cover and using natural features for stormwater management. Stormwater management means the collection, retention, detention, conveyance, storage, treatment and disposal of stormwater runoff in a manner intended to prevent increased flooding, streambank channel erosion, habitat degradation and water quality degradation, and to enhance and promote the public health, safety and general welfare. Stormwater management facility means any infrastructure that controls or conveys stormwater runoff. Stormwater management measure means any stormwater management facility or nonstructural stormwater practice. Stormwater management plan means the document(s) describing how existing runoff characteristics will be affected by a land development project and containing measures for complying with the provisions of this ordinance. Stormwater management site plan means an engineering drawing depicting how and where stormwater management facilities and practices will be installed on the site.
9 Stormwater management system means the entire set of structural and nonstructural stormwater management facilities and practices that are used to capture, convey and control the quantity and quality of the stormwater runoff from a site. Stormwater retrofit means a stormwater management practice designed for a currently developed site that previously had either no stormwater management practice in place or a practice inadequate to meet the stormwater management requirements of the site. Structural stormwater control means a structural stormwater management facility or device that controls stormwater runoff and changes the characteristics of that runoff including, but not limited to, the quantity and quality, the period of release, or the velocity of flow of such runoff. Subdivision means the division of a tract or parcel of land resulting in one or more new lots or building sites for the purpose, whether immediately or in the future, of sale, other transfer of ownership or land development, and includes divisions of land resulting from or made in connection with the layout or development of a new street or roadway or a change in an existing street or roadway. Section 4. Section of the City Code of Ordinances is hereby deleted and replaced in its Sec Applicability. (a) Development and redevelopment. This Article shall apply to all development and redevelopment, except single family residential development, unless exempt pursuant to Section (d). The standards found in this Article apply to any new development or redevelopment site that meets one or more of the following: (1) New development that involves the creation of any impervious cover; or (2) New development that involves land development activities of one disturbed acre or more; or (3) Redevelopment that involves land development activity of one disturbed acre or more; or (4) Redevelopment that includes the creation, addition, or demolition and replacement of 500 square feet or more of impervious cover; or (5) Demolition that leaves in place more than 500 square feet of impervious cover within the area of demolition, unless building permit application for replacement structure or use which includes appropriate stormwater management is in place. (b) Single family residential. Sections (a), (b), and of this Article shall apply to a single family residential development, unless exempt pursuant to
10 Section (d). For the purposes of this Article, a single family residential development shall include the following: (1) Development or redevelopment of any site involving the construction of a singlefamily residence; or (2) Addition or modification that involves the creation, addition, or demolition and replacement of 1,000 square feet or more of impervious cover to any single family residential site. A single family residential development shall not include development or redevelopment of a site intended to be developed as a larger common plan of development or sale as defined in Atlanta City Code Section (c) High risk operation and hotspot. This Article shall apply to any new development or redevelopment, regardless of size, that meets the definition of Hotspot or High Risk Operation, which includes, but is not limited to, fueling stations or industrial facilities with potential for runoff pollution. (d) Exemptions. The following activities are exempted from Sections (a), (b) and (c) above, but shall be subject to the minimum requirements in Section : (1) Agricultural or silvicultural land management activities within properly zoned agricultural areas resulting in less than 1,000 square feet of impervious surface; (2) Regrading or reshaping existing athletic fields or public parks resulting in less than1,000 square feet of new impervious surface; (3) Installations, repairs, or modifications to storm drains, drainage structures, storm water management facilities, or other drainage facilities to improve drainage capabilities; (4) Installations, repairs, or modifications to sanitary sewer facilities to expand or improve sanitary sewer service capabilities; (5) Work specifically related to the installation, repair, or maintenance of utility service connections, including but not limited to sewer, water, electric, telephone, and gas, to existing facilities; (6) Installations of dumpster pads with drains connected to sanitary sewers; (7) Installations or modifications to existing structures to accommodate Americans with Disability Act (ADA) requirements, including but not limited to elevator shafts, handicapped access ramps and parking, and enlarged entrances or exits;
11 (8) Installations or modifications to existing structures to address health and safety issues or compliance with Atlanta City Code requirements, including but not limited to fire escapes, stairways, and additional exits; (9) Installations to existing structures of incidental mechanical or electrical equipment placed on areas of previously existing impervious surfaces; (10) Installation of hardscape less than 5,000 square feet, such as uncovered parking, pedestrian, or patio areas, which utilize pervious pavement or other appropriate infiltration techniques; (11) Incidental maintenance or repair of existing impervious paved surfaces which impact less than 1,000 square feet; (12) Overlays or resurfacing of existing impervious paved surfaces; (13) Any work permitted in the public rights of way such as the installations of sidewalks, driveway aprons, and street cuts, or projects on private property necessitated by activities in the public rights of way; (14) Sidewalks or trails 15 feet wide or less where runoff is directed via sheet flow toward vegetated areas at least twice as wide as the paved area, provided that the potential for erosion is adequately addressed; (15) Stream bank stabilization or restoration activities, or activities solely for the purpose of environmental remediation; (16) Replacement of an existing driveway to access a single family residential development; or (17) Any minor work which in the professional judgment of the Commissioner is deemed in the best interest of the City of Atlanta. Section 5. Section of the City Code of Ordinances is hereby deleted and replaced in its Sec Designation of ordinance administrator. The Commissioner of the Department of Watershed Management or his designee is hereby appointed to administer and implement the provisions of this Article. Section 6. Section of the City Code of Ordinances is hereby deleted and replaced in its Sec Stormwater design manual.
12 The City of Atlanta will utilize the policy, criteria and information, including technical specifications and standards, in the Georgia Stormwater Management Manual, the applicable sections of the Coastal Stormwater Supplement and any relevant rules, regulations, or policies of the City of Atlanta, including Chapter 74 of the Code of Ordinances, or procedures of the Department of Watershed Management in effect at the time of application for the proper implementation of the requirements of this ordinance. The manual may be updated and expanded periodically based on improvements in science, engineering, monitoring and local maintenance experience. Section 7. Section of the City Code of Ordinances is hereby deleted and replaced in its Sec Permit procedures and requirements. (a) (b) (c) No owner or developer shall perform any land development activities without first meeting the requirements of this Article prior to commencing the proposed activity. Any owner or developer proposing a land development activity shall obtain a building permit or other appropriate approval from the City of Atlanta. A permit application shall be accompanied by the following items in order to be considered: (1) Stormwater consultation meeting certification in accordance with Section ; (2) Stormwater management plan in accordance with Section ; (3) Inspection and maintenance agreement in accordance with Section ; (4) Performance bond in accordance with Section , if applicable; and (5) Permit application and plan. (d) (e) (f) The approved stormwater management plan shall obligate the responsible party to accomplish all land clearing, construction, development and drainage in accordance with the stormwater management plan. Any and all permits for development activities may be revoked at any time if the construction of stormwater management facilities is not conducted in strict accordance with approved plans. Applicant or responsible party shall obtain all state and federal permits required for the proposed development activity in addition to the plans and permits required by the City of Atlanta. The City of Atlanta shall inform the applicant or responsible party whether the application, stormwater management plan and inspection and maintenance agreement are approved or disapproved. If either the permit application, stormwater management
13 plan or inspection and maintenance agreement are disapproved, the City of Atlanta 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. (g) (h) Upon a finding by the Department of Watershed Management that the permit application, stormwater management plan and inspection and maintenance agreement meet the requirements of this ordinance, the City of Atlanta may issue a permit for the land development project, provided all other legal requirements for the issuance of such permit have been met. Notwithstanding the issuance of the permit, in conducting the land development project, the applicant or responsible party shall be subject to the following requirements: (1) The applicant or responsible party shall comply with all applicable requirements of the approved plan and this ordinance and shall certify that all land clearing, construction, land development and drainage will be done according to the approved plan; (2) The land development project shall be conducted only within the area specified in the approved plan; (3) The City of Atlanta shall be allowed access to the site for inspection and enforcement; and (4) No changes may be made to an approved plan without review and written approval by the Department of Watershed Management. (i) Upon completion of the project, the applicant or responsible party shall submit the stormwater engineer's certification and as-built plan as required by Section (b). If the as-built differs substantially from the approved plan but is still acceptable to the City of Atlanta, then the applicant or responsible party shall update the recorded inspection and maintenance agreement upon approval of the City of Atlanta. Section 8. Section of the City Code of Ordinances is hereby deleted and replaced in its Sec Stormwater consultation meeting. (a) When a development, redevelopment or demolition of a site that meets at least one of the applicability criteria found in Section (a) is proposed, the owner, developer, engineer, or agent shall participate in a consultation meeting with the Department of Watershed Management to discuss the post-development stormwater management measures necessary for the proposed project, as well as to discuss and assess constraints, opportunities and ideas for stormwater management designs utilizing green infrastructure and runoff reduction techniques. The owner, developer, engineer, or agent shall receive a consultation meeting certification at the conclusion of the consultation meeting.
14 This consultation meeting shall be held prior to approval of a preliminary plat or the submittal of an application for a permit in accordance with the following procedure: (1) The Department of Watershed Management shall schedule a consultation meeting within five (5) business days from the date a written meeting request is received by the Department of Watershed Management, Office of Site Development. (2) Failure of the Department of Watershed Management to schedule a consultation meeting within the time required by this section shall waive the requirements of Section (a) and a copy of the written meeting request submitted to the Department of Watershed Management, Office of Site Development by the owner, developer, engineer, or agent attached to the permit application shall meet the requirement of the consultation meeting certification in Section (c)(1). (b) (3) If no consultation meeting is requested or attended by the owner, developer, engineer, or agent prior to the submittal of a permit application, the Department of Watershed Management may delay review of the permit application until such meeting is held; provided however that when the land development activity involves only an application for the erection of a structure governed by Chapter 16-28A of the Zoning Code, the requirements of Section (c)(1) and Section (a) shall not apply. To assist the Department of Watershed Management s review of the land development project and to assist the applicant or responsible party with the creation of a stormwater management plan, the following information should be submitted prior to or at the time of the consultation meeting: (1) Existing conditions / Proposed site plans. Existing conditions and proposed site layout sketch plans, which shall illustrate at a minimum: existing and proposed topography; perennial and intermittent streams; mapping of predominant soils from soil surveys; 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) Infiltration rates. Infiltration rates shall be determined by soil surveys, on-site soil analysis, or percolation test. If a site has been previously developed or graded or contains urban soil types, a percolation test is required. (3) Natural resources inventory. A written or graphic inventory of the natural resources in existence prior to the commencement of the project. This inventory shall address resources both on the site and in the surrounding area that is or may be impacted by the project. This inventory shall also include a description of soil conditions, forest cover, topography, wetlands, and other native vegetative
15 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, including but not limited to drinking water well setbacks and septic setbacks. Particular attention should be paid to environmentally sensitive features that present constraints for development. (4) Stormwater management system concept plan. A written or graphic concept plan of the proposed post-development stormwater management system that identifies the scope and magnitude of the project and related stormwater requirements, and identifies how stormwater better site design techniques will be used to reduce the need for structural stormwater controls. The plan shall also include: 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. Section 9. Section of the City Code of Ordinances is hereby deleted and replaced in its Sec Submittal requirements for stormwater management plans. (a) (b) (c) 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 ordinance, including the performance criteria set forth in Section 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 of Georgia, who must verify that the design of all stormwater management facilities and practices meet the submittal requirements outlined in the Georgia Stormwater Management Manual, the Coastal Stormwater Supplement and the City of Atlanta s submittal requirements for commercial and single-family residential development. Plans and studies shall be presented in a format that itemizes each of the requirements in Section (c), including performance criteria set forth in Section The stormwater management plan must ensure that the requirements and criteria in this ordinance are being complied with and that opportunities are being taken to minimize adverse post-development stormwater runoff impacts from the development. The plan shall consist of maps, narrative, and supporting design calculations (hydrologic and hydraulic) for the proposed stormwater management system. The plan shall include all of the applicable design requirements and forms found in the Georgia Stormwater Management Manual, the Coastal Stormwater Supplement and the City of Atlanta s submittal requirements for commercial and single-family residential development. This includes but is not limited to the following:
16 (1) Common address and legal description of site; (2) Vicinity map; (3) 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; 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; (4) Infiltration rates. Infiltration rates shall be determined by soil surveys, on-site soil analysis, or a percolation test. If site has been previously developed or graded or contains urban soil types, a percolation test is required; (5) Natural resources inventory. A written or graphic inventory of the natural resources in existence prior to the commencement of the project. This inventory shall address resources both on the site and in the surrounding area that is or may be impacted by the project. This inventory shall also include a description 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, including but not limited to drinking water well setbacks and septic setbacks. Particular attention should be paid to environmentally sensitive features that present constraints for development; (6) Existing conditions hydrologic analysis. The existing condition hydrologic analysis for stormwater runoff rates, volumes, and velocities, in accordance with the Georgia Stormwater Management Manual, 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 in Section ; (7) Post-development hydrologic analysis. The post-development hydrologic analysis for stormwater runoff rates, volumes, and velocities, which shall be calculated in accordance with the Georgia Stormwater Management Manual, and 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
17 for the development project to meet the post-development stormwater management performance criteria in Section ; location and boundaries of proposed natural feature protection and conservation areas; documentation and calculations for any applicable site design credits that are being utilized; and methodologies, assumptions, site parameters and supporting design calculations used in analyzing the existing conditions site hydrology. For a subdivision of land or planned development, post-development runoff volumes, rates, and velocities shall be calculated based on the built out conditions of the entire parcel to be subdivided, regardless of future ownership of individual lots. Estimates of impervious surfaces shall be made based on maximum allowable lot coverage in accordance with Section (38) of the City of Atlanta s Zoning Ordinance when meeting the performance criteria in Section (c) through (i). The developer of said subdivided parcel may provide the Runoff Reduction/Water Quality measures in accordance with Sections (a) and (b) for individual lots and must be reflected accordingly on the final plat; (8) 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 Section ; 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, TMDL implementation plans, and/or local greenspace protection plan; (9) 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
18 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 stormwater design manual; (10) Construction phase erosion and sedimentation control plan. An erosion and sedimentation control plan in accordance with the City of Atlanta Soil Erosion and Sedimentation Control provisions found in Article II of Chapter 74, the Georgia Erosion and Sedimentation Control Act, and any 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. Prior to the approval of the stormwater management plan, the applicant or responsible party shall submit a proposed staged construction and inspection control schedule for approval; otherwise, the construction and inspection control schedule will be for the entire drainage system. No stage work related to the construction of stormwater management facilities or BMPs shall proceed until the next proceeding stage of work, according to the sequence specified in the approved staged construction and inspection control schedule, as inspected and approved. Runoff reduction and water quality measures shall be installed in the final phase of construction to prevent clogging; (11) Stormwater landscaping 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; (12) 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. This plan 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 a narrative describing how stormwater management system is designed to function, including capture, runoff control, water quality treatment, channel protection and flood protection, a narrative describing ongoing operations and maintenance procedures for all stormwater management facilities and practices as shown on
19 the Stormwater Management Site Plan, an inspection and maintenance schedule, description of maintenance tasks, identification of responsible parties for ongoing maintenance, description of funding source, and a review of 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; (13) Maintenance access easements. The applicant or responsible party 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. Such easements shall be reflected in all plats and surveys; (14) Inspection and maintenance agreements. The owner must execute 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 Section ; and (15) Evidence of acquisition of applicable local and non-local permits. The applicant or responsible party shall certify and provide documentation to the City of Atlanta that all applicable environmental permits have been acquired for the site prior to approval of the site development and stormwater management plan. Section 10. Section of the City Code of Ordinances is hereby deleted and replaced in its Sec Off-site facilities. (a) 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 stormwater management facility. The off-site or regional stormwater management facility, if applicable, must comply with the following: (1) The off-site or regional stormwater management facility must be located on property legally dedicated for the purpose; (2) The off-site or regional stormwater management facility 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; (3) There must be a legally-obligated entity responsible for long-term operation and maintenance of the off-site or regional stormwater facility; and
20 (4) On-site measures shall be implemented, where necessary, to protect upstream and downstream properties and drainage channels from the site to the off-site facility. (b) (c) A stormwater management plan that shows the adequacy of the off-site or regional stormwater management facility must be submitted to the Department of Watershed Management. To be eligible for a modification, the applicant must demonstrate to the satisfaction of the Department of Watershed Management that the use of an off-site or regional stormwater management 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. Section 11. Section of the City Code of Ordinances is hereby deleted and replaced in its Sec Performance criteria for stormwater management. For new developments, the following performance criteria shall be applied to the area of the site impacted by the proposed work. For redevelopment, the following performance criteria shall be applied to the area of the site impacted by the proposed work, provided that the impacted area does not exceed 35 percent of the previously developed area. If the impacted area exceeds 35 percent of the previously developed area, the following performance criteria shall be applied to the entire development, including the previously developed area: (a) Stormwater runoff reduction. The stormwater runoff volume generated by the first 1.0 of rainfall shall be retained on-site in order to help maintain pre-development site hydrology and help protect the local watershed from several indirect impacts of the land development process, including decreased groundwater recharge, decreased baseflow and degraded water quality. A stormwater management system is presumed to comply with this criteria if: (1) It includes green infrastructure practices that provide for the interception and evapotranspiration, infiltration, or capture and reuse of stormwater runoff, that have been selected, designed, constructed and maintained in accordance with the information presented in the latest edition of the Georgia Stormwater