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Division of Coastal Management STORMWATER MASTER PLAN TOWN OF OCEAN ISLE BEACH OCEAN ISLE BEACH, NORTH CAROLINA DUNE 295 2000 Prepared By: URS GREINER WOODWARD CLYDE Raleigh, North Carolina The preparation of this report was financed in part through a grant provided by the North Carolina Coastal Management Program, through funds provided by the Coastal Zone Management Act of 1972, as amended, which is administered by the office of Ocean and Coastal Resource Management, National Oceanic and Atmospheric Administration. 1 LI 1 1 1 1 1 1 1 1 1 1 1 1 1 1 STORMWATER MASTER PLAN TOWN OF OCEAN ISLE BEACH Ocean Isle Beach, North Carolina June 29, 2000 Prepared by: URS Greiner Woodward Clyde 3109 Poplarwood Court, Suite 301 Raleigh, North Carolina 27604 (919) 850-9511 Fax: (919) 790-0217 TABLE OF CONTENTS OCEAN ISLE BEACH STORMWATER MASTER PLAN ' Section Page ExecutiveSummary .........................................................................................................................E-1 Chapter 1- Purpose and Goals ' 1.1 Purpose of the Master Plan.......................................................................................................1-1 1.2 Goals of the Plan......................................................................................................................1-1 1.3 Structure of the Plan.................................................................................................................1-2 1.4 Methodology ....................................... ...................................................................................... 1-2 Chapter 2 - Policy ' 2.1 Responsibilities........................................................................................................................2-1 2.2 Ordinances and Regulations.....................................................................................................2-1 2.2.1 Federal Regulations ' .........................................................................................................2-1 2.2.2 State Regulations .2-5 2.2.2.1 Division of Coastal Management......................................................................2-5 2.2.2.2 Division of Land Resources...............................................................................2-6 2.2.2.3 Division of Water Quality.................................................................................2-6 2.2.2.4 North Carolina Division of Highways...............................................................2-8 2.2.2.5 NCDOT Subdivision Roads..............................................................................2-13 2.2.2.6 NCDOT Policy on Street and Driveway Access to Highways ..........................2-14 2.2.3 Local Ordinances............................................................................................................2-15 2.3 Drainage System Design, Operation, and Maintenance...........................................................2-18 ' 2.4 Best Management Practices......................................................................................................2-18 2.5 Floodplain Development..........................................................................................................2-19 2.6 Stormwater Management Ordinance........................................................................................2-19 2.7 Increased Runoff Due to Development....................................................................................2-19 ' 2.8 Pollution Prevention.................................................................................................................2-19 2.9 Public Education/Public Involvement......................................................................................2-20 Chapter 3 - Island Overview 3.1 3.2 Setting.......................................................................................................................................3-1 Hydrography.............................................................................................................................3-1 3.3 Land Use......................................................................................:............................................3-1 ' 3.4 3.5 Effects on Water Quantity........................................................................................................3-1 Effects on Water Quality..........................................................................................................3-2 3.6 Storm Drain System Inventory and Mapping...........................................................................3-2 ' Chapter 4 - Watershed Characteristics 4.1 Watershed Characteristics........................................................................................................4-1 ' 4.1.1 Hydrologic and Hydraulic Characteristics..................................................................4-1 4.1.2 Water Quality Characteristics......................................................................................4-1 4.2 Future Development.................................................................................................................4-2 4.3 Evaluation and Recommendations...........................................................................................4-2 1 06/29/00 1 1 11 TABLE OF CONTENTS Section OCEAN ISLE BEACH STORMWATER MASTER PLAN Page 4.3.1 Water Quantity ............................................................................................................4-3 4.3.2 Water Quality ..............................................................................................................4-14 4.3.3 Operation and Maintenance.........................................................................................4-15 Chapter 5 - Stormwater Management Program 5.1 Recommendation Summary .....................................................................................................5-1 5.2 Project Selection Criteria..........................................................................................................5-1 5.3 Capital Improvement Program.................................................................................................5-3 5.4 Operation and Maintenance Program.......................................................................................5-3 5.5 Funding.....................................................................................................................................5-4 Chapter 6 - References ' LIST OF APPENDICES ' Appendix A Proposed Stormwater Management Ordinance Appendix B Public Information Flyers Appendix C Charlotte -Mecklenburg Stormwater Services Credit Application Instruction Manual ' LIST OF TABLES Page Table 3-1 Stormwater Pollutants..............................................................................................3-3 Table4-1 Soils Data.................................................................................................................4-1 Table 4-2 Table 5-1 Recommendations....................................................................................................4-15 Project Selection Criteria and Rankings ...................................................................5-2 Table 5-2 . Capital Improvement Program...................... ........................................................... 5-5 I F FIGURES LIST O Page Figure3-1 Location Map...........................................................................................................3-4 ' Figure 3-2 Figure 4-1 Hydrologic Unit Map...............................................................................................3-5 Existing Storm Drain System...................................................................................4-16 Figure 4-2 Stormwater Areas of Concern ..................................................................................4-17 lJ 1 06/29/00 11 OCEAN ISLE BEACH EXECUTIVE SUMMARY STORMWATER MASTER PLAN The Ocean Isle Beach Stormwater Master Plan provides an outline of the stormwater management policies and actions for the entire island of Ocean Isle Beach. This document provides direction for stormwater management for the Town OF Ocean Isle Beach. The starting point for this Plan begins with the purpose, goals, and objectives described in this chapter. The purpose of the Ocean Isle Beach Stormwater Master Plan is to provide a comprehensive and unified framework for Stormwater management which follows the Master Plan, complies with all regulations, and includes a Capital improvement Program that will benefit the entire Town. ' The following goals provide the direction in meeting the purpose of improving hydrological functions and protecting and improving water quality: ' 1) Evaluate the water quantity and quality problems on the island and recommend actions to mitigate these problems. 2) Provide a capital improvement program and outline maintenance actions that incorporate ' recommendations from the Plan. 3) Outline an implementation plan for recommended action items. ' Policy regarding responsibilities, ordinances, system operation and maintenance, easement acquisition, and public involvement is described in Chapter Two. The water quantity and water quality problems on the island are described and action items for these problems are provided in Chapter Four. The policy, ' maintenance, and capital improvement action items described in Chapter Five should be considered the first steps in working to achieve a sound Stormwater Management Program. Further information such as detailed tasks for each action item should be addressed in future tasks. 11 1 The recommendations for each area of concern were evaluated based upon the safety, water quantity, and water quality benefits provided by the recommended solution. The area determined to be the highest priority was First Street on the east end of the island. Severe flooding occurs in this area, and water often covers both travel lanes causing potential safety hazards. The remaining areas of concern and recommended solutions are described in Chapter Four. The evaluation criteria are presented in Chapter Five. Preliminary, order of magnitude cost estimates are provided in Chapter Five. Future adjustments to these program costs will have to be made as more information (survey, modeling, etc.) is completed. Additional public input is also important as the Stormwater Management Program proceeds. Public education and public involvement is critical to a successful Stormwater Management Program. 06/29/00 E-1 L� CHAPTER ONE OCEAN ISLE BEACH PURPOSE AND GOALS STORMWATER MASTER PLAN The Ocean Isle Beach Stormwater Master Plan (Plan) is a document that outlines an approach to stormwater management for the entire island of Ocean Isle Beach. This document provides direction for stormwater management for the Town of Ocean Isle Beach (Town). The starting point for this Plan begins with the purpose, goals, and objectives described in this chapter. Stormwater master plans that have the most success are the ones with clear purpose, goals and action items. In order to develop a clear purpose and goals, it is necessary to identify the problems or potential problems in the watershed. Flooding and water quality within the Town have been identified as problems and the purpose and goals described below provide direction for the future stormwater management effort to improve these problems. ' 1.1 PURPOSE ' The purpose of the Ocean Isle Beach Stormwater Master Plan is to provide a comprehensive and unified framework for stormwater management which follows the Master Plan, complies with all regulations, and includes a Capital Improvement Program that will benefit the entire Town. The purpose of the Stormwater Master Plan is to provide a framework for a Stormwater Management Program that will restore hydrological functions and protect water quality within the Town. This framework for the Stormwater Management Program will incorporate the policies and procedures already established by the Town, provide new program components, and recommend changes to existing ordinances and policies. The implementation of these recommended policies and projects is an important step to having an effective and substantial program. The Master Plan will identify the components of the Stormwater Management Program and outline the action items for implementation. The recommended action items will help to meet the goals for the program, which are described in the next section. 1.2 GOALS OF THE PLAN The following goals provide the direction in meeting the purpose of improving hydrological functions and protecting and improving water quality: ' 1) Evaluate the water quantity and water quality problems on the island and recommend actions to mitigate these problems. 2) Provide a capital improvement program and outline maintenance actions that incorporate recommendations from the plan. 3) Outline an implementation plan for recommended action items. Action items are necessary to carry out the work in achieving these goals. The action items recommended for each area of the Stormwater Management Program are summarized in Chapter 5. 1. Evaluate the water quantity and water quality problems on the island and recommend actions to mitigate these problems. 06/29/00 1-1 7 CHAPTER ONE OCEAN ISLE BEACH PURPOSE AND GOALS STORMWATER MASTER PLAN This master plan will evaluate the water quality and water quantity problems on the island and discuss recommended solutions. The solutions may need to be policy decisions that require revisions to the existing ordinances or actions such as a maintenance project to restore the capacity of an existing ditch. 2. Provide a capital improvement program and outline maintenance actions that incorporate recommendations from the Plan. The recommended capital improvements and maintenance actions will be prioritized in order to create a program that outlines budget requirements. Funding needs will be discussed and future actions with regard to the Stormwater Management Program will be provided. ' 3. Outline an implementation plan for recommended action items. An implementation plan for the action items is necessary to ensure that the vision and goals are achieved. ' A plan can only succeed if it is implemented and not collecting dust on a shelf. 1.3 STRUCTURE OF THE PLAN Chapter One - Purpose and Goals ' The purpose and goals have been described and the contents of the plan are listed in this section. The methodology is provided to describe the basis for the recommendations. Chapter Two - Policy In this chapter, the existing policy with regards to stormwater management is described. Changes to existing policy and new areas requiring a policy decision action are provided. Chapter Three — Island Overview This chapter provides a description of the physical setting and the interaction of land use, soil types, water features, and hydrology and their effect on water quantity and water quality. Chapter Four — Watershed Characteristics The characteristics of the island, along with the quantity and water quality problems, are described and action items recommended. Chapter Five - Stormwater Management Program The action items from the preceding chapters are summarized. The estimated costs for the recommended action items are provided in this chapter. Funding sources are identified. ' 1.4 METHODOLOGY The methodology for this Plan is to use existing data to evaluate and recommend the action items necessary to achieve the stated goals. Problem area locations and descriptions for each of the hydrologic units have been obtained from Town of Ocean Isle Beach personnel, citizens, and water quality 06/29/00 1-2 1 1 1 1 1 CHAPTER ONE OCEAN ISLE BEACH PURPOSE AND GOALS STORMWATER MASTER PLAN monitoring data. Public input to the Stormwater Management Plan has been obtained during a public workshop. 06/29/00 1-3 fl 1 1 J CHAPTER TWO OCEAN ISLE BEACH POLICY STORMWATER MASTER PLAN Decisions the Town makes now regarding stormwater issues have an effect on future water quality, storm drain system performance, and system condition. This chapter outlines the existing Town policies regarding stormwater management and evaluates what policies need changes for effective management in the future. Current responsibilities of the Town are explained in this chapter. 2.1 RESPONSIBILITIES Stormwater management in the Town of Ocean Isle Beach is currently the responsibility of the State of North Carolina. The Town of Ocean Isle Beach will be responsible for stormwater management when the Town implements a Stormwater Management Program. Currently the Town has the following responsibilities regarding stormwater management: • Inspection and maintenance of the Town's existing stormwater collection system. • Approval of site plans with respect to setbacks from the mean high water mark. Approval of erosion and sediment control plans. Inspection of sites for erosion and sediment control compliance in accordance with the Town's Soil Erosion and Sedimentation Ordinance. • Inspection of sites for compliance with the Town's Flood Ordinance. 2.2 ORDINANCES AND REGULATIONS 2.2.1 Federal Regulations This section provides a summary of federal regulations that presently define or in the future may affect stormwater management requirements for the Town. The goal of this review is to identify and summarize the regulatory and technical issues that must be incorporated into the Town's stormwater management and development policies. The summarized requirements presented in this section will subsequently be compared to existing Town stormwater management policies with recommended modifications provided as necessary. The Clean Water Act In 1972, Congress amended the Federal Water Pollution Control Act, referred to as the Clean Water Act (CWA), to prohibit the discharge of any pollutants to waters of the United States from a point source, unless the discharge is authorized by a National Pollutant Discharge Elimination System (NPDES) permit. As pollution control measures for industrial process wastewater and municipal sewage were implemented and refined, it became evident that more diffuse sources of water pollution were adversely impacting water quality. In particular, stormwater runoff from large surface areas, such as agricultural and urban land, was found to significantly impair water quality. At the Federal level, Sections 401, 402 and 404 of the Clean Water Act require permits for those activities that might affect water quality either through direct discharge of dredged materials or from runoff. The most recent Federal Regulations that will significantly impact existing stormwater management practices are 40 CFR Parts 9, 122, 123, and 124 - National Pollutant Discharge Elimination System (NPDES) — Regulations for Revision of the Water Pollution Control Program Addressing Storm Water Discharges; Final Rule (commonly referred to as Phase H Storm Water Regulations). 06/29/00 2-1 �7_i CHAPTER TWO OCEAN ISLE BEACH POLICY STORMWATER MASTER PLAN Phase I NPDES Stormwater Re elation In 1987, Congress amended the CWA to require implementation of a comprehensive national program for addressing stormwater discharges. This implementation has occurred in two phases. The first phase, referred to as "Phase I", was promulgated in November 1990. Phase I requires NPDES permits for stormwater discharge from a large number of priority sources including: • Municipal separate storm sewer systems generally serving populations of 100,000 or more. • Several categories of industrial activity, including construction sites that disturb five or more acres of land. Applicability to the Town of Ocean Isle Beach As of the year 2000, the Town is not required to obtain a NPDES stormwater discharge permit under the Phase I regulations because of its small population and lack of industrial activity. Phase II Stormwater Regulations The second phase, referred to as "Phase II", was promulgated in August 1995. These regulations were adopted in December 1999. Phase II expands the existing stormwater program to include: • Discharges of stormwater from smaller municipalities in urbanized areas. • Construction sites that disturb between one and five acres of land. Certain sources are excluded from Phase II based on a demonstrable lack of impact on water quality. This regulation also allows other sources not automatically regulated on a national basis to be designated for inclusion based on their increased likelihood for local impairment of water quality. Phase II ' conditionally excludes stormwater discharges from industrial facilities that have "no exposure" of industrial activities or materials to stormwater. States with NPDES permitting authority (North Carolina has permitting authority) can extend NPDES requirements to smaller towns if there is reason to anticipate that stormwater runoff from those areas has been or may impact high quality waters. Phase II requires that industrial facilities owned by Small Municipal Separate Storm Sewer Systems (MS4s) obtain coverage under an NPDES permit by March 10, 2003. The EPA believes that the implementation of six measures identified for small MS4s should cost effectively reduce pollutant discharges. In addition, they believe that the implementation of Best Management Practices (BMPs) at small construction sites will also reduce pollutants in urban stormwater. ' Expected benefits include reduced scouring and streambed erosion, improved aesthetic water quality, reduced eutrophication of aquatic systems, improved wildlife, improved tourism, and the reduced costs for siting reservoirs. These six measures and BMPs provide, the framework for the program requirements. The Stormwater Management Program requirements, as required by Phase II, are as outlined below: • Public Education and Outreach on Stormwater Impacts • Public Involvement/Public Participation • Illicit Discharge, Detection, and Elimination • Construction Site Stormwater Runoff Control • Post -Construction Stormwater Management in New Development and Redevelopment • Pollution Prevention/Good Housekeeping for Municipal Operations Public Education and Outreach on Stormwater Impacts Under Phase II, operators of small MS4s must implement a public education program or conduct outreach activities to distribute educational materials to the community. The education programs and/or outreach activities should inform individuals and households about the impacts stormwater discharges have on 06/29/00 2-2 CHAPTER TWO OCEAN ISLE BEACH ' POLICY STORMWATER MASTER PLAN water bodies and identify the steps that must be taken to reduce stormwater pollution. It is anticipated ' that public understanding will foster endorsement of the program. MS4s are encouraged to collaborate with their States to fulfill the public education requirement. In particular, MS4s are encouraged to work with any existing State implemented educational programs. Public Involvement/Public Participation As part of the Phase H Public Involvement/Public Participation requirement, municipal Stormwater Management Programs are required to comply with applicable State and local public notice requirements. The final rule recommends implementing a public participation process to reach out and engage all economic and ethnic groups. The EPA believes that early and frequent public involvement can expedite schedules, improve public support, and provide a more successful program. Illicit Discharge Detection and Elimination Under the Phase H requirements, any NPDES permit issued to an operator of a regulated small MS4 must, at a minimum, require the operator to develop, implement and enforce an illicit discharge detection and elimination program. Under this final rule, the NPDES permit will require the operator of a regulated small MS4 to: • Develop a storm sewer system map showing the location of all outfalls, and names and location of all waters of the United States that receive discharges from those outfalls. • Effectively prohibit through ordinance, or other regulatory mechanism, illicit discharges into the separate storm sewer system, and implement appropriate enforcement procedures and actions as needed, to the extent allowable under State, Tribal, or local law. • Develop and implement a plan to detect and address illicit discharges, including illegal dumping, to the system. • Inform public employees, businesses, and the general public of hazards associated with illegal discharges and improper disposal of waste. The illicit discharge and elimination program must only address non-stormwater discharges if it falls under the categories listed below and if the operator of the small MS4 identifies them as significant contributors of pollutants to its small MS4. These categories include: water line flushing, landscape irrigation, diverted stream flows, rising ground waters, uncontaminated ground water infiltration, uncontaminated pumped ground water, discharges from potable water sources, foundation drains, air conditioning condensation, irrigation water, springs, water from crawl space pumps, footing drains, lawn watering, individual residential car washing, flows from riparian habitats and wetlands, dechlorinated swimming pool discharges, and street wash water. rConstruction Site Stormwater Runoff Control The Phase II final rule requires operators of regulated small MS4s to develop, implement and enforce a pollutant control program to reduce pollutants in any stormwater runoff from construction activities that result in land disturbance of one or more acres. Construction activity on sites disturbing less than one acre must be included in the program if the construction activity is part of a larger common plan of development or sale that would disturb one or more acres. The construction runoff control program must ' include an ordinance or other regulatory mechanism to require erosion and sediment controls to the extent practicable and allowable under State, Tribal or local law. The program must also include sanctions to ensure compliance. The program must also include, at a minimum: • Requirements for construction site operators to implement appropriate erosion and sediment control. 06/29/00 2-3 CHAPTER TWO OCEAN ISLE BEACH I POLICY STORMWATER MASTER PLAN • Procedures for site plan review by the small MS4, which incorporate consideration of potential water quality impacts. • Requirements to control other waste such as discarded building materials, chemical and sanitary waste at the site that may adversely affect water quality. • Procedures for receipt and consideration of information submitted by the public to the MS4. Post -Construction Stormwater Management in New Development and Redevelopment Studies and investigations indicate that prior planning and designing for the minimization of pollutants in stormwater discharges is the most cost-effective approach to stormwater quality management. Under the Phase II requirements, any NPDES permits issued to an operator of a regulated small MS4 must require the operator to develop, implement, and enforce a program to address stormwater runoff from new development and redevelopment projects that result in land disturbance of greater than or equal to one acre. This also includes projects less than one acre, which are part of a larger common plan of development or sale, that discharge into the MS4. The NPDES permit will require the operator of a regulated small MS4 to: • Develop and implement strategies that include a combination of structural and/or non-structural BMPs. • Use an ordinance or other regulatory mechanism to address post -construction runoff from new development and redevelopment projects to the extent allowable under State, Tribal or local law. • Ensure adequate long-term operation and maintenance of BMPs. • Ensure that controls are in place that would minimize adverse water quality impacts. Pollution Prevention/Good Housekeeping for Municipal Operations Phase II specifies that operators of MS4s must develop and implement an operation and maintenance program that includes a training component and focuses on preventing or reducing stormwater from municipal operations. The program must include government employee training that addresses prevention measures pertaining to municipal operations such as: parks, golf courses and open space maintenance, fleet maintenance, new construction or land disturbance, building oversight; planning; and stormwater system maintenance. The program may use existing stormwater pollution prevention training materials offered by the State, Tribe, EPA, or environmental, public interest, or trade organizations. The EPA encourages operators of MS4s to include the following in their programs: • Implement maintenance activities, maintenance schedules, and long-term inspection procedures for structural and non-structural stormwater controls to reduce floatables and other pollutants discharged from the separate storm sewers. • Implement controls for reducing or eliminating the discharge of pollutants from street, roads, highways, municipal parking lots, maintenance and storage yards, waste transfer stations, fleet or maintenance shops with outdoor storage areas, and salt/sand storage locations and snow disposal areas operated by the MS4. • Adopt procedures for the proper disposal of waste removed from the separate storm sewer systems and areas listed above, including dredge spoil, accumulated sediments, floatables, and other debris. • Adopt procedures to ensure that new flood management projects are assessed for impacts on ' water quality and existing projects are assessed for incorporation of additional water quality protection devices or practices. 06/29/00 2-4 1 CHAPTER Two OCEAN ISLE BEACH POLICY STORMWATER MASTER PLAN Applicability to the Town of Ocean Isle Beach The final Phase II regulations, dated December 9,1999, list areas in the United States that require or may require permitting under the Phase II program. These areas include: • Urbanized areas of the United States. • Governmental entities located fully or partially within an urbanized area. • Governmental entities (located outside of an urbanized area) that must be examined by the NPDES permitting authority for potential designation. As of June 2000, the Town of Ocean: Isle Beach was not included on any of these lists, although Brunswick County is included and will be required to obtain a Phase II permit. In this situation, the Town may be required to obtain a permit jointly with the County, or the Town may be able to obtain a separate permit, if desired. The State is encouraging cooperation between entities which may be the most effective way to implement a program which complies with permit conditions. URSGWC recommends that the Town contact both the County and the State to determine its status regarding a Phase II NPDES permit. URSGWC also recommends that the Town implement applicable Phase II management measures as part of its long-term storm water management policies. These management measures are good standard practice for water quality protection, and their implementation would put the Town on the track toward implementation of Phase II requirements if a permit becomes necessary in the future. 2.2.2 State Regulations Stormwater management requirements in North Carolina fall under the jurisdiction of the North Carolina Administrative Code (NCAC), the North Carolina Coastal Area Management Act (CAMA), and the North Carolina Sedimentation Pollution Control Act. The associated agencies responsible for the implementation of stormwater management requirements are the Department of Environment and Natural Resource (NCDENR); the Sedimentation Control Commission; and the Coastal Resources Commission (CRC), respectively. Summarized stormwater management requirements for the three agencies are provided as follows and will serve as the technical basis for recommended modifications to Town ordinances. The NCDENR, Division of Coastal Management (DCM), Division of Land Resources, and the Division of Water Quality (DWQ) regulate development and land use activities to protect water quality. Additionally, the North Carolina Division of Highways has published guidelines for drainage studies and hydraulic design, and the North Carolina Department of Transportation (NCDOT) has drainage standards for subdivision highways. 2.2.2.1 Division of Coastal Management The Division of Coastal Management (DCM) regulates development activities and stormwater controls that occur in the 20 coastal counties of North Carolina through the Coastal Area Management Act (CAMA) (15A NCAC 7H, V, & G.S. 133A, Article 7). Any land disturbing activity which occurs in an area of environmental concern (AEC) must receive a CAMA permit. The DCM reviews proposed development plans and refers to the local CAMA Land Use Plans and determines if a Major, Minor or General Permit is required. A Major permit is required for land disturbing activities which: • occur in an AEC • alter more than 20 acres of land 06/29/00 2-5 CHAPTER TWO OCEAN ISLE BEACH POLICY STORMWATER MASTER PLAN • propose a structural footprint exceeding 60,000 square feet on a single parcel • require other State or Federal permits • excavates or drills for natural resources in an AEC or under water A Minor permit is required when a Major permit is not required. The following activities are exempt from a Minor permit: • maintenance and repair (excluding replacement) of existing structure which does not violate CAMA standards • accessory uses or structures related to the main use of the site that require no electricity, plumbing, or other service connections and do not exceed an area of 200 square feet For an exemption from a minor development permit, the project must meet all of the following exemptions: • development activities do not disturb more than 200 square feet on land with a slope greater than 10 percent • threatened or endangered plants and animals must not be removed, damaged or destroyed • development activities do not alter surface drainage channels • the form or vegetation of a frontal dune must not be altered • development activities must be not be within 20 feet of permanent surface waters • the project must be in compliance with CAMA standards and local land use plans and ordinances Development activities requiring a CAMA Major Permit may also require one of the following permits that are issued by the State: • permit to excavate and/or fill • easement in lands covered by water ' • water quality certification 2.2.2.2 Division of Land Resources The Division of Land Resources requires a Sedimentation and Erosion Control Plan for land disturbing activities greater than one acre (15A NCAC 413 & G.S. 113A, Article 4). The purpose of the Sedimentation and Erosion Control Plan is to show practices that will be implemented during and after construction, that will control erosion and prevent sediments from leaving the site. The Town has adopted a Sediment and Erosion Control Ordinance, which contains similar requirements to the Division of Land Resources requirements. Sediment and erosion control responsibilities lie with the Town, unless the project is funded by State money. Designs must provide protection from peak runoff resulting from a 10-year storm event and increased stormwater runoff will not allow impact of receiving waters. 2.2.2.3 Division of Water Quality rThe Classifications and Water Quality Standards Applicable to Surface Water of North Carolina (15A NCAC 213 & G.S. 143-214.1, 215.1, 215.3 Article 3) defines surface water classifications and provides development restrictions and buffer requirements. Surface waters in the Ocean Isle Beach area include the ocean and the Intracoastal Waterway. 06/29/00 2-6 CHAPTER TWO OCEAN ISLE BEACH POLICY STORMWATER MASTER PLAN The following letter system is used to define the "best usage classifications" for waters in the Ocean Isle Beach area: SA Tidal systems designated for shell fishing for market purposes, primary recreation, aquatic life propagation and survival, fishing, wildlife, and secondary recreation. SB Indicates a designation for primary recreation, aquatic life propagation/protection and secondary recreation. HQW (High Quality Waters) Indicates a supplemental classification for waters protected by an Antidegradation Policy enforced through the NCDENR. These include waters with excellent ratings based on biological & physical/chemical characteristics, such as NC Marine Fisheries Commission designated primary nursery areas (PNA) and Wildlife Resource Commission designated trout waters. The SA primary classification denotes surface waters, such as the Atlantic Intracoastal Waterway (AIWW), which are suitable for commercial shellfishing and all other tidal saltwater uses. Supplemental classifications such as HQW (high quality water) provide added protection for waterbodies. rThe Division of Water Quality enforces the Stormwater Management regulation and general statute (15A NCAC 2H and G.S.143-215.1) and the Water Supply Watershed Protection Act (15A NCAC 2B & G.S. 143-214.5) for the protection of surface waters. These rules were developed to control pollutants in stormwater runoff, limit impervious surfaces or built upon area, and ensure that adequate stormwater management practices are implemented. North Carolina Administrative Code Section 15A NCAC2H.1000 The North Carolina stormwater management regulations are located in Administrative Code Section 15A NCAC211.1000. To ensure the protection of surface waters of the State, a stormwater management permit ' is required for any development activities which require a CAMA major development permit (see Section 3.2 of this report) or a Sedimentation/Erosion Control Plan (see Section 3.3 of this report) and which meet any of the following criteria: 1. Are located in the 20 coastal counties. 2. Drain to Outstanding Resource Waters (ORW). 3. Drain to High Quality Waters (HQW). Ocean Isle Beach is included in the 20 coastal counties (Brunswick County) and is subject to permitting requirements as specified in 15A NCAC 211.1005. Permitting requirements as specified in 15A NCAC 2H.1005 are described in the following paragraph. Stormwater Permitting Requirements: Coastal Counties Stormwater management permits for development activities within the 20 coastal counties fall into one of the three following categories: 1. Development activities that drain to Outstanding Resource Waters (ORW). 2. Development activities within one-half mile of and draining to SA (saltwater shell fishing and primary recreation) waters or unnamed tributaries to SA Waters. 3. Development activities in areas except those defined in items 1 and 2. 1 06/z9/00 2-7 i CHAPTER Two OCEAN ISLE BEACH POLICY STORMWATER MASTER PLAN Ocean Isle Beach is predominantly surrounded by water (Atlantic Intracoastal Waterway), therefore permitting requirements are as specified by category 2. Ocean Isle Beach Permitting Requirements (SA Waters) Permitting requirements for the Town's SA waters are classified according to low density and high density options. Permitting requirements for the two options are summarized as follows: Low Density Option 1. Built -upon area of 25 percent or less; or proposed development of single family residences on lots with one-third of an acre (14,520 square feet) or greater with a built upon area of 25 percent or less. 2. Stormwater runoff transported primarily by vegetated conveyances; conveyance system shall not include a discrete stormwater collection system as defined in 15A NCAC 2H.1002. 3. Curb and gutter systems are allowed as specified in 15A NCAC 2H.1008(g). If curb and gutter systems are provided, a flow spreader mechanism must be located at the swale entrance and a signed Operation and Maintenance Plan must be provided. 4. A vegetative buffer at least 30-feet wide between impervious areas and surface waters. High Density Option 1. No direct outlet channels or pipes to SA waters unless permitted in accordance with 15A NCAC 211.0126. 2. Stormwater control systems must be infiltration systems designed in accordance with 15A NCAC 2H.1008. 3. Stormwater control systems must be designed to control runoff from all surfaces generated by one and one-half (1.5) inches of rainfall. 4. Runoff in excess of the design volume must flow overland through a vegetative filter with a minimum length of 50 feet. Best Management Practice (BMP) Design Criteria North Carolina's approach to stormwater quality management in the 20 coastal counties is based first on minimizing impervious surfaces and, secondly, on treating stormwater runoff from these surfaces. The State uses a pollutant removal BMP design standard of 85 percent removal for total suspended solids (TSS). 1 A stormwater BMP design manual was published by NCDENR in April 1999. The manual includes design criteria and TSS removal efficiencies for stormwater BMP types recommended by the State. As described above, the State requires specific types of stormwater BMPs for low density and high - density development in the 20 coastal counties. Design criteria for BMPs are outlined in 15A NCAC 2H.1008. 2.2.2.4 North Carolina Division of Highways Guidance in methods, policies, procedures, and criteria that must be followed during highway drainage studies and hydraulic designs is provided in the North Carolina Division of Highways, Guidelines for Drainage Studies and Hydraulic Design document. Information from this document is pertinent to the development of recommended Town stormwater management policies since a portion of NC 904 is located on the island portion of Ocean Isle Beach. 06/29/00 2-8 1 CHAPTER Two OCEAN ISLE BEACH POLICY STORMWATER MASTER PLAN L n General Drainage Policies and Practices North Carolina long adhered to the Civil Law Rule in regard to surface water drainage. This rule obligates owners of lower land to receive the natural flow of surface water from higher lands. It subjects a landowner to liability whenever he interferes with the natural flow of surface waters to the detriment of another in the use and enjoyment of his land. Since almost any use of land involves some change in the drainage and water flow, a strict application of the civil law principles was impracticable in a developing society. Thus, a more moderate application of this rule to allow a landowner reasonable use of his property evolved. The North Carolina Supreme Court formally adopted the Rule of Reasonable Use with respect to surface water drainage and abandoned the Civil Law Rule (Pendergrast V. Aiken) in August 1977. The adopted Reasonable Use Rule allows each landowner to make reasonable use of his land even though by doing so, he alters in some way the flow of surface water thereby harming other landowners. Liability is incurred only when this harmful interference is found to be unreasonable and causes substantial damage. There are still some unanswered questions in the application of the adopted Reasonable Use Rule to specific areas of State agency activities. However, the rule is in line with the realities of modern life and will provide just, fair and consistent treatment. Therefore, the policies and practices of the Division of Highways in regard to surface drainage matters follow this rule. Engineer's Responsibility The Reasonable Use Rule places responsibility on the "landowner" to make reasonable use of his land. While "reasonable use" is open for interpretation on a case -by -case basis, it would certainly infer from an engineering standpoint that provisions for, and treatment of, surface waters on the property are made in accordance with sound, reasonable and acceptable engineering practices. Therefore, the policies and practices of the Division of Highways in regard to surface drainage matters follow this rule. The rule also states that liability incurs only when harmful interference with the surface water is found to be unreasonable and causes substantial damage. Therefore, it is incumbent on the Engineer to evaluate the potential effects of surface water activities on both upstream and downstream properties and to include provisions in the design to hold these effects to reasonable levels. Augmentation. Acceleration Development of property can cause an increase in the quantity and peak rate of flow by increasing impervious areas and providing more hydraulically efficient channels and overland flow. It is the policy of the Division of Highways to develop and make reasonable use of its lands and rights -of -way through sound, reasonable and acceptable engineering practices and to deny responsibility for augmented accelerated flow caused by its improvements unless determined to cause unreasonable and substantial damage. It is likewise the policy of the Division of Highways to expect this same practice and acceptance of responsibility by other property owners and those engaged in the development of these properties. Diversions Diversions are defined as the act of altering the path of surface waters from one drainage outlet to another. It is the policy of the Division of Highways to design and maintain its road systems, so that no diversions are created, insofar as is practicable from good engineering practice. 06/29/00 W CHAPTER TWO OCEAN ISLE BEACH POLICY STORMWATER MASTER PLAN Any person(s) desiring to create a diversion into any highway rights -of -way shall do so only after receiving written permission. This permission will be granted only after it has been determined that the additional flow can be properly handled without damage to the highway, that the cost for any required adjustments to the highway system will be borne by the requester, and that appropriate consideration and measures have been taken to indemnify and hold harmless the Division of Highways from potential downstream damage claims. It is Division of Highways policy not to grant diversions unless refusal would create a considerable and real hardship to the requesting party. Improvements and Maintenance of Drainage Within the Right -Of- Way Drainage structures and ditches shall be kept open and maintained at a functioning level such that they do not present an unreasonable level of damage potential for the highway or adjacent properties. Where the elevation of the flow -line of an existing culvert under a highway is not low enough to adequately provide for natural drainage, the Division of Highways will assume full responsibility for lowering the culvert or otherwise provide needed improvement. Where a requested culvert invert adjustment is a result of a property owner lowering the flow -line of the inlet and outlet ditch in order to improve drainage of his property, the following considerations shall be given to the action taken: • The lowered drain must have a reasonable expectancy of being functional and maintainable. • Division of Highways participation (up to full cost) must be based on benefit gained by the roadway drainage system as a result of the lowering. • Where the new installation is of doubtful benefit, or of no benefit to highway drainage, the requesting party must bear the entire cost of installation. Where the size of an existing highway culvert is determined to be of unacceptable adequacy in regard to ' the roadway system functioning as a result of a general overall development of the watershed, it is the Division of Highways responsibility to replace the structure or otherwise take appropriate action. Where this same culvert inadequacy is the result of a single action or development, it is felt to fall within the realm of "unreasonable and substantially damaging" under the State adopted drainage ruling. Therefore, the party responsible for the action or development should bear the cost of replacement. Where a new culvert crossing is requested, if the culvert is required for proper highway drainage or sufficient benefits to the highway drainage system would occur, the full cost will be borne by the Division of Highways providing there is no diversion of flow involved. Where the new installation is of doubtful or no benefit to highway drainage, the property owner will bear the entire cost. When both parties receive benefit, a joint effort may be negotiated. Established culvert crossings will be maintained and requests to eliminate any culverts should have approval from the State Hydraulics Engineer. When new private drives are constructed entering the highway, the property owner can furnish, delivered to the site, the amount, type and size pipe designated by the Division of Highways, to be installed by maintenance forces. No alteration, attachment, extension, nor addition of appurtenance to any culvert shall be allowed on highway rights -of -way without written permission. 06/29/00 2-10 CHAPTER Two OCEAN ISLE BEACH POLICY STORMWATER MASTER PLAN Improvements and Maintenance of Drainage Outside the Right -Of --Way ' While it is the responsibility of the Division of Highways to provide for adequate drainage for constructing and maintaining the State Highway System, it is not its policy nor responsibility to provide improved drainage for the general area traversed by such roads, unless incidental to the drainage of the road or highway itself. Drainage involvement outside the highway rights -of -way is limited to two general areas of justification: • Sufficient benefit would be gained by such action to warrant the cost. These benefits would be in such areas as reduction in roadway flood frequency or extent, facilitation of maintenance, or a reduction in potential damages. • Work is required to correct a problem or condition created by some action of the Division of Highways. It is not the responsibility of the Division of Highways to eliminate flooding on private property that is not attributable to acts of the agency or its representative. In general, outlet ditches will be maintained for a sufficient distance below the road to provide adequate drainage. On large outlets serving considerable areas outside the right-of-way, the maintenance should be done on a cooperative basis, with the benefited properties bearing their proportionate share. Shares will, in general, be based on proportioning of runoff from the areas served by the outlet. It is not the policy of the Division of Highways to pipe inlet or outlet drains, natural or artificial, outside the right-of-way, which existed as open drains prior to existence of the highway. Where the property owner wishes to enclose an inlet or outlet, the Division of Highways may install the pipe adjacent to the right-of-way if justified by reason of reduced maintenance, safety or aesthetics, if the pipe is furnished at the site by the property owner. This does not apply to the development of commercial property. i Obstructions It is the policy of the Division of Highways that when a drain is blocked below the highway, which is detrimental to highway drainage, if from natural causes, the Division of Highways will take necessary measures to remove the block or obstruction. Where the block is caused by wrongful acts of others, it is the policy of the Division of Highways to take whatever recourse deemed advisable and necessary to cause the party responsible to remove the block. Where a block occurs downstream of a highway, whether natural or artificial, and is of no consequence to the Division of Highways, it is their policy to remain neutral in causing its removal. Drainage Easements Where runoff is discharged from the right of way at a point where there is no natural drain or existing ditch, a permanent drainage easement is required to allow construction of a ditch or channel to convey the discharge to an acceptable natural outlet. When the discharge is into a natural drain or existing ditch and the increase in flow would exceed the capacity or otherwise create a problem, a temporary drainage easement can be obtained to allow enlarging or otherwise improving the drain to a point where the increase in discharge will not cause damage. It is generally preferable that any structural feature such as a drop inlet, catch basin, or pipe -end be contained within a permanent easement. 1 ot'z9io0 2-11 1 CHAPTER TWO OCEAN ISLE BEACH POLICY STORMWATER MASTER PLAN Subdivision Streets When roads and streets built by others are accepted onto the system for maintenance, responsibility for the drainage system, discharge pattern and outlet locations is as it existed at the time of acceptance and is ' limited to the rights -of -way. HydroloQy The hydrological analysis phase involves the determination of discharge rates and/or volumes of runoff that the drainage facilities will be required to convey or control. Many hydrological methods are available and most can.be appropriately and effectively used under proper control and application. When the site involves a Federal Emergency Management Act (FEMA) flood study area, discharge methods and values provided in the report will take precedent over these methods for determining compliance with the regulation. The results from any hydrologic procedure should be compared to historical site information and adjustments made in the values estimated or procedure used when deemed appropriate. The designer must also consider potential future land use changes within a watershed over the life of a roadway structure and include this effect when estimating design discharges. Method for Calculating Peak Discharge If a watershed less than 10 acres is primarily composed of pavement, grassed shoulders and slopes, and/or other mixed surface type runoff, the rational formula should be used for discharge determination. Hiehway Desi-an Discharge Criteria One specific criterion on which the design is evaluated and generally referred to as the "design discharge" is the flood level and frequency which results in inundation of the travelway. The minimum desirable levels of protection from travelway inundation by roadway classification are listed as follows: Roadway Classification Frequency Interstate (1) 50 year Primary (US & NC) 50 year Secondary (Major, City thoroughfare) 50 year Secondary 25 year Culvert Desiyn Criteria There are four discharge levels that must be evaluated for each culvert design. These are: (1) The "design discharge". (2) The Q100 base flood. (3) Q-overtopping. This discharge is computed after a trial size is selected. (4) Q10 for outlet protection and erosion control measures. Other discharges may be required on a site -specific basis. Examples are: (1) Q-average. For permit determination. (2) Q-bank full. For fish passage, channel stability or floodplain analysis. rStorm Drainage System Design Criteria The purpose of a storm drainage system is to collect and transport stormwater runoff from the highway to an outlet. The complete system consists of the curb and gutter, inlet structures, lateral and trunk line 1 pipes, and junctions and manholes. The design process for storm drainage systems usually follows the basic steps of planning/data collection, hydrologic/hydraulic design, and outfall analysis. 1 06/29/00 2-12 ' CHAPTER TWO OCEAN ISLE BEACH POLICY STORMWATER MASTER PLAN 1 Design Frequency Roadway inlet location, capacities and gutter spread is to be analyzed using a standard rainfall intensity of four inches/hour. The storm drain pipe system is to be designed using a Q10 discharge with a minimum time of concentration of 10 minutes assuming 100 percent pick-up at each inlet. In sag areas where relief by curb overflow is not provided, the system standard design level (Q25 — Q50) is to be used for analysis to ensure traffic flow is not interrupted. Pipe System Storm drain pipes shall be concrete unless a site limitation such as grade or corrosive conditions dictate the use of an alternate material. The minimum pipe size to serve a single inlet is 12 inches. For more than one inlet, or a length of more than 100 feet, a 15-inch pipe is the minimum size. When differing size pipes enter and exit a junction, the desired practice is to match the crowns of the pipes. Roadside Ditches A roadside ditch is a man-made channel generally paralleling the roadway surface and distinguished by a regular geometric shape. Roadway ditches are to be designed to contain as a minimum the Q5 (5-year) flow. The typical roadway ditch section is established with sufficient depth to drain the pavement subbase and flat side slopes for safe vehicle traversability. This generally provides very generous capacity for the design flow requirements. Therefore, actual capacity determination can be done on a selective basis at sites on common project grades to verify adequacy and establish limitations on the length of the ditch run. The size requirements of the project special side ditches along the toes -of -fill will be established based on an analysis of the design flood. This ditch capacity analysis will be performed using Mannings' equation. The roadway section including shoulders and slopes shall be considered an urban watershed. 2.2.2.5 NCDOT Subdivision Roads A subdivision road is one that serves a parcel or tract of land that is subdivided into two or more lots, building. sites or other divisions for sale or building development for residential purposes where such subdivisions include a new road or change in an existing road. Subdivision roads may be designated public or private. Public designations will be built to minimum construction standards of the North Carolina Department of Transportation (NCDOT) as required under North Carolina General Statute 136-102.6. Private roads need not meet minimum construction requirements, but must meet minimum construction requirements before ever becoming a part of the State -maintained system. NCDOT Subdivision Roads Drainage Design and Construction Requirements Design criteria for NCDOT subdivision roads are provided in Subdivision Roads — Minimum Design Standards. Drainage design and construction requirements for state -maintained subdivision roads are summarized for review purposes in the following paragraphs. Requirements for Addition of Subdivision Roads to the State S s • Erosion and Sedimentation — All subdivision roads shall have an acceptable permanent vegetative cover established and other acceptable permanent erosion control measures installed in accordance with Division of Highways specifications, prior to addition to the State System. 1 06/19/00 2-13 ' CHAPTER TWO OCEAN ISLE BEACH POLICY STORMWATER MASTER PLAN • All pipe culverts, storm sewers and appurtenances shall be free of all debris and silt build-up and shall be structurally and hydraulically sound, and functioning in a normal manner. All drainage ' ditches shall be of such a width and depth and with such a slope as to carry the anticipated discharges. Paved ditches or riprap shall be required where necessary. ' Minimum Drainage Requirements for Subdivision Roads The Division of Highways shall review all drainage prior to acceptance of any facility to the State System. All.storm drainage shall be adequate so that the road may be maintained without excessive cost, and not cause flooding on private property from storm runoff of the design frequency. Permanent ' drainage easements may be required. The minimum design frequency shall be as follows but may be increased at the recommendation of the State. Storm sewer collector — 10 years ' Cross drainage — 25 years In areas where ditch grades or quantities of flow deem it impracticable to establish and maintain ' vegetation, an erosive resistant lining such as paving or rock riprap may be required. Subsurface drainage shall be adequate to maintain a stable subgrade. When road crossings are within areas designated as flood hazard areas under the Federal Flood Insurance Program, the design must be approved by the responsible local governing agency for its consistency with local flood zoning ordinances. ' Minimum Criteria for Curb and Gutter Design Minimum design criteria for curb and gutter include the following: • All curb and gutter sections must meet Division of Highways standards. • The standard 2' x 6" concrete curb and gutter is the preferred type to be used. Types of other curb may be used provided the 6" height is maintained. • The concrete Valley Gutter is an allowable type. ' • Any other types of gutter will be subject to the approval of the Division Engineer after review on an individual basis. Approval will be subject to the terrain factors in the area under study as they relate to potential maintenance problems. 2.2.2.6 NCDOT Policy on Street and Driveway Access to Highways The North Carolina Department of Transportation has deemed it necessary to regulate the location, design, construction, and maintenance of street and driveway connections to the State Highway System for the purpose of protection for such highways, economy of maintenance, preservation of proper drainage, safe and efficient movement of traffic thereon, and full utilization of the taxpayer's investment. The objective of this Policy is to establish uniform criteria governing such location, design, construction, and maintenance. Drainage requirements for street and driveway access to highways are summarized for review purposes in the following section. Drainage Requirements for Street and Driveway Access to Highways ' Driveways must be constructed so that they do not adversely affect the highway drainage or drainage of the adjacent properties. The drainage and the stability of the highway subgrade must not be impaired by driveway construction or roadside development. In no case may the construction of a driveway cause ' 06/29/00 2-14 ' CHAPTER TWO OCEAN ISLE BEACH POLICY STORMWATER MASTER PLAN water to flow across the highway pavement, or to pond on the shoulders or in the ditch, or result in erosion within the right-of-way. ' (1) Drainage collected by ditches, gutters, or pipes on private property shall not be discharged into the highway drainage system unless expressly approved by the Division of Highways. The applicant may be required to submit a drainage study to the Division ' of Highways justifying the drainage system proposed and the pipe or sewer sizes to be used. Natural drainage laws and practices must be observed. ' (2) Where the construction of a driveway necessitates crossing a highway ditch, a culvert pipe shall be installed in the ditch. The low point of the driveway profile shall be at or close to the ditch line. Under no circumstances will existing ditches or gutters be filled without adequate alternate provisions for drainage being made. (3) Culvert pipe shall be of a size adequate to carry the anticipated flow in the ditch as determined by the Division of Highways and shall not be smaller than 15 inches, inside diameter. (4) The structural material and gauge of the driveway culvert pipe shall be adequate to ' withstand the loads from the anticipated vehicular traffic across the driveway. The culvert shall meet or exceed the requirements of the North Carolina Standard Specifications for Roads and Structures. The length of the culvert may be determined as ' the sum of the width of the driveway (surface width and shoulder) at the ditch line and the length needed to accommodate a sideslope of at least 1 vertical to 3 horizontal from the driveway grade to the ditch. A minimum 20 feet of pipe shall be used on all ' commercial and residential subdivision driveways. Plastic pipe is not acceptable for drainage purposes. (5) Where headwalls or wingwalls are constructed with drainage facilities, a minimum roadway clearance of 30 feet, measured from the edge of pavement, should be observed unless protected by guardrail. The use of flared -end sections should be encouraged. (6) All drainage structures deemed necessary by the Division of Highways, including incidentals, shall be furnished by the applicant. The Division of Highways will install the drainage pipe for the applicant at the current rate of installation. If, however, the ' applicant makes the installation, the Division of Highways is required to inspect the installation, and the applicant will be appropriately charged for the inspection. One inspection fee will be charged for each application, regardless of the number of ' installations involved, provided all installations are available for inspection. 2.2.3 Local Ordinances and Policies ' The local ordinances are critical in regulating development through zoning and planning. The local ordinances should control the density of development and establish building codes consistent with sound environmental practice. The following provides a summary of some of the zoning and subdivision ordinances for the Town of Ocean Isle Beach. ' The Town of Ocean Isle Beach has the following ordinances in place to control development: 1 06/29/00 2-15 ' CHAPTER TWO OCEAN ISLE BEACH POLICY STORMWATER MASTER PLAN 1 j l • minimum lot size of 5,000 square feet for single family in zones R-1, R-2, R-3, C-1, C-2 and C-3. • minimum lot size requirement of 7,500 square feet for two-family homes in zones R-2, R-3, C-1, C-2, and C-3. • minimum lot size of 10,000 square feet for multi -family in zones R-2, R-3, C-1, C-2 and C-3. • minimum lot size of 5,000 square feet for mobile homes in zones R-3. and C-3. • minimum lot size of 10,000 square feet for commercial accommodations in zones R-1, C-1, C-2 and C-3. • minimum lot size of 5,000 square feet for commercial business in zones C-2 and C-3. • minimum lot size of 5,000 square feet for commercial highway in zone C-3. • 36-foot building height restrictions for zone R-1. • 55-foot building height restriction for zones C-1, C-2 and C-3. • The structure's "footprint" shall not exceed thirty-six (36) percent of the lot area, not to include driveways and walkways. The Town of Ocean Isle Beach adopted ordinances as they relate to flood damage prevention and soil erosion and sedimentation. Flood Dam a�-e Prevention Ordinance This ordinance was established under the authority of the North Carolina General Statutes, Chapter 160A- 17(4). The intent of the ordinance is to promote the public health, safety and general welfare and to minimize public and private losses due to flood conditions in specific areas by restricting or prohibiting uses in certain areas, require that uses vulnerable to floods be protected against flood damage, controlling the alteration of natural flood plains and protective barriers, controlling filling, grading, dredging and other development which may increase erosion or flood damage, and by preventing or regulating the construction of devices which will naturally divert flood water or increase flood hazard to other lands. Soil Erosion and Sedimentation Ordinance The purpose of the ordinance is to regulate certain land -disturbing activities to control accelerated erosion and sedimentation in order to prevent the pollution of water and other damage to watercourses and other public and private property by sedimentation. This ordinance also establishes procedures through which these purposes can be fulfilled. CAMA Land Use Plan Statements of local policy on land use issues which affect the Town of Ocean Isle Beach are grouped in five general categories including: • Resource Protection Issues • Resource Management Issues • Economic and Community Development Issues • Citizen Participation Issues • Natural Hazards Policies from each of these categories that affect stormwater management are discussed in the following paragraphs. 06/29/00 2-16 7 CHAPTER TWO OCEAN ISLE BEACH POLICY STORMWATER MASTER PLAN ' Areas of Environmental Concern (AECs) According to the policy statement regarding AECs, the Town of Ocean Isle Beach shall seek to ensure that these areas are protected and only those uses which are compatible with the appropriate ' management of the Estuarine System will be allowed. Such development must be compatible so as to minimize the likelihood of significant loss of private property and public resources. Enforcement of the Town's Zoning Ordinance, Subdivision Regulations, Dune Maintenance and Protection Plan, ' Extraterritorial Jurisdiction Ordinance, and jet ski regulations will continue to protect these resources. Stormwater management measures will be implemented so as to comply with the Town's policies regarding AECs. ' Stormwater Runoff The Town recognizes the value of water quality maintenance with regard to protecting commercial and recreational fishing resources and providing clean water for other recreational purposes. The ' Stormwater Management Program will provide another tool for the Town to reduce stormwater pollution to the waterways and enhance the water quality in the area. ' Surface Water Quality Problems The Town is continuing to seek methods to protect and enhance the water quality of the estuarine system, and to develop new management measures and practices to improve water quality. The ' Stormwater Management Program will provide another tool for the Town to reduce stormwater pollution to the waterways and enhance the water quality in the area. ' Residential Commercial, and Industrial Land Development Impacts on Any Resources The Town's policy is to allow residential and related commercial development to occur as long as resource degradation does not occur. The Stormwater Management Program will be a tool the Town can implement to help ensure there is no degradation of resources due to stormwater runoff from these developed areas. Types of Urban Growth Patterns Desired The Town would like to maintain its image of a quiet, relaxing family beach community. Implementation of the Stormwater Management Program will not affect the desired growth patterns on the island. The program will help to improve visual aspects on the island (reducing or eliminating ' standing water during storms), which will help encourage the desired growth patterns. Redevelopment of Developed Areas, Includiniz the Relocation of Threatened Structures ' The Town supports redevelopment of previously developed areas. It is Town policy that density allowances for redevelopment areas conform to existing Town building and zoning regulations. The proposed stormwater ordinance does impose requirements for reducing stormwater runoff from the ' property after redevelopment, but it does not restrict redevelopment. Continuing Public Participation ' Town policy is to assure that all residents have a full and adequate opportunity to be informed of and participate in the Town's planning decision -making process. The Stormwater Management Program also includes public education and public participation. ' 06/29/00 2-17 ' CHAPTER TWO OCEAN ISLE BEACH POLICY STORMWATER MASTER PLAN 0 r_ 2.3 DRAINAGE SYSTEM DESIGN, OPERATION AND MAINTENANCE A stormwater drainage system consists of manmade conduits and channels and natural ponds, streams, creeks, rivers, and floodplains. Flooding is the most noticeable problem that occurs with poorly designed or maintained drainage systems. North Carolina Department of Transportation design criteria has been reviewed for applicability in the service area and these criteria were summarized in Section 2.2.2.5 - 2.2.2.6. These design criteria, along with NCDENR stormwater design criteria are excellent references and should be followed by the Town during design and construction of additional stormwater management measures. The Town may also want to develop their own Stormwater Drainage Design Manual. It is important that the Town has an easement for its storm drain systems so maintenance and repairs can be performed when necessary. For Town -owned storm drain systems carrying runoff from public right- of-way, the Town may want to obtain an easement for any pipe, inlet, manhole, and outfall. Storm drain systems which only carry runoff from private property are considered private systems and the Town is not responsible for their maintenance. For existing inlets and pipes that carry runoff from Town streets, the Town should try to obtain easements for the pipes and inlets. The operation and maintenance of the drainage system in the service area will be the responsibility of the Town. In order for the Town to effectively maintain the stormwater drainage system, the Town should create an inventory of the major components. This inventory should include type, location, size, material, slope, length, condition, and current ownership. Some of this has been collected from previous field investigations of the drainage system. All areas of the system should be put on a schedule that identifies what type of maintenance needs are to be performed and how often it should be done. A contingency plan should be developed that outlines what maintenance activities are needed after a major storm or hurricane. A step-by-step procedure for responding to minor maintenance and repair requests should also be developed. The amount of major and minor maintenance work performed will need to be tracked as a way to evaluate Stormwater Management Program success. 2.4 BEST MANAGEMENT PRACTICES (BMPs) BMPs are methods or practices that can effectively reduce stormwater pollution. Some BMPs, such as street sweeping, prevent pollutants from reaching stormwater and other BMPs, such as an infiltration trench, reduce the amount of pollutants already in the runoff. Structural control BMPs described in the North Carolina Department of Environment and Natural Resources Stormwater Management Guidance Manual include: • infiltration trenchesibasins • dry detention basins • wet retention basins • grassed swales • filter strips 06/29/00 2-18 F ' CHAPTER TWO OCEAN ISLE BEACH POLICY STORMWATER MASTER PLAN ' 2.5 FLOODPLAIN MANAGEMENT The Town of Ocean Isle Beach has an ordinance that regulates development in the floodplain and they ' participate in the Federal Flood Insurance Program. As part of this program, if a building is located in a flood prone area, the ground floor elevation must be certified before a building permit can be issued. No changes are recommended to the existing floodplain practices and policies regulated by the Town. Any drainage system improvements proposed in the floodplain will have to comply with the existing requirements. ' 2.6 STORMWATER MANAGEMENT ORDINANCE The Town currently has a Sediment and Erosion Control Ordinance in place, which affects stormwater ' management. The Town does not currently have a Stormwater Ordinance, though. A stormwater ordinance is needed to help prevent illicit discharges and dumping into the storm drain. An ordinance can make it illegal to put gasoline, oil, antifreeze, and other pollutants into the storm drain system. It would also be illegal for any person to put anything in the ditch, storm drain, or other drainage way that impedes ' or interferes with the free flow of stormwater. Additionally, the stormwater ordinance would also assist in limiting the amount of impervious surface on lots, thus reducing the quantity of stormwater entering the storm drain system, and help to reduce the risk of flooding during storms. A recommended ' Stormwater Management Ordinance is included in Appendix A. 2.7 INCREASED RUNOFF DUE TO DEVELOPMENT As land is developed, the area of perviousness usually decreases. This decrease accelerates the runoff of rainfall and increases the peak rates of flow. If measures are not taken during design, this increased rate ' of flow can cause flooding and erosion and sedimentation problems. The use of structural BMPs can provide a solution, as can the implementation of a stormwater ordinance. 2.8 POLLUTION PREVENTION Pollution prevention can play a large part in the amount of pollution that enters the waterways through stormwater runoff. Educating business owners and citizens about pollution prevention techniques is the best approach to reduce or prevent pollution. The Town can implement programs at very little (or no) cost that are effective at reducing pollution. The following programs are recommended for stormwater ' pollution prevention: • Identify local facilities which will accept waste oil/household chemicals and if none are located in ' the area, the Town may coordinate with the State to sponsor pollution disposal drives on a designated quarterly schedule. • Develop specific lawn maintenance recommended practices for the area and make a pamphlet to ' be mailed with stormwater fee bills at the beginning of every spring. • Develop a recommended list of vegetation that are effective in filtering pollutants, promote voluntary planting of a vegetative buffer. • Coordinate with commercial business owners to establish parking lot cleaning operations ' including recommended procedures and schedules. 1 06/29/00 2-19 ' CHAPTER TWO OCEAN ISLE BEACH POLICY STORMWATER MASTER PLAN 2.9 PUBLIC EDUCATION/PUBLIC INVOLVEMENT This Stormwater Master Plan provides a way for the Town to improve stormwater management in the ' future and to reduce deficiencies of the storm drain system. An important part of the plan is educating citizens about stormwater runoff, the importance of protecting the environment by not polluting the stormwater runoff, and ways that they can reduce stormwater runoff to help decrease flooding. Two ' handouts containing information about stormwater and ways the citizens can help reduce stormwater runoff were made available to the public at the informational workshop, and in the Town Hall. Copies of these handouts are included in Appendix B. Additional information could be supplied to the public as inserts included in sewer bills or handouts provided at Town Hall or real estate offices. The Town has also provided for public involvement as part of the development of the Stormwater ' Management Program. A public workshop was held to inform the public about the program and to solicit input regarding areas of concern and potential solutions. The public provided input on additional areas of concern and other topics. -1 7 LJ 06/29/00 2-20 CHAPTER THREE OCEAN ISLE BEACH SERVICE AREA OVERVIEW STORMWATER MASTER PLAN ' This overview describes the physical features on the island of Ocean Isle Beach and how they affect stormwater quality and quantity. 3.1 SETTING The Town of Ocean Isle Beach is located in southwestern Brunswick County, North Carolina. Figure 3-1 shows the location of Ocean Isle Beach. The island of Ocean Isle Beach is mostly residential development with some commercial businesses. The Town of Ocean Isle Beach has year-round residents and an ' increase in the visiting population during the summer months because of seasonal tourism. Figure 3-2 shows the town limits of Ocean Isle Beach. 11 11 II I 3.2 HYDROGRAPHY The Town is located in the eastern portion of the Lumber River Basin that flows from North Carolina to South Carolina. This river basin is comprised of smaller watersheds or hydrological units (HUs). The primary water features include the Atlantic Intracoastal Waterway (AIWW), Tubbs Inlet and Shallotte Inlet marsh systems, and the Atlantic Ocean. Within the service area, the United States Geological Survey (USGS) classifies one smaller watershed within the Lumber River Basin. The Carolina Coastal watershed (03040207) has an 8-digit hydrologic unit code (HUC). Within this watershed, the United States Department of Agriculture Natural Resources Conservation Service (MRCS) has delineated two subwatershed areas with 14-digit HUCs for the purpose of natural resource planning. The beginning of the 14-digit code uses the 8-digit designation of the USGS HUC. These two subwatersheds are the 'AIWW, Atlantic Ocean (03040207020120) and the 2AIWW (03040207020080). Figure 3-2 shows the boundaries of these two subwatershed hydrological units. 3.3 LAND USE Land use on the island primarily consists of residential and commercial. Residential and commercial properties consist predominantly of impervious surfaces as a result of paved areas (e.g., roads, streets, parking lots, driveways, etc.) and structures (e.g., shopping centers, commercial buildings, houses, barns, etc.). Vegetation, if present, varies and includes maintained lawns, maintained scrub areas along utility easements, and landscaped areas. 3.4 EFFECTS ON WATER QUANTITY Stormwater runoff quantity problems occur in various locations across the island. These problems include: • flooding • soil erosion • freshwater flow increase to estuaries/shellfish harvest areas • clogged pipes, culverts, and ditches caused by debris from flooded areas Development typically causes an increase in the volume and velocity of stormwater runoff that can result in environmental problems. Increased impervious surfaces reduce the opportunity for stormwater runoff 06/29/00 3-1 r ' CHAPTER THREE OCEAN ISLE BEACH SERVICE AREA OVERVIEW STORMWATER MASTER PLAN to be naturally retained and filtered by vegetation, wetlands, and estuaries. Pipe culverts located under roads allow a ditch, or channel to flow under the road. Culverts located under driveways allow ditches to ' flow under the driveway. Major flooding problems observed on the island, discussed in Chapter Four, are a direct result of the inadequate size, number, and/or location of inlets and lack of vegetated ditches to accommodate the increased stormwater runoff from development of impervious surfaces. Stormwater management will allow the Town to effectively design, implement, construct, and manage stormwater controls to prevent environmental problems associated with the increasing amount of stormwater quantity. 3.5 EFFECTS ON WATER QUALITY Stormwater runoff is rainfall or snowmelt that runs off the ground or impervious surfaces (buildings, roads, parking lots, etc.) and ultimately drains to surface waters including streams, ponds, lakes, estuaries, sounds, or the ocean. Most of the island drainage system consists of several catch basins with piped ' outfalls to the canals and the AIWW. There are also several swales along roads which collect stormwater runoff . The collection systems, although not adequate, mainly address the water quantity problem by helping to reduce flooding but do not address the water quality problem of pollutant removal. Wetlands and vegetated areas perform the natural function of reducing the flow rate of stormwater runoff and allowing the pollutants to settle and filter through soils. This natural pollutant removal system by the environment helps to reduce the impact of man-made pollution on surface waters. r Land use dictates the type of pollutants that enter stormwater runoff and ultimately impact surface waters. First flush is the first portion of runoff from a storm and it usually contains the highest concentrations of pollutants. The land use within the service area affects water quality because of the associated pollutants. Table 3-1 shows the land use activities associated with pollutants. Stormwater management includes control practices and preventive measures which will improve water quality. Chapter Four discusses the water quality problems on the island and provides recommended ' mitigation measures. 3.6 STORM DRAIN SYSTEM INVENTORY AND MAPPING rThe storm drain system map was drawn using AutoCAD version 14 and the Town base map was obtained from Boney and Associates, Inc. Some of the system components (drop inlets) may have been buried r under sand/vegetation and thus were not included in this inventory. Based upon the preliminary inventory of the Town's storm drain system it was determined that there are approximately 59 storm drain inlets, 16 pipe outfalls, and 8,000 linear feet of ditches on the island of Ocean Isle Beach. The length of stormwater pipe on the island is unknown. The size of the storm drain pipe appeared to range from 2-inch to approximately 18-inch, although pipe sizes were not measured. No Town -owned stormwater management facilities (retention basins, etc.) are located on the island. 06/29/00 3-2 1 1 1 1 1 1 1 CHAPTER THREE OCEAN ISLE BEACH SERVICE AREA OVERVIEW STORMWATER MASTER PLAN Table 3-1 Stormwater Pollutants Pollutant Land Use Activity Suspended solids and turbidity • Plowing agricultural fields/gardens • Land clearing for development without proper sedimentation/erosion controls Nutrients (chlorophyll a, phosphorus, nitrogen) . Fertilizer application to lawns, golf courses, and crops Fecal colifonn . • Overuse or failure of septic tanks • Package plant malfunctions • Leaks in sewer lines • Waste from pets, domestic and wild animals Oil and grease • Leaky automobiles, industrial areas, illegal dumping Toxic chemicals • Automobiles, industrial areas, illegal dumping, pesticide application 06/29/00 3-3 m m m m m m m m m m m w m m m m m m m Ji. N HYDROLOGIC UNIT 000 500 0 1000 2000 BOUNDARIES SCALE 1' = 2000' 1 H �I 1 CHAPTER FOUR OCEAN ISLE BEACH WATERSHED CHARACTERISTICS STORMWATER MASTER PLAN 4.1 . WATERSHED CHARACTERISTICS 4.1.1 Hydrologic and Hydraulic Characteristics The AIWW is the main water body in the area of Ocean Isle Beach which discharges into Tubbs Inlet (separates Sunset Beach island and Ocean Isle Beach) and Shallotte Inlet (separates Ocean Isle Beach and Holden Beach). The AIWW is classified as a shellfishing harvest area (SA). The AIWW and the surrounding estuarine waters have been designated as a primary nursery area (PNA) which means they are considered a highly productive habitat for juvenile marine species. Salt marshes occur between the open water of the AIWW and the upland areas of the barrier islands. The majority of the island of Ocean Isle Beach is located within the 100-year flood plain (Ocean Isle Beach, 1997). Table 4-1 describes the soil types found in this watershed (USDA, 1986). Table 4-1 Soils Data Ocean Isle Beach Soil Type Symbol "';: Soil Name Sanitary Facility Rating', High Water Table Deptli�(feet) Hydric Condition . " BO Bohicket Severe: flooding, ponding, peres slowly +3.0-0.0 Yes CA Carteret Severe: flooding, ponding, poor filter +3.0-1.0 No Co Corolla Severe: wetness, poor filter 1.5-3.0 No NeE Newhan Severe: poor filter, slope >6.0 No NhE Newhan, dredged Severe: poor filter, slope >6.0 No The island has little to no relief, which creates ponding problems in various areas. These will be discussed in Section 4.3.1. The existing drainage system on Ocean Isle Beach consists of shallow swales, inlet structures and pipes. There are 16 pipe outfall locations. These locations are shown on Figure 4-1. 4.1.2 Water Quality Characteristics Some SA shellfishing areas around Ocean Isle Beach have been closed for many years due to poor water quality, specifically high fecal coliform bacteria levels, according to the NC Department of Health, Shellfish Sanitation Section. The portion of AIWW and the canals on the island of Ocean Isle Beach are closed to shellfishing. Unlike many of the other barrier islands, though, Ocean Isle Beach has a municipal sewer system instead of septic tanks. Many of the barrier islands with septic tank systems have very high fecal coliform counts in the surrounding estuarine waters. Benthic macroinvertebrate sampling has been conducted at the junction of the main canals on the east end of Ocean Isle Beach by the Division of Water Quality since 1983. A moderate impact bioclassification has been given to this location. This classification indicates that most nonpoint source problems are confined to the canals and not spreading to surrounding waters. 06/29/00 4-1 ' CHAPTER FOUR - OCEAN ISLE BEACH WATERSHED CHARACTERISTICS STORMWATER MASTER PLAN The Division of Water Quality also has an ambient water quality sampling site located in the.A1WW near the Ocean Isle Beach bridge. The most recent data from the Division of Water Quality indicates that approximately 25 percent of the samples collected had concentrations of fecal coliform bacteria above the criterion for SA waters. Approximately 15percent of the samples collected at this location had dissolved oxygen concentration less that the state standard for aquatic life. Additionally, there were a few minor exceedances of the saltwater action level for copper (DENR, 1998). Additionally, the entire Lumber River Basin has fish advisories for largemouth bass and bowfin, due to high levels of mercury in the waters. These elevated mercury levels are predominately due to airborne contaminants (DENR, 1998). 4.2 FUTURE DEVELOPMENT As outlined in the 1997 CAMA Land Use Plan for Ocean Isle Beach, the year-round population of the Town was 832 in 1997, and is projected to be 1,121 by2007. Future development on the island portion of Ocean Isle Beach will be primarily comprised of residential units, with limited additional commercial development. By 2007, it is estimated that an additional 97.6 acres will be developed for residential, 1.2 acres for commercial, 2 acres for government/utilities, and 5.5 acres for roads. The anticipated future development will increase overall imperviousness on the island. 4.3 EVALUATION AND RECOMMENDATIONS During the development of recommendations for each area of concern, several criteria were evaluated to determine the most appropriate BMP for each area. The criteria which were evaluated were: • Cost to implement and maintain • Regulatory requirements • Effectiveness at solving the problem • Acceptability to the Town and the public • Reliability • Implementability • Environmental Impact Cost to implement and maintain ' The cost to implement and maintain each BMP was evaluated and compared. Specific costs for each BMP were not determined, but relative costs of each BMP type were compared to determine the most cost effective solutions. ' Regaulatoa Requirements Each BMP was evaluated to determine if any special regulatory requirements would have to be met for implementation. Effectiveness at solving the problem Each BMP was evaluated to determine the effectiveness at solving the flooding and/or water quality ' problem(s). The recommended BMP may only alleviate the problem, not completely solve it, but the other criteria indicated that this BMP was the most appropriate. 06/29/00 4-2 I CHAPTER FOUR OCEAN ISLE BEACH WATERSHED CHARACTERISTICS STORMWATER MASTER PLAN 1 Acceptability to the Town and the public Each BMP was evaluated as to whether it would be an acceptable solution to the Town and to the public. Education is an important aspect to acceptability of a BMP. Reliability The reliability over time of each BMP was evaluated. Some BMPs retain their effectiveness longer than others with a limited amount of maintenance. Im lementabili Some structural BMPs can not be constructed in certain areas dueto regulatory and/or physical constraints. Environmental Impact Each BMP was evaluated to determine if any positive or negative environmental impacts would occur due to implementation of the BMP. 4.3.1 Water Quantity Flooding is the primary stormwater problem on the island of Ocean Isle Beach. Below is an explanation of the flooding areas of concern, and recommendations for improvements. Deficiencies and recommendations are summarized in Table 4-2. ' First Street (east end) There is significant flooding that occurs on First Street between Laurinburg Street and Greensboro Street. The flooding appears to be the worst between Chapel Hill Street and LaGrange Street, and near Goldsboro Street. Flooding is several -inches deep and extends across the entire road on many occasions. These flooding conditions cause a safety hazard for pedestrians and motorists, along with the potential for property damage to cars from hidden obstructions under the water. The only storm drain inlets identified in the area were near Chapel Hill Street, Raeford Street, Oak Ridge Street, and Greensboro Street. Only the Greensboro Street inlet is connected to an outfall (ocean discharge). It does not appear that any of the other inlets are connected to an outfall, and they are insufficient to capture the flow from the area. In order to solve the flooding problem in this area it is recommended that underground infiltration trenches be used. The island has very permeable soils, and although the water table is high, it should be possible to design an infiltration system which will have a sufficient separation distance from the bottom of the infiltration facility and the water table. With the high permeability of the soils and a correct design, stormwater runoff will infiltrate very quickly, thus eliminating the standing water on the roadway. If possible, the stormwater outfall at Greensboro Street will be removed, so as to minimize polluted stormwater from entering the ocean. Since First Street is a NCDOT roadway, there must be coordination with NCDOT. All plans and designs must be approved by NCDOT prior to implementation. It may be possible to obtain assistance from NCDOT on the construction of the system. URSGWC recommends that the Town have a meeting with NCDOT to discuss the issues along First Street and how the NCDOT and the Town can work together to alleviate the flooding problems. 06/29/00 4-3 CHAPTER FOUR OCEAN ISLE BEACH WATERSHED CHARACTERISTICS STORMWATER MASTER PLAN URSGWC understands that there are utility easements on either side of First Street. This will have to be taken into account during design of an infiltration system. The Town may want to consider obtaining an easement (from property owners) for an infiltration system outside the right of way. Another option would be to pipe the stormwater to underground infiltration basins/trenches which could be located at the CAMA beach accesses (Monroe Street, Concord Street, Newport Street, Raeford Street, Leland Street, Goldsboro Street, Chadbourne Street, Winnabow Street, and/or Greensboro Street). Coordination with DCM would be required for these facilities. URSGWC understands that DCM has, in the past, stated that they would be willing to work with the Town in the use of the CAMA accesses for use as stormwater facilities also. In designing an underground infiltration system, it is recommended that some type of oil/grit chamber or trap be constructed to pretreat the runoff before it enters the trench/basin. There are various types of oil/grit chambers, from small devices that fit into standard inlet structures to larger three -chamber facilities. The size of the oil/grit chamber will be dependent on the size of the area draining to the inlet. The location and number of storm drain inlets, along with the size of infiltration facilities, will have to be ' determined through hydraulic and hydrologic (H & H) modeling of the area. A detailed survey of the area is also necessary prior to completion of the modeling efforts. To reduce the amount of stormwater runoff which reaches the street and the Town's storm drain system, URSGWC recommends that the Town encourage its residents to reduce the amount of impervious surface on their lots and direct stormwater runoff (from rooftops and other impervious surfaces) to vegetated areas, instead of directly off their property and into the street. A recommended stormwater ordinance that will assist in accomplishing this is included in Appendix A. Depending on the method of funding of the Town's Stormwater Management Program (Section 5.5), the Town may want to offer fee/tax credits for residents constructing french drains or infiltration areas for runoff from impervious surfaces on their lots. ' (This would be applicable with a stormwater utility or stormwater fee/tax). 11 1 Through evaluation of various BMPs, underground infiltration with a stormwater ordinance was determined to be the most cost effective, applicable, and effective at solving the flooding problems in the area. With cooperation from the NCDOT, and possibly DCM, this is an implementable BMP. As long as the infiltration system is maintained, it is a reliable stormwater BMP. There are no negative environmental impacts associated with an infiltration system in this area. Public education will be necessary to inform the residents of the need for the system, how the system will solve the flooding problem, and what they need to do to comply with the stormwater ordinance (if adopted by the Town). First Street at Private Drive There is significant flooding that occurs on First Street near Private Drive. The Private Drive area is a private subdivision, thus the streets are not Town -owned or maintained. It is the understanding of URSGWC that the subdivision had obtained a stormwater permit from the State prior to construction. The roadside swales that were constructed in the subdivision have not been maintained and are virtually non-existent. Most of the stormwater runoff from this subdivision flows down onto First Street, causing flooding on the south side of First Street. The lots on the south side of First Street are also graded so that the stormwater flows directly to the street. These flooding conditions cause a safety hazard for pedestrians and motorists, along with the potential for property damage to cars from hidden obstructions under the water. 06/29/00 4-4 ' CHAPTER FOUR OCEAN ISLE BEACH WATERSHED CHARACTERISTICS STORMWATER MASTER PLAN There are no storm drain inlets identified in the area of First Street and Private Drive. Therefore, due to the grading of the lots in the area and the lack of any stormwater management facility, there is no place for the stormwater to flow. , iThe first step in solving this problem is to work with the Division of Water Quality Stormwater Section, the developer, and the homeowners in the private subdivision to reinstall the roadside drainage swales. A maintenance agreement is required by the State if a stormwater permit was issued for a high density development. It is the State's responsibility to enforce the maintenance of stormwater systems constructed under a State stormwater permit. Reinstalling the swales in the subdivision will not eliminate the flooding problem on First Street, but it will alleviate the problem. URSGWC recommends design and construction of underground infiltration trenches along the south side of First Street. As stated previously, with the high permeability of the soils and a correct design, stormwater runoff will infiltrate very quickly, thus eliminating the standing water on the roadway. As with the previously described area, First Street is a NCDOT roadway and there must be coordination with NCDOT. All plans and designs must be approved by NCDOT prior to implementation. It may be possible to obtain assistance from NCDOT on the construction of the system. URSGWC recommends that the Town have a meeting with NCDOT to discuss the issues along First Street and how the NCDOT and the Town can work together to alleviate the flooding problems. URSGWC understands that there are utility easements on either side of First Street. This will have to be taken into account during design of an infiltration system. The Town may want to consider obtaining an easement (from property owners) for an infiltration system outside the right of way. Another option would be to pipe the stormwater to underground infiltration basins/trenches which could be located at the nearest CAMA beach accesses (at Duneside Drive). On the west side of the island, the CAMA access points are only walkways, therefore space is limited. Modeling will indicate if there is enough space for an infiltration trench/basin in the CAMA access. Coordination with DCM would be required for these facilities. URSGWC understands that DCM has, in the past, stated that they would be willing to work with the Town in the use of the CAMA accesses for use as stormwater facilities also. In designing an underground infiltration system, it is recommended that some type of oil/grit chamber or trap be constructed to pretreat the runoff before it enters the trench/basin. There are various types of oil/grit chambers, from small devices that fit into standard inlet structures to larger three -chamber facilities. The size of the oil/grit chamber will be dependent on the size of the area draining to the inlet. 1 The location and number of storm drain inlets, along with the size of infiltration facilities, will have to be determined through hydraulic and hydrologic (H & H) modeling of the area. A detailed survey of the area is also necessary prior to completion of the modeling efforts. To reduce the amount of stormwater runoff which reaches the street and the Town's storm drain system, URSGWC recommends that the Town encourage its residents to reduce the amount of impervious surface on their lot, and direct stormwater runoff (from rooftops and other impervious surfaces) to vegetated areas, instead of directly off their property and into the street. A recommended stormwater ordinance that will assist in accomplishing this is included in Appendix A. Depending on the method of funding of the Town's Stormwater Management Program (Section 5.5), the Town may want to offer fee/tax credits for residents constructing french drains or infiltration areas for runoff from impervious surfaces on their lots. (This would be applicable with a stormwater utility or stormwater fee/tax). 06/29/00 4-5 1 CHAPTER FOUR OCEAN ISLE BEACH WATERSHED CHARACTERISTICS STORMWATER MASTER PLAN k Through evaluation of various BMPs, underground infiltration with a stormwater ordinance was determined to be the most cost effective, applicable, and effective at solving the flooding problems in the area. With cooperation from the NCDOT, and possibly DCM, this is an implementable BMP. As long as the infiltration system is maintained, it is a reliable stormwater BMP. There are no negative environmental impacts associated with an infiltration system in this area. Public education will be necessary to inform the residents of the need for the system, how the system will solve the flooding problem, and what they need to do to comply with the stormwater ordinance (if adopted by the Town). First Street between Shelby Street and Troy Street There is significant flooding that occurs on the south side of First Street between Shelby Street and Troy Street. Flooding is several inches deep and extends into the travel lanes on many occasions. These flooding conditions cause a safety hazard for pedestrians and motorists, along with the potential for property damage to cars from hidden obstructions under the water. There are no storm drain inlets identified in this area of First Street. Therefore, due to the grading of the lots in the area and the lack of any stormwater management facility, there is no place for the stormwater to flow. In order to solve the flooding problem in this area it is recommended that underground infiltration trenches/basins be used. Since First Street is a NCDOT roadway, there must be coordination with NCDOT. All plans and designs must be approved by NCDOT prior to implementation. It may be possible to obtain assistance from NCDOT on the construction of the system. URSGWC recommends that the Town have a meeting with NCDOT to discuss the issues along First Street and how the NCDOT and the Town can work together to alleviate the flooding problems. URSGWC understands that there are utility easements on either side of First Street. This will have to be taken into account during design of an infiltration system. The Town may want to consider obtaining an easement (from property owners) for an infiltration system outside the right of way. Another option would be to investigate the purchase of a tract of the undeveloped land on the north side of First Street in this area. The stormwater could be piped to underground infiltration basins/trenches which could be located in this area. The north side of the street is currently at a higher elevation, therefore some regrading of the land on the north side would be required. Underground infiltration in this area would allow the land to still be developed for a variety of uses (parking lot, park, etc.). In designing an underground infiltration system, it is recommended that some type of oil/grit chamber or trap be constructed to pretreat the runoff before it enters the trench/basin. There are various types of oil/grit chambers, from small devices that fit into standard inlet structures to larger three -chamber facilities. The size of the oil/grit chamber will be dependent on the size of the area draining to the inlet. The location and number of storm drain inlets, along with the size of infiltration facilities, will have to be determined through hydraulic and hydrologic (H & H) modeling of the area. A detailed survey of the area is also necessary prior to completion of the modeling efforts. To reduce the amount of stormwater runoff which reaches the street, and the Town's storm drain system, URSGWC recommends that the Town encourage its residents to reduce the amount of impervious surface on their lots and direct stormwater runoff (from rooftops and other impervious surfaces) to vegetated areas, instead of directly off their property and into the street. A recommended stormwater ordinance that will assist in accomplishing this is included in Appendix A. Depending on the method of funding of the 06/29/00 4-6 IJ CHAPTER FOUR OCEAN ISLE BEACH WATERSHED CHARACTERISTICS STORMWATER MASTER PLAN Town's Stormwater Management Program (Section 5.5), the Town may want to offer fee/tax credits for residents constructing french drains or infiltration areas for runoff from impervious surfaces on their lots. (This would be applicable with a stormwater utility or stormwater fee/tax). Through evaluation of various BMPs, underground infiltration with a stormwater ordinance was determined to be the most cost effective, applicable, and effective at solving the flooding problems in the area. With cooperation from the NCDOT, and possibly DCM, this is an implementable BMP. As long as the infiltration system is maintained, it is a reliable stormwater BMP. There are no negative environmental impacts associated with an infiltration system in this area. Public education will be necessary to inform the residents of the need for the system, how the system will solve the flooding problem, and what they need to do to comply with the stormwater ordinance (if adopted by the Town). First Street from Driftwood Drive to the west Town limit ' There is some minor flooding that occurs on First Street from Driftwood Drive to the western Town limit. Flooding is several inches deep and extends into the travel lane on many occasions. These flooding conditions cause a safety hazard for pedestrians and motorists. 1 The only storm drain inlets identified in the area were west of Starboard Street. It does not appear that either of the inlets are connected to an outfall, and they are cannot capture the flow from the area due to the lack of topographic relief. In order to solve the flooding problem in this area it is recommended that either additional inlets be installed as subsurface retention basins with perforated pipe to infiltrate the retained stormwater or roadside swales be installed on the south side of the road. Since First Street is a NCDOT roadway, there must be coordination with NCDOT. All plans and designs must be approved by NCDOT prior to implementation. It may be possible to obtain assistance from NCDOT on the construction of the system. URSGWC recommends that the Town have a meeting with NCDOT to discuss the issues along First Street and how the NCDOT and the Town can work together to alleviate the flooding problems. URSGWC understands that there are utility easements on either side of First Street. This will have to be taken into account during design. For roadside swales, there should be sufficient space both vertically and laterally to construct the BMP. Since there are inlets already located in the area, it is assumed that there would be sufficient space to install additional inlets as necessary. Utility maps will have to be obtained prior to design. It is recommended that some type of oil/grit trap be installed in the inlet to pretreat the runoff before it enters the infiltration pipe. The location, number, and size of storm drain inlets, or the size of the swale will have to be determined ' through hydraulic and hydrologic (H & H) modeling of the area. A detailed survey of the area is also necessary prior to completion of the modeling efforts. To reduce the amount of stormwater runoff which reaches the street, and the Town's storm drain system, URSGWC recommends that the Town encourage its residents to reduce the amount of impervious surface on their lots and direct stormwater runoff (from rooftops and other impervious surfaces) to vegetated areas, instead of directly off their property and into the street. A recommended stormwater ordinance that will assist in accomplishing this is included in Appendix A. Depending on the method of funding of the Town's Stormwater Management Program (Section 5.5), the Town may want to offer fee/tax credits for 06/29/00 4-7 CHAPTER FOUR OCEAN ISLE BEACH WATERSHED CHARACTERISTICS STORMWATER MASTER PLAN residents constructing french drains or infiltration areas for runoff from impervious surfaces on their lots. (This would be applicable with a stormwater utility or stormwater fee/tax). Through evaluation of various BMPs, subsurface retention with a stormwater ordinance was determined to be the most cost effective, applicable, and effective at solving the flooding problems in the area. With cooperation from the NCDOT this is an implementable BMP. As long as the storm drain inlets are periodically cleaned and maintained, it is a reliable stormwater BMP. There are no negative ' environmental impacts associated with this type of system in this area. Public education will be necessary to inform the residents of the need for the system, how the system will solve the flooding problem, and what they need to do to comply with the stormwater ordinance (if adopted by the Town). Second Street at Scotland Street There is minor flooding that occurs on Second Street at Scotland Street and on the east side of Scotland Street, just north of Second Street. These flooding conditions cause a safety hazard for pedestrians and motorists, especially if the water enters the travel lane. 1 There are no storm drain inlets identified in this area of Second Street. Therefore, due to the grading of the lots in the area and the lack of any stormwater management facility, there is no place for the stormwater to flow. ' In order to solve the flooding problem in this area it is recommended that either additional inlets be installed as subsurface retention basins with perforated pipe to infiltrate the retained stormwater, or roadside swales be installed. ' The presence of utility easements will have to be taken into account during design. For roadside swales, there should be sufficient space both vertically and laterally to construct the BMP. Utility maps will have ' to be obtained prior to design. It is recommended that some type of oil/grit trap be installed in the inlets to pretreat the runoff before it enters the infiltration pipe. The location, number, and size of storm drain inlets, or the size of the roadside swale will have to be ' determined through hydraulic and hydrologic (H & H) modeling of the area. A detailed survey of the area is also necessary prior to completion of the modeling efforts. To reduce the amount of stormwater runoff which reaches the street, and the Town's storm drain system, URSGWC recommends that the Town encourage its residents to reduce the amount of impervious surface on their lots and direct stormwater runoff (from rooftops and other impervious surfaces) to vegetated areas, instead of directly off their property and into the street. A recommended stormwater ordinance that ' will assist in accomplishing this is included in Appendix A. Depending on the method of funding of the Town's Stormwater Management Program (Section 5.5), the Town may want to offer fee/tax credits for residents constructing french drains or infiltration areas for runoff from impervious surfaces on their lots. (This would be applicable with a stormwater utility or stormwater fee/tax). Through evaluation of various BMPs, subsurface retention with a stormwater ordinance was determined to be the most cost effective, applicable, implementable and effective at solving the flooding problems in the area. As long as the storm drain inlets are periodically cleaned and maintained, it is a reliable stormwater BMP. There are no negative environmental impacts associated with this type of system in 06/19/00 4-8 CHAPTER FOUR OCEAN ISLE BEACH WATERSHED CHARACTERISTICS STORMWATER MASTER PLAN this area. Public education will be necessary to inform the residents of the need for the system, how the ' system will solve the flooding problem, and what they need to do to comply with the stormwater ordinance (if adopted by the Town). Second Street between Lee Street and Goldsboro Street There is minor flooding that occurs on Second Street between Lee Street and Goldsboro Street. These flooding conditions cause a safety hazard for pedestrians and motorists, especially if the water enters the travel lane. There are no storm drain inlets identified in this area of Second Street. Therefore, due to the grading of the lots in the area and the lack of any stormwater management facility, there is no place for the stormwater to flow. ' In order to solve the flooding problem in this area it is recommended that additional storm drain inlets be installed as subsurface retention basins with perforated pipe to infiltrate the retained stormwater The presence of utility easements will have to be taken into account during design. Utility maps will have ' to be obtained prior to design. It is recommended that some type of oil/grit trap be installed in the inlets to pretreat the runoff before it enters the infiltration pipe. The location, number, and size of storm drain inlets will have to be determined through hydraulic and ' hydrologic (H & H) modeling of the area. A detailed survey is also necessary prior to completion of the modeling efforts. To reduce the amount of stormwater runoff which reaches the street, and the Town's storm drain system, URSGWC recommends that the Town encourage its residents to reduce the amount of impervious surface on their lots and direct stormwater runoff (from rooftops and other impervious surfaces) to vegetated areas, instead of directly off their property and into the street. A recommended stormwater ordinance that will assist in accomplishing this is included in Appendix A. Depending on the method of funding of the Town's Stormwater Management Program (Section 5.5), the Town may want to offer fee/tax credits for residents constructing french drains or infiltration areas for runoff from impervious surfaces on their lots. (This would be applicable with a stormwater utility or stormwater fee/tax). Through evaluation of various BMPs, subsurface retention with a stormwater ordinance was determined to be the most cost effective, applicable, and effective at solving the flooding problems in the area. As long as the storm drain inlets are periodically cleaned and maintained, it is a reliable stormwater BMP. There are no negative environmental impacts associated with an infiltration system in this area. Public ' education will be necessary to inform the residents of the need for the system, how the system will solve the flooding problem, and what they need to do to comply with the stormwater ordinance (if adopted by the Town). Second Street at Sanford Street There is significant flooding that occurs on Second Street at Sanford Street. Flooding is several inches deep and extends across Sanford Street on many occasions. These flooding conditions cause a safety hazard for pedestrians and motorists, along with the potential for property damage to cars from hidden obstructions under the water. 06/29/00 4-9 r 11 11 1 CHAPTER FOUR OCEAN ISLE BEACH WATERSHED CHARACTERISTICS STORMWATER MASTER PLAN There are no storm drain inlets identified in this area of Second Street. Therefore, due to the grading of the lots in the area and the lack of any stormwater management facility, there is no place for the stormwater to flow. In order to solve the flooding problem in this area it is recommended that underground infiltration trenches/basins be used. The presence of utility easements will have to be taken into account during design. Utility maps will have to be obtained prior to design. The recommended option would be to investigate the purchase of a tract of the undeveloped land on the north side of Second Street, in this area. The stormwater could be piped to underground infiltration basins/trenches which could be located in this area. Regrading of the land on the north side would be required during construction. Underground infiltration in this area would allow the land to still be developed for a variety of uses (parking lot, park, etc.). In designing an underground infiltration system, it is recommended that some type of oil/grit chamber or ' trap be constructed to pretreat the runoff before it enters the trenchibasin. There are various types of oil/grit chambers, from small devices that fit into standard inlet structures to larger three -chamber facilities. The size of the oil/grit chamber will be dependent on the size of the area draining to the inlet. The location and number of storm drain inlets, along with the size of infiltration facilities, will have to be determined through hydraulic and hydrologic (H & H) modeling of the area. A detailed survey of the area is also necessary prior to completion of the modeling efforts. To reduce the amount of stormwater runoff which reaches the street, and the Town's storm drain system, URSGWC recommends that the Town encourage its residents to reduce the amount of impervious surface on their lots and direct stormwater runoff (from rooftops and other impervious surfaces) to vegetated areas, instead of directly off their property and into the street. A recommended stormwater ordinance that will assist in accomplishing this is included in Appendix A. Depending on the method of funding of the Town's Stormwater Management Program (Section 5.5), the Town may want to offer fee/tax credits for residents constructing french drains or infiltration areas for runoff from impervious surfaces on their lots. (This would be applicable with a stormwater utility or stormwater fee/tax). Through evaluation of various BMPs, underground infiltration with a stormwater ordinance was determined to be the most cost effective, applicable, and effective at solving the flooding problems in the area. With cooperation from the public, this is an implementable BMP. As long as the infiltration system is maintained, it is a reliable stormwater BMP. There are no negative environmental impacts associated with an infiltration system in this area. Public education will be necessary to inform the residents of the need for the system, how the system will solve the flooding problem, and what they need to do to comply with the stormwater ordinance (if adopted by the Town). Second Street between Charlotte Street and Shallotte Boulevard There is minor flooding that occurs on Second Street between Charlotte Street and Shallotte Boulevard, at the entrance to the Sand Dwellers Condos. These flooding conditions cause a safety hazard for pedestrians and motorists, along with the potential for property damage to cars from hidden obstructions under the water. 1 06/29/00 4-10 I CHAPTER FOUR OCEAN ISLE BEACH WATERSHED CHARACTERISTICS STORMWATER MASTER PLAN There are no storm drain inlets identified in this area of Second Street. Therefore, due to the grading of ' the lots in the area and the lack of any stormwater management facility, there is no place for the stormwater to flow. ' In order to solve the flooding problem in this area it is recommended that additional storm drain inlets be installed as subsurface retention basins with perforated pipe to infiltrate the retained stormwater. ' The presence of utility easements will have to be taken into account during design. Utility maps will have to be obtained prior to design. It is recommended that some type of oil/grit trap be installed in the inlets to pretreat the runoff before it enters the infiltration pipe. ' The location, number, and size of storm drain inlets will have to be determined through hydraulic and hydrologic (H & H) modeling of the area. A detailed survey of the area is also necessary prior to completion of the modeling efforts. 7 11 ri To reduce the amount of stormwater runoff which reaches the street, and the Town's storm drain system, URSGWC recommends that the Town encourage its residents to reduce the amount of impervious surface on their lots and direct stormwater runoff (from rooftops and other impervious surfaces) to vegetated areas, instead of directly off their property and into the street. A recommended stormwater ordinance that will assist in accomplishing this is included in Appendix A. Depending on the method of funding of the Town's Stormwater Management Program (Section 5.5), the Town may want to offer fee/tax credits for residents constructing french drains or infiltration areas for runoff from impervious surfaces on their lots. (This would be applicable with a stormwater utility or stormwater fee/tax). It is recommended that the Town work with the Sand Dwellers Condos to encourage them to reduce the amount of stormwater runoff that leaves their property. The reduction in the amount of stormwater would reduce the flooding in both the roadway and the entrance to the Sand Dwellers parking lot. Through evaluation of various BMPs, subsurface retention with a stormwater ordinance was' determined to be the most cost effective, applicable, and effective at solving the flooding problems in the area. As long as the storm drain inlets are periodically cleaned and maintained, it is a reliable stormwater BMP. There are no negative environmental impacts associated with this type of system in this area. Public education will be necessary to inform the residents of the need for the system, how the system will solve the flooding problem, and what they need to do to comply with the stormwater ordinance (if adopted by the Town). Third Street at Columbia Street There is significant flooding that occurs at Third Street and Columbia Street. Flooding is several inches deep (or more) and extends across the entire intersection on many occasions. These flooding conditions cause a safety hazard for pedestrians and motorists, along with the potential for property damage to cars from hidden obstructions under the water. There are no storm drain inlets identified in this area. Therefore, due to the grading of the lots in the area and the lack of any stormwater management facility, there is no place for the stormwater to flow. 06/29/00 4-11 ' CHAPTER FOUR OCEAN ISLE BEACH WATERSHED CHARACTERISTICS STORMWATER MASTER PLAN ' In order to solve the flooding problem in this area it is recommended that an aboveground infiltration basin be used. This area is in a less developed area, therefore an aboveground infiltration basin would be more cost effective. The presence of utility easements will have to be taken into account during design. Utility maps will have to be obtained prior to design. The recommended option would be to investigate the purchase of a tract of the undeveloped land in the immediate area. Roadside drainage swales could be used to convey the ' runoff to the infiltration basin area. If purchase of land in this area is determined not to be an option, underground infiltration trenches would be recommended. ' Although it is not as critical in aboveground construction, it is recommended that some type of oil/grit trap be constructed to pretreat the runoff before it enters the basin. The size of the oil/grit chamber will be dependent on the size of the area draining to the inlet. ' The size of infiltration facility will have to be determined through hydraulic and hydrologic (H & H) modeling -of the area. A detailed survey of the area is also necessary prior to completion of the modeling ' efforts. To reduce the amount of stormwater runoff which reaches the street, and the Town's storm dram system, ' URSGWC recommends that the Town encourage its residents to reduce the amount of impervious surface on their lots and direct stormwater runoff (from rooftops and other impervious surfaces) to vegetated areas, instead of directly off their property and into the street. A recommended stormwater ordinance that will assist in accomplishing this is included in Appendix A. Depending on the method of funding of the Town's Stormwater Management Program (Section 5.5), the Town may want to offer fee/tax credits for residents constructing french drains or infiltration areas for runoff from impervious surfaces on their lots. (This would be applicable with a stormwater utility or stormwater fee/tax). Through evaluation of various BMPs, infiltration with a stormwater ordinance was determined to be the most cost effective, applicable, and effective at solving the flooding problems in the area. With ' cooperation from the public, this is an implementable BMP. As long as the infiltration system is maintained, it is a reliable stormwater BMP. There are no negative environmental impacts associated with an infiltration system in this area. Public education will be necessary to inform the residents of the ' need for the system, how the system will solve the flooding problem, and what they need to do to comply with the stormwater ordinance (if adopted by the Town). ' Craven Street There is minor flooding that occurs along Craven Street. This flooding condition causes a safety hazard for pedestrians and motorists, especially if the water extends into the travel lanes. ' There are a few storm drain inlets, although it appears that many of them may be outside the right of way and on private property. Many of these do not appear to be effective due to the grading of the surface. ' In order to solve the flooding problem in this area it is recommended roadside swales be constructed. The presence of utility easements will have to be taken into account during design. Utility maps will have to be obtained prior to design. 06/29/00 4-12 CHAPTER FOUR OCEAN ISLE BEACH ' WATERSHED CHARACTERISTICS STORMWATER MASTER PLAN ' The size of the roadside swales will have to be determined through hydraulic and hydrologic (H & H) modeling of the area. A detailed survey of the area is also necessary prior to completion of the modeling efforts. ' To reduce the amount of stormwater runoff which reaches the street, and the Town's storm drain system, URSGWC recommends that the Town encourage its residents to reduce the amount of impervious surface on their lots and direct stormwater runoff (from rooftops and other impervious surfaces) to vegetated areas, instead of directly off their property and into the street. A recommended stormwater ordinance that will assist in accomplishing this is included in Appendix A. Depending on the method of funding of the Town's Stormwater Management Program (Section 5.5), the Town may want to offer fee/tax credits for I residents constructing french drains or infiltration areas for runoff from impervious surfaces on their lots. (This would be applicable with a stormwater utility or stormwater fee/tax). Through evaluation of various BMPs, roadside swales with a stormwater ordinance were determined to be the most cost effective, applicable, implementable and effective at solving the flooding problems in the area. As long as the swale system is maintained, it is a reliable stormwater BMP. There are no negative environmental impacts associated with roadside swales in this area. Public education will be necessary to ' inform the residents of the need for the system, how the system will solve the flooding problem, and what they need to do to comply with the stormwater ordinance (if adopted by the Town). ' Leland Street There is minor flooding that occurs along Leland Street. This flooding condition cause a safety hazard for pedestrians and motorists, especially if the water extends into the travel lanes. There are a few storm drain inlets, although they are insufficient for the area. Many of these do not appear to be effective due to the grading of the surface. In order to solve the flooding problem in this area it is recommended roadside swales be constructed. The presence of utility easements will have to be taken into account during design. Utility maps will have to ' be obtained prior to design. The size of the roadside swales will have to be determined through hydraulic and hydrologic (H & H) ' modeling of the area. A detailed survey of the area is also necessary prior to completion of the modeling efforts. To reduce the amount of stormwater runoff which reaches the street, and the Town's storm drain system, ' URSGWC recommends that the Town encourage its residents to reduce the amount of impervious surface on their lots and to direct stormwater runoff (from rooftops and other impervious surfaces) to vegetated areas, instead of directly off their property and into the street. A recommended stormwater ordinance that ' will assist in accomplishing this is included in Appendix A. Depending on the method of funding of the Town's Stormwater Management Program (Section 5.5), the Town may want to offer fee/tax credits for residents constructing french drains or infiltration areas for runoff from impervious surfaces on their lots. (This would be applicable with a stormwater utility or stormwater fee/tax). Through evaluation of various BMPs, roadside swales with a stormwater ordinance were determined to be the most cost effective, applicable, implementable and effective at solving the flooding problems in the area. As long as the swale. system is maintained, it is a reliable stormwater BMP. There are no negative environmental impacts associated with roadside swales in this area. Public education will be necessary to 06/29/00 4-13 CHAPTER FOUR OCEAN ISLE BEACH ' WATERSHED CHARACTERISTICS STORMWATER MASTER PLAN inform the residents of the need for the system, how the system will solve the flooding problem, and what ' they need to do to comply with the stormwater ordinance (if adopted by the Town). Concord Street Wilmington Street Fairmont Street, Monroe Street, and Lattrinburz Street ' There is minor flooding that occurs along Concord Street, Wilmington Street, Fairmont Street, Mon roe Street, and Laurinburg Street. These flooding conditions cause a safety hazard for pedestrians and motorists, especially if the water extends into the travel lanes. ' There are a few storm drain inlets and some roadside swales, although there are not a sufficient number of storm drain inlets. Many of the roadside swales do not appear to be effective due to the grading of the surface around them, and several residents have built wooden "boxes" around many of the swales, ' presumably for landscaping purposes. This is preventing any runoff from entering the swales. In order to solve the flooding problem in this area it is recommended the roadside swales be reconstructed and improved. In many areas these swales have become deep "ditches". Also, many of the driveway culvert pipes are blocked and/or destroyed. The presence of utility easements will have to be taken into account during design. Utility maps will have to be obtained prior to design. The size of the roadside swales will have to be determined through hydraulic and hydrologic (H & H) ' modeling of the area. A detailed survey of the area is also necessary prior to completion of the modeling efforts. ' To reduce the amount of stormwater runoff which reaches the street, and the Town's storm drain system, URSGWC recommends that the Town encourage its residents to reduce the amount of impervious surface on their lots and direct stormwater runoff (from rooftops and other impervious surfaces) to vegetated ' areas, instead of directly off their property and into the street. A recommended stormwater ordinance that will assist in accomplishing this, is included in Appendix A. Depending on the method of funding of the Town's Stormwater Management Program (Section 5.5), the Town may want to offer fee/tax credits for ' residents constructing french drains or infiltration areas for runoff from impervious surfaces on their lots. (This would be applicable with a stormwater utility or stormwater fee/tax). Through evaluation of various BMPs, roadside swales with a stormwater ordinance were determined to be ' the most cost effective, applicable, implementable and effective at solving the flooding problems in the area. As long as the swale system is maintained, it is a reliable stormwater BMP. There are no negative environmental impacts associated with a roadside swale system in this area. Public education will be ' necessary to inform the residents of the need for the system, how the system will solve the flooding problem, and what they need to do to comply with the stormwater ordinance (if adopted by the Town). 4.3.2 Water Quality Although water quality in the Ocean Isle Beach area is better than some of the surrounding areas, it is of critical importance that the quality of the stormwater runoff be improved in order to not only prevent the degradation of the water quality in the area, but to improve the water quality. Improvement in the quality of the stormwater runoff may make it possible to see openings in previously closed shellfishing waters. The above described BMP facilities (along with the stormwater ordinance and a public education program) will also help reduce the amount of pollution in the stormwater runoff, thus improving water quality in the estuaries. 06/29/00 4-14 ' CHAPTER FOUR OCEAN ISLE BEACH WATERSHED CHARACTERISTICS STORMWATER MASTER PLAN 4.3.3 Operation and Maintenance During the field inspection of the system, several inlets were covered with dirt and debris and many of the ' roadside swales were blocked and/or filled. In particular, on several of the canal streets, wood has been placed around several of the swales (for landscaping or similar reason), which blocks water from the roadway and other impervious surfaces from flowing into the swale. Most of the inlets and pipe systems ' are in need of maintenance and pumping to remove sand buildup. Additionally, all storm drain inlets should be inspected and cleaned at least once a year, and/or after each major storm. Prior to implementation of any of the above actions, an inspection of the existing system, to include determining the length of all pipes, should be completed. This will determine if any of the existing system can be used in conjunction with new systems. ' Major ditches should be identified and put into an inventory system for future maintenance tracking. Regular monitoring and maintenance of all components of the storm drain system is recommended to prevent problems. ' It is also recommended that the Town investigate purchasing or leasing a vacuum system for cleaning out storm drain pipes and the infiltration systems. Roadside swales should be periodically cleaned of debris and mowed. Vegetation is critical for infiltration and pollutant removal, but excessive vegetation will block flow. Table 4-2 Recommendations Ocean Isle Beach W Location . Problem Descri tion Recommended Action First Street east end Flooding Underground Infiltration First Street at Private Drive Flooding Underground Infiltration First Street between Shelby Street and Troy Street Flooding Underground Infiltration First Street from Driftwood Drive to the west Town limit Flooding Subsurface Retention or Roadside Swales Second Street at Scotland Street Flooding Subsurface Retention or Roadside Swales Second Street between Lee Street and Goldsboro Street Flooding Subsurface Retention Second Street at Sanford Street Flooding Underground Infiltration Second Street between Charlotte Street and Shallotte Blvd. Flooding Subsurface Retention Third Street at Columbia Street Flooding Aboveground Infiltration Basin Craven Street Flooding Roadside Swales Leland Street Flooding Roadside Swales Concord Street, Wilmington Street, Fairmont Street, Monroe Street, and Laurinburg Street Flooding Roadside Swales 06/29/00 4-15 A7C-0+� z J ABBL r OAL C H I E•ISt yL1.. PEA V pro q li A l / 7R. '1 I / N I R A C D a S T 4 l r A l E R r A r • � ^—� ... `--._ ... - .. I — — � — — -- IOW L lYl 75 � � f 1. BAYBERRY ORIVE JJ. INDIGO COURT 1 ��'•, •'�� "I I� 1• BARNACLE COURT JUNIPER CQwI 3. SA/YER COURT 15. OLEANDER LANE 4. HERON COURT /6. CHANNEL ORIVf UR'� -�~'' U .•.0 ; 5. OOLPION COT 77. OLOE COURT S. SCHOONER ORIrE 18. COOU/NA COURT /1 7. PfLICAN COURT 19. ATLANTIC rAr __ / I �•-- /• 8. SANDPIPER COURT ?0. WINDY COURT 9. EGRET COURT ?r. SPINARER COURT ??. TEAL CLWT70. EACOURT ?SWLi CDURT/I \ 1J. SEABROOtt ROAD I?. YrRTLf COURT ?I. WARBLER COURT \ •,•� / - - _ _ / 1 f \/I i E4 \•'• Eq 19• PP' H T FOURTH STREET _ r A L / 10. _ ... 9. t8• ----... mM'S /w bNL t/AMMtl N nl Y Y y Oa[S/Of rNLAS sfsT n+lao s r 1. 6 1. ?J. ' g �� J. 4. 5• 1 '�' ?�. WSr SECOND STRf[T ? ff=E N .Esr FI sr r m 75. 76.11 IAr C C Im Ap7L fAVD v LL• C5� 0.0 ]Clop .- tu0 r"," Sr.0 r [AS w MIS Wp tIK LASRL Sup VILLAS Sf 1 - II FLAK • SAG 1-II I• ... ... ... ... 500 0 500 1000 1500 GRAPHIC SCALE LEGEND Irm EXISTING STORM DRAIN -=-- EXISTING STORMWATER CHANNEL W/ OUTFALL - - - - - - TOWN LIMITS c CAMA BEACH ACCESS T I C IAAm QW FIGURE 4-1 Lit YC/A(NSl.QQ . I � eP�• Ct. W �u ! ! � flOfrATfR y PD�pt ✓...---�_...� 1 aT N I � I/MI CWSIu ORIVf / a 7r157 0 \ \ AC 'T4rb C ff C,p�rfA, C/ r A 7 E R V A Y fOW L lul 7S _ CRAYfq SlRffl IIA I I I �N I Li r r Qz fAsr slxrH N Asr 0 A ?� Sr � /h �--r� SJREfr ... ... ... .. .. -- 0 C E A N 500 0 500 1000 1500 GRAPHIC SCALE TOWN OF OCEAN ISLE BEACH STORMWATER MASTER PLAN EXISTING STORM DRAINAGE SYSTEM FIGURE 4-1 URS Greiner Woodward Clyde J � � A`2''�E V 0� A Y DAL E �+ I E4 , �`PL A -' q14 ti R If JR. 1 • I N r R A C 0 A S r A L WA r E R WA Y I NI rs I r. BAYBERRY DRIVE 1J. INDIGO COURT �'•, �� a. BARNACLE COURT 11. JUNIPER COURT J. 591)"R CO7R! /s. O[EANOER LANE 1y' 1. HERON COA41 76. CHAA►L DIVE •� •��•' r/ ; s. DOLPHIN COURT 17. DONE COURT� I •\. 1/ 6. SCfIWWR DRIVE f8. COQUINA COURT 7. PELICAN COURT 19• ATLANTIC MAY __•/ I �• J 8. SANDPIPER COURT a0. r/NOY COURT I\ < 9. ECRET COURT 11. SPIWER COURT \ --/� _ I •—.�--- � •- lo. FERN COURT ??. TEAL COURT \\\ •\ : 11. SEABROOK ROAD ?J. 51sEtt COURT 12. MYRTLE COURT 2 rARBL ER COUPI J - - - / \'•, E A jO `�.. CN A 1, yW� )9. ??. 1—` 1 (DURUM 51` N E L / to. iB. is �...�— .. 9• srWuson rr sr ti A.rs/a vnru IEsT THIRD SrRU�s■.oNr ?A. rts! SECDvO 57REFT / ^ V+ ST SEC STR£Er LIO s!a Lasnr 500 0 500 1000 1500 GRAPHIC SCALE R.C[ • K� 1-I I LEGEND ® EXISTING STORM DRAIN EXISTING STORMWATER CHANNEL W/OUTFALL %t FLOODING PROBLEM AREAS - - - - - - TOWN LIMITS c CAMA BEACH ACCESS N SI FI SiREE! m N C Ir 41Nt 010 ""o DaM, fW VAAAS rib r /Af WO riu.s QQ 58 A T L A N T FIGURE 4-2 Lit LJ LYC/A LH. SI. D e Q h TWIVArfR Mor : W 7 DRIVECDASrAt DR Os, 0, � C C't'E'FA• CrR � W A C 0 A A( I Of ��'.• �_• ��, L, _ . �_ \ ` ` \ vAnE ROAD ------ / J \ ���,,� CRAVE" SWEI 'LTs_ _ _�" •`._... .�� J "' IA I I I I� I I!W I I� I I� I I� I� i I� I � I I� I� I I� I" I` •/ �\�� Vr Q r W z J U Q m C E A N 500 0 500 1000 1500 GRAPHIC SCALE MEN `a a r r �U ASr r EAST S/XTH J F/vrH sr $T r / vl If��_-���I,1 �������ii�"'' � �, Lear" 5T fr �' J� �-•� �Q A SEC SrH/ SrRffr v0 • rgL•fl t� ... °tttc •� ::.sic; � ... ... TOWN OF OCEAN ISLE BEACH STORMWATER MASTER PLAN STORMWATER AREAS OF CONCERN FIGURE 4-2 URS Greiner Woodward Clyde 7 ' CHAPTER FIVE STORMWATER OCEAN ISLE BEACH MANAGEMENT PROGRAM STORMWATER MASTER PLAN The recommendations presented in Chapter Four are summarized in this Chapter. Some of the recommendations should be implemented as Capital Improvement Program (CIP) projects which are ' prioritized using the criteria described in Section 5.2. Recommendations for minor repair and maintenance should be made part of the Town's operating budget. Recommended policy changes may or may not have budget implications. 5.1 RECOMMENDATION SUMMARY Costs for the recommendations were estimated (order of magnitude) and are shown in Table 5-1. The ' total estimated cost for all CIP projects is approximately $1,055,000 (plus potential land costs for some items). It should be noted that these are only estimates. Surveying and H & H modeling is necessary to determine more precise estimates on sizes of facilities, length of pipe, etc. Whether the Town can obtain ' land needed for several of the projects is also a factor. Therefore, these costs should only be looked at as order of magnitude given the recommendations presented in Chapter Four. 5.2 PROJECT SELECTION CRITERIA The project selection criteria were used to evaluate which recommended projects are the most crucial and should be implemented first in the Capital Improvement Program. The following criteria were used: • Safety • Quantity Benefits • Quality Benefits Safety ' This criterion is for projects that maintain safe travelways during rain storms and protect against property damage from flooding. The safety benefits are apparent from the nature of the project. Quantity Benefits Problems that are caused by increased runoff volumes and peak discharges include sedimentation of estuaries and storm drain system components, increased maintenance, erosion and flooding problems. Quantity problems may be due to existing development or potential problems due to planned development may be averted with recommended projects. Quality Benefits ' The amount of water quality benefits are not easily determined for each project. Problems caused by poor water quality include increased sediment loading, algae blooms caused by excess pollutants in the runoff, loss of plant life due to pollutants, and loss of fishing, shellfishing, and other recreation due to pollutants. ' Projects which improve the quality of stormwater runoff will help protect and improve the quality of water in the canals and the AIWW. Table 5-1 lists the project selection criteria as well as the rankings of each proposed project. 06/19/00 5-1 1 I ll 1 CHAPTER FIVE STORMWATER OCEAN ISLE BEACH MANAGEMENT PROGRAM STORMWATER MASTER PLAN Table 5-1 Project Selection Criteria and Ranking Ocean Isle Beach Evaluation Criteria , ... " Overall., "''Problem,.,. Project. ,Recommend e ", ' Quantity 'Quality Location Descri tion SafeBenefits Benefits Rankin . Action , First Street (east Flooding 1 1 2 1 Underground end) Infiltration First Street at Underground Private Drive Flooding 2 2 8 2 Infiltration First Street Underground between Shelby Flooding 3 5 10 7 Infiltration Street and Troy Street First Street from Subsurface Driftwood Drive Flooding 9 8 11 11 Retention or to the western Roadside Swales Town limit Second Street at Subsurface Scotland Street Flooding 6 10 5 8 Retention or Roadside Swales Second Street between Lee Flooding 7 11 6 9 Subsurface Street and Retention Goldsboro Street Second Street at Underground Sanford Street Flooding 4 7 7 5 Infiltration Second Street between Flooding 8 12 12 12 Subsurface Charlotte Street Retention and Shallotte Blvd. Third Street at Aboveground Columbia Street Flooding 5 3 9 4 Infiltration Basin Craven Street Flooding 10 6 3 6 Roadside Swales Leland Street Flooding 11 9 4 10 Roadside Swales Concord Street, Wilmington Flooding 12 4 1 3 Roadside Swales Street, Fairmont Street, Monroe Street, and Laurinburg Street Ranking: 1=highest; 12=1owest. 06/21/00 5-2 CHAPTER FIVE ' STORMWATER OCEAN ISLE BEACH MANAGEMENT PROGRAM STORMWATER MASTER PLAN 5.3 CAPITAL IMPROVEMENT PROGRAM Inadequate system capacity is the biggest water quality and water quantity problem requiring capital improvements. Table 5-1 describes the capital improvement actions that have been recommended, and the recommended order of project implementation. The implementation priority was determined based ' upon the ranking of the project with regard to the project evaluation criteria described in Section 5.2. Surveying and modeling of the area is considered a top priority in order to determine the size and amount of improvements that need to be done to fix problem flooding areas. Stormwater modeling is briefly described below. ' Water Quantity Modeling Stormwater quantity is modeled to predict flooding problems and analyze drainage system capacity and hydraulic performance. A detailed hydrologic and hydraulic computer model is suited for the analysis of ' a large drainage area that links runoff hydrographs from smaller subdrainage areas. Simpler models are available to use for specific design calculations such as culverts, drop inlets, site drainage systems, etc. Water Quality Modeling Specific modeling objectives need to be defined in order to guide the work effort. Not every water quality problem needs to be modeled in order to characterize the problem or find a solution. Measured data is usually preferred in characterizing the problem. Water quality modeling can be used for reasons such as: • to determine the total maximum daily load (TMDL) to a waterbody • to help determine location and type of BMP strategies which are most effective • to analyze specific problems such as eutrophication of a lake or sediment loadings to a stream One of the watershed planning issues that could be analyzed with a model is the reduction of existing nonpoint source pollutant loadings and prevention of future additional nonpoint source pollutant loadings. This issue will use modeling as a tool to make policy decisions regarding land use controls and to provide information regarding a regional BMP program and regional riparian buffer program. The type of water quality modeling software chosen will depend on the particular objective to be achieved and the characteristics of the waterbody to be modeled. The estimated costs for the action items are preliminary, order of magnitude costs. The scheduling of these action items is dependent upon the Town's financing needs and methods. Funding options are ' described in Section 5.5. 5.4 OPERATION AND MAINTENANCE PROGRAM ' A planned program of storm drain inspections, and minor cleaning, a planned program of ditch cleaning, and a planned program of infiltration system inspection should be implemented. A work order process and form should be developed to track work progress and to record maintenance work for overall program success. I 1 06/19/00 5-3 C 1 CHAPTER FIVE STORMWATER OCEAN ISLE BEACH MANAGEMENT PROGRAM STORMWATER MASTER PLAN Maintenance costs will be dependent'on the length of pipe, length of roadside swales, number of drop inlets, and size of infiltration facilities. A few estimates for maintenance costs are approximately $1.00 per linear foot for cleaning ditches and pipes (assuming Town personnel and equipment), approximately $40-$75 per inlet for cleaning (depending on size), and approximately $1,000 per year to clean each infiltration facility (each facility will vary with size and type). It is recommended that the Town purchase a vacuum truck for cleaning pipes and infiltration facilities. The Town should also investigate the use of the spoil areas used by the Corps of Engineers for dredge spoils as a place to dispose of sediment from the pipes and inlets. Other beach towns have used this sediment for beach renourishment. Both these actions would require permitting. 5.5 FUNDING The amount necessary to fund these projects can come from several sources. The costs estimated for the action items are preliminary, order of magnitude amounts. Taxes The Town could raise property taxes to fund part or all of the program. The public usually does not respond well to this option. A dedicated millage would require a referendum, which may be difficult to sell to the public. A dedicated millage would mean that the Town could depend on a certain amount year to year being committed to a planned program of operation and maintenance (O & M) and replacement and improvements. Stormwater Utility An independent tax authority, or the creation of a stormwater utility, could be established to collect stormwater fees. A service rate study would need to be performed to critically evaluate the charges and fees, and to distribute the costs of the Stormwater Management Program proportionately among the users. The costs of the Stormwater Management Program include: administration including overhead, customer billing, customer complaint response, ditch and pipe cleaning, illicit discharge investigation, site plan review, public education, and capital improvement program. Many localities divide the total costs by the amount of impervious area in their service area to calculate a ' unit cost. An equivalent residential unit (ERU), which is the average amount of impervious area for a single family residence, is used as the billing unit. Non-residential property owners are billed according to the number of ERUs equivalent to the total impervious area on their property. ' Utility Credits A utility credit is a reduction in the stormwater utility fee for a property. It is given because of a drainage ' system improvement located on the property which causes a reduction in pollutants and/or a reduction in the peak flows and volumes leaving the property. It can be used as an incentive for voluntary construction of BMPs. The reasons and benefits of a utility credit program need to be established before ' it is implemented. Is the credit program perceived as necessary for public acceptance of the utility charges? Will it be perceived as enough of an incentive for voluntary implementation of BMPs and riparian buffers? An example of a stormwater utility credit application instruction manual from the City of Charlotte is provided in Appendix C. ' The implementation of a BMP or buffer used to receive credit will reduce some of the cost to the Town for construction of a similar facility for a water quantity/quality benefit. However, some portion of the 06/29/00 5-4 CHAPTER FIVE STORMWATER OCEAN ISLE BEACH MANAGEMENT PROGRAM STORMWATER MASTER PLAN utility charge should be retained for those properties with credits in order to receive revenue for on -going program needs such as administration, system operation and maintenance, and inspection of on -site facilities. The loss of long-term revenue due to the credit program should not unfairly cause a burden to other customers without credits by making them pay more than their share of costs. Grants and Loans ' There are several sources that the Town can apply to for grants and low interest loans. Due to the location of the Town, and its sensitive environment, the Town should have a good chance at receiving a variety of grants. Some of these programs include: • Clean Water Management Trust Fund • Clean Water Act Section 319 Grants • Small Watershed Program Grants • State Construction Grants and Loans These possible sources of additional funding will need to be evaluated by the Town to establish policy on additional funding methods. Table 5-2 Capital Improvement Program Ocean Isle Beach Location Action Description Estimated Cost First Street (east end) Underground Infiltration $400,000+ land if needed First Street at Private Drive Underground Infiltration $50,000+ land if needed First Street between Shelby Street Underground Infiltration $75,000+ land and Troy Street First Street from Driftwood Drive Subsurface Retention or $40,000 to the western Town limit Roadside Swales Second Street at Scotland Street Subsurface Retention or $30,000 Roadside Swales Second Street between Lee Street Subsurface Retention $50,000 and Goldsboro Street Second Street at Sanford Street Underground Infiltration $50,000+ land Second Street between Charlotte Subsurface Retention $50,000 Street and Shallotte Blvd. Third Street at Columbia Street Aboveground Infiltration $130,000+ land Basin Craven Street Roadside Swales $40,000 Leland Street Roadside Swales $30,000 Concord Street, Wilmington Roadside Swales $40,000 each street Street, Fairmont Street, Monroe Street, and Laurinburg Street 1 06/29/00 5-5 1 n 1 J CHAPTER SIX OCEAN ISLE BEACH REFERENCES STORMWATER MASTER PLAN Arnold, J.A., ed., D.E. Line, S.W. Coffey, and J. Spooner. 1993. Stormwater Management Guidance Manual. North Carolina Cooperative Extension Service and North Carolina Division of Environmental Management. Raleigh, NC. Center for Watershed Protection and Land Ethics, Inc. Blueprint to Protect Coastal Water Quality. A Guide to Successful Growth Management in the Coastal Region of North Carolina, Prepared for the Neuse River Council of Governments and the North Carolina Division of Environmental Management. Environmental Protection Agency. 1995. Watershed Protection: A Project Focus. Washington, DC: Office of Wetlands, Oceans, and Watersheds. 1997a. Designing an Information Management System for Watersheds. Washington, DC: Office of Wetlands, Oceans, and Watersheds, Office of Wastewater Management and Office of Water. 1997b. Top 10 Watershed Lessons Learned. EPA 840-F-97-001. Washington, DC: Office of Water and Office of Wetlands, Oceans, and Watersheds. North Carolina Department of Environment and Natural Resources. 1998. Basinwide Assessment Report — Lumber River Basin. Environmental Sciences Branch. 1999. Lumber River Basinwide Water Quality Plan. Raleigh, NC: Division of Environmental Management. A Guide to Protecting Coastal Resources Through the CAMA Permit Program. Raleigh, NC: Division of Coastal Management. Town of Ocean Isle Beach. 1997. CAMA Land Use Plan Update. Ogden Environmental and Engineering Services, Inc. 1994. City of Charlotte Storm Water Services Credit Application Instruction Manual. Charlotte, NC: City of Charlotte Stormwater Services. US Department of Agriculture. 1986. Soil Survey of Brunswick County, North Carolina. Soil Conservation Service. 06/19/00 6-1 APPENDIX A Draft Stormwater Management Ordinance C1 DRAFT 1 Section 1. STORMWATER MANAGEMENT ORDINANCE Title Ratification Number: XXXXXXX This document may be cited as the Town of Ocean Isle Beach's Stormwater Management Ordinance for implementation within Town limits. Section 2. Goals and Purposes The central environmental goal of the Town of Ocean Isle Beach is to preserve water quality and the natural ecological functions of the surface water located within the Town limits. In order to meet this important goal, the Town of Ocean Isle Beach Stormwater Ordinance will be adopted for the following purposes: a) To regulate existing developments, new developments, and construction activities consistent with State of North Carolina requirements and the Town of Ocean Isle Beach's requirements. b) To establish the authority of the Town of Ocean Isle Beach to administer and enforce stormwater quantity and quality regulations including limiting impervious surface, improvements on redevelopment and landscaping requirements. c) To create public education programs so the citizens of the Town will have knowledge of how to reduce and prevent pollution of all nature from their land, homes, and businesses. Section 3. Definitions and Abbreviations Used Within This Ordinance For the purposes of this ordinance, the following listed terms and phrases shall have these definitions: Alphabetical Listing a) Agricultural Land Management Practices shall mean those methods and procedures used in cultivation of land in order to further crop and livestock production and conservation of related soil and water resources. b) Area of Environmental Concern shall mean an area identified by the State of North Carolina Coastal Resources Commission as environmentally fragile and economically important where uncontrolled or incompatible development could result in irreversible damage. c) Built -Upon Area shall mean that portion of an individual development project that is covered by impervious or partially impervious cover including buildings, Town of Ocean Isle Beach 1 Draft Stormwater Management Ordinance ' DRAFT ' pavement, recreation facilities, roads and parking areas, etc. Wood slatted decks and the water area of a swimming pool are not considered to be built -upon area. d) BMP shall mean Best Management Practices as adopted by the Town of Ocean Isle Beach. te) CAMA shall mean Coastal Area Management Act, which was adopted by North Carolina in 1974. The Act established a comprehensive regional resource management program for the state's 20-county coastal area. The management program that has evolved since 1974 in North Carolina has land use planning, regulatory, land acquisition, and policy development components. f) CAMA Major Development Permit shall mean the permit required by the Coastal Resources Commission for developments that infringe on Areas of Environmental Concern. g) Coastal Wetland shall mean any salt marsh or other marsh subject to regular or occasional flooding by tides, including wind tides (whether or not the tide waters reach the marshland areas through natural or artificial watercourses), provided this shall not include hurricane or tropical storm tides. Coastal wetlands contain some, but not necessarily all, of ten indigenous wetland plant species. Included in this definition of coastal wetlands is "such contiguous land as the Secretary of the North Carolina Department of Environment and Natural Resources (NCDENR) reasonably deems necessary to affect any such order in carrying out the purposes [of the regulations]." (G.S. 113-230(a)). h) Customer shall mean the person or firm to which a bill for stormwater management services is sent. i) Development shall mean any land disturbing activity that increases the amount of built -upon area or that otherwise decreases the infiltration of precipitation into the soil. j) Erosion shall mean the wearing away of land surface by the action of wind, water, gravity or any combination thereof. ' k) Erosion and Sediment Control Plan shall mean a written plan including drawings or other graphic representations for the control of soil erosion and sedimentation resulting from a land disturbing activity. 1) Estuarine Shoreline shall mean a non -ocean shoreline connected to the estuarine waters that are especially vulnerable to erosion, flooding, and other adverse effects of wind and water. Estuarine shorelines extend from the mean high water level (in areas of tidal influence) or normal water level (in areas without tidal influence) along the estuaries, sounds, bays, and brackish waters for a distance of 75 feet landward unless otherwise set by the Coastal Resources Commission. 1 Town of Ocean Isle Beach 2 Draft Stormwater Management Ordinance ' FT DRA m) Estuarine Waters shall mean all the water of the Atlantic Ocean within the boundary of North Carolina and all the waters of the bays, sounds, rivers, and tributaries thereto seaward of the dividing line between coastal fishing waters, as set forth in the most recent official published agreement adopted by the Wildlife Resources Commission and NCDENR. n) Existing Development shall mean any land that has been utilized for a land - disturbing activity as of the effective date of this ordinance. o) Health Department shall mean the Brunswick County Health Department or the North Carolina State Board of Health depending on jurisdiction. p) Illegal Discharge shall mean any direct or indirect non-stormwater discharge to the storm drain system except as defined in Section 9.1. q) Illicit Connections shall mean either of the following: (1) Any drain or conveyance, whether surface or subsurface, which allows an illegal discharge to enter the storm drain system including but not limited to and conveyances which allow any non-stormwater discharge including sewage, process wastewater, and wash water to enter the storm drain system and any connections to the storm drain system from indoor drains and sinks, regardless of whether said drain or connection had been previously allowed, permitted, or approved by a government agency; or (2) Any drain or conveyance connected from a commercial or industrial land use to the storm drain system which has not been documented in plans, maps, or equivalent records and approved by the Town r) Impervious Surfaces shall mean those areas within the land of the Town which prevent or significantly impede the infiltration of water into the soil. Common impervious surfaces include, but are not limited to, roof tops, sidewalks, walkways, patio areas, driveways, parking lots, storage areas, brick or concrete pavers and other surfaces that prevent or significantly impede the natural infiltration of water into the soil. s) Improved Lands for the purposes of this Ordinance shall mean any lands that have had land disturbing activities that altered or changed the natural cover or topography of said land. t) Infiltration System shall mean a stormwater treatment system designed to allow runoff to pass or move (infiltrate) into the soil. u) Land Disturbing Activity shall mean any use of the land by any person in residential, industrial, educational, institutional or commercial development, highway and road construction and maintenance that results in a change in the natural cover or topography and that may cause or contribute to sedimentation. i Town of Ocean Isle Beach 3 Draft Stormwater Management Ordinance DRAFT v) New Development shall mean any land that is utilized for a land -disturbing activity after the effective date of this Ordinance. iw) NCAC shall mean the North Carolina Administrative Code. ' x) North Carolina Coastal Resources Commission shall mean the state policy -making organization with responsibility for the coastal region. y) NPDES shall mean the National Pollutant Discharge Elimination System permitting process of the Environmental Protection Agency (EPA). z) Ocean Hazard Area shall mean an area where there exists a substantial possibility of excessive erosion and shoreline fluctuation. The seaward limit of this boundary is the mean low water line. aa) Town shall mean that area within the Ocean Isle Beach Town limits. bb) Redevelopment shall mean any rebuilding activity that exceeds 50% of the tax value of the structure, and that has no net increase in built -upon area or that provides equal or greater stormwater controls than the previous development. cc) SA Waters shall mean tidal saltwater of the highest quality that are suitable for commercial shell fishing, swimming, and all other tidal saltwater uses. The chloride concentration of SA waters must be at least 500 parts per million. dd Sedimentation shall mean the deposition of solid material both mineral and organic, that has been transported from its site of origin by air or water. ee) Sedimentation/Erosion Control Plan shall mean a plan required by the Division of Land Resources in which developers must describe the sedimentation and erosion control devices they will use for land disturbing activities that are one acre or greater. ff) Sewerage or Septage shall mean the liquid and solid human body waste and liquid waste generated by water -using fixtures and appliances including those associated with food handling. Stormwater shall mean the flow of water that results from reci itation and that gg) p P occurs immediately following rainfall or a snowmelt. hh Stormwater Collection System shall mean an conduit, pipe channel, curb or gutter y Y Pp utilized for the primary purpose of transporting (not treating) runoff. ' ii SWMP is the Stormwater Management Plan for the Town of Ocean Isle Beach. J) State Certification shall mean one or more of the following documents: a CAMA permit application and accompanying CAMA permit from the Division of Coastal Management, a Stormwater certification or permit, as required, from the Division Town of Ocean Isle Beach 4 Draft Stormwater Management Ordinance ' DRAFT ' of Environmental Management, and/or a Sedimentation and Erosion Control Plan that has been approved by the Division of Land Quality. tkk) Surface Waters shall mean rivers, streams, creeks, channels, lakes, reservoirs, ponds, drainage systems, springs, wetlands, wells, the Atlantic Ocean, and other bodies of surface or subsurface water, natural or artificial, lying within or forming part of the boundaries of the Town. This term excludes privately owned ponds that have no entry or exit of water to or from waters of public domain. 11) Unimproved Land for the purposes of this Ordinance shall mean any land that has not had land disturbing activities as described herein. min) 10-Year, 24-Hour Storm shall mean the storm of the largest intensity expected to occur on the average once every 10 years and of a 24-hour duration. nn) 2-Year. 24-Hour Storm shall mean the storm of the largest intensity expected to occur on the average once every 2 years and of a 24-hour duration. oo) Vegetative Filter shall mean an area of natural or planted vegetation through which stormwater flows in a diffuse manner so that runoff does not become channeled and that provides for control of stormwater runoff through infiltration or filtering of pollutants. The defined length of the filter shall be provided for the direction of stormwater flow. pp) Wet Detention Pond shall mean a structure that provides for storage and treatment of runoff and includes a permanent pool of water under normal circumstances. Section 4. Jurisdiction The regulations contained herein shall govern all real property and each and every ' stormwater quantity and quality management device within the approved Town Limits of Ocean Isle Beach. Whenever conflicts exist among federal, state, or local laws and this ordinance, the more restrictive provision shall apply. Section 5. Findings 1 a) The Town of Ocean Isle Beach finds evidence that the development and implementation of a reliable SWMP to best serve the citizens of the Town will require that all sources of pollution that are carried with stormwater runoff be identified, quantified and analyzed to implement an effective SWMP pollution control and abatement plan to protect the surface and groundwater's within the Town; and 1 b) The Town of Ocean Isle Beach needs to affirm its responsibility and enhance its capability to maintain existing water quantity and quality management facilities of all natures in the Town and establish future water quantity and quality management facilities and measures that will ensure that as growth occurs and the population density increases, the Town's sensitive environment and ecosystems are protected for future generations. Town of Ocean Isle Beach 5 Draft Stormwater Management Ordinance I DRAFT ISection 6. Scope of the Ordinance This Ordinance shall apply to all real property within the jurisdiction of the Town of Ocean Isle Beach. a) All property owners and managers should give specific attention to the recommendations set forth in the General Water Quality Protection Recommendations (Section 7) of this Ordinance. b) All property owners, regardless of their previous practices, shall be subject to the regulations listed under Section 8, Landscaping/Buffer Requirements. c) All property owners, regardless of their previous practices, shall be subject to the regulations listed under Section 9, Discharge Prohibition. d) All property owners, regardless of their previous practices, shall be subject to the regulations listed under Section 10, Mandatory Standards for Existing Development. e) All new developments, regardless of its size, shall be subject to the regulations listed under Section 11, Mandatory Standards for New Developments. f) All redevelopment activities shall be subject to the regulations listed under Section 12, Mandatory Standards for Redevelopment. g) All construction activities, whether for new development or improvements on existing development, shall be subject to the regulations set forth under Section 13, Mandatory Standards for Construction Activities. Section 7. General Water Ouality Protection Recommendations a) All visitors, residents, business owners, developers, and others who utilize the resources within the Town of Ocean Isle Beach shall take all reasonable measures to protect surface waters from damage resulting from their activities. Section 8. Landscapin2/Buffer Requirements Buffer zones shall be established in accordance with the Coastal Resources Commission Shoreline Buffer Rules. The Town of Ocean Isle Beach has established additional guidelines for the management of these buffers. Failure to comply with these requirements will be subject to fines in accordance with Section 17 of this Ordinance for each incident and day of violation. a) The vegetation within a buffer zone must be either retained in a natural, undisturbed condition, or properly managed in accordance with the standards contained in this section. In cases where native flora (vegetation) does not exist within a buffer zone, the Town may require restoration efforts which include, but are not limited to, replanting the buffer zone with native plant species. b) Buffer zones shall remain covered with native flora and in an undisturbed state in order to promote the Town's goal of preserving, protecting, and restoring ecological systems. However, the Town may permit minor alterations to buffer zones that facilitate the continued enjoyment of the area's coastal resources. All alterations to Town of Ocean Isle Beach 6 Draft Stormwater Management Ordinance I DRAFT buffer zones or alterations to the natural vegetation (e.g.: areas not presently maintained in a landscaped condition) within the Town shall be conducted in accordance with the standards contained in this section, as well as all other applicable policies and standards of the Town. b) In order to promote the Town's goal to preserve, protect and, where possible, restore ecological systems, buffer zones shall be vegetated with native flora and retained in a natural, undisturbed condition, or shall be properly managed in accordance with the following: (1) Shoreline Access Paths: Pathways which provide access to the shoreline are normally considered permissible provided they are less than or equal to 6 feet wide and follow a path that minimizes erosion and gullying within the buffer zone (e.g., a winding, but direct path). Pathways should avoid, or may be prohibited in, sensitive habitat areas, including, but not limited to, coastal wetlands. Pathways may be vegetated with grasses and mowed or may be surfaced with crushed stone or mulch. (2) View Corridors: Selective tree removal and pruning and thinning of natural vegetation may be allowed within a defined corridor in order to promote a view of the shoreline. Only the minimal alteration of vegetation necessary to obtain a view shall be acceptable to the Town. Shoreline access paths shall be located within view corridors to the maximum extent practicable in order to minimize disturbance of buffer zones. View corridors shall be prohibited in sensitive or critical habitat areas. (A) Selective Tree Removal - In cases where the applicant wishes to remove a few select trees, trees proposed to be cut must be specifically identified for Town staff review. In most cases, photographs of the buffer area may be sufficient provided the affected trees are clearly shown in relation to the surrounding buffer and shoreline. Trees may also be marked on -site to allow inspection by Town staff. In order to minimize disturbance and allow monitoring by Town staff, tree stumps of fallen trees shall not be removed. Town staff may make a follow-up inspection to verify that only marked trees were cut based upon stump counts. Should the applicant wish to remove a fallen tree from the buffer zone, this must be performed in a manner which does not disturb remaining vegetation. Selective tree removal is often a preferred technique for the establishment of a view corridor. (B) Selective Pruning - Pruning as defined for Town purposes involves cutting branches from trees, tree saplings and shrubs. For certain buffer zone management options, pruning the tops of shrubs and forest undergrowth (topping) may be appropriate to discourage growth in height. On level ' ground, shrubs and forest undergrowth should be pruned to a height of not less than 4-5 feet. In areas where the ground surface descends toward the shoreline, topping should only be performed to a height that allows a view of the water. Property owners proposing pruning must describe in detail the work proposed, provide photographs and a site plan, and/or mark those portions of the buffer zone where vegetation to be pruned should be Town of Ocean Isle Beach 7 1 Draft Stormwater Management Ordinance I DRAFT identified since some species of vegetation cannot tolerate excessive pruning or topping. Selective pruning is often a preferred technique for ' the establishment of a view corridor. (C) Selective Thinning - Thinning as defined for Town purposes involves the selective removal of tree saplings, shrubs and vines occurring in brush ' areas and in the undergrowth of forested buffer zones. Applicants proposing thinning must describe in detail the work proposed, provide photographs and a site plan, and/or mark areas to be thinned on -site. The species of vegetation to be removed from a buffer zone management area must be differentiated from those species which are to be retained and encouraged. Selective thinning is often a preferred technique in areas where habitat management will be performed. (D) Mowing - In most cases, mowing of vegetation within a buffer zone shall be prohibited unless associated with the establishment and maintenance of I shoreline access path or approved shoreline recreation area. However, for certain habitat management options, annual or biannual mowing may be allowed to maintain field vegetation where such vegetation is considered valuable to wildlife and other natural values. In such cases, mowing shall be confined to 25% of the buffer zone area, or less. (E) Clearin - Clearing or clear -cutting of vegetation within a buffer zone shall only be allowed for the establishment of shoreline access paths, shoreline recreation areas and in certain cases, habitat management options, which are designed to maintain a field of native grasses and herbaceous plants. Clearing shall not affect more than 25% of the buffer zone area. Clearing for habitat management shall not be allowed in Buffer zones of less than one acre. (F) Filling rg ading - Minor filling (10 cubic yards or less) and grading shall only be allowed in buffer zone areas for the establishment of shoreline access paths and shoreline recreation areas. Certain, minor ' cutting and filling activities may also be allowed on a case -by -case basis to promote these uses. Filling and grading shall not be allowed for habitat management options. (3) Habitat Management: Management of natural vegetation within a buffer zone to enhance wildlife habitat and control nuisance and non-native species of vegetation may be allowed. Homeowner control of pest species of vegetation such as European bittersweet and nuisance species such as poison ivy is normally considered acceptable. However, the indiscriminate use of herbicides or the clear -cutting of vegetation shall be prohibited. The use of fertilizers is generally prohibited within the buffer zone except when used to enhance the replanting of native vegetation (e.g., hydro -seeding) approved by the Town. However, the clearing or outright elimination of natural vegetation for such purposes as controlling ticks or pollen shall not be permitted. (A) Restorative Planting - For purposes of buffer zone management, restorative planting shall be strictly defined as the planting or replanting of natural vegetation native to the North Carolina shoreline. However, naturalized species may be allowed, as determined by Town staff. The i Town of Ocean Isle Beach 8 1 Draft Stormwater Management Ordinance ' DRAFT rplanting of non-native, landscape and exotic species, in most cases, shall not be considered appropriate in buffer zones. 1 (4) Safety and Welfare: Selective tree removal, pruning and thinning of natural vegetation within a buffer zone may be allowed by the Town on a case -by -case basis for proven safety and welfare concerns (e.g., removal of a damaged tree in close proximity to a dwelling). In order to promote child safety and manage pets in areas harboring ticks, fences along the inland edge of a buffer zone and along shoreline access pathways may be permitted. Section 9. DischarEe Prohibitions ISection 9.1 Prohibition of Illegal Discharges No person shall discharge or cause to be discharged into the municipal storm drain system or watercourses any materials, including but not limited to pollutants or waters containing any pollutants that cause or contribute to a violation of applicable water quality standards, other than stormwater. ' The following direct discharges resulting from the improper disposal of such materials into surface waters are unlawful. Violators will be subject to fines in accordance with tSection 17 of this Ordinance for each incident and day of violation as well as any and all costs of removal, cleanup and remediation. a) Sewage or biosolids. b) Polluted household wastewater, including but not limited to laundry wash water and dishwater. c) Leaking sanitary sewers and connections, which have remained uncorrected for three days or more after seven days notice. d) Leaking water lines with flows sufficient to cause soil erosion that have remained uncorrected for three days or more after seven days notice. e) Commercial, industrial, or public vehicle, vessel, or equipment wash discharge. f) Solid, chemical, or sanitary waste. g) Dead terrestrial animals or animal fecal waste. h) Petroleum products or derivatives thereof. i) Wrecked or discarded vehicles or equipment. j) Trash, refuse, or garbage. The commencement, conduct or continuance of any illegal discharge to the storm drain system is prohibited except as follows: a) Discharges from the following activities will not be considered a source of pollutants to the storm drain system and to waters of the U.S. when properly managed to ensure that no potential pollutants are present, and therefore they shall not be considered ' illegal discharges unless determined to cause a violation of the provisions of the Clean Water Act or this ordinance: potable water line flushing; uncontaminated pumped groundwater and other discharges from potable water sources; landscape Town of Ocean Isle Beach 9 I Draft Stormwater Management Ordinance DRAFT 11 1 1 irrigation and lawn watering; diverted stream flows; rising groundwater; groundwater infiltration to the storm drain system; uncontaminated foundation and footing drains; uncontaminated water from crawl space pumps; air conditioning condensation; uncontaminated non -industrial roof drains; springs; individual residential and occasional non-commercial car washing; flows from riparian habitats and wetlands; dechlorinated swimming pool discharges; street wash waters; and flows from fire fighting. b) The prohibition shall not apply to any non-stormwater discharge permitted under a NPDES permit, waiver, or waste discharge order issued to the discharger and administered by the State of North Carolina under the authority of the Federal Environmental Protection Agency, provided that the discharger is in full compliance with all requirements of the permit, waiver, or order and other applicable laws and regulations, and provided that written approval has been granted by the Town of Ocean Isle Beach for any discharge to the storm drain system. Section 9.2 Prohibition of Illicit Connections a) The construction, use, maintenance or continued existence of illicit connections to the storm drain system is prohibited. b) This prohibition expressly includes, without limitation, illicit connections made in the past, regardless of whether the connection was permissible under law or practices applicable or prevailing at the time of connection. Section 9.3 Waste Disposal Prohibitions a) No person shall throw, deposit, leave, maintain, keep, or permit to be ,thrown, deposited, left, or maintained, in or upon any public or private property, driveway, parking area, street, alley, sidewalk, component of the storm drain system, or water of the U.S., any refuse, rubbish, garbage, litter, or other discarded or abandoned objects, articles, and accumulations, so that the same may cause or contribute to pollution. Wastes deposited in streets in proper waste receptacles for the purposes of collection are exempt from this prohibition. b) Yard wastes, including dredge spoil, leaves, and yard trimmings may not be deposited into surface waters. Acceptable management practices for yard wastes include composting and landfilling. Persons who deposit yard wastes into surface waters are subject to fines in accordance with Section 17 of this Ordinance for each incident of violation as well as any and all costs of removal, cleanup and remediation. Section 10. Mandatory Standards for Existing Development a) No landscaping using impervious materials such as solid waste and vinyl will be permitted. Property owners must remove any such materials installed after the effective date of this Ordinance. Failure to comply within 30 days of notification is ' subject to a fine of $50 for each incident and day of violation as well as any and all costs of removal. Town of Ocean Isle Beach 10 ' Draft Stormwater Management Ordinance DRAFT 7 I (1) Exemptions: Use of plastic covering for agricultural land management practices shall be permitted. b) All label directions must be followed so that fertilizers and pesticides are mixed and applied correctly and at the proper time. The label is a legal document. Persons who incorrectly mix or apply chemicals are subject to fines in accordance with Section 17 of this Ordinance for each incident of violation as well as any and all costs of removal, cleanup and remediation. c) Chemicals on both commercial and residential property must be stored in properly built and maintained storage facilities, which are located above the 100-year flood elevation. Persons who do not store chemicals safely will be given seven calendar days to correct such conditions. Failure to comply following this seven-day period will be subject to fines in accordance with Section 17 of this Ordinance for each incident and day of violation as well as any and all costs of removal, cleanup and remediation. d) No person shall intentionally or unintentionally create a nuisance or harmful stormwater problem on a neighboring property. Persons who do create such a problem, as determined by the Town, along with the Town's designated professional engineer, will be given seven calendar days to correct such conditions. Failure to comply following this seven-day period will be subject to fines in accordance with Section 17 of this Ordinance for each incident and day of violation. Section 11. Mandatory Standards for New Developments Section 11.1 Coverage and Application Process a) Site plan approval is required for all development activities within the Town. Approvals and permits may also be required by the State of North Carolina. Copies of all State certifications and permits must be submitted to the Town prior to the start of construction activities. The requirements of this section are consistent with the 15A NCAC 2H.1000 Stormwater Management Rules for application and issuance of permits for stormwater management systems. b) Other Projects: Development may also be permitted on a case -by -case basis if the proj ect: (1) controls runoff through an off -site stormwater system meeting the provisions of this Section; (2) is redevelopment which meets the requirements of this Section to the maximum extent practicable. c) Approval of new development stormwater management shall be made through the Town. A processing fee must be submitted with the plans and specifications. d) For every submittal of a new site plan, a nonrefundable processing fee shall be submitted at the time of submittal. The processing fee shall be $50. e) The applicant shall submit all necessary information to describe the site, development and stormwater management practices proposed. The following documents and information shall be submitted: (1) two sets of detailed plans and specifications for the project; Town of Ocean Isle Beach 11 ' Draft Stormwater Management Ordinance DRAFT (2) plans and specifications must be dated and sealed as outlined in Section 11.3 and show the revision number and date; (3) general location map showing orientation of the project with relation to at least two references (numbered roads, named streams/rivers, etc.) and showing the receiving water (a USGS map preferable); (4) topographic map(s) of the project area showing original and proposed contours and drainage patterns; (5) delineation of relevant boundaries including drainage areas, seasonal high water table, wetlands, property/project boundaries and drainage easements; (6) existing and proposed built -upon area including drainage areas, buildings, etc.; (7) technical information showing all final numbers, calculations, assumptions, drawing and procedures associated with the stormwater management measures including but not limited to: built -upon area, runoff coefficients, runoff volume, runoff depth, flow routing, inlet and outlet configuration (where applicable), other ' applicable information as specified; (8) operation and maintenance plan and maintenance agreement signed by responsible party; 1 (9) recorded deed restriction and protected covenants. As an alternative proposed deed restriction and protected covenants, a signed agreement to provide final recorded articles shall be accepted when final documents are not available at the time of submittal. (f) As -built drawings of the site shall be submitted to the Town within 30 days of completion of project construction. 1 Section 11.2 Stormwater Requirements a) All development activities within the Town shall manage stormwater as follows: (1) runoff from all new development, regardless of size, shall approximate the rate of flow and timing of runoff that would have occurred following the same rainfall under predevelopment conditions for the 24-hour two (2) year and ten (10) year frequency rainfall events. t11.3 (2) control systems must be infiltration systems designed in accordance with Section to control the runoff from all surfaces generated by the first one and one-half inches of rainfall along with the requirements from paragraph (1) above. Alternatives as described in Section 11.3 may also be approved if they do not discharge to surface waters in response to the design storm; (A) Development shall be approved if the following conditions are met: (i) no direct outlet channels or pipes to SA waters unless permitted in accordance with 15A NCAC 2H .0126; (ii) control systems must be infiltration systems designed in accordance with Section 11.3 to control the runoff from all surfaces generated by the two (2) and (10) year frequency rainfall event. Alternatives as described in Section 11.3 may also be approved if they do not discharge to surface 1 waters in response to the design storm; (iii)runoff in excess of the design volume must flow overland through a vegetative filter, designed in accordance with Section 11.3, with a Town of Ocean Isle Beach 12 IDraft Stormwater Management Ordinance DRAFT 1 I J minimum length of 50 feet measured from mean high water of SA waters. Section 11.3 Design of Stormwater Management Systems a) Structural Stormwater Control Options. Stormwater Control Measures which may be approved include: (1) Stormwater infiltration systems including infiltration basins/ponds, swales, dry wells and vegetative filters; (2) Wet detention ponds; and (3) Devices meeting alternative design criteria. b) Innovative measures for controlling stormwater which are not met will be established through actual experience and may be approved on a demonstration basis under the following conditions: (1) There is a reasonable expectation that the control measures will be successful; (2) The projects are not adjacent to or near High Quality Waters (HQW); (3) Monitoring requirements are included to verify the performance of the control measures; and, (4) Alternatives are available if the control measures fail and when the Town has determined that the system has failed. c) Vegetation in the filter may be natural vegetation, grasses, or artificially planted wetland vegetation appropriate for site characteristics. d) General engineering design criteria, specific stormwater management system design criteria and alternatives design criteria shall be as described in 15A NCAC 2H.1008 Design of Stormwater Management Measures. e) Stormwater systems must be designed by an individual who meets the North Carolina professional engineer requirements for the type of system proposed. Upon completion of construction, the designer for the type of stormwater system installed must certify that the system was inspected during construction, was constructed in substantial conformity with plans and specifications approved by the Town and complies with the requirements of this Section prior to issuance of the certificate of occupancy. Section 11.4 Operation and Maintenance a) Prior to site plan approval by the Town, an operation and maintenance plan or manual shall be provided by the developer for stormwater systems, indicating the operation and maintenance actions that shall be taken, specific quantitative criteria used for determining when those actions shall be taken, and who is responsible for restoring a stormwater system to design specifications if a failure occurs and must include an acknowledgment by the responsible party. Development must be maintained consistent with the requirements in the operation and maintenance plan and the original plans and any modifications to these plans must be approved by the Town. b) A maintenance agreement between the responsible party and the Town shall be signed by the responsible party in which the responsible party agrees to the continued Town of Ocean Isle Beach 13 ' Draft Stormwater Management Ordinance DRAFT 11 performance of the maintenance obligations. This agreement shall be assigned to the successors in the title upon transference of the property. Section 11.5 Staff Review a) The Town shall conduct a review of the plans, specifications and other project data to determine if all required information has been submitted and shall acknowledge receipt of a complete set of information. The Town shall notify the applicant if the information is incomplete and advise the applicant on how to make the application package complete. b) The Town shall take final action on all applications no later than 30 days following receipt of a complete application with all the required information. c) If site plan approval is denied, the letter shall state the reason(s) for denial and any reasonable measures which the applicant may take or make to receive site plan approval. Section 12. Mandatory Standards for Redevelopments a) For all redevelopment activities, the property owner must: (1) reduce the impervious surface on the lot by 20% from the original built upon amount; or (2) construct an on -site stormwater system which is designed to reduce the quantity of stormwater leaving the site by 75% from the original built -upon lot. (A) In order to achieve these requirements, the property owner may employ any control measure specified in Section 11.3. (B) Site plan approval is required for all redevelopment activities (as per Section 11.1). - (C) Stormwater system designs must be completed in accordance with Section 11.3. (D)An operation and maintenance agreement as required per Section 11.4. Section 13. Mandatory Standards for Construction Activities ' Persons who fail to comply with these regulations after they have received notice from the Town of Ocean Isle Beach will be subject to fines for each violation and other actions or penalties as may be authorized by the Town of Ocean Isle Beach. ' a) The Town of Ocean Isle Beach will require developers and individuals to furnish copies of all necessary State certifications involved with the land disturbance activity. ' b) Any person conducting a land -disturbing activity within the Town for the purpose of creating permanent impervious surface exceeding 500 square feet must notify the Town of Ocean Isle Beach if a soil erosion and sedimentation control device is necessary. c) For construction activities that are one acre or larger, the Town will require a Sedimentation and Erosion Control Plan per the Town's Erosion and Sedimentation ' Control Ordinance. Town of Ocean Isle Beach 14 ' Draft Stormwater Management Ordinance DRAFT 11 d) The Town of Ocean Isle Beach's designated official has the authority to monitor construction activities to ensure that developers comply with the Sedimentation and Erosion Control Plan. e) A 50-foot vegetated buffer strip must be retained or established adjacent to any surface water bordering a land -disturbing activity where feasible. If the land - disturbing activity is water -dependent (e.g., bulkheads, piers, marinas, and bridges) and thus is not feasible, then the activity may be permitted with the appropriate approvals from either the State of North Carolina or the local permitting officer. f j Construction activities that are under one acre and infringe upon a State of North Carolina defined Area of Environmental Concern will require a CAMA minor permit from the local CAMA permit official. g) All debris and trash must be contained on -site during construction. All garbage receptacles must have high sides or covers to prevent the airborne transport of debris such as plastic and paper. In addition, hazardous materials used during the construction process must be stored and disposed of properly to ensure that they do not enter surface waters. h) During construction, the person or firm responsible for the site development is responsible for maintenance of erosion and sedimentation control devices. Section 14. Exemptions No public or private property shall be exempt from the general enforcement requirements as set forth within this Ordinance relating to stormwater quantity and quality management unless granted through the appeal process set forth herein. No exemption shall be granted based on the age, tax or economic status, race, religion of the customer, or other conditions unrelated to the enforcement of the general requirements of this Ordinance. Section 15. Inspection and Notifications a) The Town of Ocean Isle Beach's representatives shall have the power and authority to conduct inspections as may be reasonably necessary to carry out its duties hereunder and to enforce the terms of this Ordinance. When necessary to carry out the Town of Ocean Isle Beach's duties hereunder or to enforce the terms of this Ordinance, the designated representatives of the Town of Ocean Isle Beach may enter at reasonable times upon public or private property for the purpose of inspection. b) All persons, firms, or corporations owning real estate within the Town shall allow the designated representative of the Town of Ocean Isle Beach to inspect such real estate to determine compliance with the terms and provisions of this Ordinance. c) No person shall refuse access to the designated representative of the Town of Ocean Isle Beach nor shall any person interfere with any such representative while in the process of carrying out his or her duties for the Town of Ocean Isle Beach at reasonable times. Any person, firm, or corporation that obtains a building permit, zoning permit, approval of a land use plan, subdivision approval or other development approval or permit, or that discharges into the Town of Ocean Isle Beach's stormwater system or surface waters, hereby consents to and gives Town of Ocean Isle Beach 15 Draft Stormwater Management Ordinance DRAFT permission to the designated representatives of the Town of Ocean Isle Beach to inspect its premises for compliance with the terms of this Ordinance. d) If it is determined that a person has failed to comply with this Ordinance, a notice of violation shall be served upon that person by registered or certified mail or other reasonable means to give actual notice. The notice shall set forth the measures necessary to achieve compliance with the plan and specify a reasonable time period within which such measures must be completed. The notice will warn that failure to correct the violation within the time period will result in the assessment of a civil penalty or other enforcement action. If the person in violation of this Ordinance fails to comply within the time specified, enforcement action will be initiated. Section 16. Appeals a) Any person who is found in violation of the requirements set forth under this Ordinance, or has a site plan denied, may appeal by submitting a written explanation of the appeal to the designated Town official within thirty (30) days of the date of the notification of the violation. b) The designated Town official shall render a Recommended Decision on the appeal in writing within thirty (30) days after the receipt of the written appeal to the Board of Commissioners of the Town of Ocean Isle Beach. c) The Town of Ocean Isle Beach's Board of Commissioners shall accept, reject or modify the Recommended Decision. d) Appeals from the Town of Ocean Isle Beach's action will be made through the General Court of Justice of Brunswick County, North Carolina. Section 17. Penalties Violation of this Ordinance shall subject the offender to a civil penalty of not less than two hundred dollars ($200) or more than one thousand dollars ($1,000) per violation to be recovered by the Town of Ocean Isle Beach in a civil action in the nature of debt if the offender does not pay the penalty within a prescribed period of time after he has been cited for violation of this Ordinance. Each day of continuing violation thereof shall constitute and be a separate and distinct offense. This Ordinance shall be enforced by any appropriate equitable remedy issuing from a ' court of competent jurisdiction. In such cases, the General Court of Justice shall have jurisdiction and authority to issue such orders as may be appropriate to enforce the Ordinance of the Town of Ocean Isle Beach, and it shall not be a defense to application ' made by the Town of Ocean Isle Beach therefore that there is an adequate remedy at law. Section 18. Iniunctive Relief This Ordinance may also be enforced b appropriate a uitable remedy issuing from a Y Yq court of competent jurisdiction. The General Court of Justice shall have jurisdiction to rissue such orders as may be appropriate to enforce the terms of this Ordinance. The institution of an action for injunctive relief under this section shall not relieve any party from any civil or criminal penalty prescribed for violations of this Ordinance. Town of Ocean Isle Beach 16 ' Draft Stormwater Management Ordinance DRAFT Section 19. Severability It is the declared intent of the Town of Ocean Isle Beach that the sections, subsections, paragraphs, sentences, clauses, phrases and provisions of this Ordinance are severable; and should any sections be declared unconstitutional, illegal or in conflict with any State of North Carolina or federal law or otherwise be invalid or unenforceable by a court of competent jurisdiction, the validity or enforceability of any remaining portions of this Ordinance shall not be affected thereby, and it is the intent of the Town of Ocean Isle Beach that all unaffected provisions shall continue in full force and affect. Section 20. Effective Date This Ordinance shall be in effect on RATIFIED THIS OF 12000 TOWN OF OCEAN ISLE BEACH Town of Ocean Isle Beach 17 Draft Stormwater Management Ordinance APPENDIX B Public Information Flyers 1 TOWN OF OCEAN ISLE BEACH STORMWATER MANAGEMENT PROGRAM WffX11-1yy1 ER RUNOFF? Stormwater runoff is the rain that runs off streets, rooftops, parking lots, lawns and other land surfaces. As communities develop more impervious surfaces are created and less rainfall can soak into the ground. This increases flooding and streambank erosion. POLLUTANTS IN STORMWATER Stormwater picks up pollutants as it flows across the ground. Some of these pollutants include: • Sediment • Bacteria from Leaking Septic Tanks • Pesticides and Fertilizers • Bacteria from Animal Wastes • Oil and Grease • Waste from Boats • Solvents and Cleaners Sometimes pollutants are illegally dumped into storm drains and waterways. WHAT CAN YOU DO TO PREVENT STORMWATER POLLUTION AND DECREASE RUNOFF? • Minimize impervious surfaces to reduce runoff. • Divert roof drains to vegetated areas on your property, not directly onto paved surfaces. This increases infiltration and decreases runoff. • Divert runoff from pavement to grassy, planted or wooded areas of your property, so stormwater can seep slowly into the ground. • Retain or create buffers (50 to 100 feet where possible) of vegetation between waterways and impervious areas to help filter out pollutants and increase infiltration. • Stop soil erosion — plant vegetation on all bare areas. • Design new construction to prevent runoff and stormwater pollution. • Properly use and store all household chemicals. • Clean up spilled solvents, brake fluids, grease, etc. Do not wash them into the street where they will eventually end up in local waterways. • Properly dispose of household hazardous wastes. Do not dump them on the ground or in the storm drain. • Clean litter from the street and storm drains near your home and along waterways to keep it out of the water. This also helps prevent clogged storm drains and waterways help reduce the chance of flooding. • Report any pollution, illegal dumping or soil erosion that you see to authorities. If you have any questions or comments about the Stormwater Management Program for the Town of Ocean Isle Beach, please contact Jason Walker at the Town Hall at (910) 576-2166. TOVVN OF OCEAN ISLE BEACH 9 jjjq� In WHAT IS STORMWATER MANAGEMENT? Stormwater runoff management involves utilizing control principles and practices to reduce stormwater runoff and stormwater pollution. The current approach to solving these problems is through minimizing the generation of runoff and pollutants, combined with managing runoff and pollutants to minimize its impacts in a cost effective manner. PREVENTATIVE MEASURES 'Preventative measures include non-structural best management practices (BMPs) that help prevent runoff and the contamination of runoff through controlling the sources. These measures include: 'Stormwater Ordinances/Policies Establishing greenways along waterways, limiting the amount of impervious surfaces, setting minimum lot sizes, requiring building setbacks and vegetative buffers along streams, discharging downspouts from roof gutters into vegetated areas, requiring runoff from paved areas to flow through vegetated buffers prior to entering waterways. 'Public Education Changing citizen behavior and practices through education is the key to decreasing stormwater runoff and stormwater pollution. Educating the public and town employees about stormwater problems and BMPs will help minimize runoff and protect water quality. Pollution Prevention Practicing preventative maintenance to reduce spills and leaks, covering material stored outside to 'prevent exposure to rainfall, and maintaining sanitary sewers and septic tanks are all methods of pollution prevention. 'CONTROL MEASURES Control measures include structural best management practices (BMPs) that control the volume and peak discharge rate and/or reduce the concentration of pollutants in stormwater runoff. These measures include: Vegetative Practices Grassed swales help to reduce stormwater flows and pollution. Grassed swales maximize infiltration ' and filtration. The vegetation "captures" pollutants, preventing them from entering the waterways. Infiltration Devices 'A portion of the stormwater runoff is retained in the infiltration facility, allowing it to infiltrate into the soil, and or evaporate into the air. These devices will reduce the amount of runoff and also the amount of pollutants. Retention Ponds A portion of the stormwater runoff is retained in these facilities in order to reduce the amount of runoff entering the waterways at the time of the storm. The water is slowly released over time. Some of the pollutants settle to the bottom of the facility, thus reducing the amount of pollutants in the stormwater. These and other practices will be evaluated for use by the Town of Ocean Isle Beach. If you have any questions or comments about the Stormwater Management Program for the Town of Ocean Isle Beach, please contact Jason Walker at the Town Hall at (910) 576-2166. APPENDIX C City of Charlotte Stormwater Services Credit Application Instruction Manual CITY OF CHARLOTTE STORM WATER SERVICES CREDIT APPLICATION INSTRUCTION MANUAL Charloffe-Mecklenburg STORM WATER Services JUL May 16, 1994 A note to recipients of the Charlotte -Mecklenburg Storm Water Services Credit Application Manual: This is the first revision of the City of Charlotte Storm Water Services Credit Application that contains the basis, procedures, and technical support for a professional to understand and complete a credit application. As with the first version of the Credit Application Manual, this manual is not intended to be all inclusive and should be used as a general guide. With the need to make editorial changes due to the recent consolidation of the City and County Storm Water Programs, technical changes were made based on approximately one year of it's application in the City of Charlotte. Other engineering references, previous engineering experience and sound engineering judgement must complement this manual to allow the applicant to properly fulfill the requirements of the application procedure. The Charlotte -Mecklenburg Storm Water Services staff looks forward to working with the County's design professionals in preparing and approving your future credit applications. Sincerely, James W. Schumacher, P.E. W. Dave Canaan Charlotte Storm Water Manager Associate Director of Engineering CHARLOTTE-MECKLENBURG STORM WATER SERVICES CREDIT APPLICATION INSTRUCTION MANUAL i i } CHARLOTTE-MECKLENBURG STORM WATER SERVICES CREDIT APPLICATION INSTRUCTION MANUAL Prepared For City of Charlotte Storm Water Services Prepared By Ogden Environmental and Engineering Services, Inc. Charlotte, NC December 14,1992 Revised OS116194 SECTION 1: INTRODUCTORY MATERIAL Charlotte -Mecklenburg Storm Water Services has elected to provide a credit toward reducing a ratepayer's storm water user fee. This manual provides information, instructions and an application form for applying for the credit. It is organized as: Section 1: Introductory Material Section 2: Definitions Section 3: Policies and Procedures Section 4: Technical Procedures Section 5: Example Credit Computations Section 6: Forms and Checklist When it rains a certain portion of the rainwater runs off from all properties into the channels, pipes, and streams of Mecklenburg County. Property development increases the portion of runoff and creates a negative impact on the drainage system. This increase in runoff (and thus the negative impact) is generally proportional to the amount of impervious area the developed property has. l The storm water fee a property owner pays is also proportional to the amount of impervious area on a given property. Therefore the j, credit is also developed to be proportional to the effective reduction in impervious area. S Corm water runoff primarily impacts a drainage system through: • increases in peak flow; • increases in the total volume of runoff; and • increases in pollution runoff. Therefore the crediting system allows for credit to be gained for reductions in each of these three areas. In order to keep the credit system more simple than it otherwise could be with a more "exact" methodology, these three impacts have been reduced to three easy -to -understand criteria standards which still guarantee real reductions in impact because they have a basis in technical fact. The runoff peak, volume or pollution load calculated is the total from the whole site and not simply the total at the point of the location of controls. Care should be taken to determine ` the physical location or reference point at the site outlet(s) where calculations will be made. rrclic Application Instruction Manual page.- 1 SECTION 2: DEFINITIONS Best management practices (BMPs): Structural controls and/or non-structural controls that temporarily store or treat urban storm water runoff to reduce flooding, remove pollutants, and provide other amenities. Biochemical oxygen demand (BOD): The quantity of oxygen consumed during the biochemical oxidation of matter over a specified period of time. CMSWS: Charlotte -Mecklenburg Storm Water Services. Design storm: A rainfall event of specified size and return frequency that is used to calculate the runoff volume (e.g., a storm that occurs on the average once every 2 years) and peak discharge rate (e.g., a storm that occurs on the average once every 10 years) to a BMP. Detention: The temporary storage of storm runoff in a BMP, which is used to control the peak discharge rates, and which provides gravity settling of pollutants. Detention time: The amount of time water actually is present in a BMP. Theoretical detention time for a runoff event is the average time water resides in the basin over the period of release from the BMP. Directly Connected Impervious Area: The impermeable area within the watershed which enters the drainage system without traveling across permeable surfaces, i.e. roof surfaces which drain through roof drains directly into the storm sewer system. Extended Detention Basin: Forebay: Freeboard: A structural BMP which holds storm water for a lengthened period of time in order to reduce peak discharge and enhance water quality by allowing particulates to settle out. An extra storage area provided near an inlet of a BMP to trap incoming sediments before they accumulate in a pond BMP. The space from the top of an embankment to the highest water elevation expected for the largest Credit Application lnstuvctioa Manual page - 2 design storm stored. The space is required as a safety margin in a pond or basin. HEC-1 A computer program developed by the U.S. Army Corps of Engineers which allows the user to generate hydrographs by simulating the watersheds ' response to precipitation. Hydrograph: A graph showing variation in the water depth or discharge in a stream or channel, over time, at a specified point of interest. Impervious area (imperviousness): Impermeable surfaces, such as pavement or rooftops, (but not gravel driveways) which prevent the infiltration of water into the soil. Initial losses: The amount of rainfall not transformed into runoff due to interception, depression storage, and infiltration. Lag time: The increment of time from the center of mass of rainfall to the peak of the hydrograph (may be assumed to be 0.6 * time of concentration). Low flow channel: A paved channel from inlet to outlet in a dry basin which is designed to carry low runoff flows and/or baseflow, directly to the outlet without detention. NPDES: National Pollutant Discharge Elimination System regulations for storm water discharges as described in the Federal Register 40 CFR Parts 122, 123, and 124. Peak discharge: The maximum instantaneous rate of flow during a storm, usually in reference to a specific design storm event. Pilot channel: A riprap or paved channel that routes runoff through a BMP to prevent erosion of the surface. Retention: The holding of runoff in a basin without release except by means of evaporation, infiltration, or emergency bypass. To install a new v an existing, BMP Retrofit: e BMP or improve t in a previously developed area. ■ Return frequency: A statistical term for the average time of expected t "Credit Apolication [actnution Manual mace- 3 - Riprap: Riser: Runoff coefficient: SCS: Soil group, hydrologic: Spillway: Structural control: Time of concentration: Wetpond: interval that an event of some kind will equal or exceed given conditions (e.g., a storm water flow that occurs on the average every 2 years). A combination of large stones, cobbles, and boulders used to line channels, stabilize banks, reduce runoff velocities, or filter out sediment. A vertical pipe extending from the bottom of a pond BMP that is used to control discharge rate from a BMP for a specified design storm. Ratio of runoff to precipitation. Soil Conservation Service. A classification of soils by the Soil Conservation Service into four runoff potential groups. The groups range from A soils, which are very permeable and produce little runoff, to D soils, which are not very permeable and produce much more runoff. A depression in the embankment of a pond or basin which is used to pass peak discharge greater than the maximum design storm controlled by the pond. A constructed device that temporarily stores or treats urban storm water runoff to reduce flooding and/or remove pollutants. The time required for surface runoff from the most remote part of a drainage basin to reach the basin outlet. A structural BMP which retains storm water runoff in a permanent pool for water quality enhancement by settling pollutants. 1 Credit Application Iastnuction Manual page - 4 - 1 ' SECTION 3: POLICIES AND PROCEDURES It is CMSWS's intent to encourage sound technical design practices which reduce the negative impact of development on the drainage system through a simple but effective crediting system. Credits will be granted for any combination of peak, volume and/or pollution reduction. Certain policies have been developed to help maintain this balance between simplicity and effectiveness. Further questions on these brief policy statements should be directed to CMSWS. Single Family Residences 1. Credit will be allowed for all properties except individual single-family residential properties. Credits can be granted in extraordinary situations for single- family residences through the appeals process. Credit will not be allowed for any properties which do not pay a storm water fee. Maintenance Requirements 2. Credit will only be allowed for properties which maintain their structural controls in fully functional .� condition and according to maintenance criteria and BMP standards issued by CMSWS. Existing Structure Credits 3. Credit will be allowed for previously constructed controls. The amount of credit granted will be M determined by the methods of design as outlined within the body of this document. Industrial NPDES Permits 4. The full pollution portion of the credit will be granted and Credits to those industries which -must obtain and do maintain an NPDES permit for storm water runoff from the State. .0 Watershed Protection Wet 5. Fach customer s omer maintaining an .approved Best Ponds and Credits Management Practice (BMP- wet pond) in accordance with local watershed regulations for any developed land will receive full credit for the water quality portion of the charge. Properry Location 6. Credit will not be granted solely on the basis of location of a given property in relation to a major stream, river or within a watershed. Voluntary Controls 7. For new developments, credit will be granted where CMSWS requires controls to b-- constructed and/or e maintained. Other voluntary controls or upgrades of ' existing systems through retrofitting will be granted A credits on a case -by -case basis, as determined by ■ "'"re(EE AppGcatioa Instruction Manual page - 5 - HY Tld.o.nhor.1l...1992 - - CMSWS, considering the impact of the controls on the drainage system. Percent Credits 8. A maximum of 100 percent of the user fee can be granted in credit with a maximum of: • 50 percent of the fee for peak reduction; • 25 percent of the fee for volume reduction; and 0 25 percent of the fee for pollution reduction. Types of Structural BMPs 9. Pollution credit will be granted for extended detention basins and wet ponds. Credit may be granted for other control devices on a case -by -case basis providing sufficient technical justification is available to make such determinations. Regional Basins 10. Credit will not .be granted to properties draining into a regional basin maintained by CMSWS. Credit will be granted for privately owned and maintained regional controls and will be apportioned among owners on a prearranged basis. Appeals 11. An appeal must be initially filed in writing with the Charlotte Storm Water Manager for those customers within the City. An appeal must be initially filed in writing with the Mecklenburg County Storm Water Manager for those customers outside the City. Should satisfaction not be achieved, an appeal may be lodged with the Charlotte -Mecklenburg Storm Water Citizens Advisory Committee. Timing of Applications 12. It is the intent of CMSWS that all applications will be reviewed and credits determined within thirty days after submittal of a complete and correct application package. The credit will be effective on the Ist billing cycle for the property following completion of construction. However, applications for locations outside of the City limits submitted to the Mecklenburg County Storm Water Manager by 12/31/94 will receive credit retroactively to the first billing of service charges. Credit Application Instruction Manua) page - 6 - December 14. 1992 PROCEDURES FOR SUBMITTAL New Developments Submittal of credit calculations for new developments will occur as part of the normal development and subdivision procedures! in two steps as indicated in the box at the ri?ht. Existing Controls Existing controls should be maintained to the standard in existence at the time they were constructed. Coordination with the Engineering Departments should be done if there are any questions concerning the applicable standards. Retrofit of Existing Controls Retrofit of existing structures is a two-step process similar to that of new developments. ' See the Charlotte-Mecklcnbu a Developer Handbook available from the City or the County. 'Credit Applicadoo laswction Manual page - 7 - SECTION 4: TECBNICA.L PROCEDURE Technical Criteria The credit is based on: peak, volume, and pollution runoff. Credit Distribution "Effective " Imperviousness • The 10-year, 6-hour storm is used for peak runoff (in cubic feet per second). • The total accumulated runoff volume for the 2- year 6-hour storm is measured at the 12th hour to determine the volume credit. • Annual pollutant loadings (in pounds per year) for BOD5, Total Phosphorous and Lead (one- third credit for each) are the standards for pollutant reduction. The distribution of the credit is: • Fifty (50) percent for peak reduction credit; • Twenty-five (25) percent for volume reduction credit; • Twenty-five (25) percent for pollution reduction credit. The figure above illustrates the credit calculation concept in which: • I1 is the impervious area without development (always assumed to be zero). • Q1 is the pre -development peak, volume or pollution runoff. • I3 and. Q3 are the post -development peaks, volumes or pollutant loadings without any Credit Application Instruction Manual Page _ 8 - n..-... to 1.4 1001 controls in place. • I2 is the "effective imperviousness" which results from controls reducing peak, volume or pollution runoff from Q3 to some lesser value Q2• • The property owner will pay a fee based on the "effective" impervious area I2 rather than the actual impervious area I3. Credit Calculation Equations The goal is to find 12, the effective impervious area which matches Q2. This procedure assumes that each of the credit factors (peak, volume and pollutant load) can be approximated as varying linearly with the percent impervious. Equating triangles and solving for I2 yields an effective impervious value and a credit percentage: 12 = (Q2-Ql)(I3)/(Q3-Ql) (1) Credit Percent = 100 * (142/I3) (2) This calculation is done for peak, volume, and pollution if credit is sought for all three factors. Credit may be applied in only one or two of these areas as appropriate. Examples in a later section illustrate this procedure. To obtain the actual credit for any of the three impacts the Credit Percent is multiplied by the available credit. Since fifty percent of the total monthly fee is available for the peak credit the Credit Percent for peak flow would be multiplied by 0.50. For both volume and pollution reduction the Credit Percent would be multiplied by the maximum credit available which is twenty-five percent of the monthly fee or 0.25. Three Conditions: To obtain storm water user fee credits it will be necessary to • Undeveloped develop and submit certain supporting documentation as listed • Fully Developed on the credit application checklist (Section 7). Without Controls • Fully Developed With Calculation of credit is based on impact reduction in three Controls. areas: peak, volume and pollution. Credit may be earned in any or all of these three areas. Analysis are necessary for each area to develop data and information for three conditions to find I2: (1) undeveloped conditions (Q1, I1); (2) fully developed conditions without controls (Q3, I3); and (3) fully developed conditions with controls (Q2). The next sections detail the necessary procedures. Application Instruction Manual page- 9 - 11 1002 1 PEAK CREDIT CALCULATION STEP 1: Calculate the 10-year, 6-hour storm runoff peak for undeveloped conditions. This should be done using an approved method from chapters 3.0 (Hydrology) and 7.0 (Storage and Detention). This gives Q1. Remember that the runoff calculated is the total runoff from the site, not simply the runoff at the point of the controls. A "balanced storm approach" as described in the HEC-1 model documentation is recommended for these calculations. Other methods described in this manual will also be accepted. The following inputs into the HEC-1 model and the resulting rainfall distribution for the 10-year, 6-hour storm as given below should be used if the designer chooses the model HEC-1 for the hydrologic calculations. The distribution of rainfall is similar to the Soil Conservation Service's distribution of -rainfall shown in chapter 3.0 (Hydrology). The total depth is 3.72 inches. 10-YEAR, 6-HOUR BALANCED STORM RAINFALL DISTRIBUTION Time Interval 5 min 15 min 1 hour 2 hour 3 hour 6 hour Rainfall depth (in) 0.59 1.26 2.36 2.90 3.21 3.72 STEP 2: Calculate the 10-year, 6-hour storm total runoff for fully developed conditions without any controls in place and measure the total impervious area. This should be done using the same storm information but with appropriately adjusted runoff coefficients and lag or travel times. This gives Q3 and I3. STEP 3: Insert designed controls for the fully developed condition and route the 10-year, 6- hour storm through the controls. Calculate the controlled runoffpeak. Remember that to be eligible for credits any controls must meet both the policy criteria given above and design criteria detailed elsewhere in this manual. This gives Q2. STEP 4: Calculate the credit from equations 1 and 2. Remember that the peak credit can be up to 50 percent of the monthly drainage fee. II Credit Application Instruction ,Manual page - 10 - ,00, VOLUME CR-EDTT CALCYJLAnON 1 When a site is developed the total volume of runoff from the site increases. The basis of the volume credit is to hold on -site for 12 hours the additional volume of runoff caused by development. For example (see figure below), assume the total volume of runoff over a 12 hour period for an undeveloped site was 10 acre-feet. If after development the total volume of runoff after 12 hours was 15 acre-feet it would indicate that an additional 5 acre-feet of runoff was Generated because of site development. In order to receive 100 % volume credit, the 5 acre-feet of runoff generated by development must still be held on site after 12 hours. This is accomplished by designing a basin with sufficient volume and low discharge rate such that with continual discharge from the start of runoff the basin still holds 5 acre-feet of water after 12 hours. Post Development w/o Controls Vol= 15ac-f t LA U Pre Development Vol= 10 ac-Ft Post Development w/ Controls —Vol= 10 ac-f t J Ls.; .....::: 12 hrs Volume after 12 hours measured TIME (min) from latest start of runoFF. STEP 1: Calculate the hydrograph for the 2-year, 6-hour storm for undeveloped conditions. Accumulate the total volume of runoff from the Stan of the storm for a period of twelve hours of runo . Make sure that you calculate the runoff for a period of twelve (12) hours from the start of runoff from the 2-year, 6-hour storm. This may require a calculation period longer than 12 hours to allow for initial losses. This gives Q1 in the volume calculation. Either acre-feet or inches of runoff is a convenient unit of measure. The total can be obtained by summing the ordinates of the hydrograph and applying a suitable conversion factor. • Volume, ac-ft = E(flow at each time step, cfs)(60 sec/1 min)(1 acre/43,560 ft-)(time step, min) "A. Application Instruction Manual page - 11 - ne, 14. 1992 • Depth, in = E(flow at each time step, cfs)(60 sec/1 min)(12 in/1 ft)(1 acre/43,560 ft2)(1/area, acres)(time step, min) A "balanced storm approach" as described in the HEC-1 model documentation is recommended for these calculations. Other methods described in this manual will also be accepted. The following inputs into the HEC-1 model and the resulting rainfall distribution for the 2-year, 6-hour storm, as given below, should be used if the designer chooses the model HEC-1 for the hydrologic calculations. The total depth is 2.28 inches. It is similar to the SCS storm distribution. 2-YEAR, 6-HOUR BALANCED STORM RAINFALL DISTRIBUTION Time Interval 5 min 15 min 1 hour 2 hour 3 hour 6 hour Rainfall depth (in) 0.42 0.83 1.45 1.76 1.95 2.28 STEP 2: Calculate the hydrograph for the 2-year, 6-hour storm for fully developed conditions without controls. Accumulate the total volume of runoff from the start of the storm for a period of twelve hours of runoff and measure the impervious area. All three of the hydrographs must have the same time basis... the 12-hour period must start at the same time from the latest beginning of runoff. This will generally be the undeveloped hydrograph since runoff starts later than for developed conditions. This step gives Q3 and 13. STEP 3: Calculate the 2-year, 6-hour hydrograph for fully developed conditions with controls. Accumulate the total volume of runo from the start of the storm for a period of twelve hours of runo . fl 1 This is the total runoff hydrograph at the outlet of the site. It includes the runoff from the controls as well as runoff which may not flow through the controls. This is Q2. , STEP 4: Calculate the credit from equations 1 and 2. Remember that the volume credit can be up to 25 percent of the monthly drainage fee. Credit Application Instruction Manual page _ 12 - ild wnhvr 14. 1992 ' POLLUTION CREDIT CALCULATION Introduction The calculation of pollution reduction depends on the estimation of annual loads and reduction in those loads based on standard designs for certain best management practices (BMPs). Although, without actual measured data, this calculation may not have high accuracy in predicting actual pollution runoff per storm, it is considered sufficiently accurate and consistent for the calculation of credits. The Three Constituents Three constituents have been chosen for pollution reduction credits because of their different origins, impacts on the aquatic ecosystem, and the numerous different structural , controls that can be used to reduce their concentrations: • Lead - a common measure of toxic trace metal production; • BOD5 - a measure of the easily available bio- chemical oxygen demand of such things as leaves and debris; and • Total Phosphorous - a measure of nutrient loading and normally the limiting nutrient in lake eutrophication. Methodology The method (termed the Simple Method) and much of the information is derived from several sources most notably Schueler' and The EDGe Group'-. The annual loadings in Charlotte to be used for credit calculations based on overall percent imperviousness are given in the attached table. The "undeveloped" value is to be used for all undeveloped calculations. Exceptions to these standard values can be made on a case -by -case basis.. 1 frediL Application Instruction Manual page - 13 - December 14, 1992 ANNUAL PER ACRE LOADINGS FOR CHARLOTTE' - Land Type Approximate Percent Pollutant Loading (lbs/ acre per Zoning Impervious year) Classifications Pb BODS TP Undeveloped No < 6 0.004 1 0.07 Classification Rural Residential No 6 0.017 5 0.23 Classification Low Density R-1 12 0.025 7 0.36 Residential Medium Density R-4 30 0.050 14 0.73 Residential High Density R-22MF 60 0.093 26 1.34 Residential Medium Density 0-3 75 0.114 32 1.65 Non -Residential High Density I-1, I-2 90 0.142 40 .2.06 Non -Residential STEP 1: Calculate the pollutant loading for each of the three constituents for on -site undeveloped conditions. Calculate any off -site loadings based on existing conditions. This is done simply by multiplying the total on -site area in acres by the "Undeveloped" value taken from the table. Additionally, multiply any off -site area in acres by the pollutant loading corresponding to the existing off -site percent impervious. Add both, products to determine Q1 for each of the three constituents. STEP 2: Calculate the on -site fully developed pollutant load without controls for each of the three constituents. P-1 L� This is done by multiplying the annual unit load values taken or interpolated from the table for the percent imperviousness J3) by the total on -site area in acres. A weighted percent impervious is warranted unless there are parts of the development which have a distinctly different character, in which case it is , Credit Application Instruction :Manual page - 14 - December 14.19,92 appropriate to make two calculations and add the two together. Also add any off - site loadings calculated in step one. This is Q3 and I3. STEP 3: Calculate the total pollutant load for the fully developed condition with the controls in place. From the plan for implementation of controls determine the part of the flow going through each control and its corresponding percent imperviousness. Determine the loading going to that control. Determine its percent effectiveness for each constituent (see next section) and reduce the total load coming out of it on an annual basis by that amount. Add all the loads coming to the outlet(s) of the site. This is Q2 for each of the three constituents. STEP 4: Calculate the credit from equations 1 and 2. Remember that the total credit can be 25 percent of the total monthly user fee (proportioned 1/3 for each constituent). STEP S: Develop description of BMP, documentation and maintenance requirements. For all non-standard BMPs (including modifications on standard BMPs) full documentation and background must be supplied upon which you relied for determination of pollutant reductions. Maintenance planning must be supplied and (if requested) a monitoring plan. In all cases, plans and specifications must be supplied according to CMSWS guidance for grading and drainage plans and normal detention. . � Credit Application insuvction Manua] page �- POLLUTION REDUCTION CALCULATIONS Introduction The development of types of Best Management Practices (BMP) and information on the effectiveness of BMPs in removing pollutants is in a state of constant change. CMSWS is concerned with maintaining the flexibility for designers to develop and use new innovative BMPs and modifications to old systems. Standard Designs: Initially credits will be granted automatically only for wet • Wet Ponds (retention) ponds and extended detention ponds which meet the • Extended Detention criteria in the attached Standard Specifications for BMPs. The Ponds indicated credit will be automatically granted for BMPs meeting these standard.criteria and falling among the volume criteria given. In order to obtain additional credit the designer must provide CMSWS evidence that controls contain features which further remove pollution or evidence, through sampling and monitoring, that a standard design has exceptional capabilities. BMP EFFECTIVENESS AT REMOVING IDENTIFIED POLLUTANTS Percent Removal BMP Design Criteria TP BOD Pb 1. Wet Pond Pool volume = 0.5 inch storage per impervious acre, 50 30 30 Vff (see below). 2. Wet Pond Pool volume = 2:5 * volume of runoff from mean 50 30 70 storm event, Vm (see below). 3. Wet Pond Pool volume = 4.0 * volume of runoff from mean 70 50 70 storm event, Vm (see below). 4. Extended Detention Runoff volume from a half inch storm released after 30 30 50 12 hours, Vh (see below). 5. Extended Detention Runoff volume from a one inch storm released after 50 50 70 24 hours, V 1 (see below). 6. Extended Detention Runoff volume from a one inch storm released after 70 50 70 24 hours with bottom marsh (minimum drainage area of 10 acres), V 1 (see below). 7. Watershed Pool volume = 4.0 * volume of runoff from mean 100 90 pollution Protection storm event, Vm (see below). Additionally, the credit - no discharge rate following a 1.0 inch storm shall be pollutant loading such that the basin volume does not draw down to the calculations permanent pool level in less than 2 days and does not required. exceed a maximum vertical distance of 2 feet. Design 1. The "impervious acreage" is all impervious area draining to the control. The volume Vff is the "first -flush" volume from this acreage and can be calculated as: Credit Application Instruction Manual page - 16 - n.....,.. 1— Id 1041 IVff = (A,,,PJ(0.5 in)(1 ft / 12 in) where: area of impervious (acres) The remaining storm volumes (Designs 2, 3, 4, 5 and 6) can be estimated, for the purposes of credit calculations, based on the SCS runoff curve number method as described in National Engineering Handbook, Section 4.0, Hydrology' or from the runoff procedures outline in Controlling Urban Runoff' '. SCS Formula: For pervious area and unconnected impervious (i.e., a paved parldng lot that drains by sheet flow to a grassed area) Q = (P - Ij2 /[(P - Ij + S] P > 0.2S which reduces to: Q = (P - 0.2S)2/(P + 0.8S) where: Q = runoff (in) P = rainfall (in) S = potential maximum retention after runoff begins (in), _ (1000/Cl) - 10 I, = initial abstraction (in), = 0.2S for pervious area and unconnected impervious area y Other research has found that the discharges are underestimated for connected impervious ' area in small urban watersheds by the SCS method. The losses for connected impervious area are typically in the range of 0.1 inch instead of the 0.25 as used in the previous formula. Therefore, for all connected impervious area calculations, in accordance to the losses described in Applied Hydrology and Sedimentology for Disturbed Areas4, the following formula should be applied: For connected impervious area Q = (P 0.1) 4.1 ■ where: Q = runoff (in) i P = rainfall (in) Controlling Urban Runoff' 2 formula: ' R� = 0.05 + 0.009(l) ■ -relit Application Imtruction Manual page - 17 - where: ' Rr = storm runoff (in) / storm rainfall (in) I = percent of watershed imperviousness (%) Designs The mean storm in Charlotte, based on National Weather Service 2, 3, & 7. information is 0.64 inches. The volume from the mean storm event can be calculated with SCS methodologies as: Vm = ([(0.64 - 0.2SNL)21Aper/(0.64 + 0.8SpeC) , + [(0.64 - 0.1)]Ai .p)(0.0833) (3) 0.2Sper < 0.64 where: Sper = (1000/CNpef) - 10 (Note: when the value of CNN is low the initial abstraction/maximum retention (0.2Spe) may be greater than the storm event and therefore there will be no runoff. In such cases the first term of equations 3, 4, and 5 will be zero.) A;mp = area of directly connected impervious (acres) Aper = area of watershed without the directly connected impervious (acres) CNN, = curve number of the watershed without the directly connected impervious in acres. This will include the impervious area which is not directly connected to the system. Similarly, the volume of the mean storm event can be calculated with the Rr method as: Vm = (0.64)[0.05 + 0.009(I)](A)(1 ft/ 12 in) where: I = percent of watershed imperviousness (%) A = total watershed area (acres) The volumes for designs 2 and 3 are 2.5 and 4.0 times the mean storm volume. Design 4. The volume for the half -inch storm event can be calculated as: Vh = {[(0.50 - 0.2Sper)2]Aper/(0.50 + 0.8SN , + [(0.50 - 0.1)1A;mp)(0.0833) (4) 0.2Spet < 0.50 Similarly, the volume of the one-half inch storm event can be calculated with the Rr method as: Vh = (0.50)[0.05 + 0.009(I)](A)(1 ft/ 12 in) Credit Application Instruction Manual page - tb..e- v_r 14. 1992 where: I = percent of watershed imperviousness (%) ' A = total watershed area (acres) Desizns The volume for the one -inch storm event can be calculated as: 5&6. V1 = {[(1.00 - 0.2Sp<j)Z]Ap��(1.00 + 0.8SpC7) + [(1.00 - 0.1)]Ap}(0.0833) (5) < 1.0 0.2Sp« 0 Similarly, the volume of the one inch storm event can be calculated with the Rr method as: Vh = (1.00)[0.05 + 0.009(I)](A)(1 ft/ 12 in) where: I = percent of watershed imperviousness (%) A = total watershed area (acres) The volume required in design 4 must be stored for 12 hours prior to being released. The volume required in designs 5 and 6 must be stored for 24 hours prior to being released. Vff = Half inch of runoff from the impervious area (acre-feet) Vm = Volume of runoff from the mean storm (acre-feet) Vh = Volume of runoff from the half inch storm (acre-feet) ' V1 = Volume of runoff from the one inch storm (acre-feet) r.� ■ „Iredit Application Instruction Manual page - 19 - SECTION 6: EXAMPLE CREDIT COMPUTATIONS I Example #1 Basic Information. Example design with consideration for peal- and volume control only • Site area - 15.7 acres • Pre -developed land use woods • Developed land use - high density residential (percent impervious - 61 %) ' Credit Application lastruction ,Manual Page - 20 - , 1 1 1 Pollution credit = 0 % Total credit = (100%)(0.50) + (0%)(0.25) + (0%)(0.25) = 50% edit Application Instruction Manual page - 21 - Example #2 ' Basic Information. Example design considering peak control and pollution control required for the watershed protection regulations ' • Site area - 124.6 acres • Pre -developed land use - woods • Developed land use - commercial (percent impervious - 65 %) Credit Application Instruction Manual I I I I I u 1 I 1 1 1 1 1 1 Credit AppUcatioa Instruction Manual page - 23 - Summary ' Peak credit = 99.7 % ' Volume credit = 26.4 % ' Pollution credit = 52.2 % Total credit = (99.7 %)(0.50) + (26.4 %)(0.25) + (52.2 %)(0.25) = 69.5 % ' Credit Application Lwuvction Nlanual page - 24 - .. .... • no, Example n3 Basic Information. Example design attempting to maximize available credit. Site area 16.0 acres Pre -developed land use - woods and open area Developed land use - institutional (percent impervious - 38 %) A „`Credit Application Instruction Manual page"2$" Credit Application Lxvruction Manual page - 26 - ' ..._._ti..� 14 1001 ISummary U 1 1 1 1 1 1 1 1 Peak credit = 100% Volume credit = 100% Pollution credit = 60.9 % Total credit = (100%)(0.50) + (100%)(0.25) + (60.9%)(0.25) = 90.2% Credit Application Instruction :Manual page - 27 - ' SECTION 7: FORMS AND CHECKLIST The next three pages contain forms and checklists to assist in applying for the credit. • Credit Application Form - basic information summary about the project. r • Credit Application Instructions - to accompany the form. ' • Credit Application Checklist - used by the reviewer to check the application packet. The application packet should consist of the application form on top followed by pertinent drawings and calculations sufficient to fully evaluate both the site and the proposed controls. ' Maintenance provisions, schedule, and responsible parties must be specified for each control proposed. ' Credit Application Instruction Manual page - 28 - CHARLOTTE -IN EEC K,LENBURG STORM WATER SERVICES 1 CREDIT APPLICATION FORINI Applicant Information (Financially Responsible Person): (Please print or tvpe) Name: - 1 Address: City: State: Zip Code: Telephone:( ) ' Owner's Representative (Eneineer/Landscape Architect): Name: Address: 1 City: State: Zip Code: Telephone:( 1 Registration Number (PE or RLA): 1 Proiect Information: Name of Project: ' Address: Tax Number: Property Size (acres): Brief Description of Storm Water Structures Responsible for Effective Impervious Reduction: 1 Impervious Percentage: 1 Qp-d—lop,a: Qpw: Qpo.t v/ =W"U: V• Vpo.t' Vpo.t v/ conual. Loadpb,-d- -k,W: Loads,,,: Loads,, WOw"6: LoadBpD� �k,.d: LoadBoD,.t: LoadBODpo., �/ ooauob 1 LoadTpV--k—,,p,,: Loads,,: I..oadTpp.„ L.: Requested Credit Percentage: 1 The above information is true and correct to the best of my knowledge and belief. (This form must be signed by the financially responsible person if an individual, or if not an individual by an officer, director, partner, or registered agent with authority to execute instruments for the financially responsible person). I agree to provide 1 corrected information should there be any change in the information provided herein. ' Type or print name Title or Authority 1 Signature Date I, , a Notary Public of the County of State of North Carolina, hereby certify that appeared personally before me this day and being sworn 1 acknowledged that the above form was executed by him. Witness my hand and notarial seal, this day of 19_ Notary My commission expires 1 Designer's Certification: Existing conditions are in reasonably close conformance to the conditions reflected in the calculations. Signature and Seal of P.E. or R.L.A. t .Credit Application instruction NUnual page -29- CREDIT APPLICATION CHECKLIST General Plan Requirements Seal and signature of designer (PE or RLA). Property boundaries. Scale (minimum 1"=100'). Vicinity Map. North arrow. Site Drainage Features Adjoining lakes, streams, or other major drainage ways. Existing and proposed contours, interval less than 4.0'. SCS soil types. Impervious delineations and labels (buildings, driveways, etc.). Drainage area map, including off -site areas draining through the site. Delineation of floodway fringe and encroachment areas, where applicable. Size and location of all storm water structures. HvdroloF_ic Hydraulic and Pollution Calculations Hydrologic calculations for undeveloped and developed land uses for the 2-year, 6 hour and 10-year, 6-hour storm event. Hydraulic calculations showing stage -discharge relationships of structural controls. Pollutant loading computations for undeveloped and developed land use. Pollution reduction calculations. Structural control routings Credit computations. Construction Details As -built details of existing structures. Construction drawing and details of proposed controls. Maintenance Maintenance schedule of all operations that affect the efficiency of the structural controls including mowing, sediment removal, etc. Credit Application lasuuction Manual page - 32 December 14, 1992 1. Schueler, T. R., "Controlling urban Runoff, Metropolitan Washington Council of Governments, 1S75 ' Eye St., N.W., Suite 200, Washington, D.C., 20006. (202-962-3200), July 1987. 2. The EDGe Group (Ogden Environmental &: Engineering Services, Inc.), "Mountain Island Lake Best Management Practices Feasibility Study," 1989. ' 3 United States Department of Agriculture, Soil Conservation Service, "National Engineering Handbook," Section 4.0, Hydrology. ' 4 Barfield, B.J.; Warner, R. C.; and Haan, C. T., "Applied Hydrology and Sedimentology for Disturbed Areas, " Oklahoma Technical Press, 815 Hillcrest, Stillwater, Oklahoma, 1981. 1 1 1 1 Ij •. Y; Credit Appl;cation Instruction Manual !fie - 33 - STANDARD SPECIFICATIONS FOR BMPs t 11 11 .1 G i STANDARD SPECIFICATIONS FOR BMPs CMSWS desires that all water quality BMPs be designed and constructed to allow for ease of maintenance, effectiveness of operation and aesthetic appearance. Minimum standards for such design are given below. Optional ideas for further increasing the pollution removal capability or improving the appearance or effectiveness of the BMP are also Given. Deviations from the specifications are permitted on a case -by -case basis. STANDARD SPECIFICATIONS FOR EXTENDED DETENTION BASINS REQUIRED SPECIFICATIONS • Pilot channel of paved or concrete material • Side slopes shall be no greater than 3:1 if mowed. • Inlet and outlet located to maximize flow length. • Design for full development upstream of control. • Rip -rap protection (or other suitable erosion control means) for the outlet and all inlet structures into the pond. • One-half foot minimum freeboard above peak stage for top of embankment for design storm. • Emergency spillway designed to pass the 50-year storm event (must be paved in fill areas). • Maintenance access (< 15576 slope - 10 feet wide). • Trash racks, filters or other debris protection on control. • Anti -vortex plates. • Benchmark for sediment removal. RECOMMENDED SPECIFICATIONS • Two stage design (top stage - dry during the mean storm, bottom stage - inundated during storms less than the mean storm event.) • Top stage shall have slopes between 27, and 5 %. • Bottom stale maintained as shallow wetland or pool (6" to 12"). • Manage buffer and pond as meadow. • Minimum 25-foot wide buffer around pool. • On -site disposal areas for two sediment removal cycles. • Anti -seep collars on barrel of principal spillway. • Impervious soil boundary. The figure on the next page presents a typical extended detention pond built in two staves. SCHEMATIC OF TYPICAL EXTENDED DETENTION POND T TOP VIEW POND BU//ER ♦ 2Y uON. \ i (LANDSCAPE rILOW u.INIVIANCE [uBANKUENt 1CRASSES.SNRUDS. ANO 1RCES) BOnou siAGE 1 K LOU$. SLOPE TOP SIACE 1 I I ILY 1 PILOT CItvNN(t(CONCRCIC OR PAyEO) kNDRU DRY AS YCIOQw) / SNLaUOW M[11A1N0 OR POOL STABILIZED 2 ININ 1Op E'er— RISER — ) INLEI (f21PRAP) $i l — �,f1' srlbluzCo \ � ♦ RIPRAP ♦APRON - �bYW OuifAu — — — a�,v / � \ \ W it / SIDE SLOPES DOnOu sI 3:1 "; 20A URN. swaaw u4Rs11 FOR aslcN fi (r-12' DCCP) (MOMKY(fR SIIAI.l, IuVE AT LFASi R16SER r 0.5 r001 Of ERE(DOAD ADM — - — — —� D[SICN srOR4 WATER SURFACE CILVAlION �— — — — — — — N000 / CuERC[NCY SPILLWAY Tbfr ST)ci riTsALP NfAr — - IN/lOw .ivatai+ru ►r.N.A. — — — — — — ANTI -SEC _ CavA+s uHNTARNCO CRASS 2X OR GREATER SLoPC FOR DRANuOC 00n0u A SIDE SLOPES BOTTOM STA4C 42ro 10 SIDE VIEW o/`uEM STORu `O11" E PCR/ORAICD RISER UKJSED IN GRAVEL .VCKEi (rYP.) REFERENCE: CONTROWNG URBAN Rlxrorr 1 NOT 10 SCALE STANDARD SPECIFICATIONS FOR WET PONDS REQUIRED SPECIFICATIONS • Minimum length to width ratio of 2:1 (preferably wedge shaped). • Inlet and outlet located to maximize flow length. • Minimum depth of permanent pool 2.0 feet, maximum depth of 10.0 feet. • Design for full development upstream of control. • Side slopes shall be no greater than 3:1 if mowed. • Rip -rap protection (or other suitable erosion control means) for the outlet and all inlet structures into the pond. • Minimum drainage area of 10 acres. • Anti -seep collars on barrel of principal spillway. • One-half foot minimum freeboard above peak stage for top of embankment. • Emergency drain; i.e. sluice gate, drawdown pipe; capable of draining structure within 24 hours. • Emergency spillway designed to pass the 50-year storm event (must be paved in fill areas). • Trash racks, filters, hoods or other debris control on riser. • Maintenance access (< 15 9c slope and 10 feet wide). • Benchmark for sediment removal. • Paved or concrete channel. RECOMMENDED SPECIFICATIONS • Multi -objective use such as amenities or flood control. • Landscaping management of buffer as meadow. • Design for multi -function as flood control and extended detention. • Minimum length to width ratio of 3:1 to 4:1 (preferably wedge shaped). • Use reinforced concrete instead of corrugated metal. • Sediment forebay (often designed for 10-20 5r of total volume). Forebay should have separate drain for de -watering. • Provision shall be made for vehicle access at a 4:1 slope. 0 Impervious soil boundary to prevent draw -down. • Shallow marsh area around fringe (including aquatic vegetation). • Safety bench at toe of slope (minimum 10 feet wide). • Minimum 25 foot wide buffer around pool. • Mow embankment and side slopes at least twice a year. • Emergency drain to allow draw -down within 24 hours. • On -site disposal areas for two sediment removal cycles protected from runoff. • An oil and grease skimmer for sites with high production of such pollutants. The figure on the next pace presents a typical wet pond design. TOP VI W SCHEMATIC OF TYPICAL WET POND ILATNE SIRUOS A14D TREES PLMr1O FOR WILOUrE- COVER ARWND KqF OF POND'S PERIMETER IOE SLOPES �� _ SF/[ry BENCH FESCUE NOvcl TREES OH J ~ YIIIf �.7�11"�'fi"r "��. — `- •�: •1 ' ' •RISER tTYSt',z OV1rAEE PROTCC110f1 URGE RIPRAP .'i .•. .t .1 ...� i ' • SEOIMEMY B VrpEE . 1 . .�,+.' fORCOAY ;♦'\,, (AS. REO'D) on ,� • Vt �.(`.I �{ tq .. � �,��Piytrr ;; ., ..' •... ER p ROCK DErucroas uIN vu ooWIDE \ .: ' "''.: '. /..... 1.)y/ Y �/"y !: r S rt ••�_. t �'I a ' e p (AS REO'O) •_i::. `•-' '• ' •.h �`%: s£y�� d �. {,h ���I�.`Jv. ;•s CLACROEtcy Kx ':11 �'L�L>S\ LL•�.'� t\�)uT `Lt} Cy�/�'%T"1 CNCRCCNCY �' ��� � SPILLWAY �+rf•t� l RESERVE ON-SEC•=�1'a:u' OISPOSAL AREA rOR (l DREDGEO SEDNtfli Twit HOW _—_—_--_— STORUwAIER STORAGE -----_ WEIR— Eu6WKUENT n rcRUAwilrt :voo ' Ai. SEEP SEDIUENT FOREBAY •''.�• COLtlJIS (P,.EO AS MARSN) .. .. //�r CLAY OR GCOIEXRLE LINER (IF EKISTYtG SOILS ARE P(RUEABLE) SIDE VIEW RFFFRFNCF: CONTROLuNO uRB.W RUNOrr I u G A 1 1 1 1 1 i 1 STANDARD SPECIFICATIONS FOR WATERSHED PROTECTION BASINS (A) All storm water control structures shall be designed by either a North Carolina Registered Professional Engineer or Landscape Architect, to the extent that the General Statutes, Chapter 89A, allow. (B) All storm water controls shall use wet detention ponds as a primary treatment system. Specific requirements for these systems shall be in accordance with the follow design criteria: (1) Volume of the permanent pool shall be a minimum of four (4) times the volume of runoff generated by the mean storm over the contributing watershed. In addition, the discharge rate from these ponds following a one (1) inch rainfall design storm shall be such that the runoff does not draw down to the permanent pool level in less than two (2) days and have a maximum vertical distance of two (2) feet. (2) The permanent pool surface area shall be a minimum of one percent (I %) of the drainage area. (3) The mean depth of the permanent pool shall be a minimum of three (3) feet. (4) The maximum depth of the permanent pool depth shall be ten (10) feet. (5) The pond shall have a minimum length to width ratio of 4:1 (preferably an irregular pond shape). (6) The inlet and outlet shall be located to maximize flow length. (7) The design shall assume full development (maximum allowed in accordance to current zoning regulations) in the contributing drainage area. (8) At the elevation of permanent pool, a minimum ten (10) feet wide, one (1) foot deep shelf (littoral shelf) shall be provided around the perimeter of the permanent pool, or a littoral shelf equivalent in area to 35 % of the surface area of the pond at maximum elevation of water quality storage pool, whichever is greater. (9) The littoral shelf shall be planted with aquatic vegetation shown in Attachment A, or equivalent, that is suitable for planting in this area. (10) The design must include a sediment forebay with a design volume equivalent to 20% of the permanent pool volume. The forebay shall also include a separate drain for dewatering. The forebay volume cannot be included as part of the permanent pool volume requirement. See schematic drawing for further details. (11) Side slopes of the pond shall be no greater than 4: 1. (12) Rip -rap protection (or other suitable erosion control means) shall be provided for all outlet and inlet structures. (13) All risers/barrels must be reinforced concrete rather than corrugated metal. In addition, all risers must be checked for floatation. (14) Anti -seep collars shall be provided on the barrel of the principal spillway. (15) A minimum one-half foot freeboard shall be provided above peal: stage to the top of the , embankment. (16) The pond shall be equipped with an emergency drain (i.e. sluice sate, drawn down pipe) capable ' of draining the structure within twenty-four (24) hours. (17) The pond shall have an emergency spillway designed to pass the 50-year storm event. The ' difference between the one (1) inch rainfall design storm and the 50-year storm (water quantity volume) should be released downstream in 12 hours or less. (18) The inlet structure to the forebay shall be designed to minimize turbulence using baffles or other ' appropriate design features. (19) Vegetative filters shall be constructed for the overflow and discharge of all storm water wet , detention ponds and shall be at least thirty (30) feet in length. The slope and width of the vegetative filter shall be determined so as to provide a non -erosive velocity of flow -through the filter for a 10-year 24-hour storm with a slope of five percent or less. Vegetation in the filter ' shall be natural vegetation, grasses or artificially planted wetland vegetation appropriate for the site characteristics. (20) The riser shall be located within or on the face of the embankment rather than out in the middle , of the pool. (21) Hoods or trash racks shall be installed on both the low flow and design storm orifices to prevent clogging. The low flow orifice pipe shall be negatively sloped so that it draws water at least one foot below the surface of the permanent pool. (22) Maintenance access shall be provided to the pond at a required minimum width of 12 feet and shall be constructed of grass (0-3.59o), gravel (3.5-10.57oo) or paved (10.5-205ro), to allow access during wet weather conditions. (23) A benchmark shall be provided in both the forebay and permanent pond to indicate the maximum sediment level allowed. (24) A minimum ten (10) feet wide safety bench shall be provided outside the permanent pool area for the purpose of manuerving landscaping equipment. It is recommended that this safety bench be located at the top of sloping banks. (25) A minimum ten (10) feet wide buffer shall be provided around the storm water management facility. The ten (10) feet wide safety bench mentioned above can be located within the buffer as long a other design criteria is adherted to. (26) A clay or geotextile liner may be required if the existing pond soils are permeable. (27) An oil and grease skimmer may be required for commercial or industrial use sites with a high production of such pollutants. (28) A description of the area containing the storm water control structure shall be prepared and filed as a separate deed with the County Register of Deeds along with any easements necessary for ,general access to the storm water control structure. The deeded area shall include the detention ' pond, vegetative filters, all pipes and water control structures, berms, dikes, etc., and sufficient area to perform inspections, maintenance, repairs, and reconstruction. (29) Dams 15 feet or higher (measured at the downstream side of the dam) with an impoundment I ' capacity of 10-ac-feet or greater at the top of the dam must obtain a Dam Safety permit from North Carolina Department of Natural Resources, Land Quality. See wet pond f aure for typical design. MAINTENANCE STANDARDS FOR EXTENDED DETENTION AND WET PONDS Sediment to be removed when 50% of forebay volume is filled and/or when 20% of the permanent pool volume is filled (design storage volume must account for volume lost to sediment storage). Sediment traps shall be cleaned out when filled. No woody vegetation shall be allowed to grow on the embankment without special design provisions. Other vegetation shall be cut when it exceeds 18 inches in height unless part of planned landscaping. Debris shall be removed from blocking inlet and outlet structures and from areas of potential clogging. The control shall be kept structurally sound, free from erosion, and functioning as designed. Periodic removal of dead vegetation shall be accomplished. No standing water is allowed within extended detention pond unless Design n6 is selected. An annual inspection is required, reports to be kept by owner. The site should be inspected and debris removed after every major storm. All special consideration maintenance responsibilities will be listed in the credit application. ACCEPTABLE PLAINT SPECIES FOR LITTORAL SHELF PLANTING MECKLENBURG COUNTY NORTH CAROLINA Developed by David D. Patrick, Jr., HDR Engineering, Inc. Common Name Scientific Name 1 • Fragrant water lily Nvmohaea odorata 2• Arrow -head Saoittaria latifolia var pubeseeus. S lonoirostra 3. Bacopa Mecardonia acuminata 4• Hedge hyssop Gratiola virgimans . 5• False -pimpernel Lindernia dubia 6. Soft rush Juncus effusus 7. Bulrush Scirous validus: S. atrovirene. S. cv erinus S• Spikerush. Eleocharis obtusa. among others 9- Day flower Commelina communis 10. Blue -flag Iris Iris viroinica 11. Lizard's tail Saururus cemuus 12• Maidencane Panicum spp. 13. Pickerelweed Pontederia cordata 14. Meadow-buary Rhexia mariana. R. virsinica 15. Marsh seedbox Ludwigia oalustris 16. Cutgrass Leersia viroinica. L. orvzoides 17. Hatpins Eriocaulon decangrulare is. Bog buttons Lachnocaulon ances Hvdric Resime 3 2 • 1 1 I 1 7 1 1 1 1,2 1,2 2 1 1,2 1 1 1 Common Name A. Swamp Rose B. Buttonbush C. Willow D. Virginia willow E. Alder F. Maleberry G. Fetterbush H. Swamp Dogwood SHRUBS Scientific Name Rosa_ palustns Ceohalanthus occidentalis Sal ix nigh Itealtea v_ irginica Alnus serrulata Lvonia ligustrina Leucothoe racemosa Cornus amomum Hvdric Regime 1 = less than 1 ft. of water (extended inundation) 2 = 1 ft. - 2 ft. of water 3 = more thatn 2 ft. of water Hvdric Regime 1 i 1 1 1 1 1 1 1 Common Name Scientific Name rx 19. Buttercup Ranunculus pusillus. R. carolinianus ' 20. Easter Lily Zephvranthes atamasco 21. Arrow Arum Peltandra virginica ' 22. Cattail Tvpha latifolia 23. Sedge Carex supp. 24. Flat sedge Cvperus spp. ?5. Bedstraw Galium tinctorium As! .s Hvdric Regime 1 i 1,2 2,3 1 1 1