6.02.1 PURPOSE
The purpose of these requirements is to provide criteria in addition to other ordinances, rules, regulation, and law to control and minimize the adverse impacts of drainage systems, stormwater runoff and erosion control from new development and redevelopment.
6.02.2 APPLICABILITY
A. General
Beginning with and subsequent to its effective date, this ordinance shall apply to the following unless exempt pursuant to the “Exemption” subsection of this article:
1. Residential development activities that disturb one acre or more;
2. Non-residential development activities that disturb one-half acre or more; and
3. Activities that are part of a common plan of development or sale that exceed those area thresholds, even though multiple, separate or distinct activities take place at different times on different schedules.
B. Exemptions
The following types of projects shall be exempt from the stormwater requirements of this section:
1. Redevelopment outside the floodplain that results in no net increase in built-upon area and provides equal or greater stormwater control than the previous development;
2. Redevelopment of residential structures within the floodplain that results in no net increase in built-upon area and provides equal or greater stormwater control than the previous development;
3. Redevelopment of non-residential structures within the floodplain that disturbs less than one-half acre, that is not part of a larger common plan of development or sale, and that results in no net increase in built-upon area and provides equal or greater stormwater control than the previous development; and
4. Normal farming, silviculture, and ranching activities such as plowing, seeding, cultivating, minor drainage, harvesting for the production of food, fiber, and forest products, or upland soil and water conservation practices.
C. Existing Development
1. Existing development as defined in this article, may be continued and maintained subject to the provisions provided herein. Expansions to structures classified as existing development shall meet the requirements of this article; however, the built-upon area of the existing development is not required to be included in the density calculations.
2. Existing building or built-upon area on a single-family lot that is not in conformance with the restrictions of this article that has been damaged or removed may be repaired or reconstructed.
D. Other Laws, Regulations, Ordinances, Easements and Resolutions
Where this ordinance interacts with other laws, regulations, ordinances, and resolutions, the following procedures shall apply:
1. Nothing contained herein shall repeal, modify, or amend any federal or state law or regulation, or any ordinance or regulation pertaining thereto except any ordinance which these regulations specifically replace;
2. No provision of this ordinance shall amend, modify, or restrict any provision of the Lillington Unified Development Ordinance;
3. The adoption of this section shall and does amend any and all ordinances, resolutions, and regulations in effect in Lillington at the time of the adoption of this ordinance that may be construed to impair or reduce the effectiveness of this ordinance or to conflict with any of its provisions; and
4. It is not intended that these regulations interfere with any easement, covenants or other agreements between parties. However, if the provisions of these regulations impose greater restrictions or higher standards for the use of a building or land, then the provisions of these regulations shall control.
E. Non-Conforming Lots of Record
If a nonconforming lot of record is not contiguous to any other lot owned by the same party, then that lot of record shall not be subject to the development restrictions of this ordinance if it is developed for single-family residential purposes.
6.02.3 NATURAL DRAINAGE SYSTEM UTILIZED TO EXTENT FEASIBLE
A. Natural Contours and Drainage Ways
To the extent practicable, all development shall conform to the natural contours of the land and natural and pre-existing man-made drainage ways shall remain undisturbed.
B. Lot Boundaries
To the extent practicable, lot boundaries shall be made to coincide with natural and preexisting man-made drainage ways within subdivisions to avoid the creation of lots that can be built upon only by altering such drainage ways.
at can be built upon only by altering such drainage ways.
6.02.4 DEVELOPMENTS MUST DRAIN PROPERLY
A. No Undue Retention of Surface Water
Developments shall be provided with a drainage system that is adequate to prevent the undue retention of surface water on the development site. Surface water shall not be regarded as unduly retained if:
1. The retention results from a technique, practice or device deliberately installed as part of an approved sedimentation or stormwater runoff control plan; or
2. The retention is not substantially different in location or degree than that experienced by the development site in its predevelopment stage unless such retention presents a danger to health or safety.
B. No Channeling of Surface Water to a Sanitary Sewer
No surface water may be channeled or directed into a sanitary sewer. Whenever practicable, the drainage system of a development shall coordinate with and connect to the drainage systems or drainage ways on surrounding properties or streets.
C. No Unreasonable Burden to Adjacent Properties
All developments shall be constructed and maintained so that adjacent properties are not unreasonably burdened with surface waters as a result of such developments. More specifically:
1. No development may be constructed or maintained so that such development unreasonably impedes the natural flow of water from higher adjacent properties across such development, thereby unreasonably causing substantial damage to such higher adjacent properties; and
2. No development may be constructed or maintained so that surface waters from such development are unreasonably collected and channeled onto lower adjacent properties at such locations or at such volumes as to cause substantial damage to such lower adjacent properties.
6.02.5 STORMWATER DRAINAGE DESIGN REQUIREMENTS
A. Stormwater Outlets
Stormwater outlets shall be designed so that they do not cause erosion downslope of the discharge point during the peak flow from the ten-year storm event as shown by engineering calculations.
B. Stormwater Collection Pipes
1. Systems shall be designed based on the two-year storm for street inlet spacing, the ten-year storm for street drainage pipe sizing, and the 25-year storm for cross-street drainage. Hydraulic grade line shall remain inside the pipe for the corresponding storm event;
2. Pipe slope shall be a minimum of 0.5% and a maximum 10%;
3. The minimum pipe diameter shall be 15 inches;
4. Pipe shall be installed to provide a true line and grade between structures;
5. The maximum length between access points shall be 400 feet for all pipe sizes; and
6. The minimum cover for stormwater pipe shall be two feet measured from the top of pipe to the finished subgrade under the roads and one foot to finished grade in non-load-bearing areas, and as recommended by the pipe manufacturer.
C. Catch Basins and Structures
1. Gutter flow calculations shall be submitted with the design. Water shall be picked up before the spread into the street exceeds eight feet for curb and gutter streets. In areas of heavy pedestrian traffic, the maximum allowable spread may be decreased by the Administrator;
2. No inaccessible storm drainage structures shall be allowed; and
3. All drainage structures shall conform to the Town of Lillington Standard Roadway, Sidewalk, Curb & Gutter, & Drainage Pipe Specifications.
D. Vegetated Conveyances
All vegetated conveyances shall meet the standards below regardless of whether they are installed on a low or high density project:
1. Open channels, ditches, and driveway pipes shall be designed based on the ten-year storm;
2. The minimum size for any culvert or driveway pipe is 15 inches;
3. Side slopes shall be no steeper than 3:1 (horizontal to vertical) unless it is demonstrated that the soils and vegetation will remain stable in perpetuity based on engineering calculations and on-site soil investigation; and
4. Vegetated swales shall be designed to carry the design flow at non-erosive velocities during the ten-year storm. Calculations indicating design velocities shall be provided along with typical channel cross-sections. Rip rap or synthetic matting shall be provided when velocities exceed four feet per second.
E. Curb Outlet Systems
Low density projects may use curb and gutter with outlets to convey stormwater to grassed swales or vegetated areas. Requirements for curb outlet systems shall be as follows:
1. The curb outlets shall be designed such that the swale or vegetated area carry the peak flow from the ten-year storm at a non-erosive velocity;
2. The longitudinal slope of the swale or vegetated area shall not exceed 5%, except where not practical due to physical constraints. In these cases, devices to slow the rate of runoff and encourage infiltration to reduce pollutant delivery shall be provided;
3. The swale’s cross section shall be trapezoidal with a minimum bottom width of two feet;
4. The side slopes of the swale or vegetated area shall not be steeper than 3:1 (horizontal to vertical); and
5. The minimum length of the swale or vegetated area shall be 100 feet.
6.02.6 DENSITY AND BUILT-UPON AREA REQUIREMENTS
A. Built-Upon Area Calculation
Percentage built-upon area shall be calculated by dividing the total BUA on the project by the total project area. Pervious area that is required for a project to comply with the provisions of this article shall not be included in another project’s area.
B. Maximum Built-Upon Area
Maximum built-upon area shall be as indicated in the table below, or as required by the base zoning district, whichever is less.
Classification | Maximum BUA for Low Density | Maximum BUA for High Density |
Outside of Water Supply Watershed | 24% and a maximum of 2 units/acre for single-family residential developments | Follow base zoning. |
Cape Fear River Water Supply Watershed – Critical Area (WS-IV-CA) | 24% and a maximum of 2 units/acre for single-family residential developments | 50% or base zoning, whichever is less. |
Cape Fear River Water Supply Watershed – Protected Area (WS-IV-PA) | With curb and gutter: 24% and a maximum of 2 units/acre for single-family residential developments Without curb and gutter: 36% and a maximum of 3 units/acre | 70% or base zoning, whichever is less. |
C. Cluster Development
Clustering of development is allowed under the following conditions:
1. Minimum lot sizes are not applicable to single-family cluster development projects; however, the total number of lots shall not exceed the number of lots allowed for single- family detached developments in the table above;
2. All built-upon area shall be designed and located to minimize stormwater runoff impact to the receiving waters, minimize concentrated stormwater flow, maximize the use of sheet flow through vegetated areas, and maximize the flow length through vegetated areas; and
3. The remainder of the tract shall remain in a vegetated or natural state. Title the open space area shall be conveyed to:
a. An incorporated homeowners' association for management. Where a property association is not incorporated, a maintenance agreement shall be filed with the property deeds;
b. A local government for preservation as a park or open space; or
c. A conservation organization for preservation in a permanent easement.
6.02.7 STORMWATER MANAGEMENT REQUIREMENTS
A. Low Density Projects
Low density projects shall meet the requirements set forth in 15A NCAC 02H .1003(6), including:
1. Projects shall adhere to the maximum built-upon area or lot size per Section 6.02.6.B;
2. Projects shall be designed to maximize dispersed flow through vegetated areas and minimize channelization of flow. Stormwater that cannot be released as dispersed flow shall be transported by vegetated conveyances with a minimal amount of non-vegetated conveyances for erosion protection or piping for driveways or culverts under a road shall be allowed when it cannot be avoided;
3. Vegetated conveyances shall meet the requirements; and
4. Low density projects may use curb and gutter with outlets to convey stormwater to grassed swales or vegetated areas. Curb outlet systems shall be designed in accordance with Section 6.02.5.E.
B. High Density Projects
High density projects shall meet the following requirements:
1. Developments that use a piped drainage system or an SCM shall be considered high density regardless of the percentage built-upon area in the development;
2. Stormwater control measures (SCMs) shall be provided to control the difference in stormwater runoff rate leaving the project site between the pre- and post-development conditions for, at a minimum the one-year, 24-hour storm and the ten-year, 24-hour storm. If a project contains multiple drainage basins and/or patterns, each drainage basin shall be designed with the same criteria;
3. SCMs shall provide sufficient storage volume to detain and treat on-site the runoff from the first inch of rainfall. Runoff drawdown time for the one-inch storm event shall be a minimum of 48 hours, but not more than 120 hours;
4. SCMs shall be selected based on the “Primary SCMs” category as listed in the NCDEQ Stormwater Design Manual. Alternatively, projects may be designed to meet “Runoff Volume Match” as defined in 15A NCAC 02H .1002;
5. SCMs shall be designed to meet all minimum design criteria (MDC) codified in 15A NCAC 02H .1003 and .1050 through .1062 and as published in the most recent NCDEQ Stormwater Design Manual;
6. For high density projects, stormwater and downstream impact analyses shall the provided; and
7. SCM designs and impact analyses shall be sealed by a professional engineer licensed with the North Carolina Board of Examiners for Engineers and Surveyors.
C. Deed Restrictions and Protective Covenants
The owner shall record deed restrictions and protective covenants prior to the issuance of a certificate of occupancy to ensure that projects will be maintained in perpetuity consistent with the plans and specifications approved by the permitting authority. For projects owned by public entities, the permittee shall have the option to incorporate specific restrictions and conditions into a facility management plan or another instrument in lieu of deed restrictions and protective covenants.
D. Variations from this Section
The Town shall have the authority to approve projects on a case-by-case basis that do not comply with the provisions of this section if the applicant provides technical justification based on engineering calculations and the results of research studies that the proposed design provides equal or better control of stormwater and protection of waters and that it will function in perpetuity.
6.02.8 VEGETATED SETBACKS
A. Location
Vegetated setbacks shall be required along intermittent and perennial waterbodies and streams that are indicated on the most recent versions of the United States Geological Survey (USGS) 1:24,000 scale (7.5 minute) quadrangle topographic maps, or as defined by a jurisdictional determination done as follows:
1. Where USGS topographic maps do not distinguish between perennial and intermittent streams, an on-site stream determination shall be performed by a qualified individual;
2. A qualified individual is one who has been certified to perform stream determinations by completing and passing the Surface Water Identification Training and Certification (SWITC) Course offered by the North Carolina Division of Water Resources and North Carolina State University;
3. Stream calls shall be made prior to submitting development plans to the Town for review;
4. If it disagrees with the stream call made by the qualified individual, the Town shall have the authority to require the applicant to obtain a stream call from the NCDEQ and adhere to the agency’s determination; and
5. Vegetated setbacks shall not be included in parcel lines for residential parcels.
B. Minimum Vegetation Widths
The width of a vegetated setback shall be measured in the field horizontally from the normal pool elevation of impounded structures, from the top of bank of each side of streams or rivers. The following minimum widths shall be in accordance with the table below:
Type of Development | Intermittent Streams | Perennial Streams |
Low density | 30 feet | 30 feet |
High density | 30 feet | 100 feet |
C. Stormwater Flow Through the Setback
Stormwater that has not been treated in an SCM shall not be discharged through a vegetated setback; instead it shall be released at the edge of the vegetative setback and allowed to flow through the setback as dispersed flow.
D. Allowed Uses
Vegetated stream buffers may be cleared or graded but shall be replanted and maintained as grass or other vegetation. The following types of built-upon area when it is not practical to locate it elsewhere, the footprint is minimized, and channelization of runoff is avoided:
1. Publicly-funded projects such as roads, greenways, and sidewalks;
2. Water dependent structures such as docks;
3. Minimal footprint uses such as poles, signs, utility appurtenances, and security lights;
4. Park structures such as gazebos, benches, and playground equipment;
5. SCMs within the outer 70 feet of a 100-foot high density, perennial buffer;
6. Desirable artificial stream bank or shoreline stabilization approved by the Administrator; and
7. Additional allowed uses that may be permitted at the discretion of the Administrator.
6.02.9 OPERATION AND MAINTENANCE OF STORMWATER CONTROL MEASURES
A. Posting of Financial Security
1. All new SCMs shall be conditioned on the posting of adequate financial assurance for the purpose of maintenance, repairs or reconstruction necessary for adequate performance of the SCMs;
2. The Town may, at its discretion, require the submittal of a performance security or bond with surety, cash escrow, letter of credit or other acceptable legal arrangement prior to issuance of a permit in order to ensure that the SCMs are installed by the permit holder as required by the approved stormwater management plan, and/or maintained by the owner as required by the operation and maintenance agreement;
3. The amount of an installation performance security shall be the total estimated construction cost of the SCMs approved under the permit, plus 25%; and
4. The amount of a maintenance performance security shall be the present value of an annuity of perpetual duration based on a reasonable estimate of the annual cost of inspection, operation and maintenance of the SCMs approved under the permit, at a discount rate that reflects the jurisdiction’s cost of borrowing minus a reasonable estimate of long-term inflation.
B. Uses of Performance Security
1. The performance security shall contain forfeiture provisions for failure, after proper notice, to complete work within the time specified, or to initiate or maintain any actions which may be required of the applicant or owner in accordance with this ordinance, approvals issued pursuant to this ordinance, or an operation and maintenance agreement established pursuant to this ordinance;
2. Upon default of the owner to construct, maintain, repair and, if necessary, reconstruct any SCM in accordance with the applicable permit or operation and maintenance agreement, the Administrator shall obtain and use all or any portion of the security to make necessary improvements based on an engineering estimate. Such expenditure of funds shall only be made after requesting the owner to comply with the permit or maintenance agreement; and
3. In the event of a default triggering the use of installation performance security, the Town shall not return any of the unused deposited cash funds or other security, which shall be retained for maintenance.
C. Costs in Excess of Performance Security
If the Town takes action upon such failure by the applicant or owner, the Town has the authority to collect from the applicant or owner the difference between the amount of the reasonable cost of such action and the amount of the security held, in addition to any other penalties or damages due.
D. Refund
Within 60 days of the final approval, the installation performance security shall be refunded to the applicant or terminated, except any amount attributable to the cost (plus 25%) of landscaping installation and ongoing maintenance associated with the BMPs covered by the security. Any such landscaping shall be inspected one year after installation with replacement for compliance with the approved plans and specifications and, if in compliance, the portion of the financial security attributable to landscaping shall be released.
E. Maintenance and Upkeep
1. An operation and maintenance plan or manual shall be provided by the owner(s) for each SCM, indicating what operation and maintenance actions are needed, what specific quantitative criteria will be used for determining when those actions are to be taken and, consistent with the operations maintenance agreement, who is responsible for those actions. The plan shall clearly indicate the steps that will be taken for restoring an SCM to design specifications if a failure occurs. The agreement shall be filed with the Harnett County Register of Deeds;
2. Landscaping and grounds management shall be the responsibility of the owning entity. However, vegetation shall not be established or allowed to mature to the extent that the integrity of the SCM is diminished or threatened, or to the extent of interfering with any easement or access to the SCM; and
3. Except for general landscaping and grounds management, the owning entity shall notify the Administrator prior to any repair or reconstruction of the SCM. All improvements shall be made consistent with the approved plans and specifications of the SCM and the operation and maintenance plan or manual. After notification by the owning entity, the Administrator shall inspect the completed improvements and shall inform the owning entity of any required additions, changes or modifications and of the time period to complete said improvements.
F. Minor Amendments to Plans and Specifications
1. Amendments to the plans and specifications of the SCM and/or the operation and maintenance plan or manual shall be approved by the Administrator, provided that the changes do not involve a change in the size or location of the structure; and
2. Proposed changes shall be prepared by a state registered professional engineer and submitted to and reviewed by the Administrator as follows:
a. If the Administrator approves the proposed changes, the owning entity of the SCM shall file sealed copies of the revisions with the Administrator; or
b. If the Administrator disapproves the changes, the proposal may be revised and resubmitted to the Administrator as a new proposal. If the proposal has not been revised and is essentially the same plan that was already reviewed, it shall be returned to the applicant.
G. Major Amendments to Plans and Specifications
Amendments to the plans and specifications of the SCM and/or the operation and maintenance plan or manual that involve a change in the size or location may be approved by the Administrator. Proposed changes shall be prepared by a state registered professional engineer and submitted to and reviewed by the Administrator.
H. Revision of Plan Required if Found to be Inadequate
1. If the Town finds that the operation and maintenance plan or manual is inadequate for any reason, the Administrator shall notify the owning entity of any required changes and shall prepare and file copies of the revised agreement with the Harnett County Register of Deeds, the Administrator and the owning entity; and
2. If the Administrator finds that the operation and maintenance plan or manual is inadequate for any reason, the Administrator shall notify the owner(s) of any required changes. Once the revised plan or manual has been deemed adequate, the owner(s) shall prepare and file copies of the revised agreement with the Harnett County Register of Deeds and the Administrator of this ordinance.
I. Inspection and Release of Performance Bond
1. The SCM shall be inspected by the Administrator, after the owning entity notifies the Administrator that all work has been completed. At this inspection, the owning entity shall provide:
a. The signed deed, related easements and survey plat for SCM ready for filing with the Harnett County Register of Deeds; and
b. A certification sealed by an engineer stating that the SCM is complete and consistent with the approved plans and specifications. Record drawings of the SCM shall also be provided for review;
2. The Administrator shall obtain the materials submitted by the developer and the inspection report as follows:
a. If the Administrator approves the inspection report and accepts the certification, deed and easements, the Administrator shall file the deed and easements with the Harnett County Register of Deeds, release up to 75% of the value of the performance bond or other surety and issue a zoning permit for the SCM; or
b. If deficiencies are found, the Administrator shall direct those improvements and inspections be made and/or documents corrected and resubmitted to the Administrator; and
3. No sooner than one year after the filing date of the deed, easements and maintenance agreement, the developer may petition the Administrator to release the remaining value of the performance bond or other security. Upon receipt of said petition, the Administrator shall inspect the SCM to determine whether the SCMs are performing as designed and intended as follows:
a. If the Administrator approves the SCM and accepts the petition, the developer shall deposit with the Town a cash amount equal to that described above, after which, the Administrator shall release the performance bond or other security; or
b. If the Administrator does not approve the SCM and rejects the petition, the Administrator shall provide the developer with instructions to correct any deficiencies and all steps necessary for the release of the performance bond or other surety.
J. Annual SCM Inspection and Maintenance Requirements
1. All SCMs shall be inspected at least once on an annual basis to determine whether the controls are performing as designed and intended. It shall be the responsibility of the property owner(s) to ensure such inspection is performed. Records of inspections shall be maintained on forms approved or supplied by the NCDEQ. Annual inspections shall begin within one year of the filing date of the deed for the SCM and an inspection report shall be submitted to the Town in the format approved by the Administrator;
2. In the event that an inspector discovers that an SCM needs improvements, he/she shall notify the owner and the Administrator. The owner shall make improvements consistent with the plans and specifications of the SCM and the operation plan or manual. After the improvements are made, the owner shall submit a maintenance log to the Town. The improvements shall be made, and the maintenance log shall be submitted with 90 days of the inspection unless the Administrator has granted an extension to the owner;
3. The Administrator may inspect SCMs at any time to determine if they are in compliance; and
4. In the event that the owner fails to provide an annual inspection report, perform needed maintenance, or submit a maintenance log, the Town reserves the right to levy fines against property owner until the SCM is inspected and, if necessary, brought in compliance with approved plans, specifications, and operations manual.
(Ord. passed 2-14-2017; Ord. 2022-13, passed 10-12-2021; Ord. FY2023-27, passed 5-9-2023)