City of Charlotte / County of Mecklenburg
Charlotte Post Construction Stormwater Ordinance
Division 6. Maintenance
Sec. 18-191. Dedication of BMPs, facilities and improvements.
(a) Single-family residential BMPs accepted for maintenance. The city shall accept maintenance responsibility (as specified in the administrative manual) of structural BMPs that are installed pursuant to this article following a warranty period of two years from the date of as-built certification described in section 18-123, provided the BMP:
(1) Only serves a single-family detached residential site or townhomes all of which have public street
(2) Is satisfactorily maintained during the two-year
warranty period by the owner or designee;
(3) Meets all the requirements of this article and the design manual; and
(4) Includes adequate and perpetual access and sufficient area, by easement or otherwise, for inspection, maintenance, repair or reconstruction. The stormwater administrator must receive an application for transfer of maintenance responsibilities for the structural BMP along with the stormwater management permit application. The stormwater administrator will develop and distribute this application as a component of the administrative manual (see subsection 18-122).
(b) Maintenance and operation of BMPs. The owner of a structural BMP installed pursuant to this article and not covered under subsection (a) shall maintain and operate the BMP so as to preserve and continue its function in controlling stormwater quality and quantity at the degree or amount of function for which the structural BMP was designed.
(c) Damage or removal of trees. The following provisions apply to trees contained in permitted natural area areas or in BMPs that are damaged or removed:
(1) For trees damaged or removed due to natural disasters, the owner shall be required to replace the trees in accordance with the natural area mitigation criteria described in subsection 18-175(c)(1) within a timeframe specified by the stormwater administrator.
(2) For trees damaged or removed due to reasons other than subsection (c)(1), the owner shall be required to replace the trees in accordance with the natural area mitigation criteria described in subsection 18-175(c)(1) within a time frame specified by the stormwater administrator with the following exception, the trees shall be replaced at twice the specified density. In addition, the owner may be subject to fines as described in division 7.
(d) Annual maintenance inspection and report. The person responsible for maintenance of any BMP installed pursuant to this article and not covered under subsection (a) shall submit to the stormwater administrator an inspection report from a qualified registered state professional engineer or registered landscape architect performing services only in their area of competence. All inspection reports shall be on forms supplied by the stormwater administrator that are contained in the administrative manual. An original inspection report shall be provided to the stormwater administrator beginning one year from the date of as-built certification and each year thereafter on or before the anniversary date of the as-built certification.
Sec. 18-192. Operation and maintenance agreement.
(a) General. At the time that as-built plans are provided to the stormwater administrator as described in section 18-123 and prior to final approval of a project for compliance with this article, but in all cases prior to placing the BMPs in service, the applicant or owner of the site must execute an operation and maintenance agreement that shall be binding on all current and subsequent owners of the site, portions of the site, and lots or parcels served by the structural BMP. Failure to execute an operation and maintenance agreement within the time frame specified by the stormwater administrator may result in assessment of penalties as specified in division 7. Until the transference of all property, sites, or lots served by the structural BMP, the original owner or applicant shall have primary responsibility for carrying out the provisions of the maintenance agreement. At the discretion of the stormwater administrator, certificates of occupancy may be withheld pending receipt of an operation and maintenance agreement.
The operation and maintenance agreement shall require the owner or owners to maintain, repair and, if necessary, reconstruct the structural BMP, and shall state the terms, conditions, and schedule of maintenance for the structural BMP. In addition, it shall grant to the city a right of entry in the event that the stormwater administrator has reason to believe it has become necessary to inspect, monitor, maintain, repair, or reconstruct the structural BMP; however, in no case shall the right of entry, of itself, confer an obligation on the city to assume responsibility for the structural BMP.
Standard operation and maintenance agreements for BMPs shall be developed by the stormwater administrator and made available in the administrative manual. The operation and maintenance agreement must be approved by the stormwater administrator prior to plan approval, and it shall be referenced on the final plat as described in section 18-148.
(b) Special requirement for homeowners' and other associations. For all structural BMPs required pursuant to this article not covered under subsection 18-192(a), and that are to be or are owned and maintained by a homeowners' association, property owners' association, or similar entity, the required operation and maintenance agreement shall include the provisions described in the design manual.
Sec. 18-193. Inspection program.
Inspections and inspection programs by the city may be conducted or established on any reasonable basis, including but not limited to routine inspections; random inspections; inspections based upon complaints or other notice of possible violations; and joint inspections with other agencies inspecting under environmental or safety laws. Inspections may include, but are not limited to, reviewing maintenance and repair records; sampling discharges, surface water, groundwater, and material or water in BMPs; and evaluating the condition of BMPs. If the owner or occupant of any property refuses to permit such inspection, the stormwater administrator shall proceed to obtain an administrative search warrant pursuant to G.S. 15-27.2 or its successor. No person shall obstruct, hamper or interfere with the stormwater administrator while carrying out his or her official duties.
Sec. 18-194. Performance security for installation and maintenance.
The city may 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 accordance with the provisions contained in the administrative manual.
Sec. 18-195. Records of installation and maintenance activities.
The owner of each structural BMP shall keep records of inspections, maintenance, and repairs for at least five years from the date of creation of the record and shall submit the same upon reasonable request to the stormwater administrator.
Sec. 18-196. Maintenance easement.
Every structural BMP installed pursuant to this article shall be made accessible for adequate inspection, maintenance, reconstruction and repair by a maintenance easement, which will be shown and labeled on all plans and plats. The easement shall be recorded to provided adequate and perpetual access and sufficient area, in favor of the city or otherwise, for inspection, maintenance, repair or reconstruction. All BMPs that are not located adjacent to a public right-of-way will require the owner to provide a 20- foot wide access easement in favor of the city that connects the BMP area to the public right-of-way. The easement shall be described on all plans and plats as follows: "The purpose of the Post Construction Controls Easement (PCCE) is to provide stormwater conveyance and for the control and treatment of stormwater runoff. Buildings or any other objects which impede stormwater flow, system performance or system maintenance are prohibited. This easement also provides for unlimited access for inspection and maintenance purposes to be performed on the BMP as required by the City of Charlotte's Stormwater Ordinance Post Construction Controls Regulations." The easement shall be recorded as described in section 18-148 and its terms shall specify who may make use of the easement and for what purposes.
Administrative Manual for Implementation of the Post-Construction Storm Water Ordinance
Section 2.0 Post-Construction Storm Water Ordinance
The Standards Section (Section 3) of the Post-Construction Storm Water Ordinance describes the specific criteria that all applicable development and redevelopment must meet in order to control storm water quality, volume and velocity. The following criteria are required by all jurisdictions:
1. Installation of structural best management practices (BMPs) when a built-upon area threshold is exceeded.
2. Maintaining buffers (no-build zones) adjacent to perennial and intermittent streams.
3. Installation of detention measures when a built-upon area threshold is exceeded.
In addition, new developments in all the jurisdictions except the Towns of Cornelius and Huntersville are required by the Post-Construction Storm Water Ordinance to set aside undisturbed open space as a form of non-structural BMP. This open space requirement does not apply to redevelopment. The Town of Huntersville has open space requirements outside of the Post-Construction Storm Water Ordinance. In the Towns of Mint Hill, Matthews and Davidson, the application of the criteria in the PostConstruction Storm Water Ordinance varies between designated watershed districts as described in the jurisdiction’s Post-Construction Ordinance Map. These maps are contained in Appendix 2-2. The manner in which the criteria are applied also varies significantly between the jurisdictions. Appendix 2-3 includes tables that summarize the application of these criteria by jurisdiction. Provided below is a discussion of how each of the criteria function to control storm water quality, volume and velocity. Also included below is a summary of the criteria in the different jurisdictions as described in their Post-Construction Storm Water Ordinance.
2.6.1 Structural Best Management Practices (BMPs)
A structural BMP collects storm water runoff from developed areas and provides water quality and quantity treatment to achieve water quality protection goals. Structural BMPs are designed and constructed in accordance with specifications contained in the Charlotte-Mecklenburg BMPDesign Manual. By meeting these specifications, the BMP is presumed to meet the minimum water quality performance standards of the Post-Construction Storm Water Ordinance and the Phase II laws. Failure to construct BMPs in accordance with these specifications may subject the owner to civil penalties. The Post-Construction Storm Water Ordinance requires that BMPs be designed to achieve 85% average annual removal of total suspended solids (TSS). For some watershed districts, BMPs are must be designed to achieve 70% average annual removal of total phosphorus (TP) in addition to 85% removal of TSS. These removal efficiencies must be achieved for runoff generated from the first inch of rainfall, except for in the Goose Creek Watershed District in the Town of Mint Hill where BMPs are required to treat the difference in the storm water runoff from the predevelopment and post-development conditions for the 1-year, 24-hour storm. BMPs are required to be installed at varying built-upon area (BUA) thresholds depending on the jurisdiction and watershed district where the development is located. For redevelopments that exceed this threshold, if storm water from the existing development can be split off from the redeveloped area, BMPs can be installed to treat the runoff from the area of redevelopment only and not the entire site. However, if the runoff cannot be split, then the runoff from the entire site must be treated.
The basic mechanisms of pollutant removal by structural BMPs are the gravitational settling of pollutants, infiltration of soluble nutrients through the soil profile, and to a lesser extent, biological and chemical stabilization of nutrients. The establishment of a temporary or permanent pool of water results in quiescent conditions, which can settle out particulate pollutants between storms. Infiltration relies heavily on filtration through the soil profile as pollutants are removed through aerobic decomposition and chemical precipitation. Removal of soluble pollutants is accomplished primarily through the mechanisms of chemical and biological stabilization of nutrients. Approved structural BMPs are listed in Appendix 3-1.
Structural BMPs that treat run-off from single-family residential lots should be installed in common open space areas. Installation of BMPs on single-family residential lots should not occur unless the applicant can demonstrate a hardship to the Storm Water Administrator. The hardship requirement is met when it is demonstrated that no reasonable use can be made of the property through the strict application of the ordinance. In addition, the hardship must result from conditions that are peculiar to the property, such as location, size, or topography. Hardships resulting from personal circumstances, as well as hardships resulting from conditions that are common to the neighborhood or the general public will not be considered. The hardship must not have resulted from actions taken by the applicant or the property owner.
Buffers are natural, vegetated areas (preferably forested) adjacent to lakes and creeks through which storm water runoff flows in a diffuse manner to prevent channelization. Buffers serve to filter pollutants and absorb runoff, thereby reducing storm water volume, velocity, and pollutant loads. Buffers are effective at removing a variety of pollutants, including sediment, phosphorus, nitrate, and some metals. This occurs when pollutants become trapped as surface flow passes through the buffer and slows down, causing sediment to settle out, phosphorus and metals to be taken up by the root structure of buffer plants, and nitrate to be converted to nitrogen gas by microbes found in the underlying soil media. The slowing down of runoff also allows water to infiltrate through the soil and become groundwater recharge. In order for buffers to effectively filter pollutants, storm water must sheet flow across the buffer and the buffer must be of sufficient width. A well-established buffer is generally self-perpetuating and requires little maintenance. Native trees and shrubs are recommended for their hardiness, effective canopy and root structure. Buffer canopies intercept rainfall, thereby minimizing soil disturbance. Buffers also improve water quality by providing shade, which lowers water temperatures. Cool water carries more dissolved oxygen than warmer water and is essential to the survival of fish and other aquatic wildlife that are sensitive to changes in temperature. Organic material, including woody debris, that is washed into surface waters from buffers provides a source of food and habitat that supports aquatic organisms.
In Mecklenburg County, the Surface Water Improvement and Management (S.W.I.M.) buffer rules were adopted by the City of Charlotte, Towns and Mecklenburg County between 1999 and 2000. S.W.I.M. buffers vary in width from 35 feet to the entire floodplain depending on the jurisdiction and the size of the upstream drainage area, with the larger drainage areas having wider buffers. S.W.I.M. buffers also have two (2) to three (3) zones, including the streamside, managed use and upland zones. The amount of disturbance allowed within the buffer depends on the zone. The buffer requirements of the Post-Construction Storm Water Ordinance extend the S.W.I.M. buffers upstream to include intermittent streams and in the case of the Towns of Davidson, Matthews and Mint Hill (Goose Creek District) the buffers are made considerable wider. In addition to varying buffer widths, the jurisdictions differ in how buffers are delineated. In the Towns of Cornelius, Huntersville, Mint Hill (except Goose Creek), Pineville and Mecklenburg County, the buffers are delineated using GIS as indicated by Mecklenburg County’s internet site called POLARIS. In the Towns of Davidson and Matthews, the buffers are delineated on the ground using the U.S. Army Corps of Engineers and N.C. Division of Water Quality methodology and must be shown in the Concept Plan Application. The “Stream Reach Evaluation Form” must be completed, signed by a certified professional as defined in Section 14 below, and attached to the Concept Plan Application along with a map showing the locations of streams and buffers. A third difference exists in the Town of Mint Hill where buffers in the Goose Creek District will be delineated using either the most recent version of the soil survey map prepared by the Natural Resources Conservation Service of the United States.
Department of Agriculture (USDA) or the most recent version of the 1:24,000 scale (7.5 minute) quadrangle topographic maps prepared by the United States Geologic Survey (USGS). Buffers adjacent to surface waters in the Goose Creek District that do not appear on either of the aforementioned maps are not be subject to the Ordinance. There are also provisions for excluding certain types of development from the buffer requirements in the Goose Creek District when specific provisions are met, including road, railroad, bridge, airport facility, and utility crossings as well as storm water management facilities, and parallel utilities. For all jurisdictions, buffer requirements do not apply to piped stream sections. Also, the issuance of a 401 or 404 permit does not allow an impact to the buffer unless it is already an allowed use within the buffer, such as a road crossing.
Buffers are not required on ephemeral streams. Errors may occur in the delineation of buffers using USGS and USDA maps as well as S.W.I.M. buffers delineated using GIS as indicated on POLARIS. In particular, S.W.I.M. buffers are delineated beginning at 20 acre drainages. In some cases, ephemeral and not intermittent streams occur at 20 acre drainages and as stated above the ordinances do not intend to buffer ephemeral streams; therefore, a stream buffer would be indicated in POLARIS that is not required by the ordinance. The same situation could occur when streams are delineated using USGS and USDA maps. In such situations, the property owner or other concerned party may wish to have the buffer requirement deleted from the stream section. The process for requesting a stream exemption from buffer requirements is as follows:
1. The property owner or other concerned party shall submit a “Request for Stream Exemption”
in the form of a letter to the Storm Water Administrator.
2. A completed “Stream Reach Evaluation Form” shall be enclosed with this letter (see
Appendix 2-4 (Form #PCO39)). The form must be completed and signed by a “certified professional.” As defined in Section 14 below, a certified professional includes a person who is a licensed Professional Wetland Scientist or a person who has successfully passed the written and field tests for training in Intermittent and Perennial Stream Identification For Riparian Buffer Rules sponsored by NCDEQ. The Stream Reach Evaluation Form in Appendix 2-4 (Form #PCO39) is based on the stream delineation techniques specified in the NCDEQ guidance document covered during this training.
3. A map shall also be enclosed with the letter and Form #PCO39 showing the location of the stream reach being requested for exemption.
4. Upon receipt of this letter with enclosures, the Storm Water Administrator shall assign staff to evaluate the stream reach and complete Form #PCO39 described in #2 above. These staff shall have completed the training described in #2 above and be considered certified professionals.
5. Upon completion of the evaluation, staff shall compare their completed Stream Reach Evaluation Form to the form provided by the applicant and determine if they agree that the stream reach is neither intermittent nor perennial in which case the stream exemption shall be approved. However, if the staff evaluation reveals that the reach in question is intermittent or perennial then the buffer requirement shall apply and the request for exemption shall be denied. Staff shall describe their findings in an Activity Report under program element PC-1 and attach the completed Form #PCO39 as well as the appropriate notification letter to the applicant contained in Appendices 2-5 and 2-6 (Form #PCO40 and 41). Staff shall also attach a stream reach aerial photo out of POLARIS as shown in Appendices 2-5 and 2-6. Staff shall forward this Activity Report to the Storm Water Administrator for review and approval.
6. Upon approval, the Storm Water Administrator shall sign and mail the notification letter, PCO Form #39 and the POLARIS map.
7. All stream determinations and exemptions are good for five (5) years. If development plans are submitted within that 5-year period, the determination is good as long as the plans remain valid.
8. If the stream buffer is delineated in POLARIS, the Storm Water Administrator may at their discretion inform GIS via email and the POLARIS coverage will be updated to reflect the revision.
9. If staff’s stream determination confirmations disagree with the private professional determinations, staff’s determination will be used. If the applicant wants to dispute staff’s determinations, the applicant can have NCDEQ perform a determination that will over-rule staff’s determination.
10. Appeal of a decision regarding stream reach exemption from buffer requirements is through the Storm Water Advisory Committee (SWAC). Refer to Section 13 below for instructions and appropriate forms.
For those stream buffers delineated by POLARIS, it is possible that the size of the upstream drainage area may be incorrect in which case the size of the buffer would be depicted incorrectly. In such situations, the property owner or other concerned party may wish to have the buffer requirement changed in POLARIS for that stream section. The process for requesting a changed in POLARIS stream buffer delineation is as follows:
- The property owner or other concerned party shall submit a “Request for Stream Buffer Change in POLARIS” in the form of a letter to the Storm Water Administrator.
- A topographic map shall be enclosed with this letter identifying the stream reach in question and the corresponding upstream drainage area. Calculations must be provided showing how the size of this area was determined.
- Upon receipt of this letter with enclosures, the Storm Water Administrator shall forward the information to GIS requesting confirmation of the size of the upstream drainage area for the stream section in question.
- Upon receipt of notification from GIS, the Storm Water Administrator shall make a determination regarding the requested change in POLARIS stream buffer delineation and issue written notification to the requesting party accordingly.
- The Storm Water Administrator shall direct GIS to complete appropriate revisions to the POLARIS coverage.
In some circumstances, the Storm Water Administrator may elect to delineate a stream or confirm the size of an upstream drainage basin in POLARIS without receiving a request from a property owner or other concerned party. This is a legitimate action the results of which shall dictate the required buffer width in POLARIS.
Detention is the process of collecting and detaining storm water runoff in engineered structures such as dry detention ponds to reduce volume and velocity and protect downstream areas from channel degradation and flooding. In many cases, water quality BMPs also serve to provide some degree of detention. As the amount of impervious area increases in a watershed so does the volume and velocity of storm water run-off. As discussed in Section 1.2 on page 1, replacing an acre of trees with asphalt will result in storm water runoff increasing by 27,000 gallons from an inch of rainfall. In addition, this runoff typically enters surface waters through the piped storm sewer system resulting in increased velocity. This increased volume and velocity of storm water runoff entering streams causes significant downstream channel scour and flooding. The purpose of detention is to hold back this added water and release it over time to prevent negative impacts downstream. Like water quality BMPs, detention measures are designed and constructed in accordance with specifications contained in the Charlotte-Mecklenburg BMP Design Manual. By meeting these specifications, the detention measure is presumed to meet the minimum performance standards of the Post-Construction Storm Water Ordinance and the Phase II laws.
The Post-Construction Storm Water Ordinances require that detention be provided when the built-upon area (BUA) reaches a certain threshold. The detention requirement is the same for all jurisdictions, except the Town of Huntersville.
For residential development exceeding the built-upon area threshold, the peak control requirements can be modified by the plan reviewer acting on behalf of the Storm Water Administrator based on the results of a downstream flood analysis provided
by the owner or designee using the criteria specified in the Charlotte-Mecklenburg BMP Design Manual or if a downstream analysis is not performed the peak shall be controlled for the 10-yr and 25-yr, 6-hr storms. For commercial development exceeding the built-upon area threshold, peak control shall be installed for the 10-yr, 6-hr storm and additional peak control provided for the appropriate storm frequency (i.e., 25, 50 or 100-yr, 6-hr) as determined by the plan reviewer acting on behalf of the Storm Water Administrator based on a downstream flood analysis provided by the owner or designee using the criteria specified in the Charlotte-Mecklenburg BMP Design Manual or if a downstream analysis is not performed the peak shall be controlled for the 10-yr and 25-yr, 6-hr storms. Controlling the 1-year, 24-hour volume achieves peak control for the 2-year, 6-hour storm. The plan reviewer has the discretion to vary from the downstream flood analysis parameters for peak control. In such situations, this must be documented in the comments section of the Plan Review Checklist (Appendix 5-1). The above does not apply to Town of Huntersville where peak control is required for the 2 and 10-year, 24 hour storms.
2.6.4 Mecklenburg County Detention Ordinance
As of July 1979, Mecklenburg County’s Zoning Ordinance required development that cumulatively created more than 20,000 square feet of built-upon area to develop a drainage plan to be approved by the County Engineer. Typically, but not exclusively, the drainage plan is required for commercial development (which includes industrial, institutional, multifamily, townhome, and condominium development) and must provide peak control for runoff from the 2-yr and 10-yr storm events using either the 6-hr or 24-hr return period. When the six Towns established their Zoning ordinances, these drainage plan requirements were incorporated. The reader should note that the Town of Matthews changed the grandfathering date for built-upon area to July 10, 2000 for purposes of complying with the Detention ordinance. These drainage plan requirements are separate from the Post-Construction Ordinance requirements. Development and redevelopment projects subject to both the Detention ordinance and the PostConstruction Ordinance must comply with the ordinance that is more protective of water quality.
2.6.5 Undisturbed Open Space
Undisturbed open space is the setting aside of an area of a development site to be left undisturbed thus reducing the amount of impervious area and thereby reducing storm water volume, velocity, and pollutant load. This technique is considered a nonstructural BMP for controlling storm water impacts. The undisturbed open space requirement applies to new development and not to redevelopment. Redevelopment is defined as rebuilding activity on portions of land containing built-upon area as of the effective date of the ordinance (June 30, 2007). However, if this land is subdivided after the ordinance goes into effect this rebuilding activity will be considered development and not redevelopment and the undisturbed open space requirement will apply. Disturbance of the open space is allowed with specific mitigation options as described in Section 6.0. All the Towns except for Cornelius and Huntersville have incorporated the undisturbed open space requirement into their Post-Construction Storm Water Ordinances. The Town of Huntersville has open space requirements contained in their Zoning Ordinance. The amount of undisturbed open space required varies based on the amount of builtupon area in the development. For the Towns of Davidson, Matthews and Pineville as well as Mecklenburg County the undisturbed open space requirements are as follows:
- Less than 24% built-upon area = 25% of the project site set aside for undisturbed open space.
- Greater than or equal to 24% built-upon area and less than 50% built-upon area = 17.5% of the project site set aside for undisturbed open space.
- Greater than or equal to 50% built-upon area = 10% of the project site set aside for undisturbed open space.
The undisturbed open space requirements for the Town of Mint Hill vary slightly from the other Towns and are as follows:
- Less than 20% built-upon area = no undisturbed open space requirement.
- Greater than or equal to 20% built-upon area and less than 50% built-upon area = 15% of the project site set aside for undisturbed open space.
- Greater than or equal to 50% built-upon area = 10% of the project site set aside for undisturbed open space.
Charlotte Post Construction Stormwater Ordinance
Administrative Manual for Implementation of the Post-Construction Storm Water Ordinance