<div class="chunk-title">Sec. 4.4 - Stormwater drainage standards.</div>
<div class="chunk-content">
            <p class="incr0">
               (a)
               </p>
            		
            <p class="content1">
               <span class="ital">General Requirements</span>.
               </p>
            		
            <p class="incr1">
               (i)
               </p>
            		
            <p class="content2">
               Drainage systems shall be designed utilizing low-impact design to limit disruption
               of natural water flows by eliminating stormwater runoff, increasing on-site infiltration
               and eliminating contaminants.
               </p>
            		
            <p class="incr1">
               (ii)
               </p>
            		
            <p class="content2">
               This system design shall be rendered in a drainage plan, which is a written or graphic
               concept plan of the proposed post-development stormwater management system. The drainage
               plan shall, at a minimum, include the following: preliminary selection and location
               of proposed structural stormwater controls; low impact design elements; location of
               existing and proposed conveyance systems such as grass channels, swales, and storm
               drains; flow paths; location of flood plain/floodway limits; relationship of site
               to upstream and downstream properties and drainages; and preliminary location of proposed
               stream channel modifications, such as bridge or culvert crossings.
               </p>
            		
            <p class="incr1">
               (iii)
               </p>
            		
            <p class="content2">
               The approval of the drainage plan of any subdivision shall require an enforceable
               restriction on property usage that runs with the land, such as recorded deed restrictions
               or protective covenants, to ensure that future development and redevelopment maintains
               the site consistent with the approved project plans.
               </p>
            		
            <p class="incr1">
               (iv)
               </p>
            		
            <p class="content2">
               Where major new drainage ways are required in a subdivision, they shall be coordinated
               with existing and proposed general drainage systems and designed with due regard for
               safety, appearance and geological effects.
               </p>
            		
            <p class="b1">
               <a href="https://mcclibrary.blob.core.usgovcloudapi.net/codecontent/14666/425389/4.8.png" target="_blank" data-image-filename="4.8.png"><img id="img_14" src="https://mcclibrary.blob.core.usgovcloudapi.net/codecontent/14666/425389/4.8.png" alt="4.8" width="560" height="248" data-image-filename="4.8.png"></a>
               
               
               <p class="incr1">
                  (v)
                  </p>
               		
               <p class="content2">
                  Aboveground drainage ways shall be:
                  </p>
               		
               <p class="incr2">
                  1)
                  </p>
               		
               <p class="content3">
                  Located and constructed to maintain a natural appearance;
                  </p>
               		
               <p class="incr2">
                  2)
                  </p>
               		
               <p class="content3">
                  Limited to safe water depths in easily accessible areas; and
                  </p>
               		
               <p class="incr2">
                  3)
                  </p>
               		
               <p class="content3">
                  Designed to avoid excessive rates of flow, erosion, or overflow into developed areas
                  subject to damage.
                  </p>
               		
               
               <p class="incr1">
                  (vi)
                  </p>
               		
               <p class="content2">
                  Watercourses and natural water areas downstream, from any land disturbing activity
                  shall be protected from increased degradation by accelerated erosion caused by increased
                  velocity of runoff from the land disturbing activity in accordance with the County
                  sediment control provision. In circumstances where the impact of new drainage would
                  be likely to damage or destroy significant existing natural water areas, such drainage
                  shall not be discharged through or into such areas.
                  </p>
               		
               
               <p class="incr1">
                  (vii)
                  </p>
               		
               <p class="content2">
                  The development area of any lot shall conform with subsection (iii) of this section.
                  </p>
               		
               
            <p class="incr0">
               (b)
               </p>
            		
            <p class="content1">
               <span class="ital">Development Standards for Low Density Projects.</span>
               </p>
            		
            <p class="incr1">
               (i)
               </p>
            		
            <p class="content2">
               Stormwater runoff from the development area shall be transported from the development
               by vegetated conveyances to the maximum extent practicable.
               </p>
            		
            <p class="incr0">
               (c)
               </p>
            		
            <p class="content1">
               <span class="ital">Development Standards for High Density Projects</span>.
               </p>
            		
            <p class="incr1">
               (i)
               </p>
            		
            <p class="content2">
               The measures shall control and treat the difference in stormwater runoff volume leaving
               the development area between the pre- and post-development conditions for, at a minimum,
               the ten-year, 24-hour storm. This standard refers to the surface runoff resulting
               from a 24-hour rainfall of an intensity expected to be equaled or exceeded, on average,
               once in ten years. Runoff volume drawdown time shall be a minimum of 24 hours, but
               not more than 120 hours.
               </p>
            		
            <p class="incr1">
               (ii)
               </p>
            		
            <p class="content2">
               All structural stormwater treatment systems used to meet the requirements of this
               section shall be designed to have a minimum of 85 percent average annual removal for
               total suspended solids (TSS).
               </p>
            		
            <p class="incr0">
               (d)
               </p>
            		
            <p class="content1">
               <span class="ital">Stormwater Drainage Facilities.</span>
               </p>
            		
            <p class="incr1">
               (i)
               </p>
            		
            <p class="content2">
               The application shall be accompanied by a description of the proposed method of providing
               stormwater drainage. The subdivider shall provide a drainage system that diverts stormwater
               runoff away from surface waters and incorporates best management practices to minimize
               water quality impacts. Consistent with Section 5.3.9 (Stormwater Provisions), subdivisions
               qualifying for the special intensity allocation shall provide non-structural methods
               of managing stormwater runoff.
               </p>
            		
            <p class="incr0">
               (e)
               </p>
            		
            <p class="content1">
               <span class="ital">Erosion and Sedimentation Control.</span>
               </p>
            		
            <p class="incr1">
               (i)
               </p>
            		
            <p class="content2">
               The application shall, where required, be accompanied by a written statement that
               a sedimentation and erosion control plan has been submitted to and approved by the
               State Division of Land Quality.
               </p>
            		
            <p class="incr0">
               (f)
               </p>
            		
            <p class="content1">
               <span class="ital">Roads Constructed in Critical Areas and Watershed Buffer Areas.</span>
               </p>
            		
            <p class="incr1">
               (i)
               </p>
            		
            <p class="content2">
               Where possible, roads should be located outside of critical areas and watershed buffer
               areas. Roads constructed within these areas shall be designed and constructed so to
               minimize their impact on water quality.
               </p>
            		
            <p class="incr0">
               (g)
               </p>
            		
            <p class="content1">
               <span class="ital">Erosion Protection; Preservation of Topsoil and Vegetation.</span>
               </p>
            		
            <p class="incr1">
               (i)
               </p>
            		
            <p class="content2">
               In general, during the preparation of the subdivision and installation of improvements,
               appropriate measures shall be taken to prevent erosion and damaging siltation on the
               property and on adjoining land or water areas in accord with the Article V, Section
               5.3, Erosion and Sedimentation Control.
               </p>
            		
            <p class="incr1">
               (ii)
               </p>
            		
            <p class="content2">
               In any grading or filling operations, desirable topsoil shall be conserved and redistributed
               as such, particularly to cover exposed subsoils.
               </p>
            		
            <p class="incr1">
               (iii)
               </p>
            		
            <p class="content2">
               Trees, shrubs and ground cover existing at the beginning of development operations
               shall be preserved to the maximum extent reasonably feasible where they are of species
               and in locations likely to add amenity to the completed development.
               </p>
            		
            <p class="incr1">
               (iv)
               </p>
            		
            <p class="content2">
               Ground cover. All land within the subdivision right-of-way which is not used for structures,
               vehicular or pedestrian traffic, or for other approved landscaping shall be provided
               with grass or other ground cover, appropriately installed, and consistent with the
               requirements of the County sediment control regulations. Ground cover may include
               appropriate plant materials preserved in place.
               </p>
            		
            <p class="incr1">
               (v)
               </p>
            		
            <p class="content2">
               The Planning Director may require preservation of specified trees or other vegetation
               in connection with a particular development, except upon findings that such preservation
               is not feasible in view of the requirements for the installation of public utilities
               and facilities.
               </p>
            		
            <p class="incr1">
               (vi)
               </p>
            		
            <p class="content2">
               The Planning Director may grant a conditional approval of a preliminary subdivision
               plat, provided that an erosion control plan approval letter is submitted to the Planning
               Department within 90 days and prior to commencement of site preparation or other land-disturbing
               activities.
               </p>
            		
            <p class="incr0">
               (h)
               </p>
            		
            <p class="content1">
               <span class="ital">Adequacy.</span>
               </p>
            		
            <p class="incr1">
               (i)
               </p>
            		
            <p class="content2">
               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.
               The minimum design frequency shall be as follows:
               </p>
            		
            <p class="incr2">
               1)
               </p>
            		
            <p class="content3">
               Storm sewer collector and lateral ditches: ten years.
               </p>
            		
            <p class="incr2">
               2)
               </p>
            		
            <p class="content3">
               Cross drainage: 25 years.
               </p>
            		
            <p class="incr2">
               3)
               </p>
            		
            <p class="content3">
               Minimum cross pipe diameter is 18 inches; minimum driveway pipe diameter is 15 inches.
               </p>
            		
            <p class="incr2">
               4)
               </p>
            		
            <p class="content3">
               All drainage shall be consistent with criteria found in NCDOT Guidelines for Drainage
               Studies and Hydraulic Design.
               </p>
            		
            <p class="incr2">
               5)
               </p>
            		
            <p class="content3">
               In areas where ditch grades or quantities of flow make it impracticable to establish
               and maintain vegetation, an erosive resistant lining such as paving, matting or rip
               rap shall be required. Subsurface drainage shall be adequate to maintain a stable
               subgrade.
               </p>
            		
            <p class="incr0">
               (i)
               </p>
            		
            <p class="content1">
               <span class="ital">Structures (Culverts, Dams, Retaining Walls, and Bridges).</span>
               </p>
            		
            <p class="incr1">
               (i)
               </p>
            		
            <p class="content2">
               Design, construction, and installation of culverts, dams, and retaining walls shall
               comply with NCDOT standards as set forth in NCDOT Subdivision Roads Minimum Construction
               Standards, unless other standards are approved by the Planning Board. Bridges shall
               have a travelway width equal to that required for the road type (including required
               shoulder width) and shall comply with the requirements of the U.S. Army Corps of Engineers
               and other permitting agencies. All bridge designs shall be prepared and/or approved
               by a licensed professional engineer registered in North Carolina. The Planning Director
               shall review permit documentation for bridges to assure that all required approvals
               have been obtained prior to construction.
               </p>
            		
            <p class="historynote0">
               (Ord. No. O2019-01(5), 11-2-2021)
               </p></div>