§ 17-134. Standards

(a) General standards. All development and redevelopment to which this division applies shall comply with the standards of this section.

(b) Impervious surface requirements.

(1) Setback requirement. All impervious surfaces, except for roads, paths, and water dependent structures, shall be located at least thirty (30) feet landward of all perennial and intermittent surface waters.

A perennial or intermittent surface water shall be deemed present if the feature is shown on 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 complete version of the 1:24,000 scale (7.5 minute) quadrangle topographic maps prepared by the United States Geologic Survey (USGS). An exception to this requirement may be allowed when surface waters are not present in accordance with the provisions of 15A NCAC 2B .0233 (3)(a) or similar site-specific determination made using Division-approved methodology.

(2) Land draining to shellfish waters. All development activities that are located within five hundred seventy-five (575) feet of waters designated by the environmental management commission as shellfishing waters shall be limited to a maximum impervious surface density of thirty-six (36) percent.

(3) Development in critical area of water supply watersheds. All development activities that are located within the area designated by the environmental management commission as a critical area of a water supply watershed shall be limited to a maximum impervious surface density of thirty-six (36) percent.

(c) Structural stormwater control requirements. Owners of property subject to this division and required to install structural stormwater control measures shall implement those measures in compliance with each of the following standards:

(1) The measures shall control and treat runoff from the first one and one-half (1½) inches of rain. Runoff volume drawdown time for wet detention ponds shall be a minimum of forty-eight (48) hours, but not more than one hundred-twenty (120) hours.

(2) All structural stormwater treatment systems used to meet these requirements shall be designed to have a minimum of eighty-five (85) percent average annual removal for total suspended solids (TSS);

(3) General engineering design criteria for all projects shall be in accordance with 15A NCAC 2H .1008(c), as explained in the design manual;

(4) The measure shall discharge the storage volume at a rate equal or less than the pre-development discharge rate for the one-year, twenty-four-hour storm.

(5) The approval of the stormwater permit shall require enforceable restrictions on property usage that runs with the land, including recorded deed restrictions and protective covenants, to ensure that future development and redevelopment maintains the site consistent with the approved project plans.

(d) Standards for stormwater control measures.

(1) Evaluation according to contents of design manual. All stormwater control measures and stormwater treatment practices (also referred to as best management practices, or BMPs) required under this division shall be evaluated by the stormwater administrator according to the policies, criteria, and information, including technical specifications and standards and the specific design criteria for each stormwater practice, in the design manual. The stormwater administrator shall determine whether proposed BMPs will be adequate to meet the requirements of this division.

(2) Determination of adequacy; presumptions and alternatives. Stormwater treatment practices that are designed, constructed, and maintained in accordance with the criteria and specifications in the design manual will be presumed to meet the minimum water quality and quantity performance standards of this division. Whenever an applicant proposes to utilize a practice or practices not designed and constructed in accordance with the criteria and specifications in the design manual, the applicant shall have the burden of demonstrating that the practice(s) will satisfy the minimum water quality and quantity performance standards of this division. The stormwater administrator may require the applicant to provide the documentation, calculations, and examples necessary for the stormwater administrator to determine whether such an affirmative showing is made.

(3) Separation from seasonal high-water table. For BMPs that require a separation from the seasonal high-water table, the separation shall be provided by at least twelve (12) inches of naturally occurring soil above the seasonal high-water table.

(e) Dedication of BMPs, facilities and improvements. The town may accept dedication of any existing or future stormwater management facility for maintenance, provided such facility meets all the requirements of this division and includes adequate and perpetual access and sufficient area, by easement or otherwise, for inspection and regular maintenance.

(f) Variances.

(1) Any person may petition the board of adjustment for a variance granting permission to use the person's land in a manner otherwise prohibited by this division. To qualify for a variance, the petitioner must show all of the following:

a. Unnecessary hardships would result from strict application of this division.

b. The hardships result from conditions that are peculiar to the property, such as the location, size, or topography of the property.

c. The hardships did not result from actions taken by the petitioner.

d. The requested variance is consistent with the spirit, purpose, and intent of this division; will secure public safety and welfare; and will preserve substantial justice.

(2) The board of adjustment may impose reasonable and appropriate conditions and safeguards upon any variance it grants.

(3) Statutory exceptions. Notwithstanding subdivision (f)(1) of this section, exceptions from the thirty-foot landward location of built-upon area requirement as well as the deed restrictions and protective covenants requirements shall be granted in any of the following instances:

a. When there is a lack of practical alternatives for a road crossing, railroad crossing, bridge, airport facility, or utility crossing as long as it is located, designed, constructed, and maintained to minimize disturbance, provide maximum nutrient removal, protect against erosion and sedimentation, have the least adverse effects on aquatic life and habitat, and protect water quality to the maximum extent practicable through the use of BMPs.

b. When there is a lack of practical alternatives for a stormwater management facility; a stormwater management pond; or a utility, including, but not limited to, water, sewer, or gas construction and maintenance corridor, as long as it is located fifteen (15) feet landward of all perennial and intermittent surface waters and as long as it is located, designed, constructed, and maintained to minimize disturbance, provide maximum nutrient removal, protect against erosion and sedimentation, have the least adverse effects on aquatic life and habitat, and protect water quality to the maximum extent practicable through the use of BMPs.

c. A lack of practical alternatives may be shown by demonstrating that, considering the potential for a reduction in size, configuration, or density of the proposed activity and all alternative designs, the basic project purpose cannot be practically accomplished in a manner which would avoid or result in less adverse impact to surface waters.

(Ord. of 7-17-07(2), § 3)