No land-disturbing activity shall occur except in accordance with the following standards; wherever there is a conflict between two or more of these standards, the more stringent regulation is controlling.
- General Requirements
- Prior Plan Approval
- An erosion and sedimentation control plan must be approved by the Engineering Services Director at least 30 days prior to any regulated land-disturbing activity. This does not restrict the initiation of land disturbing activities when the plan is approved and the permit is issued in less than 30 days from initial submission. Failure to approve, approve with modifications, or disapprove a completed draft erosion and sedimentation control plan within 30 days of receipt shall be deemed approval of the plan.
- When determining the area of land-disturbance, the square footage of land-disturbance of all land and bodies of water disturbed or to be disturbed shall be aggregated, regardless of whether under single or diverse ownership.
- A surety for permanent stabilization based on the total disturbed area as identified in the submitted plans. The surety shall be $2,000/acre of disturbed land rounded to the nearest 1/10 acre. If the property is subject to a continuing violation the City may cash the surety.
- An approved erosion and sedimentation control plan is required for any land-disturbing activity of 12,000 square feet or greater.
- An approved erosion and sedimentation control plan is required for any land-disturbing activity below 12,000 square feet for the following:
- Land-disturbing activity in any Watershed Protection Area;
- Relocation of any natural watercourse;
- Upon the occurrence of off-site sedimentation; or
- When a person conducting a land-disturbing activity has been issued two or more Notices of Violation, within the last 2 years, for failure to comply with the provisions of Article 9.4. For purposes of this subsection, an applicant's record is considered for the 2 years prior to the development permit application date.
- Protection of Property
Persons conducting land-disturbing activity must take all reasonable measures to protect all public and private property from damage caused by land-disturbing activity. - NPDES Stormwater Permit for Construction Activity
Documentation required under the site National Pollutant Discharge Elimination System (NPDES) stormwater permit for construction activity shall be submitted to the City.
- Prior Plan Approval
- Adequate Erosion Control Measures
Adequate erosion control measures shall be planned, designed, installed, and maintained so as to control accelerated erosion and prevent sedimentation from leaving the site during construction for the maximum calculated peak rates of
runoff from the 10- and 25-year storms and in accordance with Sec. 9.2.2.E. - Design and Performance Standards and Guidelines
- Copies of design and performance standards which are contained in the Raleigh Stormwater Design Manual will be published by the City and placed on file in the Office of the City Clerk and the Engineering Services Director.
- All erosion control plans, erosion control measures, ground covers, maintenance and calculations must be in accordance with the applicable Raleigh Stormwater Design Manual and State of North Carolina Erosion and Sediment Control Planning and Design Manual; in the event of any conflict, the more stringent regulation applies.
- Buffer Zones
- Buffer Zones Generally
- No land-disturbing activity during periods of construction or improvement to land are allowed in proximity to a lake or natural watercourse unless a buffer zone is provided along the watercourse to confine visible siltation within 25% of the buffer zone nearest the landdisturbing activity.
- Unless otherwise provided, the width of a buffer zone is measured from the edge of the watercourse to the nearest edge of the disturbed area.
- Buffer Zone Exceptions
This section does not apply to a land-disturbing activity in connection with the construction of facilities to be located on, over or under a lake or natural watercourse. No land-disturbing activity, except as permitted in Sec. 9.2.3.B. and Sec. 9.2.3.C. or Article 9.5. Watershed Protection Areas, shall take place:- Within any watercourse buffer area unless it conforms to the requirements of Sec. 9.2.3.B. and Sec. 9.2.3.C. and the provisions of this Article; and
- Within any high-quality water zone unless it conforms to the requirements of Article 9.5. Watershed Protection Areas and the provisions of this Article.
- Buffer Zones Generally
- Graded Slopes and Fills
The angle for graded slopes and fills shall be no greater than the angle which can be retained by vegetative cover or other adequate erosion control devices or structures. In any event, slopes left exposed shall be provided with ground cover, devices or structures sufficient to restrain erosion. For all areas of moderate or steep slopes, temporary ground cover shall be provided if the slope has not been disturbed for a period of 14 days. - Ground Cover
- Whenever a land-disturbing activity occurs, the person undertaking the activity shall install such ground cover, devices or structures sufficient to restrain erosion and retain sediment within the boundaries of the tract at all times.
- Any portion of a site upon which further land-disturbing activity is not being undertaken shall be provided with ground cover sufficient to restrain erosion within 14 calendar days of temporarily or permanently suspending the land disturbing activity. Permanent ground cover shall be installed within 14 calendar days following completion of construction or development.
- Downstream Protection of Discharge Points and Receiving Watercourses
- Permanent Protection
Any area of a land-disturbing activity and all receiving watercourses or discharge point must be permanently protected from accelerated erosion caused by increased velocity of stormwater runoff resulting from a land disturbing activity. - Post Construction Velocity
For any land-disturbing activity, the post construction velocity of the 10-year storm runoff in the receiving water-course to the discharge point does not exceed the greater of:- The velocity of the 10-year storm runoff in the receiving watercourse prior to a development;
- The velocity specified according to the following table for a discharge point into a receiving watercourse with bare soil or rock bed or banks; or
Maximum Permissible Velocities Material (F.P.S.) (M.P.S.) Fine sand (noncolloidal) 2.5 0.8 Sandy loam (noncolloidal) 2.5 0.8 Silt loam (noncolloidal) 3.0 0.9 Ordinary firm loam 3.5 1.1 Fine gravel 5.0 1.5 Stiff clay (very colloidal) 5.0 1.5 Graded, loam to cobbles (noncolloidal) 5.0 1.5 Graded, silt to cobbles (colloidal) 5.5 1.7 Alluvial silts (noncolloidal) 3.5 1.1 Alluvial silts (colloidal) 5.0 1.5 Course gravel (noncolloidal) 6.0 1.8 Cobbles and shingles 5.5 1.7 Shales and hard pans 6.0 1.8 - The velocity specified according to the following for a discharge point
into a vegetated receiving watercourse.Group No. Vegetation Depth of Flow (feet) Maximum Permissible Velocity* (F.P.S.) 1 Bermudagrass t1 4 u1 6 2 Tall fescue t1 3 Reed canarygrass Kentucky bluegrass u1 6 3 Grass and legumes, mixed t1 3 Weeping lovegrass u1 4 4 Lespedeza, sericea t1 2.5 Red fescue, Red top u1 2.5 5 Annuals:** Annual lespedeza (KOBE) t1 2.5 Sundangrass Small grain (rye, oats, barley): Ryegrass u1 2.5
- General Velocity Standard
Any area of a land-disturbing activity or receiving watercourses subject to stormwater runoff velocities in excess of those specified in Sec. 9.4.4.G.2. above from accelerated erosion by provision of an erosion-resistant lining of vegetation in accordance with Sec. 9.4.4.G.2.c. above provided, armored, paved or otherwise nonvegetative watercourse lining shall be provided
anywhere the velocity in the receiving watercourse exceeds Sec. 9.4.4.G.2.c. and the prior development velocity by 10%. - Critical Soils
When the following soils (as defined and described in the soil survey of Wake County North Carolina Soil Conservation Service, United States Department of Agricultural, November, 1970) which are especially vulnerable to erosion from stormwater discharge from land-disturbing activities, occur between a point of stormwater discharge and the next confluence of concentrated stormwater runoff, such areas, on- or off-site shall be protected from accelerated erosion by diverting the stormwater discharge from those soil surfaces. The application of this section may not prevent discharge of
stormwater from a land-disturbing activity site. Diversion may include the provision of piped, paved or armored storm drainage facilities:- Appling sandy loam, 10% to 15% slopes (ApP);
- Cecil sandy loam, 10% to 15% slopes (CeD);
- Cecil sandy loam, 15% to 45% slopes (CeF);
- Creedmore sandy loam, 10% to 20% slopes (CrE);
- Enon fine sandy loam, 10% to 15% slopes (EnD2);
- Georgeville silt loam, 10% to 15% slopes (GeD2);
- Granville sandy loam, 10% to 15% slopes (GrD);
- Helena sandy loam, 10% to 15% slopes (HeD);
- Herndon silt loam, 10% to 25% slopes (HrD2);
- Herndon silt loam, 15% to 25% slopes (HrE);
- Lloyd loam, 10% to 15% slopes (LdD2);
- Louisburg loamy sand, 10% to 15% slopes (LoD);
- Made land, (Ma) greater than 4% slopes under actual field conditions;
- Madison sandy loam, 10% to 15% slopes (MdD2);
- Madison sandy loam, 15% to 25% slopes (MdE2);
- Mayodon sandy loam, 10% to 15% slopes (MfD2);
- Mayodan sandy loam, 15% to 25% slopes (MfE);
- Mayodan silt loam, 10% to 15% slopes (MyD);
- Pinkston sandy loam, 10% to 45% slopes (PkF);
- Wake, 10% to 25% slopes (WkE);
- Wedowee sandy loam, 10% to 15% slopes (WmD2);
- Wedowee sandy loam, 15% to 25% slopes (WmE);
- White Store sandy loam, 10% to 20% slopes (WsE);
- White Store clay loam, 2 to 15% slopes (WvD3);
- Wilkes, 10% to 20% slopes (WwE);
- Wilkes, 20% to 45% slopes (WwF); and
- Wilkes, 15% to 25% slopes (WxE).
- Armored
Armored or otherwise non-vegetatively lined watercourse lining shall, in addition to the requirements of Sec. 9.4.4.G.3. above, be provided at the storm outlet and for those portions of the receiving watercourse which have undergone land-disturbing activity. - Exception
Where piped, paved or armored storm drainage facilities connect to existing off-site piped, paved or armored storm drainage facilities or where it can be demonstrated that stormwater discharge velocities will not create an erosion problem in the receiving watercourse, none of the foregoing provisions of this section shall apply. - Equivalent Alternatives
The management of stormwater runoff to minimize or control downstream channel and bank erosion is a developing technology. Innovative techniques and ideas will be considered and may be used when shown to have the potential to produce successful results. Alternatives include, but are not limited to:- Avoid increases in surface runoff volume and velocity by including measures to promote infiltration to compensate for increased runoff from areas rendered impervious;
- Avoid increases in stormwater discharge velocities by using vegetated or roughened swales and waterways in lieu of closed drains and high velocity paved sections;
- Provide energy dissipators at outlets of storm drainage facilities to reduce flow velocities to the discharge point. These may range from simple rip-rapped sections to complex structures; and
- Protect watercourses subject to accelerated erosion by improving cross-sections or providing erosion-resistant lining.
- Permanent Protection
- Operations in Lakes or Natural Watercourses
- Any land-disturbing activity in connection with construction in, on, over or under a lake or natural watercourse shall be planned and conducted in such a manner so as to minimize the extent and duration of disturbance of the stream channel and to prevent off-site sedimentation.
- The relocation of a natural watercourse must meet the provisions of Sec. 9.4.4.G. and must minimize changes to the stream flow characteristics. The relocation of a natural watercourse may not occur in natural resource buffer yards of a -UWPOD, -FWPOD, -SWPOD, -MPOD or CM District.
- High-Quality-Water Zones
Within high-quality-water (HQW) zones the following additional design standards shall apply.- Uncovered areas in HQW zones shall be limited at any time to a maximum total area within the boundaries of the tract of 20 acres. Only the portion of the land-disturbing activity within an HQW zone shall be governed by this section. Larger areas may be uncovered within the boundaries of the tract with the written approval of both the Director of the Division of Land Resources of the North Carolina Department of Environment, Health and Natural Resources and the City Council.
- Sediment basins shall be designed and constructed such that the basin will have a settling efficiency of at least 85% for the 40 micron size soil particle transported into the basin by the runoff of that two-year storm which produces the maximum peak rate of runoff as calculated according to procedures required by this Article.
- Newly constructed open channels in HQW zones shall be designed and constructed with side slopes no steeper than 2 horizontal to 1 vertical if vegetative cover is used for stabilization unless soil conditions permit a steeper slope or where the slopes are stabilized by using mechanical devices, structural devices or other acceptable ditch liners. In any event, the angle for side slopes shall be sufficient to restrain accelerated erosion.
- Keep Dirt and Mud Off Public Streets
The accumulation of more than 1/32 inch of dirt, mud or both on any public street, measured 6 feet from an entrance or exit of any land disturbing activity, is prohibited.