15A NCAC 04B .0132       Design Standards for the Upper Neuse River Basin (Falls Lake Watershed)

In addition to any other requirements of State, federal, and local law, land-disturbing activity in the watershed of the drinking water supply reservoir that meets the applicability requirements of Session Law 2009-486, Section 3.(a), shall meet all of the following design standards for sedimentation and erosion control:

(1)           Erosion and sedimentation control measures, structures, and devices shall be planned, designed, and constructed to provide protection from the runoff of the 25-year storm that produces the maximum peak rate of runoff as calculated according to procedures set out in the United States Department of Agriculture Soil Conservation Service's "National Engineering Field Manual for Conservation Practices" or according to procedures adopted by any other agency of the State or the United States.

(2)           Sediment basins shall be planned, designed, and constructed so that the basin will have a settling efficiency of at least 70 percent for the 40-micron size soil particle transported into the basin by the runoff of the two-year storm that produces the maximum peak rate of runoff as calculated according to procedures in the United States Department of Agriculture Soil Conservation Service's "National Engineering Field Manual for Conservation Practices" or according to procedures adopted by any other agency of the State or the United States.

(3)           Newly constructed open channels shall be planned, designed, and constructed with side slopes no steeper than two horizontal to one vertical if a vegetative cover is used for stabilization unless soil conditions permit steeper side slopes or where the side slopes are stabilized by using mechanical devices, structural devices, or other ditch liners sufficient to restrain accelerated erosion. The angle for side slopes shall be sufficient to restrain accelerated erosion.

(4)           For an area of land-disturbing activity where grading activities have been completed, temporary or permanent ground cover sufficient to restrain erosion shall be provided as soon as practicable, but in no case later than seven days after completion of grading. For an area of land-disturbing activity where grading activities have not been completed, temporary ground cover shall be provided as follows:

(a)           For an area with no slope, temporary ground cover shall be provided for the area if it has not been disturbed for a period of 14 days.

(b)           For an area of moderate slope, temporary ground cover shall be provided for the area if it has not been disturbed for a period of 10 days. For purposes of this Item, "moderate slope" means an inclined area, the inclination of which is less than or equal to three units of horizontal distance to one unit of vertical distance.

(c)           For an area of steep slope, temporary ground cover shall be provided for the area if it has not been disturbed for a period of seven days.  For purposes of this Item, "steep slope" means an inclined area, the inclination of which is greater than three units of horizontal distance to one unit of vertical distance.

 

History Note:        Authority S.L. 2009-486;

Eff. February 1, 2012.