15A NCAC 18C .0706      SEDIMENTATION BASINS

(a)  Inlets. Inlets to sedimentation basins shall be designed to dissipate inlet velocities before the diffusion walls or before other entrance arrangements designed to provide uniform flow across the basins.

(b)  Detention Period. A theoretical detention period of four hours shall be the minimum standard unless case specific engineering evidence is presented to demonstrate equivalent treatment efficiency at a shorter period of detention.

(c)  Bottom of Basin. The bottom of the basin shall be sloped and provided with a drain valve or valves for removal of sludge.

(d)  Outlet. Sedimentation basin outlets shall consist of submerged weirs or orifices. The equivalent rate of flow over or through the outlet device shall not exceed 20,000 gallons per day per foot of equivalent weir length.

(e)  Overflow. Sedimentation basins shall be equipped with an overflow pipe or pipes to limit the maximum water level over the filters and to prevent flooding above the walls of filters and basins.

History Note:        Authority G.S. 130A-315; 130A-317; P.L. 93-523;

Eff. January 1, 1977;

Readopted Eff. December 5, 1977;

Amended Eff. April 1, 2014;

Readopted Eff. July 1, 2019.