15A NCAC 18C .0704      BAFFLED MIXING AND FLOCCULATION BASINS

(a)  Detention Period.  The theoretical detention period of baffled mixing and flocculation shall be at least 25 minutes.

(b)  Velocities

(1)           The velocity of the water between the baffles shall be as follows:

(A)          first third of basin ‑‑ 1.5 feet per second;

(B)          second third of basin ‑‑ 0.75 feet per second; and

(C)          last third of basin ‑‑ 0.4 to 0.5 feet per second.

(2)           The velocity of the water under and over the baffles shall not exceed the velocity between the baffles.

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

Eff. January 1, 1977;

Readopted Eff. December 5, 1977;

Pursuant to G.S. 150B-21.3A, rule is necessary without substantive public interest Eff. November 23, 2015.