1. (a) In conducting tests or making analytical determinations of classified waters to determine whether they conform with the water quality standards established in accordance with this Subchapter, samples shall be collected outside of mixing zones. However, if required by NPDES permit, samples shall be collected within the mixing zone in order to ensure compliance with in‑zone water quality requirements as outlined in Paragraph (b) of this Rule.

2. (b) A mixing zone may be established in the area of a discharge in order to provide opportunity for the mixture of the wastewater with the receiving waters. Water quality standards shall not apply within regions designated as mixing zones, except that such zones shall be subject to the conditions established in accordance with this Rule. The need for and limits of such mixing zones shall be determined by the Division on a case‑by‑case basis after consideration of the magnitude and character of the waste discharge and the size and character of the receiving waters. Mixing zones shall be designated such that discharges will not:

   1. (1) result in acute toxicity to aquatic life, defined in Rule .0202(1) of this Section, or prevent free passage of aquatic organisms around the mixing zone;
   2. (2) result in offensive conditions;
   3. (3) produce undesirable aquatic life or result in a dominance of nuisance species outside of the assigned mixing zone; or

   4. (4) endanger the public health or welfare.

      In addition, a mixing zone shall not be designated for point source discharges of fecal coliform organisms in waters classified "WS‑II," "WS‑III," "B," or "SA," as defined in Rule .0301 of this Subchapter. Mixing zones shall not be designated for point source discharges of enterococci in waters classified "SB" or "SA," as defined in Rule .0301 of this Subchapter. For the discharge of heated wastewater, compliance with federal rules and regulations pursuant to Section 316(a) of the Clean Water Act, as amended, shall constitute compliance with Paragraph (b) of this Rule.

History Note: Authority G.S. 143‑214.1;
Eff. February 1, 1976;
Amended Eff. May 1, 2007; October 1, 1989; February 1, 1986; September 9, 1979;
Readopted Eff. November 1, 2019.