(a) Policy: Zone of mixing

Human activities may result in the practical need to discharge pollutants through point sources into the waters of the territory. And, because of technological, .economic and other factors, it may not always be feasible to achieve an effluent quality that equals or exceeds the standards established herein at the point of discharge. Therefore, subject to the prohibitions, criteria and procedures set forth below, alternate water quality standards may be defined by the EQC in the immediate vicinity surrounding the point of discharge. The area within which the alternate standards apply shall be a zone of mixing. All applicable water quality standards shall be met at the boundary of any zone of mixing. It is the policy of the EQC that zones of mixing shall only be .granted upon a finding that no other practicable means of waste treatment and disposal are available. Further, it is the policy of the EQC that zones of mixing shall be limited to the smallest area possible.

(b) Criteria: Zone of Mixing

A zone of mixing can only be granted by the EQC if the application and the supporting information clearly shows that all of the following conditions and criteria have been met:

(1) It is in the public interest that a zone of mixing be granted to begin or continue the function or operation associated with the discharge;

(2) The proposed discharge does not substantially endanger human health or safety, or the environment;

(3) Compliance with the existing water quality standards at the point of discharge would produce serious economic hardships without equal or greater benefit to the public;

(4) Alterations generated by a proposed discharge do not disrupt the marine ecology of the receiving waters outside the zone of mixing;

(5) A zone of mixing shall not be granted for fresh surface waters, Pala Lagoon, Fagatele Bay, that portion of Pago Pago Harbor described in 24.0205(e)(1)(C), or in those waters in Manu’a described in 24.0205(f)(2)(G);¬

(6) The size of any zone of mixing granted for any toxic pollutant shall not exceed the dimensions and volume of the zone of initial dilution and in no event shall the concentration of a toxic pollutant exceed chronic toxic levels at the boundary of the zone of initial dilution. Except for limited portions of the ZID, acute toxic standards shall be achieved within the ZID;

(7) The standards set forth in 24.0206(a)-(d) shall be met at the boundary of the zone of initial dilution;

(8) Alternate standards may be established within a Zone of Mixing for those standards set forth at 24.0206(h), (j), (I), (m), (o), and (p); provided that the standards shall be met at the boundary of the Zone of Mixing;

(9) A zone of mixing shall not be granted if it would include the surface of the water body, any part of the shoreline, or any part of any barrier or fringing reef; and

(10) Further, the following shall be considered by the EQC in determining whether to grant or deny a zone of mixing:

(A) Protected uses of the body of water;

(B) Existing natural conditions of the receiving water;

(C) Character of the effluent;

(D) Adequacy of the design of the outfall and diffuser system to achieve the desired dispersion and assimilation in the receiving waters; and

(E) Other pertinent policies, plans or territorial agencies.

(c) Procedures to Apply for Zone of Mixing

(1) The owner and/or operator of a point source of pollutants where the effluent quality of the discharge does not meet the applicable standards defined in 24.0206 at the point of discharge shall be in violation of these standards until such time as the EQC grants a zone of mixing upon receiving arid acting upon an application for a zone of mixing from the discharger. At its discretion the EQC may grant extensions to discharges existing on the effective date of these standards, but in no event shall an existing discharge requiring a zone of mixing continue to discharge if a complete application for a zone of mixing has not been submitted to the EQC within 180 days of the effective date of these standards.

(2) Every application for a zone of mixing shall be accompanied by a complete and detailed description of:

(A) the nature of the discharge including, but not limited to, volume, effluent quality, discharge location and configuration, and treatment applied;

(B) present ambient water quality conditions in the vicinity of the discharge;

(C) how present conditions compare to standards;

(D) proposed alternate water quality standards within the proposed zone• of mixing;

(E) proposed dimensions and volume of the zone on mixing;

(F) a calculation of the dimensions and volume of the zone of initial dilution and the dilution ratio achieved at the boundaries of the zone of initial dilution;

(G) the reasons why it is not practicable to achieve water quality standards for any specific parameter at the point of discharge or to eliminate the discharge and why the operation of the discharge is in the best interest of the territory; and

(H) such other information as the EQC prescribes.

(3) Each application for a zone of mixing shall be reviewed in light of descriptions, statements, plans, histories, and other supporting information as may be submitted in the application or upon the request of the EQC and the effect on the water quality standards established in 24.0206.

(4) A zone of mixing, or a renewal, may be granted upon the EQC’s determination that the requirements of these standards have been met for the following time periods and conditions:

(A) If a zone of mixing is granted on the grounds that there is no technically and/or financially efficient means known or available for elimination or adequate prevention, control, or abatement of the discharge involved, it shall be only until the necessary means of prevention, control, or abatement becomes practicable and it shall be subject to the taking of substitute or alternative measures that the EQC may prescribe. No renewal of a zone of mixing granted under this section shall be allowed without a thorough review of known and available means of preventing, controlling of abating the discharge involved;

(B) The EQC may grant a zone of mixing for a period not exceeding 5 years, subject to be reopened if these water quality standards are revised during the 5-year period;

(C) Every zone of mixing granted under this section may include, but not be limited to, applicant requirements to perform effluent and receiving water sampling and testing as specified by the EQC and to report the results to the EQC. A program of research to develop practicable alternatives to the methods of treatment or control in use by the applicant may be required as a condition of the granting of the zone of mixing; and

(D) Upon application any zone of mixing granted pursuant to this section may be renewed periodically for periods not exceeding 5 years, provided that:

(i) the applicant for renewal has met all of the conditions specified in the previously prescribed zone of mixing;

(ii) no renewal shall be granted except upon application. Any such application shall be made at least 120 days prior to the expiration of the current zone of mixing;

(iii) upon timely application for renewal, the terms and conditions of them original zone of mixing shall remain in effect until such time as the EQC acts upon the application for renewal; and

(iv) if no timely application for renewal is made, the zone of mixing shall automatically expire.

(5) The EQC, on its own motion or upon the application of any person, shall terminate a zone of mixing if, after a hearing, it is determined that:

(A) the water quality outside the zone of mixing does not meet the standards applicable to that water as given in 24.0206;

(B) the zone of mixing granted has interfered with any protected uses of the water area; or

(C) any NPOES permit condition has not been met and the discharger has failed to take prudent action to bring the discharge into compliance. Such termination shall be made after a hearing held by the EQC in accordance with Title 04, Chapter 10, ASCA. Upon such termination, the standards of water quality applicable shall be those established in 24.0206.

(6) The granting of a mixing zone shall be subject to approval by USEPA.

History: Rule 8-81, eff 16 Jun 81, § 1; Rule 6-05, eff 2005.