(a) Bacteria criteria for waters in Indian lands. (1) The bacteria content of Class AA and Class A waters shall be as naturally occurs, and the minimum number of Escherichia coli bacteria shall not exceed a geometric mean of 100 colony-forming units per 100 milliliters (cfu/100 ml) in any 30-day interval; nor shall 320 cfu/100 ml be exceeded more than 10% of the time in any 30-day interval.

(2) In Class B, Class C, and Class GPA waters, the number of Escherichia coli bacteria shall not exceed a geometric mean of 100 colony forming units per 100 milliliters (cfu/100 ml) in any 30- day interval; nor shall 320 cfu/100 ml be exceeded more than 10% of the time in any 30-day interval.

(3) The bacteria content of Class SA waters shall be as naturally occurs, and the number of Enterococcus spp. bacteria shall not exceed a geometric mean of 30 cfu/100 ml in any 30-day interval, nor shall 110 cfu/100 ml be exceeded more than 10% of the time in any 30-day interval.

(4) In Class SA shellfish harvesting areas, the numbers of total coliform bacteria or other specified indicator organisms in samples representative of the waters in shellfish harvesting areas may not exceed the criteria recommended under the National Shellfish Sanitation Program, United States Food and Drug Administration, as set forth in the Guide for the Control of Molluscan Shellfish, 2015 Revision. The Director of the Federal Register approves this incorporation by reference in accordance with 5 U.S.C. 552(a) and 1 CFR part 51. You may obtain a copy from the U.S. Food and Drug Administration Center for Food Safety and Applied Nutrition, Shellfish and Aquaculture Policy Branch, 5100 Paint Branch Parkway (HFS-325), College Park, MD 20740 or http://www.fda.gov/Food/GuidanceRegulation/FederalStateFoodPrograms/ucm2006754.htm. You may inspect a copy at the U.S. Environmental Protection Agency Docket Center Reading Room, William Jefferson Clinton West Building, Room 3334, 1301 Constitution Avenue NW., Washington, DC 20004, (202) 566-1744, or at the National Archives and Records Administration (NARA). For information on the availability of this material at NARA, call 202-741-6030, or go to: http://www.archives.gov/federal_register/code_of_federal_regulations/ibr_locations.html.

(5) In Class SB and SC waters, the number of Enterococcus spp. bacteria shall not exceed a geometric mean of 30 cfu/100 ml in any 30-day interval, nor shall 110 cfu/100 ml be exceeded more than 10% of the time in any 30-day interval.

(b) Ammonia criteria for fresh waters in Indian lands. (1) The one-hour average concentration of total ammonia nitrogen (in mg TAN/L) shall not exceed, more than once every three years, the criterion maximum concentration (i.e., the “CMC,” or “acute criterion”) set forth in Tables 2 and 3 of this section.

(2) The thirty-day average concentration of total ammonia nitrogen (in mg TAN/L) shall not exceed, more than once every three years, the criterion continuous concentration (i.e., the “CCC,” or “chronic criterion”) set forth in Table 4.

(3) In addition, the highest four-day average within the same 30-day period as in (2) shall not exceed 2.5 times the CCC, more than once every three years.

(c) pH Criteria for fresh waters in Indian lands. The pH of fresh waters shall fall within the range of 6.5 to 8.5.

(d) Temperature criteria for tidal waters in Indian lands. (1) The maximum acceptable cumulative increase in the weekly average temperature resulting from all artificial sources is 1 °C (1.8 °F) during all seasons of the year, provided that the summer maximum is not exceeded.

(i) Weekly average temperature increase shall be compared to baseline thermal conditions and shall be calculated using the daily maxima averaged over a 7-day period.

(ii) Baseline thermal conditions shall be measured at or modeled from a site where there is no artificial thermal addition from any source, and which is in reasonable proximity to the thermal discharge (within 5 miles), and which has similar hydrography to that of the receiving waters at the discharge.

(2) Natural temperature cycles characteristic of the waterbody segment shall not be altered in amplitude or frequency.

(3) During the summer months (for the period from May 15 through September 30), water temperatures shall not exceed a weekly average summer maximum threshold of 18 °C (64.4 °F) (calculated using the daily maxima averaged over a 7-day period).

(e) Natural conditions provisions for waters in Indian lands. (1) The provision in Title 38 of Maine Revised Statutes 464(4.C) which reads: “Where natural conditions, including, but not limited to, marshes, bogs and abnormal concentrations of wildlife cause the dissolved oxygen or other water quality criteria to fall below the minimum standards specified in section 465, 465-A and 465-B, those waters shall not be considered to be failing to attain their classification because of those natural conditions,” does not apply to water quality criteria intended to protect human health.

(2) The provision in Title 38 of Maine Revised Statutes 420(2.A) which reads “Except as naturally occurs or as provided in paragraphs B and C, the board shall regulate toxic substances in the surface waters of the State at the levels set forth in federal water quality criteria as established by the United States Environmental Protection Agency pursuant to the Federal Water Pollution Control Act, Public Law 92-500, Section 304(a), as amended,” does not apply to water quality criteria intended to protect human health.

(f) Mixing zone policy for waters in Indian lands. (1) Establishing a mixing zone. (i) The Department of Environmental Protection (“department”) may establish a mixing zone for any discharge at the time of application for a waste discharge license if all of the requirements set forth in paragraphs (g)(2) and (3) of this section are satisfied. The department shall attach a description of the mixing zone as a condition of a license issued for that discharge. After opportunity for a hearing in accordance with 38 MRS section 345-A, the department may establish by order a mixing zone with respect to any discharge for which a license has been issued pursuant to section 414 or for which an exemption has been granted by virtue of 38 MRS section 413, subsection 2.

(ii) The purpose of a mixing zone is to allow a reasonable opportunity for dilution, diffusion, or mixture of pollutants with the receiving waters such that an applicable criterion may be exceeded within a defined area of the waterbody while still protecting the designated use of the waterbody as a whole. In determining the extent of any mixing zone to be established under this section, the department will require from the applicant information concerning the nature and rate of the discharge; the nature and rate of existing discharges to the waterway; the size of the waterway and the rate of flow therein; any relevant seasonal, climatic, tidal, and natural variations in such size, flow, nature, and rate; the uses of the waterways that could be affected by the discharge, and such other and further evidence as in the department's judgment will enable it to establish a reasonable mixing zone for such discharge. An order establishing a mixing zone may provide that the extent thereof varies in order to take into account seasonal, climatic, tidal, and natural variations in the size and flow of, and the nature and rate of, discharges to the waterway.

(2) Mixing zone information requirements. At a minimum, any request for a mixing zone must:

(i) Describe the amount of dilution occurring at the boundaries of the proposed mixing zone and the size, shape, and location of the area of mixing, including the manner in which diffusion and dispersion occur;

(ii) Define the location at which discharge-induced mixing ceases;

(iii) Document the substrate character and geomorphology within the mixing zone;

(iv) Document background water quality concentrations;

(v) Address the following factors;

(A) Whether adjacent mixing zones overlap;

(B) Whether organisms would be attracted to the area of mixing as a result of the effluent character; and

(C) Whether the habitat supports endemic or naturally occurring species.

(vi) Provide all information necessary to demonstrate whether the requirements in paragraph (g)(3) of this section are satisfied.

(3) Mixing zone requirements. (i) Mixing zones shall be established consistent with the methodologies in Sections 4.3 and 4.4 of the “Technical Support Document for Water Quality-based Toxics Control” EPA/505/2-90-001, dated March 1991.

(ii) The mixing zone demonstration shall be based on the assumption that a pollutant does not degrade within the proposed mixing zone, unless:

(A) Scientifically valid field studies or other relevant information demonstrate that degradation of the pollutant is expected to occur under the full range of environmental conditions expected to be encountered; and

(B) Scientifically valid field studies or other relevant information address other factors that affect the level of pollutants in the water column including, but not limited to, resuspension of sediments, chemical speciation, and biological and chemical transformation.

(iii) Water quality within an authorized mixing zone is allowed to exceed chronic water quality criteria for those parameters approved by the department. Acute water quality criteria may be exceeded for such parameters within the zone of initial dilution inside the mixing zone. Acute criteria shall be met as close to the point of discharge as practicably attainable. Water quality criteria shall not be violated outside of the boundary of a mixing zone as a result of the discharge for which the mixing zone was authorized.

(iv) Mixing zones shall be as small as practicable. The concentrations of pollutants present shall be minimized and shall reflect the best practicable engineering design of the outfall to maximize initial mixing. Mixing zones shall not be authorized for bioaccumulative pollutants (i.e., chemicals for which the bioconcentration factors (BCF) or bioaccumulation factors (BAF) are greater than 1,000) or bacteria.

(v) In addition to the requirements above, the department may approve a mixing zone only if the mixing zone:

(A) Is sized and located to ensure that there will be a continuous zone of passage that protects migrating, free-swimming, and drifting organisms;

(B) Will not result in thermal shock or loss of cold water habitat or otherwise interfere with biological communities or populations of indigenous species;

(C) Is not likely to jeopardize the continued existence of any endangered or threatened species listed under section 4 of the Endangered Species Act of 1973, as amended (16 U.S.C. 1531 et seq.) or result in the destruction or adverse modification of such species' critical habitat;

(D) Will not extend to drinking water intakes and sources;

(E) Will not otherwise interfere with the designated or existing uses of the receiving water or downstream waters;

(F) Will not promote undesirable aquatic life or result in a dominance of nuisance species;

(G) Will not endanger critical areas such as breeding and spawning grounds, habitat for state-listed threatened or endangered species, areas with sensitive biota, shellfish beds, fisheries, and recreational areas;

(H) Will not contain pollutant concentrations that are lethal to mobile, migrating, and drifting organisms passing through the mixing zone;

(I) Will not contain pollutant concentrations that may cause significant human health risks considering likely pathways of exposure;

(J) Will not result in an overlap with another mixing zone;

(K) Will not attract aquatic life;

(L) Will not result in a shore-hugging plume; and

(M) Is free from:

(1) Substances that settle to form objectionable deposits;

(2) Floating debris, oil, scum, and other matter in concentrations that form nuisances; and

(3) Objectionable color, odor, taste, or turbidity.

(g) Dissolved oxygen criteria for class A waters throughout the State of Maine, including in Indian lands. The dissolved oxygen content of Class A waters shall not be less than 7 ppm (7 mg/L) or 75% of saturation, whichever is higher, year-round. For the period from October 1 through May 14, in fish spawning areas, the 7-day mean dissolved oxygen concentration shall not be less than 9.5 ppm (9.5 mg/L), and the 1-day minimum dissolved oxygen concentration shall not be less than 8 ppm (8.0 mg/L).

(h) Waiver or modification of protection and improvement laws for waters throughout the State of Maine, including in Indian lands. For all waters in Maine, the provisions in Title 38 of Maine Revised Statutes 363-D do not apply to state or federal water quality standards applicable to waters in Maine, including designated uses, criteria to protect existing and designated uses, and antidegradation policies.

[81 FR 92487, Dec. 19, 2016, as amended at 85 FR 82939, Dec. 21, 2020]