(1) (a) Establishment of Effluent Limitations. The Department will limit or prohibit discharges of pollutants to surface waters to assure that surface water quality standards of the receiving waters are protected and maintained or attained. The level of treatment for an individual discharger will be established by the discharge permit in accordance with 314 CMR 3.00: Surface Water Discharge Permit Program. In establishing water quality based effluent limitations the Department shall take into consideration natural background conditions and existing discharges. Discharges shall be limited or prohibited to protect existing uses and not interfere with the attainment of designated uses in downstream and adjacent segments. The Department will provide a reasonable margin of safety to account for any lack of knowledge concerning the relationship between the pollutants being discharged and their impact on water quality. Where the Department has not established water quality based effluent limitations in a permit and a violation of water quality standards attributable to a discharge occurs, the Department may modify, suspend or revoke the permit, in whole or in part, for cause in accordance with 314 CMR 3.00.

1. (b) Compliance Schedules. A permit may, when appropriate, specify a schedule leading to compliance with the Massachusetts and Federal Clean Water Acts and regulations. The purpose of a schedule of compliance generally is to afford a permittee adequate time to comply with one or more permit requirements or limitations that are based on new, newly interpreted or revised water quality standards that became effective after both issuance of the

initial permit for a discharge and July 1, 1977. The Department may include a schedule of compliance in a permit at the time of permit reissuance or modification where the permittee either cannot comply with such permit requirements or limitations, or there is insufficient information available to determine whether the permittee can comply with such permit requirements or limitations. A schedule of compliance shall require compliance at the earliest practicable time, as determined by the Department. A schedule of compliance shall include dates for specified tasks or activities leading to compliance and may include interim effluent limitations, as the Department deems appropriate. (c) TMDLs. The Department may develop and enforce compliance with TMDLs and TMDL implementation plans for waters or segments impaired by a pollutant or pollutants.

(2) Mixing Zones. In applying 314 CMR 4.00, the Department may recognize a limited area or volume of a waterbody as a mixing zone for the initial dilution of a discharge. Waters within a mixing zone may fail to meet specific water quality criteria, provided the following conditions are met:

1. (a) Mixing zones shall be limited to an area or volume as small as feasible. There shall be no lethality to organisms passing through the mixing zone as determined by the Department. The location, design and operation of the discharge shall minimize impacts on aquatic life and other existing and designated uses within and beyond the mixing zone.
2. (b) Mixing zones shall not interfere with the migration or free movement of fish or other aquatic life. There shall be safe and adequate passage for swimming and drifting organisms with no deleterious effects on their populations.
3. (c) Mixing zones shall not create nuisance conditions, accumulate pollutants in sediments or biota in toxic amounts or otherwise interfere with the existing or designated uses of surface waters.

(3) Hydrologic Conditions. The Department will determine the most severe hydrologic condition at which water quality criteria must be applied. The Department may further stipulate the magnitude, duration and frequency of allowable excursions from the magnitude component of criteria and may determine that criteria should be applied at flows lower than those specified in order to prevent adverse impacts of discharges on existing and designated uses.

1. (a) For rivers and streams, the lowest flow condition at and above which aquatic life criteria must be applied is the lowest mean flow for seven consecutive days to be expected once in ten years. When records are not sufficient to determine this condition, the flow may be estimated using methods approved by the Department.
2. (b) In waters where flows are regulated by dams or similar structures, the lowest flow condition at which aquatic life criteria must be applied is the flow equaled or exceeded 99% of the time on a yearly basis, or another equivalent flow agreed upon by the Department and the federal, state or private entity controlling the flow. The minimum flow established in such an agreement will become the critical low flow for those waters covered by the agreement. When the Department issues a 401 Water Quality Certification of an activity subject to licensing by the Federal Energy Regulatory Commission, flows shall be maintained or restored to protect existing and designated uses.
3. (c) In coastal and marine waters and for lakes and ponds, the Department will establish extreme hydrologic conditions at which aquatic life criteria must be applied on a case-by-case basis. In all cases existing uses shall be protected and the selection shall not interfere with the attainment of designated uses.
4. (d) For rivers and streams and waters whose flows are regulated by dams or similar structures, human health based criteria may be applied at the harmonic mean flow. For coastal and marine waters and lakes and ponds, human health based criteria may be applied at conditions the Department determines will result in protection at least equivalent to that provided for rivers and streams.

(4) National Goal Uses, Partial Uses, and Variances.

1. (a) The Department may remove a national goal use that is not an existing use, designate a segment as partial use, or grant a variance to authorize a discharge, provided the applicant demonstrates that:

   1. 1. Naturally occurring pollutant concentrations prevent the attainment of the use;
   2. 2. Natural, ephemeral, intermittent or low-flow conditions or water levels prevent the attainment of the use, unless these conditions may be compensated for by the discharge of sufficient volume of effluent discharges without violating state water conservation requirements to enable uses to be met;
   3. 3. Human-caused conditions or sources of pollution prevent the attainment of the use and cannot be remedied or would cause more environmental damage to correct than to leave in place;
   4. 4. Dams, diversions or other types of hydrologic modifications preclude the attainment of the use, and it is not feasible to restore the water body to its original condition or to operate such modification in a way that would result in the attainment of the use;
   5. 5. Physical conditions related to the natural features of the water body, such as the lack of a proper substrate, cover, flow, depth, pools, riffles, and the like, unrelated to water quality, preclude attainment of aquatic life protection uses; or
   6. 6. Controls more stringent than those required by sections 301(b) and 306 of the Federal Act would result in substantial and widespread economic and social impact, this demonstration may include documentation of median household income or other economic measures adjusted to reflect the cost of living or other circumstances particular to the affected area.
2. (b) Prior to removal of a use or the designation of a partial use, the Department shall provide public notice and the opportunity for a public hearing in accordance with M.G.L.
3. c. 30A and the applicant shall submit to the Department the information necessary for completion of a Use Attainability Analysis.
4. (c) The Department may grant a variance for a specified period of time for a particular discharger and for specific pollutants so that it can be determined through a Use Attainability Analysis whether uses can be attained. A variance applicant shall submit to the Department a detailed assessment of the types of information that will be needed for completion of the Use Attainability Analysis. A variance may be granted only for the pollutants causing noncompliance with criteria and all other provisions of 314 CMR 4.00 apply for the term of the variance. Prior to granting a variance, the Department will provide or require public notice and provide an opportunity for a public hearing in accordance with 314 CMR 2.00: Permit Procedures. An applicant granted a variance shall submit to the Department information necessary for completion of a Use Attainability Analysis in accordance with the provisions of the variance and the permit.

(6) Procedures for Sampling and Analyses. All procedures used for the purpose of collecting, preserving and analyzing samples in connection with 314 CMR 4.00 shall be approved by the Department.

1. (a) Approved procedures currently include the following:

   1. 1. E.W. Rice, R.B. Baird, A.D. Eaton, editors; Standard Methods for the Examination

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   of Water and Wastewater, 23 Edition; published by the American Public Health Association, et al., 2017; 2. Clean Water Act Analytical Methods approved by EPA and described at 40 C.F.R. Part 136, as amended by 82 Federal Register 40846, August 28, 2017; 3. Annual Book of ASTM Standards. Section 11, vol. 11.01-11.08; published by West Conshohocken: ASTM International, 2018; 4. Parsons, T.R., Maita, Y., and Lalli, C.M., A Manual of Chemical and Biological Methods for Seawater Analysis; published by New York: Pergamon Press, 1984; and 5. EPA, Methods for the Determination of Chemical Substances in Marine and

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   Estuarine Environmental Matrices - 2 Edition; EPA/600/R-97/072; published by Washington, DC: U.S. Environmental Protection Agency, 1997.

2. (b) MassDEP may approve the use of additional or alternative procedures. Any additional or alternative procedures not listed in 314 CMR 4.03(6)(a)1. through 5. must meet one or more of the following evaluation criteria for approval:

   1. 1. A procedure that is authored or approved by a nationally-recognized, competent and authoritative source, such as the EPA, U.S. Geological Survey, American Society for Testing and Materials, and the American Public Health Association.
   2. 2. A new or modified procedure that has been approved through the EPA Alternative Test Procedure (ATP) Program, or is shown to be compliant with the Clean Water Act ATP program as described at 40 CFR 136.4 and 136.5.
   3. 3. A new or modified procedure that provides a preferred alternative to a promulgated method due to greater sensitivity, improved technological rigor, enhanced performance, and/or greater applicability, and is included as part of an approved Quality Assurance Project Plan.