Current through Register Vol. XLI, No. 21, May 23, 2024
Section 47-10-7 - Calculating NPDES Conditions7.1. Outlets and discharge points. -- All permit effluent limitations, standards, and prohibitions shall be established for each outlet or discharge point of the permitted facility, except as otherwise provided under subdivision 6.3.i and subsection 7.8 of this rule.7.2. Production-based limitations:7.2.a. In the case of sewage facilities, permit limitations, standards, or prohibitions shall be calculated based on design flow.7.2.a.1. Except in the case of sewage facilities, or as provided, in paragraph 7.2.a.3 below, calculation of any permit limitations, standards, or prohibitions that are based on production (or other measure of operation) shall be based not upon the designed production capacity but rather upon a reasonable measure of actual production of the facility. For new sources or new dischargers, actual production shall be estimated using projected production. The time period of the measure of production shall correspond to the time period of the calculated permit limitation; for example, monthly production shall be used to calculate average monthly discharge limitations.7.2.a.2. Where production-based limitations, standards or prohibitions apply, the Director may include a condition establishing alternate permit limitations, standards or prohibitions based upon anticipated increased or decreased production levels, not to exceed maximum production capability.7.2.a.3. If the Director establishes permit conditions under paragraph 7.2.a.2 above: 7.2.a.3.A. The permit shall require the permittee to notify the Director at least two (2) business days prior to the month in which the permittee expects to operate at a level higher than the lowest production level identified in the permit. The notice shall specify the anticipated level and the period during which the permittee expects to operate at the alternate level. If the notice covers more than one (1) month, the notice shall specify the reasons for the anticipated production level increase. New notice of discharge at alternate levels is required to cover a period or production level not covered by prior notice or, if during two (2) consecutive months otherwise covered by a notice, the production level at the permitted facility does not in fact meet the higher level designated in the notice.7.2.a.3.B. The permittee shall comply with the limitations, standards, or prohibitions that correspond to the lowest level of production specified in the permit, unless the permittee has notified the Director, in which case the permittee shall comply with the lower of the actual level of production during each month or the level specified in the notice.7.2.a.3.C. The permittee shall submit with the DMR the level of production that actually occurred during each month and the limitations, standards, or prohibitions applicable to that level of production.7.2.b. In the case of facilities and activities providing services and where water usage is not related to a product, limitations, standards, and prohibitions shall be based upon water usage. For those facilities covered by 47CSR1 ''3 and 4, those requirements shall also be considered in these determinations.7.3. Metals. -- All permit effluent limitations, standards, or prohibitions for a metal shall be expressed in terms of "total recoverable metal" as defined in 40 C.F.R. '136.3, unless: 7.3.a. An applicable effluent standard or limitation has been promulgated under the CWA and specifies the limitation for the metal in the dissolved or valent or total for; or7.3.b. In establishing permit limitations on a case-by-case basis, it is necessary to express the limitation on the metal in the dissolved or valent or total form in order to carry out the provisions of the CWA; or7.3.c. All approved analytical methods for the metal inherently measure only its dissolved form (e.g. hexavalent chromium).7.4. Continuous discharges. -- For all continuous discharges, all permit effluent limitations, standards, and prohibitions, including those necessary to achieve water quality standards, shall be stated as maximum daily and average monthly discharge limitations, unless impracticable.7.5. Noncontinuous discharges. -- Discharges that are not continuous shall be particularly described and limited, considering the following factors as appropriate: 7.5.c. Maximum rate of discharge of pollutants during the discharge; or7.5.d. Prohibition or limitation of specified pollutants by mass, concentration, or other appropriate measure.7.6. Mass limitations: 7.6.a. All pollutants limited in permits shall have limitations, standards, or prohibitions expressed in terms of mass except: 7.6.a.1. For pH, temperature, radiation, or other pollutants that cannot appropriately be expressed by mass;7.6.a.2. When applicable standards and limitations are expressed in terms of other units of measurement; or7.6.a.3. If, in establishing permit limitations on a case-by-case basis, limitations expressed in terms of mass are infeasible because the mass of the pollutant discharged cannot be related to a measure of operation and permit conditions ensure that dilution will not be used as a substitute for treatment.7.6.b. Pollutants limited in terms of mass additionally may be limited in terms of other units of measurement, and the permit shall require the permittee to comply with both limitations.7.7. Pollutants in intake water. 7.7.a. Upon request of the permittee, technology-based effluent limitations or standards shall be adjusted to reflect credit for pollutants in the permittee's intake water, if: 7.7.a.1. The applicable effluent limitations and standards specifically provide that they shall be applied on a net basis; or7.7.a.2. The permittee demonstrates that the control system it proposes or uses to meet applicable technology-based limitations and standards would, if properly installed and operated, meet the limitations and standards in the absence of pollutants in the intake waters.7.7.b. Credit for generic pollutants such as biochemical oxygen demand (BOD) or total suspended solids (TSS) should not be granted unless the permittee demonstrates that the constituents of the generic measure in the effluent are substantially similar to the constituents of the generic measure in the intake water or unless appropriate additional limits are placed on process water pollutants either at the outlet or elsewhere.7.7.c. Effluent limitations or standards shall not be calculated on a "net" basis for permittees whose intake water comes from underground water systems.7.7.d. Credit shall be granted only to the extent necessary to meet the applicable limitation or standard, up to a maximum value equal to the influent value. Additional monitoring may be necessary to determine eligibility for credits and compliance with permit limits.7.7.e. Credit shall be granted only if the permittee demonstrates that the intake water is drawn from the same body of water into which the discharge is made. The Director may waive this requirement if he finds that no environmental degradation will result.7.7.f. This section does not apply to the discharge of raw water clarifier sludge generated from the treatment of intake water.7.8. Internal waste streams. -- When permit effluent limitations or standards imposed at the point of discharge are impractical or infeasible, effluent limitations or standards for discharges of pollutants may be imposed on internal waste streams before mixing with other waste streams or cooling water streams. In those instances, the monitoring requirements under subdivision 6.3.h above shall also be applied to the internal waste streams.7.9. Disposal of pollutants into wells, into POTWs, or by land application: 7.9.a. When part of a discharger's process wastewater is not being discharged into waters of the State because it is disposed into a well, into a POTW or by land application, thereby reducing the flow or level of pollutants being discharged into waters of the State, applicable effluent standards and limitations for the discharge in a NPDES permit shall be adjusted to reflect the reduced raw waste resulting from such disposal. Effluent limitations and standards in the permit shall be calculated by one (1) of the following methods: 7.9.a.1. If none of the waste from a particular process is discharged into waters of the State, and effluent limitations guidelines provide separate allocation for wastes from that process, all allocations for the process shall be eliminated from calculation of permit effluent limitations or standards.7.9.a.2. In all cases other than those described in paragraph 7.9.a.1 above, effluent limitations shall be adjusted by multiplying the effluent limitation derived by applying effluent limitation guidelines to the total waste stream by the amount of wastewater flow to be treated and discharged into waters of the State, and dividing the result by the total wastewater flow. Effluent limitations and standards so calculated may be further adjusted to make them more stringent if discharges to wells, publicly owned treatment works, or by land application change the character or treatability of the pollutants being discharged to receiving waters.7.9.b. Subdivision 7.9.a above shall not apply to the extent that promulgated effluent limitations guidelines: 7.9.b.1. Control concentrations of pollutants discharged but not mass; or7.9.b.2. Specify a different specific technique for adjusting effluent limitations to account for well injection, land application, or disposal into POTWs.7.9.c. Subdivision 7.9.a above does not alter a discharger's obligation to meet any more stringent requirements established under sections 5 and 6 of this series.