Idaho Admin. Code r. 58.01.25.303 - CALCULATING PERMIT PROVISIONS

01. Outfalls and Discharge Points. All permit effluent limitations, standards and prohibitions shall be established for each outfall or discharge point of the permitted facility, except as otherwise provided under Subsection 302.13, (Best Management Practices,) and Subsection 303.08, (Internal Waste Streams.) (3-24-22)

02. Production-Based Limitations. (3-24-22)

a. In the case of POTWs, permit effluent limitations, standards, or prohibitions shall be calculated based on design flow. (3-24-22)

b. Except in the case of POTWs or as provided in Subsection 303.02.b.ii., calculation of any permit limitations, standards, or prohibitions which are based on production (or other measure of operation) shall be based upon a reasonable measure of actual production of the facility. (3-24-22)

i. 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 limitations; for example, monthly production shall be used to calculate average monthly discharge limitations. (3-24-22)

ii. The Department may include a condition establishing alternate permit limitations, standards, or prohibitions based upon anticipated increased (not to exceed maximum production capability) or decreased production levels. (3-24-22)

iii. For the automotive manufacturing industry only, the Department shall establish an alternate condition under 303.02.b.ii., if the applicant satisfactorily demonstrates to the Department, at the time the application is submitted, that: (3-24-22)

(1) Its actual production, as indicated in Subsections 303.02.b. and 303.02.b.i. is substantially below maximum production capability, and (3-24-22)

(2) There is a reasonable potential for an increase above actual production during the duration of the permit. (3-24-22)

iv. If the Department establishes permit conditions under Subsection 303.02.b.ii.: (3-24-22)

(1) The permit shall require the permittee to notify the Department at least two (2) business days prior to a 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: (3-24-22)

(a) The anticipated level, and the period during which the permittee expects to operate at the alternate level; and (3-24-22)

(b) If the notice covers more than one (1) month, the notice shall specify the reasons for the anticipated production level increase; and (3-24-22)

(c) 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; (3-24-22)

(2) 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 Department under Subsection 303.02.b.ii., 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; and (3-24-22)

(3) The permittee shall submit, with the Discharge Monitoring Report, the level of production that actually occurred during each month and the limitations, standards, or prohibitions applicable to that level of production. (3-24-22)

03. Metals. All permit effluent limitations, standards, or prohibitions for a metal shall be expressed in terms of total recoverable metal as defined in 40 CFR Part 136 , unless: (3-24-22)

a. An applicable effluent standard or limitation has been promulgated under the Clean Water Act and specifies the limitation for the metal in the dissolved or valent or total form; (3-24-22)

b. In establishing permit limitations on a case-by-case basis under 40 CFR 125.3, it is necessary to express the limitation on the metal in the dissolved or valent or total form to carry out the provisions of the Clean Water Act; or (3-24-22)

c. All approved analytical methods for the metal inherently measure only its dissolved form (e.g., hexavalent chromium). (3-24-22)

04. Continuous Discharges. For continuous discharges all permit effluent limitations, standards, and prohibitions, including those necessary to achieve water quality standards, shall, unless impracticable, be stated as: (3-24-22)

a. Maximum daily and average monthly discharge limitations for all dischargers other than POTWs; or (3-24-22)

b. Average weekly and average monthly discharge limitations for POTWs. (3-24-22)

05. Noncontinuous Discharges. Discharges which are not continuous, as defined in Section 010 (Definitions), shall be particularly described and limited, considering the following factors, as appropriate: (3-24-22)

a. Frequency (for example, a batch discharge shall not occur more than once every three (3) weeks); (3-24-22)

b. Total mass (for example, not to exceed one hundred (100) kilograms of zinc and two hundred (200) kilograms of chromium per batch discharge); (3-24-22)

c. Maximum rate of discharge of pollutants during the discharge (for example, not to exceed two (2) kilograms of zinc per minute); and (3-24-22)

d. Prohibition or limitation of specified pollutants by mass, concentration, or other appropriate measure (for example, shall not contain at any time more than one-tenth (0.1) mg/L zinc or more than two hundred fifty (250) grams (one-fourth (A) kilogram) of zinc in any discharge). (3-24-22)

06. Mass Limitations. (3-24-22)

a. All pollutants limited in permits shall have limitations, standards, or prohibitions expressed in terms of mass except: (3-24-22)

i. pH, temperature, radiation, or other pollutants which cannot appropriately be expressed by mass; (3-24-22)

ii. When applicable standards and limitations are expressed in terms of other units of measurement; or (3-24-22)

iii. If in establishing permit limitations on a case-by-case basis under 40 CFR 125.3, limitations expressed in terms of mass are infeasible because the mass of the pollutant discharged cannot be related to a measure of operation (for example, discharges of TSS from certain mining operations), and permit conditions ensure that dilution will not be used as a substitute for treatment. (3-24-22)

b. Pollutants limited in terms of mass, may also be limited in terms of other units of measurement, and the permit shall require the permittee to comply with both limitations. (3-24-22)

07. Pollutant Credits for Intake Water. (3-24-22)

a. The following definitions apply to the consideration of intake credits in determining reasonable potential and establishing technology based and water quality based effluent limits for IPDES permits. (3-24-22)

i. An intake pollutant is the amount of a pollutant that is present in waters of the United States (including ground water as provided in Subsection 303.07.a.iv.) at the time water is removed from the same body of water by the discharger or other facility supplying the discharger with intake water. (3-24-22)

ii. An intake pollutant must be from the same body of water as the discharge in order to be eligible for an intake credit. An intake pollutant is considered to be from the same body of water as the discharge if the Department finds that the intake pollutant would have reached the vicinity of the outfall point in the receiving water within a reasonable period had it not been removed by the permittee. This finding will be established if: (3-24-22)

(1) The background concentration of the pollutant in the receiving water (excluding any amount of the pollutant in the facility's discharge) is similar to that in the intake water; (3-24-22)

(2) There is a direct hydrological connection between the intake and discharge points; and (3-24-22)

(3) Water quality characteristics (e.g., temperature, pH, hardness) are similar in the intake and receiving waters. (3-24-22)

iii. The Department may also consider other site-specific factors relevant to the transport and fate of the pollutant to make the finding in a particular case that a pollutant would or would not have reached the vicinity of the outfall point in the receiving water within a reasonable period had it not been removed by the permittee. (3-24-22)

iv. An intake pollutant from ground water may be considered to be from the same body of water if the Department determines that the pollutant would have reached the vicinity of the outfall point in the receiving water within a reasonable period had it not been removed by the permittee, except that such a pollutant is not from the same body of water if the ground water contains the pollutant partially or entirely due to human activity, such as industrial, commercial, or municipal operations, disposal actions, or treatment processes. (3-24-22)

v. The determinations made under Subsections 303.07.b. and c. will be made on a pollutant-by-pollutant and outfall-by-outfall basis. (3-24-22)

vi. These provisions do not alter Department's obligation under Subsection 302.06.a.vii(2) to develop effluent limitations consistent with the assumptions and requirements of any available waste load allocations for the discharge, that is part of a TMDL prepared by the Department and approved by EPA pursuant to 40 CFR 130.7, or prepared by EPA pursuant to 40 CFR 130.7(d). (3-24-22)

b. Consideration of intake pollutants for technology based effluent limitations: (3-24-22)

i. Upon request of the discharger, technology-based effluent limitations or standards shall be adjusted to reflect credit for pollutants in the discharger's intake water if: (3-24-22)

(1) The applicable effluent limitations and standards contained in 40 CFR Part 401 through 471 , specifically provide that they shall be applied on a net basis; or (3-24-22)

(2) The discharger 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. (3-24-22)

ii. Credit for generic pollutants such as BOD or 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 outfall or elsewhere. (3-24-22)

iii. 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. (3-24-22)

iv. Credit shall be granted only if the discharger demonstrates that the intake water is drawn from the same body of water into which the discharge is made. The Department may waive this requirement if the Department finds that no environmental degradation will result. (3-24-22)

v. This section does not apply to the discharge of raw water clarifier sludge generated from the treatment of intake water. (3-24-22)

c. Consideration of intake pollutants for water quality based effluent limitations: (3-24-22)

i. The Department will evaluate if there is reasonable potential for the discharge of an identified intake pollutant to cause or contribute to an exceedance of a narrative or numeric water quality criterion. If the Department determines that an intake pollutant in the discharge does not have the reasonable potential to cause or contribute to an exceedance of an applicable water quality standard, the Department is not required to include a water quality-based effluent limit for the identified intake pollutant in the facility's permit. (3-24-22)

ii. If a reasonable potential exists, then water quality-based effluent limits may be established that reflect a credit for intake pollutants where a discharger demonstrates that the following conditions are met: (3-24-22)

(1) The facility removes the intake water containing the pollutant from the same body of water into which the discharge is made; (3-24-22)

(2) The ambient background concentration of the pollutant does not meet the most stringent applicable water quality criterion for that pollutant; (3-24-22)

(3) The facility does not alter the identified intake pollutant chemically or physically in a manner that would cause adverse water quality impacts to occur that would not occur if the pollutants had not been removed from the body of water; (3-24-22)

(4) The timing and location of the discharge would not cause adverse water quality impacts to occur that would not occur if the identified intake pollutant had not been removed from the body of water; (3-24-22)

(5) For the purpose of determining water quality-based effluent limits, the facility does not increase the identified intake pollutant concentration at the point of discharge as compared to the pollutant concentration in the intake water. (3-24-22)

iii. Where the conditions in Subsection 303.07.c.i. and ii are met, the Department may establish a water quality-based effluent limitation allowing a facility to discharge a mass and concentration of the intake pollutant that are no greater than the mass and concentration found in the facility's intake water. A discharger may add mass of the pollutant to its waste stream if an equal or greater mass is removed prior to discharge, so there is no net addition of the pollutant in the discharge compared to the intake water. (3-24-22)

iv. Where intake water for a facility is provided by a municipal water supply system and the supplier provides treatment of the raw water that removes an intake water pollutant, the concentration of the intake water pollutant will be determined at the point where the water enters the water supplier's distribution system. (3-24-22)

v. Where a facility discharges intake pollutants from multiple sources that originate from the receiving water body and from other water bodies, the Department may derive an effluent limit reflecting the flow-weighted amount of each source of the pollutant provided that conditions in 303.07.c.ii. of this subsection are met and adequate monitoring to determine compliance can be established and is included in the permit. (3-24-22)

vi. The permit will specify how compliance with mass and concentration-based limitations for the intake water pollutant will be assessed. This may be done by basing the effluent limitation on background concentration data. Alternatively, the Department may determine compliance by monitoring the pollutant concentrations in the intake water and in the effluent. This monitoring may be supplemented by monitoring internal waste streams or by a Department evaluation of the use of best management practices. (3-24-22)

vii. Effluent limitations must be established to comply with all other applicable state and federal laws and regulations including technology-based requirements and anti-degradation policies. (3-24-22)

viii. When determining whether water quality based effluent limitations are necessary, information from chemical-specific, whole effluent toxicity and biological assessments will be considered independently. (3-24-22)

ix. Permit limits must be consistent with the assumptions and requirement of waste load allocations or other provisions in a TMDL that has been approved by the EPA. (3-24-22)

08. Internal Waste Streams. (3-24-22)

a. 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 required by Section 304 (Monitoring and Reporting Requirements) shall also be applied to the internal waste streams. (3-24-22)

b. Limits on internal waste streams will be imposed only when the fact sheet sets forth the exceptional circumstances which make such limitations necessary, such as: (3-24-22)

i. When the final discharge point is inaccessible (for example, under ten (10) meters of water); (3-24-22)

ii. The wastes at the point of discharge are so diluted as to make monitoring impracticable; or (3-24-22)

iii. The interferences among pollutants at the point of discharge would make detection or analysis impracticable. (3-24-22)

09. Disposal of Pollutants into Wells, into POTWs, or by Land Application. (3-24-22)

a. When part of a discharger's process wastewater is not being discharged into waters of the United States 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 United States, applicable effluent standards and limitations for the discharge in an IPDES 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: (3-24-22)

i. If none of the waste from a particular process is discharged into waters of the United States, 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; or (3-24-22)

ii. In all cases other than those described in Subsection 303.09.a.i., 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 United States, and dividing the result by the total wastewater flow. Effluent limitations and standards so calculated may be further adjusted under 40 CFR Part 125 , subpart D, to make them more or less stringent if discharges to wells, POTWs, or by land application change the character or treatability of the pollutants being discharged to receiving waters. This method may be algebraically expressed as:

P=(E x N)/T; where P is the permit effluent limitation, E is the limitation derived by applying effluent guidelines to the total waste stream, N is the wastewater flow to be treated and discharged to waters of the United States, and T is the total wastewater flow.

(3-24-22)

b. Subsection 303.09.a. does not apply to the extent that promulgated effluent limitations guidelines: (3-24-22)

i. Control concentrations of pollutants discharged but not mass; or (3-24-22)

ii. Specify a different specific technique for adjusting effluent limitations to account for well injection, land application, or disposal into POTWs. (3-24-22)

c. Subsection 303.09.a. does not alter a discharger's obligation to meet any more stringent requirements established under Sections 300 (Conditions Applicable to all Permits), 301 (Permit Conditions for Specific Categories), 40 CFR 122.42(e), and 302 (Establishing Permit Provisions). (3-24-22)

d. Disposal of discharge into injection wells is regulated by: (3-24-22)

i. Idaho Department of Water Resources, in compliance with the IDAPA 37.03.03, "Rules and Minimum Standards for the Construction and Use of Injection Wells," for a Class I injection well; or (3-24-22)

ii. Health District having jurisdiction, in compliance with IDAPA 58.01.03, "Individual/Subsurface Sewage Disposal Rules," for a Class V injection well. (3-24-22)

e. Disposal of discharge onto the surface of the land is regulated by the Department under IDAPA 58.01.17, "Recycled Water Rules." (3-24-22)

Notes

Idaho Admin. Code r. 58.01.25.303