Idaho Admin. Code r. 58.01.25.303

Current through September 2, 2024

Section 58.01.25.303 - CALCULATING PERMIT PROVISIONS

01.Outfalls and Discharge Points. Permit effluent limits, standards and prohibitions will be established for each outfall or discharge point of the permitted facility, except as otherwise provided under Subsections 302.13, and 303.08.

02.Production-Based Limits.

a. For POTWs, permit effluent limitat, standards, or prohibitions will be calculated based on design flow.

b. Except for POTWs or as provided in Subsection 303.02.b.ii., calculation of permit limits, standards, or prohibitions based on production (or other measure of operation) will be based upon a reasonable measure of actual production of the facility.

i. For new sources or new dischargers, actual production must be estimated using projected production. The time period of the measure of production must correspond to the time period of the calculated permit limit (e.g., monthly production is used to calculate average monthly discharge limits.

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

iii. For the automotive manufacturing industry only, the Department will establish an alternate condition under Subsection 303.02.b.ii., if the applicant satisfactorily demonstrates to the Department, during application submittal, that:

(1) Actual production, as indicated in Subsections 303.02.b. and 303.02.b.i., is substantially below maximum production capability, and

(2) Reasonable potential exists for an increase above actual production during the duration of the permit.

iv. If the Department establishes permit conditions under Subsection 303.02.b.ii.:

(1) The permit will require the permittee to notify the Department at least two (2) business days before the month the permittee expects to operate at a level higher than the lowest production level identified in the permit. The notice must specify:

(a) Anticipated level and the period the permittee expects to operate at the alternate level; and

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

(c) New notice of discharge at alternate levels must cover a period or production level not covered by a prior notice or, if during two (2) consecutive months otherwise covered by a notice, the production level at the permitted facility does not meet the higher level designated in the notice;

(2) The permittee must comply with the limit, 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 must comply with the lower of the actual level of production during each month or the level specified in the notice; and

(3) The permittee must submit, with the Discharge Monitoring Report, the level of production that occurred during each month and the limits, standards, or prohibitions applicable to that level of production.

03.Metals. Permit effluent limits, standards, or prohibitions for a metal will be expressed in terms of total recoverable metal as defined in 40 CFR Part 136, unless:

a. An applicable effluent standard or limit has been promulgated under the CWA and specifies the limit for the metal in the dissolved or valent or total form;

b. In establishing permit limits on a case-by-case basis under 40 CFR 125.3, specify the limit on the metal in the dissolved or valent or total form to carry out the provisions of the CWA; or

c. Approved analytical methods for the metal inherently measure only its dissolved form (e.g., hexavalent chromium).

04.Continuous Discharges. For continuous discharges, permit effluent limits, standards, and prohibitions, including those necessary to achieve water quality standards, will, unless impracticable, state:

a. Maximum daily and average monthly discharge limits for all dischargers other than POTWs; or

b. Average weekly and average monthly discharge limits for POTWs.

05.Noncontinuous Discharges. Discharges that are not continuous, as defined in Section 010, will be described and limited, considering the following factors, as appropriate:

a. Frequency (e.g., a batch discharge must not occur more than once every three (3) weeks);

b. Total mass (e.g., not to exceed one hundred (100) kilograms of zinc and two hundred (200) kilograms of chromium per batch discharge);

c. Maximum rate of discharge of pollutants during the discharge (e.g., not to exceed two (2) kilograms of zinc per minute); and

d. Prohibition or limit of specified pollutants by mass, concentration, or other appropriate measure (e.g., must not contain at any time more than one-tenth (0.1) mg/L zinc or more than two hundred fifty (250) grams (one-fourth (1/4) kilogram) of zinc in a discharge).

06.Mass Limits.

a. Pollutants limited in permits will have limits, standards, or prohibitions expressed in terms of mass except:

i. pH, temperature, radiation, or other pollutants that cannot be expressed by mass;

ii. When applicable standards and limits are expressed in other units of measurement; or

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

b. Pollutants limited by mass, may also be limited by other units of measurement, and the permit requires the permittee to comply with both limits.

07.Pollutant Credits for Intake Water.

a. The following definitions apply to intake credits in determining reasonable potential and establishing technology- and water quality- based effluent limits for IPDES permits.

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

ii. To be eligible for intake credit, an intake pollutant must be from the same body of water as the discharge, and the Department finds the intake pollutant would have reached the vicinity of the outfall point in the receiving water within a reasonable period if it had not been removed by the permittee. This finding will be established if:

(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 the intake water;

(2) A direct hydrological connection exists between the intake and discharge points; and

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

iii. The Department may consider other site-specific factors relevant to the transport and fate of the pollutant to determine in a particular case that a pollutant would have reached the vicinity of the outfall point in the receiving water within a reasonable period if it had not been removed by the permittee.

iv. An intake pollutant from ground water may be considered from the same body of water if the Department determines the pollutant would have reached the vicinity of the outfall point in the receiving water within a reasonable period if it had not been removed by the permittee, except that the 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.

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

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

b. Consideration of intake pollutants for technology-based effluent limits:

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

(1) Applicable effluent limits and standards contained in 40 CFR Part 401 through 471, specifically provide that they will be applied on a net basis; or

(2) Discharger demonstrates the control system proposed or used to meet applicable technology-based limits and standards would, if properly installed and operated, meet the limits and standards in the absence of pollutants in the intake waters.

ii. Credit for generic pollutants such as BOD or TSS will not be granted unless the permittee demonstrates the constituents of the generic measure in the effluent are substantially similar to the constituents of the generic measure in the intake water or appropriate additional limits are placed on process water pollutants either at the outfall or elsewhere.

iii. Credit will be granted only to the extent necessary to meet the applicable limit or standard, up to a maximum value equal to the influent value. Additional monitoring may determine eligibility for credits and compliance with permit limits.

iv. Credit will be granted only if the discharger demonstrates the intake water is drawn from the same body of water where the discharge is made. The Department may waive this requirement if the Department finds that no environmental degradation will result.

v. This section does not apply to the discharge of raw water clarifier sludge generated from the treatment of intake water.

c. Consideration of intake pollutants for water quality based effluent limits:

i. The Department will evaluate if reasonable potential exists 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 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.

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

(1) Facility removes the intake water containing the pollutant from the same body of water where the discharge is made;

(2) Ambient background concentration of the pollutant does not meet the most stringent applicable water quality criterion for that pollutant;

(3) Facility does not alter the identified intake pollutant chemically or physically to cause adverse water quality impacts that would not occur if the pollutants had not been removed from the body of water;

(4) Timing and location of the discharge does 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; and

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

iii. Where the conditions in Subsection 303.07.c.i. and ii are met, the Department may establish a water quality-based effluent limit 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 before discharge, so there is no net addition of the pollutant in the discharge compared to the intake water.

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.

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 if conditions in Subsection 303.07.c.ii. are met and adequate monitoring to determine compliance can be established and is included in the permit.

vi. The permit will specify how compliance with mass and concentration-based limitations for the intake water pollutant will be assessed. This assessment may be based on the effluent limit on background concentration data. Alternatively, the Department may determine compliance by monitoring the pollutant concentrations in the intake water and effluent. Monitoring may be supplemented by monitoring internal waste streams or by a Department evaluation of the use of BMPs.

vii. Effluent limits will be established to comply with all other applicable state and federal laws and regulations including technology-based requirements and anti-degradation policies.

viii. When determining whether water quality based effluent limits are necessary, information from chemical-specific, WET and biological assessments will be considered independently.

ix. Permit limits will be consistent with the assumptions and requirement of waste load allocations or other provisions in a TMDL that has been approved by the EPA.

08.Internal Waste Streams.

a. When permit effluent limits or standards imposed at the point of discharge are impractical or infeasible, effluent limits 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 will also be applied to the internal waste streams.

b. Limits on internal waste streams will be imposed only when the fact sheet states the exceptional circumstances that make the limits necessary, such as:

i. When the final discharge point is inaccessible (e.g., under ten (10) meters of water);

ii. Wastes at the point of discharge are so diluted it makes monitoring impracticable; or

iii. Interferences among pollutants at the point of discharge make detection or analysis impracticable.

09.Disposal of Pollutants into Wells, into POTWs, or by Land Application.

a. When part of a discharger's process wastewater is not discharged into waters of the United States because it is disposed into a well, into a POTW, or by land application, reducing the flow or level of pollutants discharged into waters of the United States, applicable effluent standards and limits for the discharge in an IPDES permit will be adjusted to reflect the reduced raw waste resulting from the disposal. Effluent limits and standards in the permit are calculated by one (1) of the following methods:

i. If none of the waste from a particular process is discharged into waters of the United States, and ELGs provide separate allocation for wastes from that process, allocations for the process are eliminated from calculation of permit effluent limits or standards; or

ii. In all cases other than those described in Subsection 303.09.a.i., effluent limits are adjusted by multiplying the effluent limitation derived by applying ELGs 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 limits and standards 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 discharged to receiving waters. This method may be algebraically expressed as:

P=(E x N)/T; where P is the permit effluent limit, E is the limit 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.

b. Subsection 303.09.a. does not apply to the extent that promulgated ELGs:

i. Control concentrations of pollutants discharged but not mass; or

ii. Specify a different specific technique for adjusting effluent limits to account for well injection, land application, or disposal into POTWs.

c. Subsection 303.09.a. does not alter a discharger's obligation to meet 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).

d. Disposal of discharge into injection wells is regulated by:

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,"; or

ii. Health District with jurisdiction, in compliance with IDAPA 58.01.03, "Individual/Subsurface Sewage Disposal Rules," for a Class V injection well.

e. Disposal of discharge onto the surface of the land is regulated by the Department under IDAPA 58.01.17, "Recycled Water Rules."

Idaho Admin. Code r. 58.01.25.303

Effective July 1, 2024