40 CFR Part 423 — Steam Electric Power Generating Point Source Category

PART 423—STEAM ELECTRIC POWER GENERATING POINT SOURCE CATEGORY Authority: 33 U.S.C. 1251 et seq.; Source: 47 FR 52304, Nov. 19, 1982, unless otherwise noted. § 423.10 Applicability and severability. (a) Applicability. e.g., (b) Severability. [89 FR 40293, May 9, 2024] § 423.11 Specialized definitions. In addition to the definitions set forth in 40 CFR part 401, the following definitions apply to this part: (a) The term total residual chlorine (b) The term low volume waste sources (c) The term chemical metal cleaning waste (d) The term metal cleaning waste (e) The term fly ash (f) The term bottom ash (g) The term once through cooling water (h) The term recirculated cooling water (i) The term 10 year, 24/hour rainfall event Rainfall Frequency Atlas of the United States, (j) The term blowdown (k) The term average concentration (l) The term free available chlorine (m) The term coal pile runoff (n) The term flue gas desulfurization (FGD) wastewater (o) The term flue gas mercury control wastewater means any wastewater generated from an air pollution control system installed or operated for the purpose of removing mercury from flue gas. This includes fly ash collection systems when the particulate control system follows sorbent injection or other controls to remove mercury from flue gas. FGD wastewater generated at plants using oxidizing agents to remove mercury in the FGD system and not in a separate FGMC system is not included in this definition. (p) The term transport water e.g., e.g., (q) The term gasification wastewater means any wastewater generated at an integrated gasification combined cycle operation from the gasifier or the syngas cleaning, combustion, and cooling processes. Gasification wastewater includes, but is not limited to the following: Sour/grey water; CO 2 (r) The term combustion residual leachate e.g., (s) The term oil-fired unit means a generating unit that uses oil as the primary or secondary fuel source and does not use a gasification process or any coal or petroleum coke as a fuel source. This definition does not include units that use oil only for start up or flame-stabilization purposes. (t) The phrase “as soon as possible” means November 1, 2018 (except for purposes of § 423.13(g)(1)(i) and (k)(1)(i), in which case it means October 13, 2021), unless the permitting authority establishes a later date, after receiving site-relevant information from the discharger, which reflects a consideration of the following factors: (1) Time to expeditiously plan (including to raise capital), design, procure, and install equipment to comply with the requirements of this part. (2) Changes being made or planned at the plant in response to: (i) New source performance standards for greenhouse gases from new fossil fuel-fired electric generating units, under sections 111, 301, 302, and 307(d)(1)(C) of the Clean Air Act, as amended, 42 U.S.C. 7411, 7601, 7602, 7607(d)(1)(C); (ii) Emission guidelines for greenhouse gases from existing fossil fuel-fired electric generating units, under sections 111, 301, 302, and 307(d) of the Clean Air Act, as amended, 42 U.S.C. 7411, 7601, 7602, 7607(d); or (iii) Regulations that address the disposal of coal combustion residuals as solid waste, under sections 1006(b), 1008(a), 2002(a), 3001, 4004, and 4005(a) of the Solid Waste Disposal Act of 1970, as amended by the Resource Conservation and Recovery Act of 1976, as amended by the Hazardous and Solid Waste Amendments of 1984, 42 U.S.C. 6906(b), 6907(a), 6912(a), 6944, and 6945(a). (3) For FGD wastewater requirements only, an initial commissioning period for the treatment system to optimize the installed equipment. (4) Other factors as appropriate. (u) The term “FGD paste” means any combination of FGD wastewater treated with fly ash, lime, Portland cement, and/or other pozzolanic material prior to being landfilled, and which is engineered to form a solid through pozzolanic reactions. (v) The term “FGD paste equipment cleaning water” means any wastewater generated from the cleaning of pugmills, piping, or other equipment used to make, process, or transport FGD paste from its point of generation to a landfill. (w) The term permanent cessation of coal combustion (x) The term “high FGD flow” means the maximum daily volume of FGD wastewater that could be discharged by a facility is above 4 million gallons per day after accounting for that facility's ability to recycle the wastewater to the maximum limits for the FGD system materials of construction. (y) The term “capacity utilization rating” means the total MWh production of an electric generating unit over a calendar year divided by the product of the number of hours in that year times the nameplate capacity. (z) The term low utilization electric generating unit (aa) The term “primary active wetted bottom ash system volume” means the maximum volumetric capacity of bottom ash transport water in all non-redundant piping (including recirculation piping) and primary bottom ash collection and recirculation loop tanks (e.g., bins, troughs, clarifiers, and hoppers) of a wet bottom ash system, excluding the volumes of surface impoundments, secondary bottom ash system equipment (e.g., installed spares, redundancies, and maintenance tanks), and non-bottom ash transport systems that may direct process water to the bottom ash. (bb) The term tank e.g., (cc) The term “bottom ash purge water” means any water being discharged subject to § 423.13(k)(2)(i) or 423.16(g)(2)(i). (dd) The term “30-day rolling average” means the series of averages using the measured values of the preceding 30 days for each average in the series. (ee) The term coal combustion residual surface impoundment (ff) The term unmanaged combustion residual leachate (1) Is determined by the permitting authority to be the functional equivalent of a direct discharge to waters of the United States (WOTUS) through groundwater; or (2) Has leached from a waste management unit into the subsurface and mixed with groundwater prior to being captured and pumped to the surface for discharge directly to WOTUS. [47 FR 52304, Nov. 19, 1982, as amended at 77 FR 29834, May 18, 2012; 80 FR 67893, Nov. 3, 2015; 82 FR 43500, Sept. 18, 2017; 85 FR 64716, Oct. 13, 2020; 89 FR 40293, May 9, 2024] § 423.12 Effluent limitations guidelines representing the degree of effluent reduction attainable by the application of the best practicable control technology currently available (BPT). (a) In establishing the limitations set forth in this section, EPA took into account all information it was able to collect, develop and solicit with respect to factors (such as age and size of plant, utilization of facilities, raw materials, manufacturing processes, non-water quality environmental impacts, control and treatment technology available, energy requirements and costs) which can affect the industry subcategorization and effluent levels established. It is, however, possible that data which would affect these limitations have not been available and, as a result, these limitations should be adjusted for certain plants in this industry. An individual discharger or other interested person may submit evidence to the Regional Administrator (or to the State, if the State has the authority to issue NPDES permits) that factors relating to the equipment or facilities involved, the process applied, or other such factors related to such discharger are fundamentally different from the factors considered in the establishment of the guidelines. On the basis of such evidence or other available information, the Regional Administrator (or the State) will make a written finding that such factors are or are not fundamentally different for that facility compared to those specified in the Development Document. If such fundamentally different factors are found to exist, the Regional Administrator or the State shall establish for the discharger effluent limitations in the NPDES Permit either more or less stringent than the limitations established herein, to the extent dictated by such fundamentally different factors. Such limitations must be approved by the Administrator of the Environmental Protection Agency. The Administrator may approve or disapprove such limitations, specify other limitations, or initiate proceedings to revise these regulations. The phrase “other such factors” appearing above may include significant cost differentials. In no event may a discharger's impact on receiving water quality be considered as a factor under this paragraph. (b) Any existing point source subject to this subpart must achieve the following effluent limitations representing the degree of effluent reduction by the application of the best practicable control technology currently available (BPT): (1) The pH of all discharges, except once through cooling water, shall be within the range of 6.0-9.0. (2) There shall be no discharge of polychlorinated biphenyl compounds such as those commonly used for transformer fluid. (3) The quantity of pollutants discharged from low volume waste sources shall not exceed the quantity determined by multiplying the flow of low volume waste sources times the concentration lised in the following table: Pollutant or pollutant property BPT effluent limitations Maximum for any 1 day (mg/l) Average of daily values for 30 consecutive days shall not exceed (mg/l) TSS 100.0 30.0 Oil and grease 20.0 15.0 (4) The quantity of pollutants discharged in fly ash and bottom ash transport water shall not exceed the quantity determined by multiplying the flow of fly ash and bottom ash transport water times the concentration listed in the following table: Pollutant or pollutant property BPT effluent limitations Maximum for any 1 day (mg/l) Average of daily values for 30 consecutive days shall not exceed (mg/l) TSS 100.0 30.0 Oil and grease 20.0 15.0 (5) The quantity of pollutants discharged in metal cleaning wastes shall not exceed the quantity determined by multiplying the flow of metal cleaning wastes times the concentration listed in the following table: Pollutant or pollutant property BPT effluent limitations Maximum for any 1 day (mg/l) Average of daily values for 30 consecutive days shall not exceed (mg/l) TSS 100.0 30.0 Oil and grease 20.0 15.0 Copper, total 1.0 1.0 Iron, total 1.0 1.0 (6) The quantity of pollutants discharged in once through cooling water shall not exceed the quantity determined by multiplying the flow of once through cooling water sources times the concentation listed in the following table: Pollutant or pollutant property BPT effluent limitations Maximum concentration (mg/l) Average concentration (mg/l) Free available chlorine 0.5 0.2 (7) The quantity of pollutants discharged in cooling tower blowdown shall not exceed the quantity determined by multiplying the flow of cooling tower blowdown sources times the concentration listed in the following table: Pollutant or pollutant property BPT effluent limitations Maximum concentration (mg/l) Average concentration (mg/l) Free available chlorine 0.5 0.2 (8) Neither free available chlorine nor total residual chlorine may be discharged from any unit for more than two hours in any one day and not more than one unit in any plant may discharge free available or total residual chlorine at any one time unless the utility can demonstrate to the Regional Administrator or State, if the State has NPDES permit issuing authority, that the units in a particular location cannot operate at or below this level or chlorination. (9) Subject to the provisions of paragraph (b)(10) of this section, the following effluent limitations shall apply to the point source discharges of coal pile runoff: Pollutant or pollutant property BPT effluent limitations Maximum concentration for any time (mg/l) TSS 50 (10) Any untreated overflow from facilities designed, constructed, and operated to treat the volume of coal pile runoff which is associated with a 10 year, 24 hour rainfall event shall not be subject to the limitations in paragraph (b)(9) of this section. (11) The quantity of pollutants discharged in FGD wastewater, flue gas mercury control wastewater, combustion residual leachate, gasification wastewater, or bottom ash purge water shall not exceed the quantity determined by multiplying the flow of the applicable wastewater times the concentration listed in the table 7: Table 7 to Paragraph ( b Pollutant or pollutant property BPT effluent limitations Maximum for any 1 day Average of TSS 100.0 30.0 Oil and grease 20.0 15.0 (12) At the permitting authority's discretion, the quantity of pollutant allowed to be discharged may be expressed as a concentration limitation instead of the mass-based limitations specified in paragraphs (b)(3) through (b)(7), and (b)(11), of this section. Concentration limitations shall be those concentrations specified in this section. (13) In the event that wastestreams from various sources are combined for treatment or discharge, the quantity of each pollutant or pollutant property controlled in paragraphs (b)(1) through (b)(12) of this section attributable to each controlled waste source shall not exceed the specified limitations for that waste source. (The information collection requirements contained in paragraph (a) were approved by the Office of Management and Budget under control number 2000-0194) [47 FR 52304, Nov. 19, 1982, as amended at 48 FR 31404, July 8, 1983; 80 FR 67894, Nov. 3, 2015; 85 FR 64716, Oct. 13, 2020] § 423.13 Effluent limitations guidelines representing the degree of effluent reduction attainable by the application of the best available technology economically achievable (BAT). Except as provided in 40 CFR 125.30 through 125.32, any existing point source subject to this part must achieve the following effluent limitations representing the degree of effluent reduction attainable by the application of the best available technology economically achievable (BAT). (a) There shall be no discharge of polychlorinated biphenyl compounds such as those commonly used for transformer fluid. (b)(1) For any plant with a total rated electric generating capacity of 25 or more megawatts, the quantity of pollutants discharged in once through cooling water from each discharge point shall not exceed the quantity determined by multiplying the flow of once through cooling water from each discharge point times the concentration listed in the following table: Pollutant or pollutant property BAT Effluent Limitations Maximum concentration (mg/l) Total residual chlorine 0.20 (2) Total residual chlorine may not be discharged from any single generating unit for more than two hours per day unless the discharger demonstrates to the permitting authority that discharge for more than two hours is required for macroinvertebrate control. Simultaneous multi-unit chlorination is permitted. (c)(1) For any plant with a total rated generating capacity of less than 25 megawatts, the quantity of pollutants discharged in once through cooling water shall not exceed the quantity determined by multiplying the flow of once through cooling water sources times the concentration listed in the following table: Pollutant or pollutant property BAT effluent limitations Maximum concentration (mg/l) Average concentration (mg/l) Free available chlorine 0.5 0.2 (2) Neither free available chlorine nor total residual chlorine may be discharged from any unit for more than two hours in any one day and not more than one unit in any plant may discharge free available or total residual chlorine at any one time unless the utility can demonstrate to the Regional Administrator or State, if the State has NPDES permit issuing authority, that the units in a particular location cannot operate at or below this level of chlorination. (d)(1) The quantity of pollutants discharged in cooling tower blowdown shall not exceed the quantity determined by multiplying the flow of cooling tower blowdown times the concentration listed below: Pollutant or pollutant property BAT effluent limitations Maximum concentration (mg/l) Average concentration (mg/l) Free available chlorine 0.5 0.2 Pollutant or pollutant property Maximum for any 1 day −(mg/l) Average of daily values for 30 consecutive days shall not exceed = (mg/l) The 126 priority pollutants (Appendix A) contained in chemicals added for cooling tower maintenance, except: ( 1 ( 1 Chromium, total 0.2 0.2 Zinc, total 1.0 1.0 1 (2) Neither free available chlorine nor total residual chlorine may be discharged from any unit for more than two hours in any one day and not more than one unit in any plant may discharge free available or total residual chlorine at any one time unless the utility can demonstrate to the Regional Administrator or State, if the State has NPDES permit issuing authority, that the units in a particular location cannot operate at or below this level of chlorination. (3) At the permitting authority's discretion, instead of the monitoring specified in 40 CFR 122.11(b) compliance with the limitations for the 126 priority pollutants in paragraph (d)(1) of this section may be determined by engineering calculations which demonstrate that the regulated pollutants are not detectable in the final discharge by the analytical methods in 40 CFR part 136. (e) The quantity of pollutants discharged in chemical metal cleaning wastes shall not exceed the quantity determined by multiplying the flow of chemical metal cleaning wastes times the concentration listed in the following table: Pollutant or pollutant property BAT effluent limitations Maximum for any 1 day (mg/l) Average of daily values for 30 consecutive days shall not exceed −(mg/l) Copper, total 1.0 1.0 Iron, total 1.0 1.0 (f) [Reserved—Nonchemical Metal Cleaning Wastes]. (g) FGD wastewater 2020 BAT. Table 5 to Paragraph ( g i Pollutant or pollutant property BAT effluent limitations Maximum for any 1 day Average of daily values for 30 Arsenic, total (µg/L) 18 8 Mercury, total (ng/L) 103 34 Selenium, total (µg/L) 70 29 Nitrate/nitrite as N (mg/L) 4 3 (ii) For FGD wastewater generated before the date determined by the permitting authority, as specified in paragraph (g)(1)(i) of this section, the EPA is declining to establish BAT limitations and is reserving such limitations to be established by the permitting authority on a case-by-case basis using the permitting authority's best professional judgment. (2) 2020 BAT subcategories. (A) For any electric generating unit for which the owner has submitted a certification pursuant to § 423.19(g), where such unit has permanently ceased coal combustion by December 31, 2028, there shall be no discharge of pollutants in FGD wastewater after April 30, 2029. (B) For any electric generating unit for which the owner has submitted a certification pursuant to § 423.19(g), where such unit has failed to permanently cease coal combustion by December 31, 2028, there shall be no discharge of pollutants in FGD wastewater after December 31, 2028. (ii) For FGD wastewater discharges from a high FGD flow facility, the quantity of pollutants in FGD wastewater shall not exceed the quantity determined by multiplying the flow of FGD wastewater times the concentration listed in table 6 to this paragraph (g)(2)(ii). Dischargers must meet the effluent limitations for FGD wastewater in this paragraph (g)(2)(ii) by a date determined by the permitting authority that is as soon as possible beginning October 13, 2021, but no later than December 31, 2023. The effluent limitations in this paragraph (g)(2)(ii) apply to the discharge of FGD wastewater generated on and after the date determined by the permitting authority for meeting the effluent limitations, as specified in this paragraph (g)(2)(ii), until the date determined by the permitting authority for meeting the effluent limitations in paragraph (g)(4) of this section. Table 6 to Paragraph ( g ii Pollutant or pollutant property BAT effluent limitations Maximum for any 1 day Average of daily values for 30 Arsenic, total (µg/L) 11 8 Mercury, total (ng/L) 788 356 (iii) For FGD wastewater discharges from a low utilization electric generating unit, the quantity of pollutants in FGD wastewater shall not exceed the quantity determined by multiplying the flow of FGD wastewater times the concentration listed in table 6 to paragraph (g)(2)(ii) of this section. Dischargers must meet the effluent limitations for FGD wastewater in this paragraph (g)(2)(iii) by a date determined by the permitting authority that is as soon as possible beginning October 13, 2021, but no later than December 31, 2023. These effluent limitations apply to the discharge of FGD wastewater generated on and after the date determined by the permitting authority for meeting the effluent limitations, as specified in this paragraph (g)(2)(iii), until the date determined by the permitting authority for meeting the effluent limitations in paragraph (g)(4) of this section. (3) Voluntary incentives plan. Table 7 to Paragraph ( g i Pollutant or pollutant property BAT effluent limitations Maximum for any 1 day Average of daily values for 30 Arsenic, total (ug/L) 5 NA Mercury, total (ng/L) 23 10 Selenium, total (ug/L) 10 NA Nitrate/Nitrite (mg/L) 2.0 1.2 Bromide (mg/L) 0.2 NA TDS (mg/L) 306 149 (ii) For discharges of FGD wastewater generated before December 31, 2023, the quantity of pollutants discharged in FGD wastewater shall not exceed the quantity determined by multiplying the flow of FGD wastewater times the concentration listed for TSS in § 423.12(b)(11). (4) 2024 BAT. (A) Dischargers must meet the effluent limitations for FGD wastewater in this paragraph (g)(4)(i) by a date determined by the permitting authority that is as soon as possible beginning July 8, 2024, but no later than December 31, 2034. These effluent limitations apply to the discharge of FGD wastewater generated on and after the date determined by the permitting authority for meeting the effluent limitations, as specified in this paragraph (g)(4)(i). (B) A facility which submits a request under § 423.19(n) may discharge permeate or distillate from an FGD wastewater treatment system designed to achieve the limitations in this paragraph (g)(4)(i) for an additional period of up to one year from the date determined in paragraph (g)(4)(i)(A) of this section. (ii) For any electric generating unit with a total nameplate capacity of less than or equal to 50 megawatts or that is an oil-fired unit, the quantity of pollutants discharged in FGD wastewater shall not exceed the quantity determined by multiplying the flow of FGD wastewater times the concentration listed for TSS in § 423.12(b)(11). (iii) For any electric generating unit for which the owner has submitted a certification pursuant to § 423.19(h), the quantity of pollutants discharged in FGD wastewater shall continue to be subject to limitations specified in paragraph (g)(1) or (g)(2)(ii) or (iii) of this section as incorporated into the existing permit. (A) Where such unit has permanently ceased coal combustion by December 31, 2034, there shall be no discharge of pollutants in FGD wastewater after April 30, 2035. (B) Where such unit has failed to permanently cease coal combustion by December 31, 2034, there shall be no discharge of pollutants in FGD wastewater after December 31, 2034. (iv) For FGD wastewater discharged from any coal combustion residual surface impoundment which commences closure pursuant to 40 CFR 257.102(e) after July 8, 2024, the quantity of pollutants in FGD wastewater shall not exceed the quantity determined by multiplying the flow of FGD wastewater times the concentration listed in table 8 to this paragraph (g)(4)(iv). Table 8 to Paragraph ( g iv Pollutant or pollutant property BAT effluent limitations Maximum for any 1 day Average of daily values for 30 Arsenic, total (µg/L) 11 8 Mercury, total (ng/L) 788 356 (h) Fly ash transport water. Fly ash transport water. (ii) Legacy fly ash transport water. (2) For any electric generating unit with a total nameplate generating capacity of less than or equal to 50 megawatts or that is an oil-fired unit, the quantity of pollutants discharged in fly ash transport water shall not exceed the quantity determined by multiplying the flow of fly ash transport water times the concentration listed for TSS in § 423.12(b)(4). (i) Flue gas mercury control wastewater. Flue gas mercury control wastewater. (ii) Legacy flue gas mercury control wastewater. (2) For any electric generating unit with a total nameplate generating capacity of less than or equal to 50 megawatts or that is an oil-fired unit, the quantity of pollutants discharged in flue gas mercury control wastewater shall not exceed the quantity determined by multiplying the flow of flue gas mercury control wastewater times the concentration for TSS listed in § 423.12(b)(11). (j)(1)(i) Gasification wastewater. Pollutant or pollutant property BAT Effluent limitations Maximum for Average of daily Arsenic, total (ug/L) 4 Mercury, total (ng/L) 1.8 1.3 Selenium, total (ug/L) 453 227 Total dissolved solids (mg/L) 38 22 (ii) For discharges of gasification wastewater generated before the date determined by the permitting authority, as specified in paragraph (j)(1)(i) of this section, the quantity of pollutants discharged in gasification wastewater shall not exceed the quantity determined by multiplying the flow of gasification wastewater times the concentration for TSS listed in § 423.12(b)(11). (2) For any electric generating unit with a total nameplate generating capacity of less than or equal to 50 megawatts or that is an oil-fired unit, the quantity of pollutants discharged in gasification wastewater shall not exceed the quantity determined by multiplying the flow of gasification wastewater times the concentration listed for TSS in § 423.12(b)(11). (k) Bottom ash transport water 2020 BAT. (ii) For bottom ash transport water generated before the date determined by the permitting authority, as specified in paragraph (k)(1)(i) of this section, the EPA is declining to establish BAT limitations and is reserving such limitations to be established by the permitting authority on a case-by-case basis using the permitting authority's best professional judgment. (2) 2020 BAT subcategories. ( 1 e.g., ( 2 ( 3 ( 4 1 2 3 (B) The total volume that may be discharged for the activities in paragraph (k)(2)(i)(A) of this section shall be reduced or eliminated to the extent achievable using control measures (including best management practices) that are technologically available and economically achievable in light of best industry practice. The total volume of the discharge authorized in this paragraph (k)(2)(i)(B) shall be determined on a case-by-case basis by the permitting authority and in no event shall such discharge exceed a 30-day rolling average of ten percent of the primary active wetted bottom ash system volume. The volume of daily discharges used to calculate the 30-day rolling average shall be calculated using measurements from flow monitors. (ii) For any electric generating unit with a total nameplate generating capacity of less than or equal to 50 megawatts, that is an oil-fired unit, or for which the owner has certified to the permitting authority that it will cease combustion of coal pursuant to § 423.19(g), the quantity of pollutants discharged in bottom ash transport water shall not exceed the quantity determined by multiplying the flow of the applicable wastewater times the concentration for TSS listed in § 423.12(b)(4). (A) Where a unit has certified that it will cease combustion of coal pursuant to § 423.19(g) and such unit has permanently ceased coal combustion by December 31, 2028, there shall be no discharge of pollutants in bottom ash transport water after April 30, 2029. (B) Where a unit has certified that it will cease combustion of coal pursuant to § 423.19(g) and such unit has failed to permanently cease coal combustion by December 31, 2028, there shall be no discharge of pollutants in bottom ash transport water after December 31, 2028. (iii) For bottom ash transport water generated by a low utilization electric generating unit, the quantity of pollutants discharged in bottom ash transport water shall not exceed the quantity determined by multiplying the flow of the applicable wastewater times the concentration for TSS listed in § 423.12(b)(4), until the date determined by the permitting authority for meeting the effluent limitations in paragraph (k)(4) of this section, and shall incorporate the elements of a best management practices plan as described in paragraph (k)(3) of this section. (3) Best management practices plan. (i) Identification of the low utilization coal-fired generating units that contribute bottom ash to the bottom ash transport system. (ii) A description of the existing bottom ash handling system and a list of system components ( e.g., (iii) A detailed water balance, based on measurements, or estimates where measurements are not feasible, specifying the volume and frequency of water additions and removals from the bottom ash transport system, including: (A) Water removed from the BA transport system: ( 1 ( 2 ( 3 ( 4 ( 5 1 4 (B) Water entering or recycled to the BA transport system: ( 1 ( 2 ( 3 1 2 (iv) Measures to be employed by all facilities: (A) Implementation of a comprehensive preventive maintenance program to identify, repair and replace equipment prior to failures that result in the release of bottom ash transport water. (B) Daily or more frequent inspections of the entire bottom ash transport water system, including valves, pipe flanges and piping, to identify leaks, spills and other unintended bottom ash transport water escaping from the system, and timely repair of such conditions. (C) Documentation of preventive and corrective maintenance performed. (v) Evaluation of options and feasibility, accounting for the associated costs, for eliminating or minimizing discharges of bottom ash transport water, including: (A) Segregation of bottom ash transport water from other process water. (B) Minimization of the introduction of stormwater by diverting ( e.g., (C) Recycling bottom ash transport water back to the bottom ash transport water system. (D) Recycling bottom ash transport water for use in the FGD scrubber. (E) Optimization of existing equipment ( e.g., (F) Utilization of “in-line” treatment of transport water ( e.g., (vi) Description of the bottom ash recycle system, including all technologies, measures, and practices that will be used to minimize discharge. (vii) A schedule showing the sequence of implementing any changes necessary to achieve the minimized discharge of bottom ash transport water, including the following: (A) The anticipated initiation and completion dates of construction and installation associated with the technology components or process modifications specified in the plan. (B) The anticipated dates that the discharger expects the technologies and process modifications to be fully implemented on a full-scale basis, which in no case shall be later than December 31, 2023. (C) The anticipated change in discharge volume and effluent quality associated with implementation of the plan. (viii) Description establishing a method for documenting and demonstrating to the permitting/control authority that the recycle system is well operated and maintained. (ix) Performance of weekly flow monitoring for the following: (A) Make up water to the bottom ash transport water system. (B) Bottom ash transport water sluice flow rate ( e.g., (C) Bottom ash transport water discharge to surface water or publicly owned treatment works (POTW). (D) Bottom ash transport water recycle back to the bottom ash system or FGD scrubber. (4) 2024 BAT. (ii) For any electric generating unit with a total nameplate generating capacity of less than or equal to 50 megawatts or that is an oil-fired unit, the quantity of pollutants discharged in bottom ash transport water shall not exceed the quantity determined by multiplying the flow of the applicable wastewater times the concentration for TSS listed in § 423.12(b)(4). (iii) For any electric generating unit for which the owner has submitted a certification pursuant to § 423.19(h), the quantity of pollutants discharged in bottom ash transport water shall continue to be subject to limitations specified in paragraph (k)(1) or (k)(2)(i) or (iii) of this section as incorporated into the existing permit. (A) Where such unit has permanently ceased coal combustion by December 31, 2034, there shall be no discharge of pollutants in bottom ash transport water after April 30, 2035. (B) Where such unit has failed to permanently cease coal combustion by December 31, 2034, there shall be no discharge of pollutants in bottom ash transport water after December 31, 2034. (iv) For bottom ash transport water discharged from any coal combustion residual surface impoundment which commences closure pursuant to 40 CFR 257.102(e) after July 8, 2024, the quantity of pollutants in bottom ash transport water shall not exceed the quantity determined by multiplying the flow of bottom ash transport water times the concentration listed in table 10 to this paragraph (k)(4)(iv). Table 10 to Paragraph (k)(4)(iv) Pollutant or pollutant property BAT effluent limitations Maximum for any 1 day Average of daily values for 30 Arsenic, total (µg/L) 11 8 Mercury, total (ng/L) 788 356 (l) Combustion residual leachate 2024 BAT. (A) Dischargers must meet the effluent limitations for FGD wastewater in this paragraph (g)(4)(i) by a date determined by the permitting authority that is as soon as possible beginning July 8, 2024, but no later than December 31, 2034. These effluent limitations apply to the discharge of FGD wastewater generated on and after the date determined by the permitting authority for meeting the effluent limitations, as specified in this paragraph (g)(4)(i). (B) A facility which submits a request under § 423.19(n) may discharge permeate or distillate from a combustion residual leachate treatment system designed to achieve the limitations in this paragraph (l)(1)(i) for an additional period of up to one year from the date determined in paragraph (l)(1)(i)(A) of this section. (C) After the retirement of all units at a facility, the quantity of pollutants in combustion residual leachate (CRL) shall not exceed the quantity determined by multiplying the flow of CRL permeate times the concentrations listed in the table 7 to paragraph (g)(3)(i) of this section or the flow of CRL distillate times the concentrations listed in the table following § 423.15(b)(13). (ii) For combustion residual leachate generated before the date determined by the permitting authority, as specified in paragraph (l)(1)(i) of this section, the EPA is declining to establish BAT limitations and is reserving such limitations to be established by the permitting authority on a case-by-case basis using the permitting authority's best professional judgment. (2) 2024 BAT subcategories. (A) Where such unit has permanently ceased coal combustion by December 31, 2034, the quantity of pollutants in combustion residual leachate shall not exceed the quantity determined by multiplying the flow of combustion residual leachate times the concentration listed in table 11 to this paragraph (l)(2)(i)(A) by a date determined by the permitting authority that is as soon as possible beginning 120 days after the facility permanently ceases coal combustion, but no later than April 30, 2035. Table 11 to paragraph (l)(2)(i)(A) Pollutant or pollutant property BAT effluent limitations Maximum for any 1 day Average of daily values for 30 Arsenic, total (µg/L) 11 8 Mercury, total (ng/L) 788 356 (B) Where such unit has failed to permanently cease coal combustion by December 31, 2034, there shall be no discharge of pollutants in combustion residual leachate after December 31, 2034. (ii) For discharges of unmanaged combustion residual leachate, the quantity of pollutants in unmanaged combustion residual leachate shall not exceed the quantity determined by multiplying the flow of unmanaged combustion residual leachate times the concentration listed in the table 11 to paragraph (l)(2)(i)(A) of this section. (A) Dischargers must meet the effluent limitations for unmanaged combustion residual leachate in this paragraph (l)(2)(ii) by a date determined by the permitting authority that is as soon as possible beginning July 8, 2024, but no later than December 31, 2029. The effluent limitations in this paragraph (l)(2)(ii) apply to the discharge of unmanaged combustion residual leachate generated on and after the date determined by the permitting authority for meeting the effluent limitations, as specified in this paragraph (l)(2)(ii). (B) Discharges of unmanaged combustion residual leachate before the date determined in paragraph (l)(2)(ii)(A) of this section. (iii) For combustion residual leachate discharged from any coal combustion residual surface impoundment which commences closure pursuant to 40 CFR 257.102(e) after July 8, 2024, the quantity of pollutants in combustion residual leachate shall not exceed the quantity determined by multiplying the flow of combustion residual leachate times the concentration listed in table 12 to this paragraph (l)(2)(iii). Table 12 to Paragraph (l)(2)(iii) Pollutant or pollutant property BAT effluent limitations Maximum for any 1 day Average of daily values for 30 Arsenic, total (µg/L) 11 8 Mercury, total (ng/L) 788 356 (m) At the permitting authority's discretion, the quantity of pollutant allowed to be discharged may be expressed as a concentration limitation instead of any mass based limitations specified in paragraphs (b) through (l) of this section. Concentration limitations shall be those concentrations specified in this section. (n) In the event that wastestreams from various sources are combined for treatment or discharge, the quantity of each pollutant or pollutant property controlled in paragraphs (a) through (m) of this section attributable to each controlled waste source shall not exceed the specified limitation for that waste source. (o) Transfers. (i) On or before December 31, 2023, a facility may convert: (A) From limitations for electric generating units permanently ceasing coal combustion under paragraph (g)(2)(i) or (k)(2)(ii) of this section to limitations for low utilization electric generating units under paragraph (g)(2)(iii) or (k)(2)(iii) of this section; or (B) From voluntary incentives program limitations under paragraph (g)(3)(i) of this section or generally applicable limitations under paragraph (k)(1)(i) of this section to limitations for low utilization electric generating units under paragraph (g)(2)(iii) or (k)(2)(iii) of this section. (ii) On or before December 31, 2025, a facility may convert: (A) From voluntary incentives program limitations under paragraph (g)(3)(i) of this section to limitations for electric generating units permanently ceasing coal combustion under paragraph (g)(2)(i) of this section; or (B) From limitations for electric generating units permanently ceasing coal combustion under paragraph (g)(2)(i) or (k)(2)(ii) of this section to voluntary incentives program limitations under paragraph (g)(3)(i) of this section or generally applicable limitations under (k)(1)(i) of this section; or (C) From limitations for low utilization electric generating units under paragraph (g)(2)(iii) or (k)(2)(iii) of this section to generally applicable limitations under paragraph (g)(1)(i) or (k)(1)(i) of this section; or (D) From limitations for low utilization electric generating units under paragraph (g)(2)(iii) or (k)(2)(iii) of this section to voluntary incentives program limitations under paragraph (g)(3)(i) of this section or generally applicable limitations under paragraph (k)(1)(i) of this section; or (E) From limitations for low utilization electric generating units under paragraph (g)(2)(iii) or (k)(2)(iii) of this section to limitations for electric generating units permanently ceasing coal combustion under paragraph (g)(2)(i) and (k)(2)(ii) of this section. (iii) On or before December 31, 2034, a facility may convert: (A) From the generally applicable zero discharge limitations under paragraphs (g)(4)(i), (k)(4)(i), or (l)(1)(i) of this section to limitations for electric generating units permanently ceasing coal combustion under paragraphs (g)(4)(iii), (k)(4)(iii), or (l)(2)(i) of this section; or (B) From limitations for electric generating units permanently ceasing coal combustion under paragraphs (g)(4)(iii), (k)(4)(iii), or (l)(2)(i) of this section to the generally applicable zero discharge limitations under paragraphs (g)(4)(i), (k)(4)(i), or (l)(1)(i) of this section. (2) A facility must be in compliance with all of its currently applicable requirements to be eligible to file a notice under § 423.19(l) and to become subject to a different set of applicable requirements under paragraph (o)(1) of this section. (3) Where a facility seeking a transfer under paragraph (o)(1)(ii) of this section is currently subject to more stringent limitations than the limitations being sought, the facility must continue to meet those more stringent limitations. (The information collection requirements contained in paragraphs (c)(2) and (d)(2) were approved by the Office of Management and Budget under control number 2040-0040. The information collection requirements contained in paragraph (d)(3) were approved under control number 2040-0033) [47 FR 52304, Nov. 19, 1982, as amended at 48 FR 31404, July 8, 1983; 80 FR 67894, Nov. 3, 2015; 82 FR 43500, Sept. 18, 2017; 85 FR 64716, Oct. 13, 2020; 89 FR 40294, May 9, 2024; 90 FR 61352, Dec. 31, 2025] § 423.14 Effluent limitations guidelines representing the degree of effluent reduction attainable by the application of the best conventional pollutant control technology (BCT). [Reserved] § 423.15 New source performance standards (NSPS). (a) 1982 NSPS. (1) pH. (2) PCBs. (3) Low volume waste sources, FGD wastewater, flue gas mercury control wastewater, combustion residual leachate, and gasification wastewater. Pollutant or pollutant property NSPS Maximum for any 1 day (mg/l) Average of daily TSS 100.0 30.0 Oil and grease 20.0 15.0 (4) Chemical metal cleaning wastes. Pollutant or pollutant property NSPS Maximum for Average of daily TSS 100.0 30.0 Oil and grease 20.0 15.0 Copper, total 1.0 1.0 Iron, total 1.0 1.0 (5) [Reserved] (6) Bottom ash transport water. Pollutant or pollutant property NSPS Maximum for Average of daily TSS 100.0 30.0 Oil and grease 20.0 15.0 (7) Fly ash transport water. (8)(i) Once through cooling water. Pollutant or pollutant property NSPS Maximum concentrations Total residual chlorine 0.20 (ii) Total residual chlorine may only be discharged from any single generating unit for more than two hours per day when the discharger demonstrates to the permitting authority that discharge for more than two hours is required for macroinvertebrate control. Simultaneous multi-unit chlorination is permitted. (9)(i) Once through cooling water. Pollutant or pollutant property NSPS Maximum concentration Average concentration Free available chlorine 0.5 0.2 (ii) Neither free available chlorine nor total residual chlorine may be discharged from any unit for more than two hours in any one day and not more than one unit in any plant may discharge free available or total residual chlorine at any one time unless the utility can demonstrate to the Regional Administrator or state, if the state has NPDES permit issuing authority, that the units in a particular location cannot operate at or below this level of chlorination. (10)(i) Cooling tower blowdown. Pollutant or pollutant property NSPS Maximum concentration Average concentration Free available chlorine 0.5 0.2 Pollutant or pollutant property NSPS Maximum for Average of daily The 126 priority pollutants (appendix A) contained in chemicals added for cooling tower maintenance, except: ( 1 ( 1 Chromium, total 0.2 0.2 zinc, total 1.0 1.0 1 (ii) Neither free available chlorine nor total residual chlorine may be discharged from any unit for more than two hours in any one day and not more than one unit in any plant may discharge free available or total residual chlorine at any one time unless the utility can demonstrate to the Regional Administrator or state, if the state has NPDES permit issuing authority, that the units in a particular location cannot operate at or below this level of chlorination. (iii) At the permitting authority's discretion, instead of the monitoring in 40 CFR 122.11(b), compliance with the standards for the 126 priority pollutants in paragraph (a)(10)(i) of this section may be determined by engineering calculations which demonstrate that the regulated pollutants are not detectable in the final discharge by the analytical methods in 40 CFR part 136. (11) Coal pile runoff. Pollutant or pollutant property NSPS for any time TSS not to exceed 50 mg/l. (12) Coal pile runoff. (13) At the permitting authority's discretion, the quantity of pollutant allowed to be discharged may be expressed as a concentration limitation instead of any mass based limitations specified in paragraphs (a)(3) through (10) of this section. Concentration limits shall be based on the concentrations specified in this section. (14) In the event that wastestreams from various sources are combined for treatment or discharge, the quantity of each pollutant or pollutant property controlled in paragraphs (a)(1) through (13) of this section attributable to each controlled waste source shall not exceed the specified limitation for that waste source. (b) 2015 NSPS. (1) pH. (2) PCBs. (3) Low volume waste sources. Pollutant or pollutant property NSPS Maximum for Average of daily TSS 100.0 30.0 Oil and grease 20.0 15.0 (4) Chemical metal cleaning wastes. Pollutant or pollutant property NSPS Maximum for Average of daily TSS 100.0 30.0 Oil and grease 20.0 15.0 Copper, total 1.0 1.0 Iron, total 1.0 1.0 (5) [Reserved] (6) Bottom ash transport water. (7) Fly ash transport water. (8)(i) Once through cooling water. Pollutant or pollutant property NSPS Maximum concentration Total residual chlorine 0.20 (ii) Total residual chlorine may only be discharged from any single generating unit for more than two hours per day when the discharger demonstrates to the permitting authority that discharge for more than two hours is required for macroinvertebrate control. Simultaneous multi-unit chlorination is permitted. (9)(i) Once through cooling water. Pollutant or pollutant property NSPS Maximum concentration Average concentration Free available chlorine 0.5 0.2 (ii) Neither free available chlorine nor total residual chlorine may be discharged from any unit for more than two hours in any one day and not more than one unit in any plant may discharge free available or total residual chlorine at any one time unless the utility can demonstrate to the Regional Administrator or state, if the state has NPDES permit issuing authority, that the units in a particular location cannot operate at or below this level of chlorination. (10)(i) Cooling tower blowdown. Pollutant or pollutant property NSPS Maximum concentration Average concentration Free available chlorine 0.5 0.2 Pollutant or pollutant property NSPS Maximum for Average of daily The 126 priority pollutants (appendix A) contained in chemicals added for cooling tower maintenance, except: ( 1 ( 1 Chromium, total 0.2 0.2 zinc, total 1.0 1.0 1 (ii) Neither free available chlorine nor total residual chlorine may be discharged from any unit for more than two hours in any one day and not more than one unit in any plant may discharge free available or total residual chlorine at any one time unless the utility can demonstrate to the Regional Administrator or state, if the state has NPDES permit issuing authority, that the units in a particular location cannot operate at or below this level of chlorination. (iii) At the permitting authority's discretion, instead of the monitoring in 40 CFR 122.11(b), compliance with the standards for the 126 priority pollutants in paragraph (b)(10)(i) of this section may be determined by engineering calculations demonstrating that the regulated pollutants are not detectable in the final discharge by the analytical methods in 40 CFR part 136. (11) Coal pile runoff. Pollutant or pollutant property NSPS for any time TSS not to exceed 50 mg/l. (12) Coal pile runoff. (13) FGD wastewater. Pollutant or pollutant property NSPS Maximum for Average of daily Arsenic, total (ug/L) 4 Mercury, total (ng/L) 39 24 Selenium, total (ug/L) 5 TDS (mg/L) 50 24 (14) Flue gas mercury control wastewater. (15) Gasification wastewater. Pollutant or pollutant property NSPS Maximum for Average of daily Arsenic, total (ug/L) 4 Mercury, total (ng/L) 1.8 1.3 Selenium, total (ug/L) 453 227 Total dissolved solids (mg/L) 38 22 (16) Combustion residual leachate. Pollutant or pollutant property NSPS Maximum for Average of daily Arsenic, total (ug/L) 11 8 Mercury, total (ng/L) 788 356 (17) At the permitting authority's discretion, the quantity of pollutant allowed to be discharged may be expressed as a concentration limitation instead of any mass based limitations specified in paragraphs (b)(3) through (16) of this section. Concentration limits shall be based on the concentrations specified in this section. (18) In the event that wastestreams from various sources are combined for treatment or discharge, the quantity of each pollutant or pollutant property controlled in paragraphs (b)(1) through (16) of this section attributable to each controlled waste source shall not exceed the specified limitation for that waste source. (c) 2024 NSPS for combustion residual leachate. (2) After the retirement of all units at a facility, the quantity of pollutants in CRL shall not exceed the quantity determined by multiplying the flow of CRL permeate times the concentrations listed in table 7 to § 423.13(g)(3)(i) or the flow of CRL distillate times the concentrations listed in the table in paragraph (b)(13) of this section. (The information collection requirements contained in paragraphs (a)(8)(ii), (a)(9)(ii), and (a)(10)(ii), (b)(8)(ii), (b)(9)(ii), and (b)(10)(ii) were approved by the Office of Management and Budget under control number 2040-0040. The information collection requirements contained in paragraphs (a)(10)(iii) and (b)(10)(iii) were approved under control number 2040-0033.) [80 FR 67896, Nov. 3, 2015, as amended at 89 FR 40299, May 9, 2024] § 423.16 Pretreatment standards for existing sources (PSES). Except as provided in 40 CFR 403.7 and 403.13, any existing source subject to this subpart which introduces pollutants into a publicly owned treatment works must comply with 40 CFR part 403 and achieve the following pretreatment standards for existing sources (PSES) by July 1, 1984: (a) There shall be no discharge of polychlorinated biphenol compounds such as those used for transformer fluid. (b) The pollutants discharged in chemical metal cleaning wastes shall not exceed the concentration listed in the following table: Pollutant or pollutant property PSES pretreatment standards Maximum for 1 day (mg/l) Copper, total 1.0 (c) [Reserved—Nonchemical Metal Cleaning Wastes]. (d)(1) The pollutants discharged in cooling tower blowdown shall not exceed the concentration listed in the following table: Pollutant or pollutant property PSES pretreatment standards Maximum for any time (mg/l) The 126 priority pollutants (Appendix A) contained in chemicals added for cooling tower maintenance, except: ( 1 Chromium, total 0.2 Zinc, total 1.0 1 (2) At the permitting authority's discretion, instead of the monitoring in 40 CFR 122.11(b), compliance with the limitations for the 126 priority pollutants in paragraph (d)(1) of this section may be determined by engineering calculations which demonstrate that the regulated pollutants are not detectable in the final discharge by the analytical methods in 40 CFR part 136. (e) FGD wastewater 2020 PSES. Table 3 to Paragraph (e)(1) Pollutant or pollutant property PSES Maximum for any 1 day Average of daily values for 30 Arsenic, total (µg/L) 18 8 Mercury, total (ng/L) 103 34 Selenium, total (µg/L) 70 29 Nitrate/nitrite as N (mg/L) 4 3 (2) 2020 PSES subcategories. (ii) If any low utilization electric generating unit fails to timely recertify that the two year average capacity utilization rating of such an electric generating unit is below 10 percent per year as specified in § 423.19(f), regardless of the reason, within two years from the date such a recertification was required, the quantity of pollutants in FGD wastewater shall not exceed the quantity determined by multiplying the flow of FGD wastewater times the concentration listed in the table 3 to paragraph (e)(1) of this section. Table 4 to Paragraph (e)(2)(ii) Pollutant or pollutant property PSES Maximum for any 1 day Average of daily values for 30 Arsenic, total (µg/L) 11 8 Mercury, total (ng/L) 788 356 (3) 2024 PSES. (i) Dischargers must meet the standards in paragraph (e)(1) of this section by January 1, 2029. The standards in paragraph (e)(1) of this section apply to the discharge of FGD wastewater generated on and after January 1, 2029. (ii) By the dates in paragraph (e)(3)(ii)(A) or (B) of this section there shall be no discharge of pollutants in FGD wastewater: (A) January 2, 2029; or (B) Where a certification statement has been submitted pursuant to § 423.19(p), December 31, 2034. (4) 2024 PSES subcategories. (A) Where such unit has permanently ceased coal combustion by December 31, 2034, there shall be no discharge of pollutants in FGD wastewater after April 30, 2035. (B) Where such unit has failed to permanently cease coal combustion by December 31, 2034, there shall be no discharge of pollutants in FGD wastewater after December 31, 2034. (ii) For FGD wastewater discharged from any coal combustion residual surface impoundment which commences closure pursuant to 40 CFR 257.102(e) after July 8, 2024, the quantity of pollutants in FGD wastewater shall not exceed the quantity determined by multiplying the flow of FGD wastewater times the concentration listed in the table 5 to this paragraph (e)(4)(ii). Table 5 to Paragraph (e)(4)(ii) Pollutant or pollutant property PSES Maximum for any 1 day Average of daily values for 30 consecutive days shall not exceed Arsenic, total (µg/L) 11 8 Mercury, total (ng/L) 788 356 (f) Fly ash transport water. (g) Bottom ash transport water 2020 PSES. (2) 2020 PSES subcategories. (A) To maintain system water balance when precipitation-related inflows are generated from a 10-year storm event of 24-hour or longer duration ( e.g., (B) To maintain system water balance when regular inflows from wastestreams other than bottom ash transport water exceed the ability of the bottom ash system to accept recycled water and segregating these other wastestreams is feasible; or (C) To maintain system water chemistry where current operations at the facility are unable to currently manage pH, corrosive substances, substances or conditions causing scaling, or fine particulates to below levels which impact system operation or maintenance; or (D) To conduct maintenance not otherwise included in paragraphs (g)(2)(i)(A), (B), or (C) of this section and not exempted from the definition of transport water in § 423.11(p), and when water volumes cannot be managed by installed spares, redundancies, maintenance tanks, and other secondary bottom ash system equipment. (ii) The total volume that may be discharged to a POTW for the activities in paragraphs (g)(2)(i)(A) through (D) of this section shall be reduced or eliminated to the extent achievable as determined by the control authority. The control authority may also include control measures (including best management practices) that are technologically available and economically achievable in light of best industry practice. In no event shall the total volume of the discharge exceed a 30-day rolling average of ten percent of the primary active wetted bottom ash system volume. The volume of daily discharges used to calculate the 30-day rolling average shall be calculated using measurements from flow monitors. (iii) For bottom ash transport water generated by a low utilization electric generating unit, the quantity of pollutants discharged in bottom ash transport water shall incorporate the elements of a best management practices plan as described in § 423.13(k)(3). (3) 2024 PSES. (i) Dischargers must meet the standards in paragraph (g)(1) of this section by January 1, 2029. The standards in paragraph (g)(1) of this section apply to the discharge of bottom ash transport water generated on and after January 1, 2029. (ii) By the dates in paragraph (g)(3)(ii)(A) or (B) of this section, there shall be no discharge of pollutants in bottom ash transport water: (A) January 2, 2029; or (B) Where a certification statement has been submitted pursuant to § 423.19(p), December 31, 2034. (4) 2024 PSES subcategories. (A) Where such unit has permanently ceased coal combustion by December 31, 2034, there shall be no discharge of pollutants in bottom ash transport water after April 30, 2035. (B) Where such unit has failed to permanently cease coal combustion by December 31, 2034, there shall be no discharge of pollutants in bottom ash transport water after December 31, 2034. (ii) For bottom ash transport water discharged from any coal combustion residual surface impoundment which commences closure pursuant to 40 CFR 257.102(e) after July 8, 2024, the quantity of pollutants in bottom ash transport water shall not exceed the quantity determined by multiplying the flow of bottom ash transport water times the concentration listed in table 6 to this paragraph (g)(4)(ii). Table 6 to Paragraph (g)(4)(ii) Pollutant or pollutant property PSES Maximum for any 1 day Average of daily values for 30 Arsenic, total (µg/L) 11 8 Mercury, total (ng/L) 788 356 (h) Flue gas mercury control wastewater. (i) Gasification wastewater. Pollutant or pollutant property PSES Maximum for Average of daily Arsenic, total (µg/L) 4 Mercury, total (ng/L) 1.8 1.3 Selenium, total (µg/L) 453 227 Total dissolved solids (mg/L) 38 22 (j) Combustion residual leachate (1) 2024 PSES. (i) Except for those discharges to which paragraph (j)(1)(ii) of this section applies, by the dates in paragraph (j)(1)(i)(A) or (B) of this section, there shall be no discharge of pollutants in combustion residual leachate: (A) January 2, 2029; or (B) Where a certification statement has been submitted pursuant to section 423.19(p), December 31, 2034. (ii) After the retirement of all units at a facility, the quantity of pollutants in CRL shall not exceed the quantity determined by multiplying the flow of CRL permeate times the concentrations listed in the table 7 to § 423.13(g)(3)(i) or the flow of CRL distillate times the concentrations listed in the table in § 423.15(b)(13). (2) 2024 PSES subcategories. (A) Where such unit has permanently ceased coal combustion by December 31, 2034, the quantity of pollutants in combustion residual leachate shall not exceed the quantity determined by multiplying the flow of combustion residual leachate times the concentration listed in the table 7 to this paragraph (j)(2)(i)(A) no later than April 30, 2035. Table 7 to paragraph (j)(2)(i)(A) Pollutant or pollutant property PSES Maximum for any 1 day Average of daily values for 30 consecutive days shall Arsenic, total (µg/L) 11 8 Mercury, total (ng/L) 788 356 (B) Where such unit has failed to permanently cease coal combustion by December 31, 2034, there shall be no discharge of pollutants in FGD wastewater after December 31, 2034. (ii) For combustion residual leachate discharged from any coal combustion residual surface impoundment which commences closure pursuant to 40 CFR 257.102(e) after July 8, 2024, the quantity of pollutants in combustion residual leachate shall not exceed the quantity determined by multiplying the flow of combustion residual leachate times the concentration listed in table 8 to this paragraph (j)(2)(ii). Table 8 to Paragraph (j)(2)(ii) Pollutant or pollutant property PSES Maximum for any 1 day Average of daily values for 30 Arsenic, total (µg/L) 11 8 Mercury, total (ng/L) 788 356 [47 FR 52304, Nov. 19, 1982, as amended at 80 FR 67901, Nov. 3, 2015; 82 FR 43500, Sept. 18, 2017; 85 FR 64720, Oct. 13, 2020; 89 FR 40299, May 9, 2024; 90 FR 61353, Dec. 31, 2025; 91 FR 4017, Jan. 30, 2026] § 423.17 Pretreatment standards for new sources (PSNS). (a) 1982 PSNS. (1) PCBs. (2) Chemical metal cleaning wastes. Pollutant or pollutant property PSNS Maximum for any 1 day Copper, total 1.0 (3) [Reserved] (4)(i) Cooling tower blowdown. Pollutant or pollutant property PSNS Maximum for any time The 126 priority pollutants (appendix A) contained in chemicals added for cooling tower maintenance, except: ( 1 Chromium, total 0.2 zinc, total 1.0 1 (ii) At the permitting authority's discretion, instead of the monitoring in 40 CFR 122.11(b), compliance with the standards for the 126 priority pollutants in paragraph (a)(4)(i) of this section may be determined by engineering calculations which demonstrate that the regulated pollutants are not detectable in the final discharge by the analytical methods in 40 CFR part 136. (5) Fly ash transport water. (b) 2015 PSNS. (1) PCBs. (2) Chemical metal cleaning wastes. Pollutant or pollutant property PSNS Maximum for 1 day Copper, total 1.0 (3) [Reserved] (4)(i) Cooling tower blowdown. Pollutant or pollutant property PSNS Maximum for any time The 126 priority pollutants (appendix A) contained in chemicals added for cooling tower maintenance, except: ( 1 Chromium, total 0.2 zinc, total 1.0 1 (ii) At the permitting authority's discretion, instead of the monitoring in 40 CFR 122.11(b), compliance with the standards for the 126 priority pollutants in paragraph (b)(4)(i) of this section may be determined by engineering calculations which demonstrate that the regulated pollutants are not detectable in the final discharge by the analytical methods in 40 CFR part 136. (5) Fly ash transport (6) FGD wastewater. Pollutant or pollutant property PSNS Maximum for Average of daily Arsenic, total (µg/L) 4 Mercury, total (ng/L) 39 24 Selenium, total (µg/L) 5 TDS (mg/L) 50 24 (7) Flue gas mercury control wastewater. (8) Bottom ash transport water. (9) Gasification wastewater. Pollutant or pollutant property PSNS Maximum for Average of daily Arsenic, total (µg/L) 4 Mercury, total (ng/L) 1.8 1.3 Selenium, total (µg/L) 453 227 Total dissolved solids (mg/L) 38 22 (10) Combustion residual leachate. Pollutant or pollutant property PSNS Maximum for Average of daily Arsenic, total (µg/L) 11 8 Mercury, total (ng/L) 788 356 (c) 2024 PSNS for combustion residual leachate. (2) After the retirement of all units at a facility, the quantity of pollutants in CRL shall not exceed the quantity determined by multiplying the flow of CRL permeate times the concentrations listed in table 7 to § 423.13(g)(3)(i) or the flow of CRL distillate times the concentrations listed in the table in § 423.15(b)(13). [80 FR 67902, Nov. 3, 2015, as amended at 89 FR 40302, May 9, 2024] § 423.18 Permit conditions. All permits subject to this part shall include the following permit conditions: (a) An electric generating unit shall qualify as a low utilization electric generating unit, permanently ceasing the combustion of coal by December 31, 2028, or permanently ceasing the combustion of coal by December 31, 2034, if such qualification would have been demonstrated absent the following qualifying event: (1) An emergency order issued by the Department of Energy under section 202(c) of the Federal Power Act; (2) A reliability must run agreement issued by a Public Utility Commission; or (3) Any other reliability-related order, energy emergency alert, or agreement issued by a competent electricity regulator ( e.g., (4) The operation of the electric generating unit was necessary for load balancing in an area subject to a declaration under 42 U.S.C. 5121 et seq., (i) An “Emergency”; or (ii) A “Major Disaster”; and (iii) That load balancing was due to the event that caused the “Emergency” or “Major Disaster” in paragraphs (a)(4)(i) and (ii) of this section to be declared. (b) Any facility providing the required documentation pursuant to § 423.19(i) may avail itself of the protections of the permit condition in paragraph (a) of this section. (c) A facility discharging permeate or distillate from an FGD wastewater or combustion residual leachate treatment system and satisfying § 423.19(n) shall be deemed to meet the following requirements: (1) The FGD wastewater requirements of § 423.13(g)(4) for up to one year after the date determined pursuant to § 423.11(t); and (2) The combustion residual leachate requirements of § 423.13(l)(1) for up to one year after the date determined pursuant to § 423.11(t). (d)(1) Notwithstanding the dates associated with any limitations in § 423.13(g), (k), or (l), a permitting authority shall establish, in a facility's permit, an alternative applicability date and, where appropriate, an associated schedule of milestones, for achieving the required limitations when the facility meets one of the circumstances in paragraph (d)(3) of this section, provided that the facility submits an initial request letter pursuant to § 423.19(q) and the permitting authority finds that request factually supported in the letter and attachments provided. (2) Notwithstanding the dates associated with any notice of planned participation required to be submitted under § 423.19(g), (j), or (l), a permitting authority may accept a late notice of planned participation provided that the facility meets one of the circumstances in paragraph (d)(3) of this section, submits an initial request letter pursuant to § 423.19(q), and the permitting authority finds that request factually supported in the letter and attachments provided. Transfers pursuant to § 423.13(o)(1)(ii) but receiving alternative § 423.19(l) submission dates in this paragraph (d)(2) shall be deemed timely. In no case may a late notice of planned participation be accepted pursuant to this paragraph (d)(2) after December 31, 2028. (3) Circumstances which a permitting authority shall find warrant an alternative applicability date or later notice of planned participation submission date based on factual support under paragraph (d)(1) or (2) of this section include: (i) Where a facility needs an alternative applicability date upon making a permissible transfer between limitations prior to the deadlines in § 423.13(o) due to: (A) An unexpected change in regional capacity market prices; or (B) An unexpected change in local demand which materially exceeds projections made in the most recent iterations of integrated resource plans or other planning documents; (ii) Where a facility has one or more electric generating units using a wastewater treatment system treating combined wastewater ( e.g., (A) An unexpected change in regional capacity market prices; or (B) An unexpected change in local demand which materially exceeds projections made in the most recent iterations of integrated resource plans or other planning documents; (iii) Where a facility needs an alternative applicability date because it faces an unexpected supply chain issue that delays a necessary component (not merely a preferred component where there are reasonable substitutes) at a key stage of fabrication or installation such that the timeline for reaching steady-state treatment is delayed; or (iv) Where a facility faces any other circumstance that requires additional time and is wholly outside both the facility's control and the facility's ability to plan for. (4) A facility availing itself of this paragraph (d) may consider the alternative applicability dates or alternative notice of planned participation submission dates when evaluating compliance for purposes of § 423.13(o)(2). [89 FR 40302, May 9, 2024, as amended at 90 FR 61353, Dec. 31, 2025] § 423.19 Reporting and recordkeeping requirements. (a) In general. (b) Signature and certification. (c) Publicly accessible internet site requirements. e.g., i.e., (2)(i) When an owner or operator subject to this section already maintains a “CCR Rule Compliance Data and Information” website pursuant to 40 CFR 257.107, the postings required under this section may be made to the existing “CCR Rule Compliance Data and Information” website and shall be delineated under a separate heading that shall state “ELG Rule Compliance Data and Information.” When electing to use an existing website pursuant to this paragraph (c)(2), the facility shall notify EPA via the “contact us” form on EPA's Effluent Guidelines website and the permitting authority or control authority no later than July 8, 2024, or upon first becoming subject to paragraphs (d) through (o) of this section, whichever is later. (ii) When the same owner or operator is subject to the provisions of this part for multiple facilities, the owner or operator may comply with the requirements of this section by using the same internet site for multiple facilities provided the ELG website clearly delineates information by the name of each facility. (3) Unless otherwise required in this section, the information required to be posted to the ELG website must be made available to the public for at least 10 years following the date on which the information was first posted to the ELG website, or the length of the permit plus five years, whichever is longer. All required information must be clearly identifiable and must be able to be immediately downloaded by anyone accessing the site in a format that enables additional analysis ( e.g., (4) Unless otherwise required in this section, the information must be posted to the ELG website: (i) Within 30 days of submitting the information to the permitting authority or control authority; or (ii) Where information was submitted to the permitting authority or control authority prior to July 8, 2024, by July 8, 2024. (d) Requirements for facilities discharging bottom ash transport water under this part Certification statement. (2) Signature and certification. (3) Contents. (i) A statement that the professional engineer is a licensed professional engineer. (ii) A statement that the professional engineer is familiar with the requirements in this part. (iii) A statement that the professional engineer is familiar with the facility. (iv) The primary active wetted bottom ash system volume in § 423.11(aa). (v) Material assumptions, information, and calculations used by the certifying professional engineer to determine the primary active wetted bottom ash system volume. (vi) A list of all potential discharges under § 423.13(k)(2)(i)(A)( 1 4 (vii) Material assumptions, information, and calculations used by the certifying professional engineer to determine the expected volume and frequency of each discharge including a narrative discussion of why such water cannot be managed within the system and must be discharged. (viii) A list of all wastewater treatment systems at the facility currently, or otherwise required by a date certain under this section. (ix) A narrative discussion of each treatment system including the system type, design capacity, and current or expected operation. (e) Requirements for a bottom ash best management practices plan Initial and annual certification statement. (2) Signature and certification. (3) Contents for initial certification. (i) A statement that the professional engineer is a licensed professional engineer. (ii) A statement that the professional engineer is familiar with the requirements in this part. (iii) A statement that the professional engineer is familiar with the facility. (iv) The best management practices plan. (v) A statement that the best management practices plan is being implemented. (4) Additional contents for annual certification. (i) Any updates to the best management practices plan. (ii) An attachment of weekly flow measurements from the previous year. (iii) The average amount of recycled bottom ash transport water in gallons per day. (iv) Copies of inspection reports and a summary of preventative maintenance performed on the system. (v) A statement that the plan and corresponding flow records are being maintained at the office of the plant. (f) Requirements for low utilization electric generating units Notice of Planned Participation. (2) Contents. (3) Initial and annual certification statement. (4) Contents. (g) Requirements for units that will achieve permanent cessation of coal combustion by December 31, 2028 Notice of Planned Participation. (2) Contents. (3) Annual progress report. (4) Contents. (i) A copy of the official suspension filing (or equivalent filing) made to the facility's reliability authority detailing the conversion to a fuel source other than coal; (ii) A copy of the official retirement filing (or equivalent filing) made to the facility's reliability authority which must include a waiver of recission rights; or (iii) An initial certification, or recertification for subsequent annual progress reports, containing either a statement that the facility will make the filing required in paragraph (g)(4)(i) of this section or a statement that the facility will make the filing required in paragraph (g)(4)(ii) of this section. The certification or recertification must include the estimated date that such a filing will be made. (iv) A facility shall not include a certification or recertification under paragraph (g)(4)(iii) of this section in the final annual progress report submitted prior to permanent cessation of coal combustion. Rather, this final annual progress report must include the filing under paragraph (g)(4)(i) or (ii) of this section. (h) Requirements for units that will achieve permanent cessation of coal combustion by December 31, 2034 Notice of Planned Participation. (2) Contents. (i) The applicable limitations or standards for FGD wastewater in § 423.13(g)(1) or (g)(2)(ii) or (iii) or § 423.16(e)(1) or (2); and (ii) The applicable limitations or standards for bottom ash transport water in § 423.13(k)(1) or (k)(2)(i) or (iii) or § 423.16(g)(1) or (2). (3) Annual progress report. (4) Contents. (i) A copy of the official suspension filing (or equivalent filing) made to the facility's reliability authority detailing the conversion to a fuel source other than coal; (ii) A copy of the official retirement filing (or equivalent filing) made to the facility's reliability authority which must include a waiver of recission rights; or (iii) An initial certification, or recertification for subsequent annual progress reports, containing either a statement that the facility will make the filing required in paragraph (h)(4)(i) of this section or a statement that the facility will make the filing required in paragraph (h)(4)(ii) of this section. The certification or recertification must include the estimated date that such a filing will be made. (iv) A facility shall not include a certification or recertification under paragraph (h)(4)(iii) of this section in the final annual progress report submitted prior to permanent cessation of coal combustion. Rather, this final annual progress report must include the filing under paragraph (h)(4)(i) or (ii) of this section. (i) Requirements for facilities seeking protections under this part Certification statement. (i) In the case of an order or agreement under § 423.18(a)(1), 30 days from receipt of the order or agreement attached pursuant to paragraph (i)(2)(ii) of this section; or (ii) In the case of an “Emergency” or “Major Disaster” under § 423.18(a)(2), 30 days from the date that a load balancing need arose. (2) Contents. (i) The qualifying event from the list in § 423.18(a), the individual or entity that issued or triggered the event, and the date that such an event was issued or triggered. (ii) A copy of any documentation of the qualifying event from the individual or entity listed under paragraph (i)(2)(i) of this section, or, where such documentation does not exist, other documentation with indicia of reliability for the permitting authority to confirm the qualifying event. (iii) An analysis and accompanying narrative discussion which demonstrates that an electric generating unit would have qualified for the subcategory at issue absent the event detailed in paragraph (i)(2)(i) of this section, including the material data, assumptions, and methods used. (3) Termination of need statement. (4) Contents. (j) Requirements for facilities voluntarily meeting limits in this part Notice of Planned Participation. (2) Contents. (3) Annual progress report. (4) Contents. (5) Rollover certification. (k) Requirements for facilities with discharges of unmanaged combustion residual leachate Annual combustion residual leachate monitoring report. (2) Contents. (i) A list of coal combustion residual landfills and surface impoundments which the permitting authority has determined are point sources with functional equivalent direct discharges. (ii) Groundwater monitoring data as the combustion residual leachate leaves each of the landfills or surface impoundment listed in paragraph (k)(2)(i) of this section. (iii) Groundwater monitoring at the point the combustion residual leachate enters a surface waterbody. (iv) Effluent monitoring data reported pursuant to 40 CFR part 127. (v) Summary statistics for the data described in paragraphs (k)(2)(ii) through (iv) of this section including the monthly average and daily maximum of each pollutant in the table 1 to this paragraph (k)(2)(v) and a comparison to any limitation in § 423.13(l)(2)(ii). Table 1 to Paragraph (k)(2)(v) BAT Treated Pollutants in Combustion Residual Leachate Antimony Magnesium Arsenic Manganese Barium Mercury Beryllium Molybdenum Cadmium Nickel Chromium Thallium Cobalt Titanium Copper Vanadium Lead Zinc (l) Requirements for facilities seeking protections under this part Notice of Planned Participation. (2) Contents. (m) Notice of material delay Notice. (2) Contents. (n) Requirements for facilities seeking a one-year flexibility to discharge permeate or distillate from an FGD wastewater or combustion residual leachate treatment system designed to achieve limitations in this part Initial request letter. (2) Discharge monitoring and reporting. e.g., (o) Certification for wastewater generated by a 10-year, 24-hour or longer duration storm event Storm Event Discharge Certification Statement. (2) Signature and certification. (3) Contents. (i) A statement that the professional engineer is a licensed professional engineer. (ii) A statement that the professional engineer is familiar with the requirements in this part. (iii) A statement that the professional engineer is familiar with the facility. (iv) A statement that the facility experienced a storm event exceeding a 10-year, 24-hour or longer duration, including specifics of the actual storm event that are sufficient for a third party to verify the accuracy of the statement. (v) A statement that a discharge of low volume wastewater that would otherwise meet the definition of FGD wastewater, bottom ash transport water, or combustion residual leachate was necessary, including a list of the best management practices at the site and a narrative discussion of the ability of on-site equipment and practices to manage the wastewater. (vi) The duration and volume of any such discharge. (vii) A statement that the discharge does not otherwise violate any other limitation or permit condition. (p) Requirements for facilities subject to zero discharge pretreatment standards for existing sources by 2034. (q) Requirements for facilities seeking an alternative applicability date under this part Initial request letter. (2) Contents and timing. , (3) Progress reports. (4) Contents and timing. (i) The estimated duration of the alternative applicability timing; (ii) The timeframes of various milestones, tasks, and sub-tasks; (iii) The number and magnitude of contingencies; and (iv) Any other appropriate and relevant factor. (5) Request letter. [85 FR 64721, Oct. 13, 2020, as amended at 88 FR 18442, Mar. 29, 2023; 89 FR 40303, May 9, 2024; 90 FR 61354, Dec. 31, 2025; 91 FR 4017, Jan. 30, 2026] Appendix A to Part 423—126 Priority Pollutants 001 Acenaphthene 002 Acrolein 003 Acrylonitrile 004 Benzene 005 Benzidine 006 Carbon tetrachloride (tetrachloromethane) 007 Chlorobenzene 008 1,2,4-trichlorobenzene 009 Hexachlorobenzene 010 1,2-dichloroethane 011 1,1,1-trichloreothane 012 Hexachloroethane 013 1,1-dichloroethane 014 1,1,2-trichloroethane 015 1,1,2,2-tetrachloroethane 016 Chloroethane 018 Bis(2-chloroethyl) ether 019 2-chloroethyl vinyl ether (mixed) 020 2-chloronaphthalene 021 2,4, 6-trichlorophenol 022 Parachlorometa cresol 023 Chloroform (trichloromethane) 024 2-chlorophenol 025 1,2-dichlorobenzene 026 1,3-dichlorobenzene 027 1,4-dichlorobenzene 028 3,3-dichlorobenzidine 029 1,1-dichloroethylene 030 1,2-trans-dichloroethylene 031 2,4-dichlorophenol 032 1,2-dichloropropane 033 1,2-dichloropropylene (1,3-dichloropropene) 034 2,4-dimethylphenol 035 2,4-dinitrotoluene 036 2,6-dinitrotoluene 037 1,2-diphenylhydrazine 038 Ethylbenzene 039 Fluoranthene 040 4-chlorophenyl phenyl ether 041 4-bromophenyl phenyl ether 042 Bis(2-chloroisopropyl) ether 043 Bis(2-chloroethoxy) methane 044 Methylene chloride (dichloromethane) 045 Methyl chloride (dichloromethane) 046 Methyl bromide (bromomethane) 047 Bromoform (tribromomethane) 048 Dichlorobromomethane 051 Chlorodibromomethane 052 Hexachlorobutadiene 053 Hexachloromyclopentadiene 054 Isophorone 055 Naphthalene 056 Nitrobenzene 057 2-nitrophenol 058 4-nitrophenol 059 2,4-dinitrophenol 060 4,6-dinitro-o-cresol 061 N-nitrosodimethylamine 062 N-nitrosodiphenylamine 063 N-nitrosodi-n-propylamin 064 Pentachlorophenol 065 Phenol 066 Bis(2-ethylhexyl) phthalate 067 Butyl benzyl phthalate 068 Di-N-Butyl Phthalate 069 Di-n-octyl phthalate 070 Diethyl Phthalate 071 Dimethyl phthalate 072 1,2-benzanthracene (benzo(a) anthracene 073 Benzo(a)pyrene (3,4-benzo-pyrene) 074 3,4-Benzofluoranthene (benzo(b) fluoranthene) 075 11,12-benzofluoranthene (benzo(b) fluoranthene) 076 Chrysene 077 Acenaphthylene 078 Anthracene 079 1,12-benzoperylene (benzo(ghi) perylene) 080 Fluorene 081 Phenanthrene 082 1,2,5,6-dibenzanthracene (dibenzo(,h) anthracene) 083 Indeno (,1,2,3-cd) pyrene (2,3-o-pheynylene pyrene) 084 Pyrene 085 Tetrachloroethylene 086 Toluene 087 Trichloroethylene 088 Vinyl chloride (chloroethylene) 089 Aldrin 090 Dieldrin 091 Chlordane (technical mixture and metabolites) 092 4,4-DDT 093 4,4-DDE (p,p-DDX) 094 4,4-DDD (p,p-TDE) 095 Alpha-endosulfan 096 Beta-endosulfan 097 Endosulfan sulfate 098 Endrin 099 Endrin aldehyde 100 Heptachlor 101 Heptachlor epoxide (BHC-hexachlorocyclohexane) 102 Alpha-BHC 103 Beta-BHC 104 Gamma-BHC (lindane) 105 Delta-BHC (PCB-polychlorinated biphenyls) 106 PCB-1242 (Arochlor 1242) 107 PCB-1254 (Arochlor 1254) 108 PCB-1221 (Arochlor 1221) 109 PCB-1232 (Arochlor 1232) 110 PCB-1248 (Arochlor 1248) 111 PCB-1260 (Arochlor 1260) 112 PCB-1016 (Arochlor 1016) 113 Toxaphene 114 Antimony 115 Arsenic 116 Asbestos 117 Beryllium 118 Cadmium 119 Chromium 120 Copper 121 Cyanide, Total 122 Lead 123 Mercury 124 Nickel 125 Selenium 126 Silver 127 Thallium 126 Silver 128 Zinc 129 2,3,7,8-tetrachloro-dibenzo-p-dioxin (TCDD)

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