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 Code of Federal Regulations (Last Updated: November 8, 2024)
 Title 40 - Protection of Environment
 Chapter I - Environmental Protection Agency
 SubChapter N - Effluent Guidelines and Standards
 Part 423 - Steam Electric Power Generating Point Source Category

  § 423.15 - New source performance standards (NSPS).  

Latest version.

  • § 423.15 New source performance standards (NSPS).

    Cross Reference
    Link to an amendment published at 89 FR 40299, May 9, 2024.

    (a) 1982 NSPS. Any new source as of November 19, 1982, subject to paragraph (a) of this section, must achieve the following new source performance standards, in addition to the limitations in § 423.13 of this part, established on November 3, 2015. In the case of conflict, the more stringent requirements apply:

    (1) pH. The pH of all discharges, except once through cooling water, shall be within the range of 6.0-9.0.

    (2) PCBs. There shall be no discharge of polychlorinated biphenyl compounds such as those commonly used for transformer fluid.

    (3) Low volume waste sources, FGD wastewater, flue gas mercury control wastewater, combustion residual leachate, and gasification wastewater. The quantity of pollutants discharged in low volume waste sources, FGD wastewater, flue gas mercury control wastewater, combustion residual leachate, and gasification wastewater shall not exceed the quantity determined by multiplying the flow of low volume waste sources times the concentration listed in the following table:

    Pollutant or pollutant property NSPS
    Maximum for any 1 day (mg/l) Average of daily
    values for 30
    consecutive days
    shall not exceed
    (mg/l)
    TSS100.030.0
    Oil and grease20.015.0

    (4) Chemical metal cleaning wastes. 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 NSPS
    Maximum for
    any 1 day
    (mg/l)     		Average of daily
    values for 30
    consecutive days
    shall not exceed
    (mg/l)
    TSS100.030.0
    Oil and grease20.015.0
    Copper, total1.01.0
    Iron, total1.01.0

    (5) [Reserved]

    (6) Bottom ash transport water. The quantity of pollutants discharged in bottom ash transport water shall not exceed the quantity determined by multiplying the flow of the bottom ash transport water times the concentration listed in the following table:

    Pollutant or pollutant property NSPS
    Maximum for
    any 1 day
    (mg/l)     		Average of daily
    values for 30
    consecutive days
    shall not exceed
    (mg/l)
    TSS100.030.0
    Oil and grease20.015.0

    (7) Fly ash transport water. There shall be no discharge of pollutants in fly ash transport water.

    (8)

    (i) Once through cooling water. 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 NSPS
    Maximum concentrations
    (mg/l)
    Total residual chlorine0.20

    (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. 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 NSPS
    Maximum concentration
    (mg/l)     		Average concentration
    (mg/l)
    Free available chlorine0.50.2

    (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. 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 NSPS
    Maximum concentration
    (mg/l)     		Average concentration
    (mg/l)
    Free available chlorine0.50.2
    Pollutant or pollutant property NSPS
    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, total0.20.2
    zinc, total1.01.0

    1 No detectable amount.

    (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. Subject to the provisions of paragraph (a)(12) of this section, the quantity or quality of pollutants or pollutant parameters discharged in coal pile runoff shall not exceed the standards specified below:

    Pollutant or pollutant property NSPS for any time
    TSSnot to exceed 50 mg/l.

    (12) Coal pile runoff. Any untreated overflow from facilities designed, constructed, and operated to treat the coal pile runoff which results from a 10 year, 24 hour rainfall event shall not be subject to the standards in paragraph (a)(11) of this section.

    (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. Any new source as of November 17, 2015, subject to paragraph (b) of this section, must achieve the following new source performance standards:

    (1) pH. The pH of all discharges, except once through cooling water, shall be within the range of 6.0-9.0.

    (2) PCBs. There shall be no discharge of polychlorinated biphenyl compounds such as those commonly used for transformer fluid.

    (3) Low volume waste sources. 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 listed in the following table:

    Pollutant or pollutant property NSPS
    Maximum for
    any 1 day
    (mg/l)     		Average of daily
    values for 30
    consecutive days
    shall not exceed
    (mg/l)
    TSS100.030.0
    Oil and grease20.015.0

    (4) Chemical metal cleaning wastes. 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 NSPS
    Maximum for
    any 1 day
    (mg/l)     		Average of daily
    values for 30
    consecutive days
    shall not exceed
    (mg/l)
    TSS100.030.0
    Oil and grease20.015.0
    Copper, total1.01.0
    Iron, total1.01.0

    (5) [Reserved]

    (6) Bottom ash transport water. There shall be no discharge of pollutants in bottom ash transport water. Whenever bottom ash transport water is used in any other plant process or is sent to a treatment system at the plant, the resulting effluent must comply with the discharge standard in this paragraph.

    (7) Fly ash transport water. There shall be no discharge of pollutants in fly ash transport water. Whenever fly ash transport water is used in any other plant process or is sent to a treatment system at the plant, the resulting effluent must comply with the discharge standard in this paragraph.

    (8)

    (i) Once through cooling water. 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 NSPS
    Maximum concentration
    (mg/l)
    Total residual chlorine0.20

    (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. 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 NSPS
    Maximum concentration
    (mg/l)     		Average concentration
    (mg/l)
    Free available chlorine0.50.2

    (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. 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 NSPS
    Maximum concentration
    (mg/l)     		Average concentration
    (mg/l)
    Free available chlorine0.50.2
    Pollutant or pollutant property NSPS
    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, total0.20.2
    zinc, total1.01.0

    1 No detectable amount.

    (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. Subject to the provisions of paragraph (b)(12) of this section, the quantity or quality of pollutants or pollutant parameters discharged in coal pile runoff shall not exceed the standards specified below:

    Pollutant or pollutant property NSPS for any time
    TSSnot to exceed 50 mg/l.

    (12) Coal pile runoff. Any untreated overflow from facilities designed, constructed, and operated to treat the coal pile runoff which results from a 10 year, 24 hour rainfall event shall not be subject to the standards in paragraph (b)(11) of this section.

    (13) FGD wastewater. 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 in the following table:

    Pollutant or pollutant property NSPS
    Maximum for
    any 1 day     		Average of daily
    values for 30
    consecutive days
    shall not exceed
    Arsenic, total (ug/L)4
    Mercury, total (ng/L)3924
    Selenium, total (ug/L)5
    TDS (mg/L)5024

    (14) Flue gas mercury control wastewater. There shall be no discharge of pollutants in flue gas mercury control wastewater. Whenever flue gas mercury control wastewater is used in any other plant process or is sent to a treatment system at the plant, the resulting effluent must comply with the discharge standard in this paragraph.

    (15) Gasification wastewater. 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 in the following table:

    Pollutant or pollutant property NSPS
    Maximum for
    any 1 day     		Average of daily
    values for 30
    consecutive days
    shall not exceed
    Arsenic, total (ug/L)4
    Mercury, total (ng/L)1.81.3
    Selenium, total (ug/L)453227
    Total dissolved solids (mg/L)3822

    (16) Combustion residual leachate. The quantity of pollutants discharged in combustion residual leachate shall not exceed the quantity determined by multiplying the flow of combustion residual leachate times the concentration listed in the following table:

    Pollutant or pollutant property NSPS
    Maximum for
    any 1 day     		Average of daily
    values for 30
    consecutive days
    shall not exceed
    Arsenic, total (ug/L)118
    Mercury, total (ng/L)788356

    (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.

    (1) Except as provided in paragraph (c)(2) of this section, there shall be no discharge of pollutants in combustion residual leachate (CRL). Whenever CRL is used in any other plant process or is sent to a treatment system at the plant, the resulting effluent must comply with the discharge standard in this paragraph (c).

    (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]