SAN DIEGO COUNTY AIR POLLUTION CONTROL DISTRICT

RULE 20.1 - NEW SOURCE REVIEW - GENERAL PROVISIONS
(ADOPTED AND EFFECTIVE 5/17/94); (REV. ADOPTED AND EFFECTIVE 5/15/96); (REV. ADOPTED AND EFFECTIVE 12/17/97); (REV. ADOPTED 11/4/98; EFFECTIVE 12/17/98)

Table of Contents

SECTION TITLE

(a) APPLICABILITY

(b) EXEMPTIONS

(c) DEFINITIONS

Table 20.1-1: Air Quality Increments (Class I Areas)
Table 20.1-2: Air Quality Increments (Class II Areas)
Table 20.1-3: Class I Areas
Table 20.1-4: BACT Cost Modifier
Table 20.1-5: Major Modification
Table 20.1-6: Major Stationary Source - Federal Serious Ozone Non-attainment Area ..
Table 20.1-7: California and National Ambient Air Quality Standards
Table 20.1-7 appears in a separate document.
Table 20.1-8: Non-Criteria Pollutant Emissions Significance Levels
Table 20.1-9: Precursor Air Contaminants
Table 20.1-10: PSD Modification
Table 20.1-11: PSD Stationary Sources and Trigger Levels
Table 20.1-12: Stationary Sources Impacting Any Class I Area
Table 20.1-13: Stationary Sources Impacting Any Class II Area

(d) EMISSION CALCULATIONS

1. Potential to Emit
   1. Calculation of Potential to Emit
   2. Calculation of Aggregate Potential to Emit - Stationary Source
2. Actual Emissions
   1. Time Period for Calculation
   2. Time Periods Less Than Six Months - Potential to Emit
3. Emission Increase
   1. New Emission Units
   2. Modified Emission Units
   3. Relocated Emission Units
   4. Replacement Emission Units
   5. Portable Emission Units
   6. Determining Emission Increases for AQIA Trigger Levels
4. Emission Reduction - Potential to Emit & Actual Emission Reduction
   1. Reduction in the Potential to Emit
   2. Actual Emission Reduction
   3. Adjustments for Determining Actual Emission Reductions
5. Emission Offsets

(e) OTHER PROVISIONS

1. Continuity of Existing Permits

1. Any emission unit for which a permit is required solely due to a change in Rule 11, provided the unit was operated in San Diego County at any time within one year prior to the date on which the permit requirements became applicable to the unit and provided a District permit application for the unit is submitted within one year after the date upon which permit requirements became applicable to the unit. An emission unit to which this subsection applies shall be included in the calculation of a stationary source's aggregate potential to emit, as provided in Subsection (d)(1)(ii).
   
   
2. The following changes, provided such changes are not contrary to any permit condition, and the change does not result in an increase in the potential to emit of any air contaminant not previously emitted:
   1. Repair or routine maintenance of an existing emission unit.
   2. A change of ownership.
   3. An increase in the hours of operation.
   4. Use of alternate fuel or raw material.
      
      
3. Portable and stationary abrasive blasting equipment for which the California Air Resources Board (ARB) has established standards pursuant to Sections 41900 and 41905 of the Health and Safety Code, and which comply with the requirements of 17 CCR Section 92000 et. seq. This exemption shall not apply if the abrasive blasting equipment would be, by itself, a major stationary source, nor to any equipment used in conjunction with the abrasive blasting equipment the use of which may cause the issuance of air contaminants.
   
   
4. Oxides of nitrogen (NOx) emission increases from new, modified or replacement emission units subject to the requirements of Rule 69(d)(6) shall not be subject to the offset provisions of Subsection (d)(5) of Rule 20.2 or of Subsections (d)(5) and (d)(8) of Rule 20.3. Only those NOx emission increases in compliance with Rule 69 and associated with generating capacity which the California Energy Commission or California Public Utilities Commission or their successor, as applicable, has determined a need for shall be eligible for this exemption.
   
   
5. Piston engines used at airplane runways at military bases and which engines are used exclusively for purposes of hoisting cable to assist in the capture of errant aircraft during landings.
   
   
6. Air compressors used exclusively to pressurize nuclear reactor containment domes, provided the compressors are not operated more than 50 hours over any two-year period, and that the compressors satisfy the Air Quality Impact Analysis (AQIA) provisions of Subsections (d)(2) of Rules 20.2 and 20.3, as applicable.
   
   
7. Applications for modified Authority to Construct or modified Permit to Operate which are for the sole purpose of reducing an emission unit's potential to emit and which will not result in a modified emission unit, a modified stationary source or an actual emission reduction calculated pursuant to Rule 20.1(d)(4)(ii) shall be exempt from the Best Available Control Technology (BACT), Lowest Achievable Emission Rate (LAER), AQIA and Emission Offset provisions of Rules 20.1, 20.2, 20.3 and 20.4.

(c) DEFINITIONS
For purposes of Rules 20.1, 20.2, 20.3, 20.4 and 20.5, the following definitions shall apply:

1. "Actual Emissions" means the emissions of an emission unit calculated pursuant to Subsection (d)(2) of this rule.
   
   
2. "Actual Emission Reductions" means emission reductions which are real, surplus, enforceable, and quantifiable and may be permanent or temporary in duration. Actual emission reductions shall be calculated pursuant to Subsection (d)(4) of this rule.
   
   
3. "Aggregate Potential to Emit" means the sum of the post-project potential to emit of all emission units at the stationary source, calculated pursuant to Section (d) of this rule.
   
   
4. "Air Contaminant Emission Control Project" means any activity or project undertaken at an existing emission unit which, as its primary purpose, reduces emissions of air contaminants from such unit in order to comply with a District, ARB or federal Environmental Protection Agency (EPA) emission control requirement. Such activities or projects do not include the replacement of an existing emission unit with a newer or different unit, or the reconstruction of an existing emission unit, or a modification or replacement of an existing emission unit to the extent that such replacement, reconstruction, or modification results in an increase in capacity of the emissions unit, or any air contaminant emission control project for a new or modified emission unit which project is proposed to meet New Source Review Rules 20.1, 20.2, 20.3 and 20.4, or Banking Rules 26.0 through 26.10.
   
   Air contaminant emission control projects include, but are not limited to, any of the following:
   
   
   1. The installation of conventional or advanced flue gas desulfurization, or sorbent injection for emissions of oxides of sulfur;
   2. Electrostatic precipitators, baghouses, high efficiency multiclones, or scrubbers for emissions of particulate matter or other pollutants;
   3. Flue gas recirculation, low-NOx burners, selective non-catalytic reduction or selective catalytic reduction for emissions of oxides of nitrogen;
   4. Regenerative thermal oxidizers, catalytic oxidizers, condensers, thermal incinerators, flares, absorption equipment or carbon adsorbers for volatile organic compounds or hazardous air pollutants;
   5. Activities or projects undertaken to accommodate switching to an inherently less polluting fuel, including but not limited to, natural gas firing, or the cofiring of natural gas and other inherently less polluting fuels, for the purpose of controlling emissions. The air contaminant emission control project shall include any activity that is necessary to accommodate switching to an inherently less polluting fuel; and
   6. Activities or projects undertaken to replace or reduce the use and emissions of stratospheric ozone depleting compounds subject to regulation by the federal EPA.
      
      
5. "Air Quality Impact Analysis (AQIA)" means an analysis of the air quality impacts of the air contaminant emissions from an emission unit or a stationary source, as applicable, conducted by means of modeling approved by the Air Pollution Control Officer. Methods other than modeling may be used, as the Air Pollution Control Officer and the federal EPA may approve. An AQIA shall include an analysis of the impacts on State and National Ambient Air Quality Standards.
   
   
6. "Air Quality Increment" means any of the following maximum allowable cumulative increases in air contaminant concentration from all increment consuming and increment expanding sources (see Tables 20.1-1 and 20.1-2).
   
   

   TABLE 20.1 - 1 Air Quality Increments (Class I Areas)
   Air Contaminant		Increment
   Nitrogen Dioxide (NO2)
   	Annual arithmetic mean	2.5 µg/m3
   Sulfur Dioxide (SO2)
   	Annual arithmetic mean	2.0 µg/m3
   	24-hr. maximum	5.0 µg/m3
   	3-hr. maximum	25.0 µg/m3
   Particulate Matter (PM10)
   	Annual arithmetic mean	4.0 µg/m3
   	24-hr. maximum	8.0 µg/m3

   
   

   TABLE 20.1 - 2 Air Quality Increments (Class II Areas)
   Air Contaminant		Increment
   Nitrogen Dioxide (NO2)
   	Annual arithmetic mean	25.0 µg/m3
   Sulfur Dioxide (SO2)
   	Annual arithmetic mean	20.0 µg/m3
   	24-hr. maximum	91.0 µg/m3
   	3-hr. maximum	512.0 µg/m3
   Particulate Matter (PM10)
   	Annual arithmetic mean	17.0 µg/m3
   	24-hr. maximum	30.0 µg/m3

7. "Area Fugitive Emissions" means fugitive emissions of particulate matter (PM10) which occur as a result of drilling, blasting, quarrying, stockpiling, front end loader operations and vehicular travel of haul roads used to move materials to, from or within a stationary source.
   
   
8. "Attainment" means designated as attainment of the National Ambient Air Quality Standards (NAAQS) pursuant to Section 107(d) of the federal Clean Air Act or of the State Ambient Air Quality Standards (SAAQS) pursuant to Section 39608 of the California Health and Safety Code, as applicable.
   
   
9. "Baseline Concentration" means the ambient concentration of an air con-taminant for which there is an air quality increment, which existed in an impact area on the major and non-major source baseline dates. As specified by 40 CFR §52.21(b)(13), the baseline concentration includes the impact of actual emissions from any stationary source in existence on the baseline date and the impacts from the potential to emit of Prevention of Significant Deterioration (PSD) stationary sources which commenced construction but were not in operation by the baseline date. The baseline concentration excludes impacts of actual emission increases and decreases at any stationary source occurring after the baseline date and actual emissions from any PSD stationary source which commenced construction after January 6, 1975. There are two baseline concentrations for any given impact area, a baseline concentration as of the major source baseline date and a baseline concentration as of the non-major source baseline date.
   
   
10. "Baseline Date" means either the major source baseline date or non-major source baseline date, as applicable.
    
    
11. "Best Available Control Technology (BACT)" means and is applied as follows:
    
    
    1. The lowest emitting of any of the following:
       1. the most stringent emission limitation, or the most effective emission control device or control technique, which has been proven in field application and which is cost-effective for such class or category of emission unit, unless the applicant demonstrates to the satisfaction of the Air Pollution Control Officer that such limitation, device or control technique is not technologically feasible, or
       2. any emission control device, emission limitation or control technique which has been demonstrated but not necessarily proven in field application and which is cost-effective for such class or category of emission unit, as determined by the Air Pollution Control Officer, unless the applicant demonstrates to the satisfaction of the Air Pollution Control Officer that such limitation, device or control technique is not technologically feasible, or
       3. any control equipment, process modifications, changes in raw material including alternate fuels, and substitution of equipment or processes with any equipment or processes, or any combination of these, determined by the Air Pollution Control Officer on a case-by-case basis to be technologically feasible and cost-effective, including transfers of technology from another category of source, or
       4. the most stringent emission limitation, or the most effective emission control device or control technique, contained in any State Implementation Plan (SIP) approved by the federal EPA for such emission unit category, unless the applicant demonstrates to the satisfaction of the Air Pollution Control Officer that such limitation or technique has not been proven in field application, that it is not technologically feasible or that it is not cost-effective for such class or category of emission unit.
          
          In determining BACT, the Air Pollution Control Officer may also consider lower-emitting alternatives to a proposed new emission unit or process.
          
          
    2. For modified emission units, the entire emission unit's post-project potential to emit shall be subject to BACT, except as follows. The provisions of this Subsection (c)(11)(ii) shall not apply to relocated or replacement emission units.
       1. BACT applies to the emissions increase associated with the modifica-tion and not the emission unit's entire potential to emit, if control technology, an emission limit or other emission controls meeting the BACT definition was previously applied to the unit and if the project's emission increase is less than the major modification thresholds of Table 20.1-5.
       2. BACT applies to the emission unit's entire post-project potential to emit, if the emission unit was previously subject to BACT but BACT was determined to not be cost-effective, technologically feasible or proven in field application.
       3. BACT applies to the emissions increase associated with the emission unit and not the emission unit's entire potential to emit if the emissions increase associated with the modification is less than 25 percent of the emission unit's preproject potential to emit and if the project's emission increase is less than the major modification thresholds of Table 20.1-5.
          
          
    3. In no event shall application of BACT result in the emission of any air con-taminant which would exceed the emissions allowed by any District rule or regulation, or by any applicable standard under 40 CFR Part 60 (New Source Performance Stan-dards) or 40 CFR Part 61 (National Emission Standards for Hazardous Pollutants). Whenever feasible, the Air Pollution Control Officer may stipulate an emission limit as BACT instead of specifying control equipment. In making a BACT determination, the Air Pollution Control Officer shall take into account those environmental and energy impacts identified by the applicant.
       
       
12. "Class I Area" means any area designated as Class I under Title I, Part C of the federal Clean Air Act. As of May 17, 1994, the Agua Tibia National Wilderness Area was the only area so designated within San Diego County. As of May 17, 1994, the following were the only designated Class I areas within 100 km of San Diego County (see Table 20.1-3):
    

    TABLE 20.1 - 3 Class I Areas
    Class I Area	Approximate Location
    Agua Tibia Wilderness Area	San Diego County
    Cucamonga Wilderness Area	80 km North - San Bernardino County
    Joshua Tree Wilderness Area	40 km NE - Riverside County
    San Gabriel Wilderness Area	90 km NW - Los Angeles County
    San Gorgonio Wilderness Area	70 km North - San Bernardino County
    San Jacinto Wilderness Area	30 km North - Riverside County

13. "Class II Area" means any area not designated as a Class I area.
    
    
14. "Commenced Construction" means that the owner or operator of a stationary source has an Authority to Construct or a Determination of Compliance issued pursuant to these rules and regulations and either has:
    
    
    1. Begun, or caused to begin, a continuous program of actual on-site construction of the source to be completed within a reasonable time, or
    2. Entered into binding agreements or contractual obligations, which cannot be canceled or modified without substantial loss to the owner or operator, to undertake a program of actual construction of the source to be completed within a reasonable time.
       
       
15. "Construction" means any physical change or change in the method of operation, including fabrication, erection, installation, demolition or modification of an emission unit, which would result in a change in actual emissions.
    
    
16. "Contemporaneous Emissions Increase" means the sum of emission increases from new or modified emission units occurring at a stationary source within the calendar year in which the subject emission unit(s) is expected to commence operation and the preceding four calendar years, including all other emission units with complete applications under District review and which are expected to commence operation within such calendar years. The sum of emission increases may be reduced by the following:
    
    
    1. Actual emission reductions occurring at the stationary source, and
    2. Reductions in the potential to emit of a new or modified unit, which unit resulted in an emission increase within the five-year contemporaneous period at the stationary source. In no case shall the reduction in the potential to emit exceed the emission increases from the new or modified unit that occurred within the five-year contemporaneous period.
    .
    When an emissions increase from a new or modified emission unit or project has been determined to be subject to, and approved as in compliance with, the LAER and/or federal emission offset requirements of Rule 20.3, the contemporaneous emissions increase for the subject air contaminant or precursor shall thereafter not include any residual emission increase from such new or modified emis-sion unit or project.
17. "Contiguous Property" means two or more parcels of land with a common boundary or separated solely by a public or private roadway or other public or private right-of-way. Non-adjoining parcels of land which are connected by a process line, conveyors or other equipment shall be considered to be contiguous property. Non-adjoining parcels of land separated by bodies of water designated "navigable" by the U.S. Coast Guard, shall not be considered contiguous properties.
    
    
18. "Cost-Effective" means that the annualized cost in dollars per pound of emissions of air contaminant(s) reduced does not exceed the highest cost per pound of emissions reduced by other control measures required to meet stationary source emission standards contained in these rules and regulations, for the specific air contaminant(s) under consideration, multiplied by the BACT Cost Multiplier indicated in Table 20.1- 4. When determining the highest cost per pound of emissions reduced by other control measures, the cost of measures used to comply with the requirements of New Source Review shall be excluded.
    

    TABLE 20.1 - 4 BACT Cost Multiplier
    Stationary Source's Post-Project Aggregate BACT Potential to Emit	Cost Multiplier
    Potential < 15 tons/year	1.1
    Potential > 15 tons/year	1.5

19. "Emergency Equipment" means an emission unit used exclusively to drive an electrical generator, an air compressor or a pump in emergency situations, except for operations up to 52 hours per calendar year for non-emergency purposes. Emission units used for supplying power for distribution to an electrical grid shall not be considered emergency equipment.
    
    
20. "Emergency Situation" means an unforeseen electrical power failure from the serving utility or of on-site electrical transmission equipment such as a transformer, an unforeseen flood or fire, or a life-threatening situation. In addition, operation of emergency generators at Federal Aviation Administration licensed airports for the purpose of providing power in anticipation of a power failure due to severe storm activity shall be considered an emergency situation. Emergency situations do not include operation for purposes of supplying power for distribution to an electrical grid, operation for training purposes, or other foreseeable event.
    
    
21. "Emission Increase" means an increase in the potential to emit, calculated pursuant to Subsection (d)(3).
    
    
22. "Emission Unit" means any article, machine, equipment, contrivance, process or process line, which emit(s) or reduce(s) or may emit or reduce the emission of any air contaminant.
    
    
23. "Emission Offsets" means emission reductions used to mitigate emission increases, calculated pursuant to Subsection (d)(5).
    
    
24. "Enforceable" means capable of being enforced by the District, including through either the SIP or inclusion of conditions on an Authority to Construct, Permit to Operate, Determination of Compliance or Emission Reduction Credit (ERC) Certificate.
    
    
25. "Essential Public Services" means any of the following:
    
    
    1. Water, wastewater and wastewater-sludge treatment plants which are publicly owned or are public-private partnerships under public control. This shall not include facilities treating hazardous materials other than hazardous materials which may be used in the process or hazardous materials whose presence in the water, wastewater or wastewater sludge being treated is incidental.
    2. Solid waste landfills and solid waste recycling facilities which are publicly owned or are public-private partnerships under public control, not including trash to energy facilities or facilities processing hazardous waste.
       
       
26. "Federally Enforceable" means, for purposes of permitting new or modified sources, can be enforced by the federal EPA including through either the SIP or terms and conditions of an Authority to Construct or Permit to Operate as they apply to the following requirements:
    
    
    1. Any standard or other requirement provided for in the SIP, including any revisions approved or promulgated by the federal EPA through rulemaking under Title I of the federal Clean Air Act.
    2. Any term or condition of an Authority to Construct issued pursuant to these rules and regulations which term or condition is imposed pursuant to 40 CFR Parts 60 or 61, 40 CFR Part 52.21 or 40 CFR Part 51, Subpart I.
    3. Any standard or other requirement under Sections 111 or 112 of the federal Clean Air Act.
    4. Any standard or other requirement of the Acid Rain Program under Title IV of the federal Clean Air Act or the regulations promulgated thereunder.
    
    This does not preclude enforcement by the Air Pollution Control Officer. Authority to Construct or Permit to Operate terms and conditions imposed pursuant to these rules and regulations or state law and not for purposes of compliance with paragraphs (i) through (iv) above shall not be federally enforceable unless specifically requested by the owner or operator.
    
    For purposes of creating, banking and/or using creditable emission reductions to meet federal offset requirements, federally enforceable means capable of being enforced by the federal EPA including through either the SIP, terms and conditions of a Permit to Operate or an Emission Reduction Credit (ERC) Certificate that are necessary to ensure compliance with Rules 26.0 et seq., and to ensure the validity of the emission reduction, or through terms and conditions of an Authority to Construct, Permit to Operate or Determination of Compliance as they apply to the creation of emission reductions eligible for banking under Rules 26.0 et seq.
27. "Federal Land Manager" means the National Park Service's Western Regional Director, the U.S. Forest Service's Pacific Southwest Regional Air Program Manager and the U.S. Fish and Wildlife Service.
    
    
28. "Fugitive Emissions" means those quantifiable emissions which could not reasonably pass through a stack, chimney, flue, vent or other functionally equivalent opening.
    
    
29. "Impact Area" means the circular area with the emission unit as the center and having a radius extending to the furthest point where a significant impact is expected to occur, not to exceed 50 kilometers.
    
    
30. "Increment Consuming" means emission increases which consume an air quality increment. Emission increases which consume increment are those not accounted for in the baseline concentration, including:
    1. Actual emission increases occurring at any major stationary source after the major source baseline date, and
    2. Actual emission increases from any non-major stationary source, area source, or mobile source occurring after the non-major source baseline date.
       
       
31. "Increment Expanding" means actual emission reductions which increase an available air quality increment. Actual emission reductions which increase available increment include:
    1. Actual emission reductions occurring at any major stationary source after the major source baseline date, and
    2. Actual emission reductions from any non-major stationary source, area source, or mobile source occurring after the non-major source baseline date.
       
       
32. "Lowest Achievable Emission Rate (LAER)" means and is applied as follows:
    1. The lowest emitting of any of the following:
       1. the most stringent emission limitation, or most effective emission control device or control technique, contained in any SIP approved by the federal EPA for such emission unit class or category, unless the applicant demonstrates to the satisfaction of the Air Pollution Control Officer that such emission limitation, device or technique is not achievable, or
       2. the most stringent emission limitation which is achieved in practice by such class or category of emission unit, or
       3. Best Available Control Technology (BACT).
    2. For modified emission units subject to the LAER requirements of these rules, the entire emission unit's post-project potential to emit shall be subject to LAER.
    3. In no event shall application of LAER result in the emission of any air con-taminant which would exceed the emissions allowed by any District Rule or Regulation, or by any applicable standard under 40 CFR Part 60 (New Source Performance Standards) or 40 CFR Part 61 (National Emission Standards for Hazardous Pollutants).
       
       
33. "Major Modification" means a physical or operational change which results, or may result, in a contemporaneous emissions increase at an existing major stationary source which source is major for the pollutant for which there is a contemporaneous emissions increase, equal to or greater than any of the emission rates listed in Table 20.1 - 5.
    

    TABLE 20.1 - 5 Major Modification
    Air Contaminant:	Emission Rate (Ton/yr)
    Particulate Matter (PM10)	15
    Oxides of Nitrogen (NOx)	25
    Volatile Organic Compounds (VOC)	25
    Oxides of Sulfur (SOx)	40
    Carbon Monoxide (CO)	100
    Lead (Pb)	0.6

34. "Major Source Baseline Date" means January 6, 1975 for sulfur dioxide (SO2) and particulate matter (PM10), and February 8, 1988 for nitrogen dioxide (NO2).
    
    
35. "Major Stationary Source" means any emission unit or stationary source which has, or will have after issuance of a permit, an aggregate potential to emit one or more air contaminants, including fugitive emissions, in amounts equal to or greater than any of the emission rates listed in Table 20.1 - 6.
    
    

    TABLE 20.1 - 6 Major Stationary Source Federal Serious Ozone Non-attainment Area
    Air Contaminant:	Emission Rate (Ton/yr)
    Particulate Matter (PM10)	100
    Oxides of Nitrogen (NOx)	50
    Volatile Organic Compounds (VOC)	50
    Oxides of Sulfur (SOx)	100
    Carbon Monoxide (CO)	100
    Lead (Pb)	100

36. "Military Tactical Support Equipment" means any equipment owned by the U.S Department of Defense or the National Guard and used in combat, combat support, combat service support, tactical or relief operations, or training for such operations.
    
    
37. "Modeling" means the use of an applicable ARB or federal EPA approved air quality model to estimate ambient concentrations of air contaminants or to evaluate other air quality related data. Applicable state or federal guidelines shall be followed when performing modeling.
    
    
38. "Modified Emission Unit" means any physical or operational change which results or may result in an increase in an emission unit's potential to emit, including those air contaminants not previously emitted. The following shall not be considered a modified emission unit, provided such a change is not contrary to any permit condition, and the change does not result in an increase in the potential to emit of any air contaminant:
    1. The movement of a portable emission unit from one stationary source to another.
    2. Repair or routine maintenance of an existing emission unit.
    3. An increase in the hours of operation.
    4. Use of alternate fuel or raw material.
       
       
39. "Modified Stationary Source" means a stationary source where a new or modified emission unit is or will be located or where a change in the aggregation of emission units occurs, including, but not limited to, the movement of a relocated emission unit to or from a stationary source or where a modification of an existing unit occurs. The following shall not be considered a modification of a stationary source:
    1. The replacement of an emission unit, provided there is no increase in the unit's potential to emit or in the potential to emit of any other unit at the stationary source.
    2. The movement to or from the stationary source of any portable emission unit, provided there is no increase in the potential to emit of any other unit at the stationary source.
       
       
40. "National Ambient Air Quality Standards (NAAQS)" means maximum allowable ambient air concentrations for specified air contaminants and monitoring periods as established by the federal EPA (see Table 20.1 - 7).
    

    TABLE 20.1 - 7 California and National Ambient Air Quality Standards

    California Standards National Standards Pollutant Averaging Time Concentration Method Primary Secondary Method  Ozone  1 Hour  0.09 ppm  -  0.12 ppm (235 µg/m3) Same as Primary  Ethylene Chemiluminescence Carbon Monoxide  8 Hour  9.0 ppm (10 mg/m3) Non-Dispersive Infrared Spectrascopy (NDIR)  9 ppm (10 mg/m3)  - Non-Dispersive Infrared Spectrascopy (NDIR)  1 Hour  20 ppm (23 mg/m3)  35ppm (40 mg/m3) Nitrogen Dioxide Annual Average   - Gas Phase Chemiluminescence  0.053 ppm (100 µg/m3) Same as Primary Standards Gas Phase Chemiluminescence  1 Hour   0.25 ppm (470 µg/m3)  -  Sulfur Dioxide  Annual Average   -  Ultraviolet Fluorescence  80 µg/m3 (0.03 ppm)  -  Pararosaniline  24 Hour  0.04 ppm (105 µg/m3) 365 µg/m3 (0.14 ppm)  - 3 Hour   -  -  1300 µg/m3 (0.14 ppm) 1 Hour   0.25 ppm (655 µg/m3)  -  - Suspended Particulate Matter (PM10) Annual Mean   30 µg/m3  Size Selective Inlet High Volume Sampler  50 µg/m3  - High Volume Sampling  24 Hour  50 µg/m3  150 µg/m3  Sulfates 24 Hour  25  µg/m3 Turbidimetric Barium Sulfate -   -  -  Lead 30-Day Average  1.5 µg/m3  Atomic Absorption  -  -  Atomic Absorption Calendar Quarter -  1.5 µg/m3  Same as Primary Hydrogen Sulfide  1 Hour 0.03 ppm (42 µg/m3) Cadmium Hydroxide Stractan   - -   - Vinyl Chloride (Chloroethene)  24 Hour 0.010 ppm (26 µg/m3) Tedlar Bag Collection, Gas Chromatography  -  -  - Visibility Reducing Particles  1 Observation In sufficient amount to produce an extinc-tion coefficient of 0.23 per kilometer due to particles when relative humidity <70%. Measure-ment in accordance with ARB Method V.  -  -  - Notes to Table 20.1-7 1. California standards, other than ozone, carbon monoxide, sulfur dioxide (1 hour), nitrogen dioxide, and particulate matter (PM10), are values that are not to be equaled or exceeded. The ozone, carbon monoxide, sulfur dioxide (1 hour), nitrogen dioxide, and particulate matter (PM10) standards are not to be exceeded. 2. National standards, other than ozone and those based on annual averages or annual geometric means, are not to be exceeded more than once a year. The ozone standard is attained when the expected number of days per calendar year with maximum hourly average concentrations above standard is equal to or less than one. 3. Concentration expressed first in units in which it was promul-gated. Equivalent units given in parentheses are based upon a reference temperature of 25oC and a reference pressure of 760 mm of mercury. All measurements of air quality are to be corrected to a reference temperature of 25oC and a reference pressure of 760 mm of mercury (1,013.2 millibar). Ppm in this table refers to ppm by volume or micromoles of pollutant per mole of gas. 4. Any equivalent procedure that can be shown to the satisfac-tion of the Air Resources Board to give equivalent results at or near the level of the air quality standard may be used. 5. National Primary Standards: The levels of air quality neces-sary, with an adequate margin of safety, to protect the public health. Each state must attain the primary standards within a specified number of years after that state's implementation plan is approved by the Environmental Protection Agency (EPA). 6. National Secondary Standards: The levels of air quality necessary to protect the public welfare from any known or anticipated adverse effects of a pollutant. Each state must attain the secondary standards within a "reasonable time" after the implementation plan is approved by the EPA. 7. Reference method as described by the EPA: An "equivalent method" of measurement may be used but must have a "consistent relationship to the reference method" and must be approved by the EPA. 8. Prevailing visibility is defined as the greatest visibility that is attained or surpassed around at least half of the horizon circle but not necessarily in continuous sector. 9. The annual PM10 state standard is based on the geometric mean of all reported values taken during the year. The annual PM10 national standard is based on averaging the quarterly arithmetic means.

41. "New Emission Unit" means any of the following:
    1. Any emission unit not constructed or installed in San Diego County as of December 17, 1997.
    2. Any emission unit which was constructed, installed or operated without a valid Authority to Construct or Permit to Operate from the District, except as provided for in Subsection (b)(1).
    3. Any emission unit which was inactive for a one-year period or more and which did not hold a valid Permit to Operate during that period.
       
       
42. "New Major Stationary Source" means a new emission unit or new stationary source which will be a major stationary source.
    
    
43. "New Stationary Source" means a stationary source which prior to the project under review, did not contain any other permitted equipment.
    
    
44. "Non-Criteria Pollutant Emissions Significance Level" means a contempora-neous emissions increase occurring at any new or modified PSD stationary source, equal to or greater than the amounts listed in Table 20.1 - 8.
    
    

    TABLE 20.1 - 8 Non-Criteria Pollutant Emissions Significance Levels
    Air Contaminant:	Emission Rate (Ton/yr)
    Asbestos	0.007
    Beryllium	0.0004
    Fluorides	3
    Hydrogen Sulfide (H2S)	10
    Mercury	0.1
    Reduced Sulfur Compounds	10
    Sulfuric Acid Mist	7
    Vinyl Chloride	1
    Trichlorofluoromethane (CFC-11)	100
    Dichlorodifluoromethane (CFC-12	100
    Trichlorotrifluoromethane (CFC-113)	100
    Dichlorotetrafluoroethane (CFC-114)	100
    Chloropentafluoroethane (CFC-115)	100
    Bromochlorodifluoromethane (Halon - 1191)	100
    Bromotrifluoromethane (Halon - 1301)	100
    Dibromotetrafluoroethane (Halon - 2402)	100

45. "Non-Major Source Baseline Date" means December 8, 1983, for sulfur dioxide (SO2). For particulate matter (PM10) and nitrogen dioxide (NO2), the non-major source baseline date is the date after August 7, 1977, or February 8, 1988, respectively, when the first Authority to Construct application for any stationary source which will be a PSD Major Stationary Source for PM10 or NOx or which is a PSD Major Modification for PM10 or NOx as applicable, is deemed complete. As of May 17, 1994, neither the particulate matter nor the nitrogen dioxide non-major source baseline date have been established.
    
    
46. "Offset Ratio" means the required proportion of emission offsets to emission increases, as specified in Rules 20.2, 20.3 or 20.4.
    
    
47. "Particulate Matter or Particulate Matter (PM10)" means particulate matter with an aerodynamic diameter less than or equal to a nominal 10 microns. For non-fugitive emissions, any applicable test method approved by the federal EPA, the state ARB and the Air Pollution Control Officer shall be used to measure PM10. The Air Pollution Control Officer may require the use of an applicable test method prior to final approval by EPA and ARB if the Officer determines that the method is consistent with these rules, or results in an improved measure of PM10 emissions, and has received written initial concurrence from ARB and EPA for use of the method.
    
    
48. "Permanent" means enforceable and which will exist for an unlimited period of time. For purposes of meeting the emission offset requirements of Rules 20.3 and 20.4, permanent means also federally enforceable.
    
    
49. "Portable Emission Unit" means an emission unit that is designed to be and capable of being carried or moved from one location to another. Indicia of portability include, but are not limited to, wheels, skids, carrying handles, dolly, trailer or platform. For the purposes of this regulation, dredge engines on a boat or barge are considered portable. An emission unit is not portable if any of the following apply:
    1. The unit, or its replacement, is attached to a foundation or, if not so attached, will reside at the same location for more than 12 consecutive months. Any portable emission unit such as a backup or standby unit that replaces a portable emission unit at a location and is intended to perform the same function as the unit being replaced will be included in calculating the consecutive time period. In that case, the cumulative time of all units, including the time between the removal of the original unit(s) and installation of the replacement unit(s), will be counted toward the consecutive time period; or
    2. The emission unit remains or will reside at a location for less than 12 con-secutive months if the unit is located at a seasonal source and operates during the full annual operating period of the seasonal source. A seasonal source is a stationary source that remains in a single location on a permanent basis (i.e., at least two years) and operates at that single location at least three months each year; or
    3. The emission unit is moved from one location to another in an attempt to circumvent the portable emission unit residence time requirements.
       
       
    Days when portable emission units are stored in a designated holding or storage area shall not be counted towards the above time limits, provided the emission unit was not operated on that calendar day except for maintenance and was in the designated holding or storage area the entire calendar day.
    
    Emission units which exceed the above time limits will be considered as relocated equipment and will be subject to the applicable requirements for relocated emission units contained in Rules 20.1, 20.2, and 20.3.
50. "Post-Project Potential to Emit" means an emission unit's potential to emit after issuance of an Authority to Construct for the proposed project, calculated pursuant to Section (d).
    
    
51. "Potential to Emit" means the maximum quantity of air contaminant emissions, including fugitive emissions, that an emission unit is capable of emitting or permitted to emit, calculated pursuant to Section (d).
    
    
52. "Precursor Air Contaminants" means any air contaminant which forms or contributes to the formation of a secondary air contaminant for which an ambient air quality standard exists. For purposes of this rule, the precursor relationships are listed in Table
    

    TABLE 20.1 - 9 Precursor Air Contaminants
    Precursor Air Contaminant	Secondary Air Contaminant
    NOx	NO2 PM10 Ozone
    VOC	PM10 Ozone
    SOx	SO2 PM10

53. "Pre-Project Actual Emissions" means an emission unit's actual emissions prior to issuance of an Authority to Construct for the proposed project, calculated pursuant to Section (d).
    
    
54. "Pre-Project Potential to Emit" means an emission unit's potential to emit prior to issuance of an Authority to Construct for proposed project, calculated pursuant to Section (d).
    
    
55. "Project" means an emission unit or aggregation of emission units for which an application or combination of applications for Authority to Construct or modified Permit to Operate is under District review.
    
    
56. "Proven in Field Application" means demonstrated in field application to be reliable, in continuous compliance and maintaining a stated emission level for a period of at least one year, as determined by the Air Pollution Control Officer.
    
    
57. "PSD Modification" means a contemporaneous emissions increase occurring at a modified PSD stationary source equal to or greater than the amounts listed in Table
    
    

    TABLE 20.1 - 10 PSD Modification
    Air Contaminant:	Emission Rate (Ton/yr)
    Particulate Matter (PM10)	15
    Oxides of Nitrogen (NOx)	40
    Volatile Organic Compounds (VOC)	40
    Oxides of Sulfur (SOx)	40
    Carbon Monoxide (CO)	100
    Lead and Lead Compounds(Pb)	0.6

58. "PSD Stationary Source or Prevention of Significant Deterioration Stationary Source" means any stationary source, as specified in Table 20.1 - 11, which has, or will have after issuance of a permit, an aggregate potential to emit one or more air contami-nants in amounts equal to or greater than any of the emission rates listed in Table 20.1 - 11.
    

    TABLE 20.1 - 11 PSD Stationary Sources and Trigger Levels
    For stationary sources consisting of: Fossil fuel fired steam electrical plants of more than 250 MM Btu/hr heat input Fossil fuel boilers or combinations thereof totaling more than 250 MM Btu/hr of heat input Municipal incinerators capable of charging more than 250 tons of refuse per day Petroleum storage and transfer units with a total storage capacity exceeding 300,000 barrels Charcoal production plants Chemical process plants Coal cleaning plants with thermal dryers Coke oven batteries Fuel conversion plants Furnace process carbon black plants Glass fiber processing plants Hydrofluoric acid plants Iron and steel mill plants Kraft pulp mills Lime plants Nitric acid plants Phosphate rock processing plants Petroleum refineries Primary aluminum ore reduction plants Primary copper smelters Primary lead smelters Primary zinc smelters Portland cement plants Secondary metal production plants Sintering plants Sulfuric acid plants Sulfur recovery plants Taconite ore processing plants
    The following emission rates:
    Air Contaminant	(Ton/yr)
    Particulate Matter (PM10)	100
    Oxides of Nitrogen (NOx)	100
    Volatile Organic Compounds (VOC)	100
    Oxides of Sulfur (SOx)	100
    Carbon Monoxide (CO)	100
    For all other stationary sources:
    Air Contaminant	(Ton/yr)
    Particulate Matter (PM10)	250
    Oxides of Nitrogen (NOx)	250
    Volatile Organic Compounds (VOC)	250
    Oxides of Sulfur (SOx)	250
    Carbon Monoxide (CO)	250

59. "Quantifiable" means that a reliable basis to estimate emission reductions in terms of both their amount and characteristics can be established, as determined by the Air Pollution Control Officer. Quantification may be based upon emission factors, stack tests, monitored values, operating rates and averaging times, process or production inputs, mass balances or other reasonable measurement or estimating practices.
    
    
60. "Real" means actually occurring and which will not be replaced, displaced or transferred to another emission unit at the same or other stationary source within San Diego County, as determined by the Air Pollution Control Officer.
    
    
61. "Reasonably Available Control Technology" or "RACT" means the lowest emission limit that a particular source is capable of meeting by the application of control technology that is reasonably available, as determined by the Air Pollution Control Officer pursuant to the federal Clean Air Act, considering technological and economic feasibility.
    
    
62. "Relocated Emission Unit" means a currently permitted emission unit or grouping of such units which is to be moved within San Diego County from one stationary source to another stationary source. The moving of a portable emission unit shall not be considered a relocated emission unit.
    
    
63. "Replacement Emission Unit" means an emission unit which supplants another emission unit where the replacement emission unit serves the same function and purpose as the emission unit being replaced, as determined by the Air Pollution Control Officer. Identical replacements as specified in Rule 11 shall not be considered to be a replacement emission unit.
    
    
64. "Secondary Emissions" means emissions which would occur as a result of the construction, operation or modification of a PSD stationary source, but which are not directly emitted from any emission unit at the stationary source. Except as provided below, secondary emissions exclude emissions which come directly from mobile sources, such as emissions from the tailpipe of a motor vehicle. Secondary emissions include, but are not limited to:
    1. Emissions from ships or trains coming to or from the stationary source, unless such emissions are regulated by Title II of the federal Clean Air Act, and
    2. Emission increases from any emission unit at a support facility not located at the stationary source, but which would not otherwise be constructed or increase emis-sions, and
    3. Emissions from any emission unit mounted on a ship, boat, barge, train, truck or trailer, where the operation of the emission unit is dependent upon, or affects the process or operation (including duration of operation) of any emission unit located on the stationary source.
       
       
65. "Significant Impact" means an increase in ambient air concentration, resulting from emission increases at a new or modified stationary source, equal to or greater than any of the levels listed in Tables 20.1 - 12 and 20.1 - 13:
    
    
66. "State Ambient Air Quality Standards (SAAQS)" means the maximum allowable ambient air concentrations for specified air contaminants and monitoring periods as established by the California ARB (see Table 20.1 - 7).
    

    TABLE 20.1 - 12 Stationary Sources Impacting Any Class I Area
    Air Contaminant	Significant Impact (24-hour Maximum)
    Particulate Matter (PM10)	1.0 µg/m3
    Nitrogen Dioxide (NO2)	1.0 µg/m3
    Sulfur Dioxide (SO2)	1.0 µg/m3
    Carbon Monoxide (CO)	1.0 µg/m3

    TABLE 20.1 - 13 Stationary Sources Impacting Any Class I Area
    Air Contaminant		Significant Impact (24-hour Maximum)
    Particulate Matter (PM10)
    	Annual arithmetic mean	1.0 µg/m3
    	24-hr. maximum	5.0 µg/m3
    Nitrogen Dioxide (NO2)
    	Annual arithmetic mean	1.0 µg/m3
    Sulfur Dioxide (SO2)
    	Annual arithmetic mean	1.0 µg/m3
    	24-hr. maximum	5.0 µg/m3
    Carbon Monoxide (CO)
    	8-hr. maximum	500.0 µg/m3
    	1-hr. maximum	2000.0 µg/m3

67. "Stationary Source" means an emission unit or aggregation of emission units which are located on the same or contiguous properties and which units are under common ownership or entitlement to use. Stationary sources also include those emission units or aggregation of emission units located in the California Coastal Waters.
    
    
68. "Surplus" means the same as defined in Rule 26.0.
    
    
69. "Temporary" means enforceable, existing and valid for a specified, limited period of time. For purposes of meeting the federal emission offset requirements of Rules 20.3 and 20.4, temporary means also federally enforceable.
    
    
70. "Volatile Organic Compound (VOC)" means any volatile compound contain-ing at least one atom of carbon excluding methane, carbon monoxide, carbon dioxide, carbonic acid, metallic carbides or carbonates, ammonium carbonates, and exempt com-pounds. Exempt compound means the same as defined in Rule 2.

(d) EMISSION CALCULATIONS

1. POTENTIAL TO EMIT
   The potential to emit of each air contaminant shall be calculated on an hourly, daily and yearly basis.
   1. Calculation of Potential to Emit
      Except as provided in Subsections (d)(1)(i)(A), (B), and (C), the potential to emit shall be calculated based on the maximum design capacity or other operating conditions which reflect the maximum potential emissions, including fugitive emissions.
      1. Permit Limitations Shall be Used
         If specific limiting conditions contained in an Authority to Construct or Permit to Operate restrict or will restrict emissions to a lower level, these limitations shall be used to calculate the potential to emit.
      2. Potential to Emit Shall Not Exceed Maximum Potential
         If specific conditions limiting a unit's pre-project potential to emit are not contained in an Authority to Construct or Permit to Operate, the pre-project potential to emit shall be limited to the emission unit's actual emissions or to a lower level of emissions, as the applicant and the Air Pollution Control Officer may agree, provided such limitation is enforceable through permit conditions and does not violate any District, state or federal law, rule, regulation, order or permit condition. The Air Pollution Control Officer may base the pre-project potential to emit on the highest level of emissions occurring during a one-year period within the five-year period preceding the receipt date of the application, provided that the emission level was not in excess of any District, state or federal law, rule, regulation, order or permit condition. If the potential to emit is being determined for purposes of calculating an actual emission reduction, the provisions of Subsection (d)(2) shall apply.
      3. Calculation of Pre-Project Potential to Emit for Emission Units Located at Major Stationary Sources
         If a new or modified emission unit is or will be located at a major stationary source, the pre-project potential to emit of the emission unit shall be calculated as follows. For purposes of determining the post-project aggregate potential to emit pursuant to Subsection (d)(1)(ii), these calculation procedures shall not apply to emission units not being modified and instead the procedures of Subsections (d)(1)(i)(A) and (B) shall apply.
         1. If an emission unit's pre-project actual emissions are less than 80 percent of the emission unit's potential to emit calculated pursuant to Subsections (d)(1)(i)(A) and (B), then the emission unit's pre-project potential to emit shall be the same as the unit's actual emissions.
         2. If an emission unit's pre-project actual emissions are equal to or greater than 80 percent of the emission unit's potential to emit calculated pursuant to Subsection (d)(1)(i)(A) and (B), then the emission unit's pre-project potential to emit shall be as calculated pursuant to Subsection (d)(1)(i)(A) and (B).
         If an Authority to Construct has previously been issued for an emission unit pursuant to New Source Review rules approved by EPA into the SIP for the District, and the previous emission increases that resulted from that emission unit were offset in accordance with the approved New Source Review rules in effect at that time, the emission unit's pre-project potential to emit shall be as calculated pursuant to Subsection (d)(1)(i)(A) and (B).
   2. Calculation of Aggregate Potential to Emit - Stationary Source
      Except as provided for below in Subsections (d)(1)(ii)(A), (B), and (C), the aggregate potential to emit of a stationary source shall be calculated as the sum of the post-project potential to emit of all emission units permitted for the stationary source, including emission units under District review for permit and those to which Subsection (b)(1) applies.
      
      
      1. Permit-Exempt Equipment
         The potential to emit of emission units exempt from permit requirements by Rule 11, and of emission units that are registered under District Rules 12 or 12.1 or an ARB registration program, shall not be included in the aggregate potential to emit of a stationary source except that emissions of any federal criteria air conta-minant or precursor from an emission unit shall be included if the actual emission of any such air contaminant or precursor from the unit, without consideration of any add-on emission control devices, equals or exceeds 5 pounds per day or 25 pounds per week.
         
         The applicant and the Air Pollution Control Officer may agree to place all permit-exempt and registered emission units which would be classified under the same class or category of source under permit for purposes of creating emission reduction credits (ERCs). In such case, the potential to emit ofsuch emission units shall be included in the stationary source's aggregate poten-tial to emit.
         
         
      2. Emergency Equipment
         The potential to emit from the operation of emergency equipment during emergency situations shall not be included in the calculation of a stationary source's aggregate potential to emit. The potential to emit from operation of emergency equipment during non-emergency situations shall only be included in the calculation of a stationary source's aggregate potential to emit if the actual emissions of any federal criteria air contaminant or precursor from the unit, with-out consideration of any add-on emission control devices, equals or exceeds 5 pounds per day or 25 pounds per week.
         
         
      3. Portable Emission Units
         Portable emission units shall be excluded from the calculation of a stationary source's aggregate potential to emit.
         
         
      4. Military Tactical Support Equipment Engines
         Emissions from portable engines, including gas turbines, used exclusively in conjunction with portable military tactical support equipment shall be excluded from the calculation of a stationary source's aggregate potential to emit.
         
         
2. ACTUAL EMISSIONS
   Actual emissions are calculated based on the actual operating history of the emission unit.
   1. Time Period for Calculation
      1. Actual emissions of an existing emission unit shall be calculated on an operating hour, day and year basis averaged over the most representative two consecutive years within the five years preceding the receipt date of an applica-tion, as determined by the Air Pollution Control Officer.
         
         
      2. For emission units which have not been operated for a consecutive two-year period which is representative of actual operations within the five years preceding the receipt date of the application, the calculation of actual emissions shall be based on the average of any two one-year operating periods determined by the Air Pollution Control Officer to be representative within that five-year period. If a representative two-year operating time period does not exist, the calculation of actual emissions shall be based on the average of the total operational time period within that five-year period.
         
         
   2. Time Periods Less Than Six Months - Potential to Emit: For determining potential to emit, actual emissions for emission units operated for a period less than six months shall be based on the longest operating time period dete-rmined by the Air Pollution Control Officer to be most representative of actual operations.
3. EMISSION INCREASE
   A project's or emission unit's emission increase shall be calculated as follows:
   1. New Emission Units
      Emission increases from a new project or emission unit shall be calculated by using the potential to emit for the project or emission unit.
      
      
   2. Modified Emission Units
      Emission increases from a modified project or emission unit shall be calculated as the project's or emission unit's post-project potential to emit minus the project's or emission unit's pre-project potential to emit.
      
      
   3. Relocated Emission Units
      Emission increases from a relocated project or emission unit shall be calculated as the project's or emission unit's post-project potential to emit minus the project's or emission unit's pre-project potential to emit.
      
      
   4. Replacement Emission Units
      Emission increases from a replacement project or emission unit shall be calculated as the replacement project's or emission unit's post-project potential to emit minus the existing project's or emission unit's pre-project potential to emit.
      
      
   5. Portable Emission Units
      Emission increases from a portable emission unit shall be calculated as the emission unit's post-project potential to emit minus the emission unit's pre-project potential to emit.
      
      
   6. Determining Emission Increases for AQIA Trigger Levels
      When calculating emission increases for purposes of comparing with the Air Quality Impact Analysis (AQIA) trigger levels of Rules 20.2 or 20.3, area fugitive emissions of particulate matter (PM10) shall be excluded from the pre-project potential to emit and the post-project potential to emit calculations, unless the Air Pollution Control Officer determines, on a case-by-case basis, that a project's area fugitive emissions of PM10 must be evaluated in order to protect public health and welfare.
      
      
4. EMISSION REDUCTION - POTENTIAL TO EMIT & ACTUAL EMISSION REDUCTION
   A project's or emission unit's emission reduction shall be calculated as follows:
   
   
   1. Reduction in the Potential to Emit
      1. Modified Emission Units: Reduction in the potential to emit for a modified project or emission unit shall be calculated as the project's or emission unit's pre-project potential to emit minus the project's or emission unit's post-project potential to emit.
      2. Relocated Emission Units: Reduction in the potential to emit for a relocated project or emission unit shall be calculated as the project's or emission unit's pre-project potential to emit minus the project's or emission unit's post-project potential to emit.
      3. Replacement Emission Units: Reduction in the potential to emit for a replacement project or emission unit shall be calculated as the existing project's or emission unit's pre-project potential to emit minus the replacement project's or emission unit's post-project potential to emit.
      4. Portable Emission Units: Reduction in the potential to emit for a portable emission unit shall be calcu-lated as the emission unit's pre-project potential to emit minus the emission unit's post-project potential to emit.
   2. Actual Emission Reduction: Notwithstanding any other provision of this rule, actual emissions calculated pur-suant to Subsection (d)(2) shall be used for purposes of determining an actual emission reduction in accordance with this Subsection (d)(4)(ii). An actual emission reduction must be real, surplus, enforceable, quantifiable and may be permanent or temporary in duration. A temporary actual emission reduction shall be identified as temporary and shall include a specific date beyond which the reductions are no longer valid.
      1. Shutdowns: Actual emission reductions from the shutdown of an emission unit shall be calculated based on the emission unit's pre-project actual emissions.
      2. Modified Emission Units: Actual emission reductions from a modified project or emission unit shall be calculated as the project's or emission unit's pre-project actual emissions minus the project's or emission unit's post-project potential to emit.
      3. Relocated Emission Units: Actual emission reductions from a relocated project or emission unit shall be calculated as the project's or emission unit's pre-project actual emissions minus the project's or emission unit's post-project potential to emit.
      4. Replacement Emission Units: Actual emission reductions from a replacement project or emission unit shall be calculated as the existing project's or emission unit's pre-project actual emis-sions minus the replacement project's or emission unit's post-project potential to emit.
      5. Portable Emission Units: Actual emission reductions from a portable emission unit shall be calculated as the emission unit's pre-project actual emissions minus the emission unit's post-project potential to emit.
   3. Adjustments For Determining Actual Emission Reductions
      The following adjustments shall be made in determining actual emission reductions:
      1. Units Permitted and Operated Less Than Two Years
         If an emission unit has been permitted and operated for a period less than two years, the emission unit's actual emissions (in tons per year) shall be calculated as the unit's actual emissions (in tons) that occurred during the actual operating time period times the actual operating time period in days divided by 1460 days.
         
         
      2. Adjustments for Rule Violations
         If an emission unit was operated in violation of any District, state or federal law, rule, regulation, order or permit condition during the period used to deter-mine actual emissions, the actual emissions shall be adjusted to reflect the level of emissions which would have occurred if the emission unit had not been in violation.
         
         
      3. Adjustments for Federal Reasonably Available Control Technology (RACT)
         Actual emission reductions shall exclude emission reductions which would have occurred had RACT requirements, determined by the Air Pollution Control Officer to meet the requirements of the 1990 federal Clean Air Act Amendments, been applied. This provision shall not apply to emission reductions from an emission unit which is exempt from permit requirements pursuant to Rule 11. However, at the time of use the emission reduction credits (ERCs) created from actual emission reductions from such an exempt emission unit shall be discounted by the emission reductions which would have occurred had RACT, determined by the Air Pollution Control Officer to meet the requirements of the federal Clean Air Act, been applied. A condition shall be included in the Emission Reduction Credit (ERC) Certificate for such an exempt emission unit requiring such discounting to occur at the time of use of the emission reduction credit.
         
         
5. EMISSION OFFSETS (Rev. Adopted 11/4/98; Effective 12/17/98)
   Emission offsets are actual emission reductions which are provided to mitigate emission increases. Emission offsets must meet the applicable criteria specified in Rules 20.1 and Rules 20.3 and 20.4.
   1. Emission offsets shall consist of actual emission reductions calculated in accordance with Subsection (d)(4)(ii) or shall be Class 'A' ERCs pursuant to Rules 26.0 through 26.10 or a mobile source ERC issued pursuant to Rule 27. In order to be considered an emission offset, actual emission reductions or ERCs must be valid for the life of the emission increase which they are offsetting.
   2. In order to qualify as an emission offset, actual emission reductions shall be banked pursuant to District Banking Rules 26.0 through 26.10 or Rule 27, unless the actual emission reductions are being proposed to offset emission increases occurring concurrently at the stationary source. In such a case, the Air Pollution Control Officer may choose to administratively forego the issuance of ERCs.
   3. Emission offsets shall be in effect and enforceable at the time of startup of the emission unit requiring the offsets. Emission offsets must be federally enforceable if the source is major for the pollutant for which offsets are being provided. If interpollutant offsets are being provided, the offsets must be federally enforceable if the pollutant they are offsetting is major.
   4. Emission offsets shall be provided on a ton per year basis.
   5. Emission offsets shall be located in San Diego County.

(e) OTHER PROVISIONS (Rev. Adopted 11/4/98; Effective 12/17/98)

1. CONTINUITY OF EXISTING PERMITS: All of the conditions contained in any Authority to Construct or Permit to Operate issued prior to December 17, 1998 shall remain valid and enforceable for the life of the Authority to Construct or Permit to Operate, unless specifically modified by the District.