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Standards." For purposes of clarity in the following discussion, it is convenient to use the term "exceedance" to describe a daily maximum hourly average ozone measurement that is greater than the level of the standard. Therefore, the phrase "expected number of days with maximum hourly average ozone concentrations above the level of the standard" may be simply stated as the “expected number of exceedances."

The basic principle in making this determination is relatively straightforward. Most of the complications that arise in determining the expected number of annual exceed ances relate to accounting for incomplete sampling. In general, the average number of exceedances per calendar year must be less than or equal to 1. In its simplest form, the number of exceedances at a monitoring site would be recorded for each calendar year and then averaged over the past 3 calendar years to determine if this average is less than or equal to 1. 2. Interpretation of Erpected Exceedances

The ozone standard states that the expected number of exceedances per year must be less than or equal to 1. The statistical term "expected number" is basically an arithmetic average. The following example explains what it would mean for an area to be in compliance with this type of standard. Suppose a monitoring station records a valid daily maximum hourly average ozone value for every day of the year during the past 3 years. At the end of each year, the number of days with maximum hourly concentrations above 0.12 ppm is determined and this number is averaged with the results of previous years. As long as this average remains "less than or equal to 1,” the area is in compliance. 3. Estimating the Number of Exceedances

for a Year

In general, a valid daily maximum hourly average value may not be available for each day of the year, and it will be necessary to account for these missing values when esti: mating the number of exceedances for a particular calendar year. The purpose of these computations is to determine if the expected number of exceedances per year is less than or equal to 1. Thus, if a site has two or more observed exceedances each year, the standard is not met and it is not necessary to use the procedures of this section to account for incomplete sampling.

The term "missing value" is used here in the general sense to describe all days that do not have an associated ozone measure. ment. In some cases, a measurement might actually have been missed but in other cases no measurement may have been scheduled for that day. A daily maximum ozone value is defined to be the highest hourly ozone value recorded for the day. This daily maxi.

mum value is considered to be valid if 75 percent of the hours from 9:01 a.m. to 9:00 p.m. (LST) were measured or if the highest hour is greater than the level of the standard.

In some areas, the seasonal pattern of ozone is so pronounced that entire months need not be sampled because it is extremely unlikely that the standard would be exceeded. Any such waiver of the ozone monitoring requirement would be handled under provisions of 40 CFR, Part 58. Some allowance should also be made for days for which valid daily maximum hourly values were not obtained but which would quite likely have been below the standard. Such an allowance introduces a complication in that it becomes necessary to define under what conditions a missing value may be assumed to have been less than the level of the standard. The following criterion may be used for ozone:

A missing daily maximum ozone value may be assumed to be less than the level of the standard if the valid daily maxima on both the preceding day and the following day do not exceed 75 percent of the level of the standard.

Let z denote the number of missing daily maximum values that may be assumed to be less than the standard. Then the following formula shall be used to estimate the expected number of exceedances for the year:

e=V+[(v/n)8(N-n-z)] (1)

(*Indicates multiplication.) where: e=the estimated number of exceedances

for the year, N=the number of required monitoring

days in the year, n=the number of valid daily maxima, V=the number of daily values above the

level of the standard, and 2=the number of days assumed to be less

than the standard level. This estimated number of exceedances shall be rounded to one decimal place (fractional parts equal to 0.05 round up).

It should be noted that N will be the total number of days in the year unless the appropriate Regional Administrator has granted a waiver under the provisions of 40 CFR Part 58.

The above equation may be interpreted intuitively in the following manner. The estimated number of exceedances is equal to the observed number of exceedances (v) plus an increment that accounts for incomplete sampling. There were (N-n) missing values for the year but a certain number of these, namely z, were assumed to be less than the standard. Therefore, (N-n-z) missing values are considered to include possible exceedances. The fraction of measured

Subpart D-Maintenance of National


values that are above the level of the standard is v/n. It is assumed that this same fraction applies to the (N-n-z) missing values and that (v/n)*(N-n-2) of these values would also have exceeded the level of the standard. (Secs. 109, 301 of the Clean Air Act, as amended (42 U.S.C. 7409, 7601)) (44 FR 8220, Feb. 8, 1979)

Sec. 51.40 Scope.



AQMA ANALYSIS 51.41 AQMA analysis: Submittal date. 51.42 AQMA analysis: Analysis period. 51.43 AQMA analysis: Guidelines. 51.44 AQMA analysis: Projection of emis

sions. 51.45 AQMA analysis: Allocation of emis

sions. 51.46 AQMA analysis: Projection of air

quality concentrations. 51.47 AQMA analysis: Description of data

sources. 51.48 AQMA analysis: Data bases. 51.49 AQMA analysis: Techniques descrip

tion. 51.50 AQMA analysis: Accuracy factors. 51.51 AQMA analysis: Submittal of calcula


Subpart A-General Provisions

Sec. 51.1 Definitions. 51.2 Stipulations. 51.3 Classification of regions. 51.4 Public hearings. 51.5 Submission of plans; preliminary

review of plans. 51.6 Revisions. 51.7 (Reserved) 51.8 Approval of plans.

Subpart B-Plan Content and Requirements

AQMA PLAN 51.52 AQMA plan: General. 51.53 AQMA plan: Demonstration of ade

quacy. 51.54 AQMA plan: Strategies. 51.55 AQMA plan: Legal authority. 51.56 AQMA plan: Future strategies. 51.57 AQMA plan: Future legal authority. 51.58 AQMA plan: Intergovernmental co

operation. 51.59 (Reserved) 51.60 AQMA plan: Resources. 51.61 AQMA plan: Submittal format. 51.62 AQMA analysis and plan: Data avail.

ability. 51.63 AQMA analysis and plan: Alternative


51.10 General requirements. 51.11 Legal authority. 51.12 Control strategy: General. 51.13 Control strategy: Sulfur oxides and

particulate matter. 51.14 Control strategy: Carbon monoxide,

hydrocarbons, ozone, and nitrogen diox

ide. 51.15 Compliance schedules. 51.16 Prevention of air pollution emergen

cy episodes. 51.17 (Reserved) 51.18 Review of new sources and modifica

tions. 51.19 Source surveillance. 51.20 Resources. 51.21 (Reserved) 51.22 Rules and regulations. 51.23 Exceptions. 51.24 Prevention of significant deteriora

tion of air quality.

Subpart E-Control Strategy: Lead 51.80 Demonstration of attainment. 51.81 Emissions data. 51.82 Air quality data. 51.83 Certain urbanized areas. 51.84 Areas around significant point

sources. 51.85 Other areas. 51.86 Data bases. 51.87 Measures. 51.88 Data availability.

Subpart C-Extensions

51.30 Request for 2-year extension. 51.31 Request for 18-month extension. 51.32 Request for 1-year postponement. 51.33 Hearings and appeals relating to re

quest for one year postponement. 51.34 Variances.

Subparts F-14[Reserved) Subpart J—Ambient Air Quality Surveillance 51.190 Ambient air quality monitoring re



Subparts K-L-[Reserved]

51.328 Plan prescribed actions. Subpart M-Intergovernmental Consultation




AVAILABLE TECHNOLOGY 11.240 General plan requirements.

APPENDIX C-MAJOR POLLUTANT SOURCES 11.241 Nonattainment areas for carbon


APP monoxide and ozone.




APPENDIX F-AREA SOURCE DATA 51.243 Consultation process objectives. APPENDIX G-(POLLUTANT) EMISSIONS INVEN51.244 Plan elements affected.

TORY SUMMARY, TONS/YR. (OR METRIC 51.245 Organizations and officials to be



APPENDIX H-AIR QUALITY DATA SUMMARY 51.247 Hearings on consultation process





CY EPISODES 51.248 Coordination with other programs. APPENDIX M-TRANSPORTATION CONTROL 51.249 (Reserved]

SUPPORTING DATA SUMMARY 51.250 Transmittal of information.

APPENDIX N-EMISSIONS REDUCTIONS 51.251 A-95 clearinghouse review.



Subpart N—[Reserved]


ING REQUIREMENTS Subpart 0–Miscellaneous Plan Content APPENDIX Q-(RESERVED) Requirements


QUALITY MAINTENANCE AREA PLANS FOR 51.285 Public notification.


---- FOR THE YEAR --Subpart P-Protection of Visibility

APPENDIX S-EMISSION OFFSET INTERPRETA51.300 Purpose and applicability.

TIVE RULING 51.301 Definitions.

APPENDIX T-[RESERVED] 51.302 Implementation control strategies.

APPENDIX U-CLEAN AIR AcT SECTION 174 51.303 Exemptions from control.

GUIDELINES 51.304 Identification of integral Vistas.

AUTHORITY: Sec. 301(a), Clean Air Act (42 51.305 Monitoring.

U.S.C. 1857(a)), as amended by sec. 15(c)(2), 51.306 Long-term strategy.

Pub. L. 91-604, 84 Stat. 1713, unless other51.307 New source review.

wise noted.

SOURCE: 36 FR 22398, Nov. 25, 1971, unless Subpart Q-Reports

otherwise noted. AIR QUALITY Data REPORTING

NOMENCLATURE CHANGES: 44 FR 8237, Feb. 51.320 Annual air quality data report.

8, 1979.

Subpart A-General Provisions 51.321 Annual source emissions and State

ind state


851.1 Definitions. action report. 51.322 Sources subject to emissions report As used in this part, all terms not deing.

fined herein shall have the meaning 51.323 Reportable emissions data and in

given them in the Act: formation.

(a) “Act" means the Clean Air Act 51.324 Progress in plan enforcement.

(42 U.S.C. 1857-18571, as amended by 51.325 Contingency plan actions. 51.326 Reportable revisions.

Pub. L. 91-604, 84 Stat. 1676). 51.327 Enforcement orders and other State (b) "Administrator" means the Adactions.

ministrator of the Environmental Pro

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tection Agency (EPA) or his author (2) For lead, any stationary source ized representative.

the actual emissions of which are in (c) "Primary standard” means a na- excess of 4.54 metric tons (5 tons) per tional primary ambient air quality year of lead or lead compounds meas. standard promulgated pursuant to sec. ured as elemental lead. tion 109 of the Act.

(1) “Area source" means any small (d) "Secondary standard” means a residential, governmental, institutionnational secondary ambient air quality al, commercial, or industrial fuel com standard promulgated pursuant to sec bustion operations: Onsite solid waste tion 109 of the Act.

disposal facility; motor vehicles, air(e) “National standard” means craft, vessels, or other transportation either a primary or a secondary stand facilities; or other miscellaneous ard.

sources such as those listed in Appen(f) “Owner or operator" means any dix D to this part, as identified person who owns, leases, operates, con through inventory techniques similar trols, or supervises a facility, building, to those described in: “A Rapid Survey structure, or installation which direct Technique for Estimating Community ly or indirectly results or may result in Air Pollution Emissions," Public emissions of any air pollutant for Health Service Publication No. 999which a national standard is in effect. AP-29, October 1966.

(g) "Local agency" means any local (m) “Region" means (1) an air qualgovernment agency, other than the ity control region designated by the State agency, which is charged with Secretary of Health, Education, and the responsibility for carrying out a Welfare or the Administrator, (2) any portion of a plan.

area designated by a State agency as (h) “Regional Office" means one of an air quality control region and apthe ten (10) EPA Regional Offices. proved by the Administrator, or (3)

(i) “State agency” means the air pol any area of a State not designated as lution control agency primarily re an air quality control region under sponsible for development and imple paragraph (m) (1) or (2) of this secmentation of a plan under the Act. tion.

(j) “Local agency” means any air (n) “Control strategy" means a compollution control agency other than a bination of measures designated to State agency, which is charged with achieve the aggregate reduction of responsibility for carrying out a por emissions necessary for attainment tion of a plan.

and maintenance of a national stand(k) “Point source" means the follow ard, including, but not limited to,

measures such as: (1) For particulate matter, sulfur (1) Emission limitations. oxides, carbon monoxide, hydrocar (2) Federal or State emission charges bons, and nitrogen dioxide

or taxes or other economic incentives (i) Any stationary source the actual or disincentives. emissions of which are in excess of (3) Closing or relocation of residen90.7 metric tons (100 tons) per year of tial, commercial, or industrial facilithe pollutant in a region containing an ties. area whose 1970 "urban place" popula- (4) Changes in schedules or methods tion, as defined by the U.S. Bureau of of operation of commercial or industri. the Census, was equal to or greater al facilities or transportation systems, than 1 million;

including, but not limited to, short(ii) Any stationary source the actual term changes made in accordance with emissions of which are in excess of standby plans. 22.7 metric tons (25 tons) per year of (5) Periodic inspection and testing of the pollutant in a region containing an motor vehicle emission control sysarea whose 1970 “urban place" popula- tems, at such time as the Administration, as defined by the U.S. Bureau of tor determines that such programs are the Census was less than 1 million; or feasible and practicable.

(iii) Without regard to amount of (6) Emission control measures appliemissions, stationary sources such as cable to in-use motor vehicles, includthose listed in Appendix C to this part. ing, but not limited to, measures such


as mandatory maintenance, installa- (1) Date of submittal of the source's tion of emission control devices, and final control plan to the appropriate conversion to gaseous fuels.

air pollution control agency; (7) Measures to reduce motor vehicle (2) Date by which contracts for traffic, including, but not limited to, emission control systems or process measures such as commuter taxes, gas

modifications will be awarded; or date oline rationing; parking restrictions, or

by which orders will be issued for the staggered working hours.

purchase of component parts to ac(8) Expansion or promotion of the

complish emission control or process use of mass transportation facilities


(3) Date of initiation of on-site conthrough measures such as increases in

struction or installation of emission the frequency, convenience, and pas

control equipment or process change; senger-carrying capacity of mass

(4) Date by which on-site constructransportation systems or providing

tion or installation of emission control for special bus lanes on major streets

equipment or process modification is and highways.

to be completed; and (9) Any land use or transportation

(5) Date by which final compliance control measures not specifically de- is to be achieved. lineated herein.

(r) “Transportation control meas(10) Any variation of, or alternative ure” means any measure, such as reto, any measure delineated herein. ducing vehicle use, changing traffic

(11) Control or prohibition of a fuel flow patterns, decreasing emissions or fuel additive used in motor vehicles, from individual motor vehicles, or alif such control or prohibition is neces- tering existing modal split patterns sary to achieve a national primary or that is directed toward reducing emissecondary air quality standard and is sions of air pollutants from transporapproved by the Administrator under tation sources. section 211(c)(4)(C) of the Act.

(s) “Vehicle trip" means any move(0) "Reasonably available control ment of a motor vehicle from one locatechnology" means devices, systems,

tion to another that results in the process modifications, or other appa

emission of air pollutants by the ratus or techniques, the application of

motor vehicle. which will permit attainment of the

(t) "Trip type" means any class of emission limitations set forth in Ap

vehicle trips possessing one or more pendix B to this part, provided that

characteristics (e.g., work, nonwork; Appendix B to this part is not intend

peak, off-peak; freeway, nonfreeway) ed, and shall not be construed, to re.

that distinguish vehicle trips in the

class from vehicle trips not in the quire or encourage State agencies to adopt such emission limitations with

class. out due consideration of (1) the neces

(u) “Vehicle type" means any class sity of imposing such emission limita

of motor vehicles (e.g., precontrolled,

heavy duty vehicles, gasoline powered tions in order to attain and maintain a

trucks) whose emissions characterisnational standard, (2) the social and

tics are significantly different from economic impact of such emission limi.

the emissions characteristics of motor tations, and (3) alternative means of

vehicles not in the class. providing for attainment and mainte

(V) "Traffic flow measure" means nance of such national standard.

any measure, such as signal light syn(p) “Compliance schedule" means

chronization, freeway metering and the date or dates by which a source or

curbside parking restrictions, that is category of sources is required to taken for the purpose of improving comply with specific emission limita- the flow of traffic and thereby reductions contained in an implementation ing emissions of air pollutants from plan and with any increments of prog- motor vehicles. ress toward such compliance.

(w) “Roadway type" means any class (q) "Increments of progress" means of roadway facility that can be broadly steps toward compliance which will be categorized as to function and astaken by a specific source, including: signed average speed and capacity

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