United States Office of Air Quality EPA-450/4-86-007 Environmental Protection Planning and Standards July 1986 Agency Research Triangle Park NC 27711 + Air

>W , 

# EPA Guideline on the

ldentificatiori and Use of Air Qijality

Data Affected by Exceptional Eventsa

DISCLAIMER
This report has been reviewed by the Office of Air Quality Planning and Standards, Environmental Protection Agency, and approved for publication. Mention of trade names or commercial products is not intended to constitute endorsement or recommendation for use. CM

n

## EPA-450/4-86-007



# Guideline on the Identification and Use of Air QLiality Data Affected by Exceptional Events ~



# ri

U.S. ENVIRONMENTAL PROTECTION AGENCY Office of Air and Radiation Office of Air Quality Planning and Standards Monitoring and Data Analysis Division Research Triangle Park, NC 27711

July 1986~



### CONTENTS r

1. INTRODUCTION

. . . . . . . . . . .. . . . . . . . . . . . . . 1



### 2. PURPOSE AND MANAGEMENT OF FLAGGING SYSTEM . . . . . . . . . . 5 2.1 Pre-Ai rs . . . . . . . . . . . . . . . . . . . . . . . . 5 2.2 Post-Ai rs . . . . . . . . . . . . . . . . . . . . . . . 6

3. USES OF FLAGGED DATA . . . . . . .. . . . . . . . . . . . . . 8 

### .3.1 General Guidelines on the Use of Flagged Data ..... 8 3.2 NAAQS Status . . . . . . . . .. . . . . . . . . . . . . . 9 

### 3.3 Trends Analysis . . . . . . . . . . . . . . . . . . . . 10 

### 3.4 SIP Regulatory Activities . . . . . . . . . . . . . . . 11

4. DEFINITION AND APPLICATION OF EXCEPTIONAL EVENTS ...... 12 4.1 Definitions of Exceptional Events . .
. . . . . . . 12 4.1.1 General Exceptional Event Criteria . . . . . . . 13 4.1.2 Specific Definitions . . . . . . . . . . . . . . 

### 14 4.2 Demonstration of Causai Relation . . . . . . . . . . . . 24 4.3 Application of Definitions and/or Criteria ....... 25 4.4 Documentation . . . . . . . „ . . . . . . . . . . . . . 

### 26

APPENDIX . . . . . . . . . . . . . . . . . .. . . . . . . . . . . . . . 

### 28 Development of Criteria for Possible Exceptional Events I. Identification of Events . . . ,. . . . . . . . . . . . . . 

### 28
II. Events Not Considered Exceptional for Data Flagging Purposes . . . . . . . . . . . . . . . . .... . . . . . . . 

### 31 s REFERENCES . . . . . . . . . . . . . . . ,; . . . . . . . . . . . . . 

### 34

iia .Xa

SECTION 1

INTRODUCTION
Federal, State, and local air pollution control officials have expressed a great deal of concern rega'rding the handling of air quality data that are influenced by both natural and man-made event:s that are considered exceptional. These events are considered exceptional for two reasons; they are not expected to recur routinely at a given location, or thiay are possibly uncontrollable or unrealistic to control through the State Implementation • Plan (SIP) process. In some cases in the past, air quality data collected during these "exceptional" events have not been submitted to the National Air Data Bank (NADB) because State or local agencies were concerned about 'the potential misuse of such data. This guideline document was prepared as a response to this concern and is intended to provide national guidance for identifying ("flagging") and using ambient air quality data influenced by except l ional events. The guidance includes definitions of 18 acceptable exceptional events and describes the procedures for submitting f'lagged data influenced`by these events to EPA's Aerometric Information Retrieval System (AIRS). The Appendix provides information on other events which were also initially proposed for consideration as "exceptional" but are not included in the final flagging system. The need for a flagging (or "identification") system was implied in previous Agency guidelines and regulations. 'The first example is Office of Air Quality Planning and Standards' Guideline No. 1.2-008 (revised February

~ 1977) entitled, "Guidelines for the Interpretation of Air Quality Standards." 1

1 ■At

This guideline addressed the submission and use of

- all valid air quality data for determining an area's overall compliance status with respect to National

~ Ambient Air Quality Standards (NAAQS). Issue 9 in the guideline posed the following question: "How should particulate matter (PM), carbon monoxide (CO), and other pollutant concentrations resulting from severe recurring dust storms, forest fires, volcanic activity, and other natural sources be taken into account in determining compliance with NAAQS?" The guideline recommended,

" ° Regardless of the source, ambient pollutant concentrations exceeding a NAAQS constitute a violation." The guideline, however, implied a need for data flagging by further stating, "Detailed information establishing that viola- , tions are due to uncontrollable natural sources may be used in determining the feasibility of modifying control strategies." The second example is in 40 CFR 51.12 (d), the regulations for the development, adoption, and submittal of SIP's. 2 The regulations stated: "For purposes of developing a control strategy, data derived from measurements of existing ambient levels of a pollutant may be adjusted to reflect the extent to which occasional natural or accidental phenomena, e.g., dust storms, forest fires, industrial accidents, demonstrably affected such ambient levels during the measurement period." A third example is provided in the March 20, 1984, 40 CFR Part 50Federal Register proposed revisions to the national ambient air qual,ity standards for particulate matter. 3 Appendix K of Part 50 would allow consideration of the influence of rare or unusual events on PM10 data by various techniques.



## Pa

### A11 three examples, OAQPS 1.2-008, 4.0 CF'R 51.12(d), and the proposed

A 

### 40 CFR 50 Appendix K reflect concern that sonie air quality data associated

, with the occurrence of certain types of event':s may require special consideration in order to avoid misuse. The guideiine's general policy is to alliow consideration of excluding flagged data from use in regulatory actions. The actual exclusion of the use of flagged data would only be allowed if, as a result of a public review process, the responsible government agency e„g., the State Air Agency during the State regulatory process, and the U. S. EPA during the Federal review/ approval process, determines that the data are inappropriate for use in a specific regulatory activity. This consider<ition for exclusion of flagged data carries with it no prior presumption towards use or non-use of flagged data. By establishing uniform procedures and criteria for flagging and determining the use of data associated with exceptional events, EPA expects data collectors to submit to the NADB

- aII va'lid ambient air quality data, i.e., data collected in accordance with 40 CFR 58. Having a complete national air q-uality data file will provide a data base adequate to evaluate and substantiate the impact of exceptional events on air quality and to assist users in interpreting the data. The guideline provides criteria and procedures by which potential users of air quality data can be informed of "excelitional events" which may have influenced the data. The guideline has no riegulatory or legal significance regarding use of any air quality data. Use or non-use of air quality data, whether flagged or not, must be subjected to full public disclosure and rulemaking procedures.

3The criteria for identification of "exceptional events" are designed to

be expansive enough to encompass most good faith claims by State and local agencies of when data should be considered for special treatment. It is not intended to reflect EPA's views on the validity of these claims. The flagging of data is merely a way for a State or local agency to state that it regards the data as influenced by exceptional events, and may later claim that the data should be discounted for certain purposes. As experience with this guideli-ne is gained, periodic revisions may be made. The guideline is to be implemented on a trial basis for approximately 2 years, after which the Standing Air Monitoring Work Group (SAMWG) will assess its effectiveness and make any appropriate recommeridations for revision. The SAMWG is composed of Federal, State, and local air pollution control officials who constitute a forum for discussion and resolution of ambient air quality monitoring issues. A

9SECTION 2
PURPOSE AND MANAGEMENT OF THE FLAGGING SYSTEM
The basic purpose of the flagging system is to identify those air quality measurements that are influenced by exceptional events. These are events which, if unidentified, could lead to possible misinterpretation or misuse of the data. Because the fiagging system relies heavily on the identification and understanding of events that may have influenced a particuiar air quality measurement, its major thrust is information ,exchange. If a particular air quality measurement is influenced by an exceptional event, it is important for all those who may review and ultimately use the data to be aware of this influence and to take care that such data are not misinterpreted or misused. Knowledge and understanding of what the data represent are critical in the overall air quality planning process. Under the flagging system, State and local air poliution control agencies will be responsible 

### for initially identifying and documenting data influencedby exceptional events. These agencies also must develop the appropriate background information used to support the decision to flag an individual piece of data; they must submit the information to EPA for concurrence and make it available for the public°s review upon request. Because of the potential implications on the use of flagged data, the agency flagging the data must (as discussed in Section 4.2) clearly demonst;rate a causality between the exceptionai event and the flagged air quality l data.

2.1 PRE-AIRS PROCEDURES

- Until the Aerometric Information Retrieval System (AIRS) is operational,

the flagged data should be specifically identified and discussed in the

5 1annual State and Local Air Monitoring System (SLAMS) Report. The EPA Regional



### Offices will be responsible for review and concurrence or non-concurrence with the flag, except for data related to stratospheric ozone intrusions which will be reviewed and concurred or non-concurred with by OAQPS. States should initiate discussions with EPA Regional Offices regarding data that may be flagged as soon as possible after data collection, and should not wait until 

### the annual SLAMS Report is submitted.

2.2 POST-AIRS PROCEDURES After AIRS is operational, all flagged data will be entered and storeci in the AIRS; and as data are retrieved, a user will be able to identify those data that have been flagged. Each exceptional event will be assigned a unique flag code by the AIRS for the exceptional events included in this guideline. The procedure for submitting, reviewing, and assigning appropr

- iate flags for data identtified by State or local agencies to be associated with an exceptional event are as follows: (1) The State or local agency should submit their flagged data with the proper unique flag code to AIRS as part of their routine data submissions i:o EPA's data bank. (2) The State or local agency should provide to the Regional Office, within 30 days, appropriate documentation and demonstration of causality as 

### discussed in Section 4.4. (3) The Regional Office should concur or non-concur with the data flagand notify the State or local agency within 30 days of receipt of documentation from the agency. If the Regional Office concurs with the flagging of , the data, they will change the unique flag code associated with the data to

~a

designate EPA Regional Office concurrence wi

- th the flag. If the Region non-

• concurs with the data.flag, the State or local agency flag will remain in

AIRS with the particular data point. The non-concurrence by the Regional . Office could be revised upon subsequent submission of adequate justification by the State and local agency. The exception to the procedure is stratospheric ozone intrusion, which is to be reviewed and acted upon by OAQPS rather than the Regional Office. (4) Those States electing to submit to;NADB only an annual SLAMS report rather than raw data should include a section in their annual report which lists all flagged data, SAROAD I.D., date of occurrence, and type of acceptable exceptional event. Notification must be sent to AIRS and the Regional Office by the responsible State or local agency when flaggEad data are to be changed to a nonflagged status for any reason. Two data records will be maintained in AIRS. One record will contain all the data including the flagged data, and,the other will contain only data that have not been flagged. A11 users of the data will have access to both records, including the rationale for the flag and the EPA Regional Office concurrence or non-concurrence with ttie flag.

7, ,.1

### SECTION 3 USES OF FLAGGED DATA

3.1 GENERAL GUIDELINES ON THE USE OF FLAGGED DATA Concern over the potential for misuse h'as made some State and local agencies reluctant to submit air quality data that were influenced by what they consider to be an exceptional event, i.e., an event that is not expected to recur routinely at a given location, or that is possibly uncontrollable or unrealistic to control through the State Implementation Plan (SIP) process. The views of Federal,

- State, and local agency officials have varied concerning the use of air quality data collected during,an exceptional event. Some believed that air quality data collected during an exceptional event shouldnot be used under any circumstances; some believed that all valid (i.e., collected in accordance with 40 CFR 58) data shiiuld be 

### used (without exception); 

### some believed that the data should be used oiily to determine the status of the area with respect to the NAAQS; and stil'I others believed that the data not only should be used to determine the compliance status of the area, butalso to develop trends analyses and control <,;trategies (with some qualifications). This document addresses these differ°ences by requiring the States (and EPA) to identify and explain the use or non-use of data influenced by exceptional events during a public review prcicess. Furthermore, the guidance provided does not dictate any prior presumption toward use or non-use for any specific purpose.

v 

### In general, decisions on the use or non=.use of flagged data will be made

.. , .

t 

### on a case-by-case basis for specific purposes; (attainment designations, control

strategies, etc.), and the public rnust be inf

- ormed that the data exist, whether

Nthe data are used or not. The main concern lies with understanding what the

flagged data represent. Three steps usually should be taken in order to decide whether questionable data should be flagged, and to assist potentia1users in determining how the data should be used. The first step is to determine the portion of the measured air quality level attributable to the sinc3le event, as well as the cumulative effect of several similar exceptional everits, that create substantial impacts at a monitoring site. In some cases, mode1ing (either source apportionment or dispersion) or other procedures may be used to determine the relative contribution of the event. The relative contribution of the event provides a better understanding of what the air quality level for the day or days in question actually represents. The second step is to determine the area influenced by the event. Inmost cases, the impact will be limited. Therefore, if the data are being c:onsidered for use in or exclusion from regulatory purposes, the agency should determine the area which would be influenced by the determination. The third step is to demonstrate how the flagged data relate to data previously collected at the monitoring site. This step is extremely critical for trends analyses and for preparing reports to the public on air quality levels for a given area. Obviously, if flagged data are used or excluded

- in preparing summaries of air quality data, the reader should be made aware of how the data were used.

3.2 

### NAAQS Status NAAQS compliance status involves the use of data to determine whether the • area represented by the data is meeting or exceeding the NAAQS for the pol1utant being monitored. It is EPA's policy and a regulatory requirement to have valid '

9NAMS and SLAMS data (i.e., data collected in'accordance with 40 CFR 58)

. submitted to the NADB or included in the annual SLAMS report. A11 data,

~ flagged or unflagged, should be avaiiable to the public for comparison to the

NAAQS to determine if exceedances have occurired. A11 relevant flagged data along with the reasons for flagging, and a diemonstration of causality betweenthe exceptional event and the flagged data, shall be submitted for consideration of use/non-use during any public hearin ~~ or comment period called under Sections 107, 110-113, 119, 120, 122, 123, 126, Part C or Part D of the Clean Air Act. 4 Consideration of ambient air qua'lity data during public reviews called under the authority of other sections or titles of the Clean Air Act, although not prohibited, does not appear to be relevant to the purpose of those reviews. For example, consideration of ambii

~ nt data at a hearing held regarding automotive emissions standards may or may noi: be appropriate. Such consideration is neither mandator.y nor prohibited.
3.3 Trends Analysis Trends analysis involves the evaluation of 'the long-term trends associated with the measured levels of a given pollutani: for a given area. These analysesare useful in evaluating the overall progress of the air pollution control program for the given pollutant and in understariding why the concentration levels of a pollutant are increasing or decreasing. In some cases the data collected during'an exceptional event can be used for trends analysis (as long as the analyst understands the limitations

, associated with the data). The trends analyses should clearly state how the

flagged data were treated and to what extent the flagged data were or were ` not included in the analyses and why. The tr•ends analyses also should consider

10(to the extent possible) what effect the flagged data have on the overall

trend line for the area in light of other confounding variables that may also affect the trend line. 9
3.4 

### SIP Regulatory Activities The use of flagged air quality.data for SIP regulatory activities (areawide or local control strategy development, SIP design values, attain-• ment/non-attainment status, enforcement actions, etc.) shall be considered ona case-by-case basis and discussed during the public review process. Excliasion of the flagged data would only be allowed if the responsible control agency determines in conjunction with a public review that the flagged data are inappropriate for use.

0

11

### SECTION 4 DEFINITION AND APPLICATION OF EXCEPTIONAL EVENTS
4.1 DEFINITIONS OF EXCEPTIONAL EVENTS This guideline provides general definit'ions for these events and general criteria for their use in flagging air qualii:y data. The application of a definition may vary frorn area to area because of differing air quality and. control situations. For example, salting anci sanding of streets for snow and ice control rnay be an exceptional event in ttie southern sections of the country, whereas they may be routine, controllable events in the northern sections. Therefore, the following definitions are only a na

- tional guide and are not meant to replace reasonable judgment on theFiart o

- P the Regional, State, and local air pollution control agency officials in defining and identifying exceptional events for the purpose of flaggirig data. In situations where it can be shown that: the national criteria are generally inappropriate, a State Agency may propose alternate criteria to their EPA Regional office. These proposals would hiave to be subjected to public review within the State. The Regional office would be responsible for review and preliminary approval of the alternative criteria. The OAQPS wili have final approval authority and if approved, will include the alternative criteria as a supplement to this national giaideline. With the above limitations in mind, the following general definitions have been developed to promote consistency with respect to flagging data that havebeen collected during an exceptional event. Whenever possible, specific criteria or terms have been used to define the event to minimize inconsistent interpretations. Of course, no term can be absolutely defined so that there is

12no room for interpretation. Thus, these definitions and associated criteria

provide for some flexibility in their application to an individual event. a What may be unusual or exceptional for one part of the country may be typical for another and this variability requires flexibility in national definitions ` and criteria. The definitions that follow have in some cases specific numbers included within the definition. Although they are not fully supported by technicalstudies, they are included as a practical alternative to deleting weakly supported values and, to the extent possible, reflect the comments received during development of this guideline. These numbers rnay require adjustments as experience is obtained with the guideline.

4.1.1 

### General Exceptional Event Criteria Before one can define an individual exceptional event, one must have a general definition of "exceptional." In a sense, this definition also serves as an overriding criterion with regard to the specific definitions presented in 4.1.2. Webster defines "exceptional" as forming an exception, rare, uncommon,extraordinary, deviating from the norm. With respect to air quality considerations in this guideline, an exceptional event is defined as an event that isnot expected to recur routinely at a given location, or that is possibly uncontrollable or unrealistic to control through the SIP process. As noted previously, what is exceptional in one area of the country may not be ex :eptional in another. Therefore, some judgment is needed in identifying whether an event is exceptional in the area of the country where it has occurred.

13. 4.1.2 

### Specific Definitions

The following definitions are provided'for the purpose of identifying an exceptional event. Some additional discussion is provided in each case to aid in the application of these definitions.


### HIGH WINDS (PM) Definition: An hourly windspeed of greater than or equal to 30 mph or gusts equal to or greater than 40 mph, with no precipitation 5 , 6 or only a trace of precipitation (observed as scattered drops that do not completeiy wet or cover an exposed area up to a rate of 0.01 inch/hr. 7 ). , The high wind condition with no precipi'tation or only light precipitation and dry soil must be associated with a significant contribution (estimated to be > 85% by weight) of crustal material on the PM sampling medium. High winds without unusually high PM levels due to the.'suspension or resuspension of crustal material should not be considered an'.exceptional event. Additionally, fugitive emissions or dust from any part of an industrial source should not be fl agged.


### STRATOSPHERIC OZONE INTRUSION (03) Definition: A stratospheric ozone intrusion occurs when a parcel of air originating in the stratosphere, ayerage height 20 km (12.4 mi), 8 is entrained directly to the surface of the earth. ` Although this event is exceptional, the circumstances or the criteria

under which it occurs are difficult to measure or document given current

L4measured meteorological parameters. Stratospheric ozone intrusions are

infrequent and very localized events of short duration, which makes it difficult to use currently available airport data to determine whether a str<ito- ^ spheric ozone intrusion has occurred. Stratospheric ozone intrusions are typically associated with strong frontal passages or severe thunderstorms and, thus, may occur primarily during the spring of the year. The above defin
- ition is provided only as a general guide for differentiating between stratospheric ozone intrusion, which is an exceptional event for the purpose of flagging data, and other nonexceptional meteorological events. Although data have been identified in the past as being the result of stratospheric ozone intrusion, no standard definition or criteria have been established for concrete identi

- Fication. Therefore, determining whether a stratospheric ozone intrusion has occurred should be a case-by-case decision based on reasonable judgment regarding the season of the year, time of day, and accompanying meteorological conditions associated with the ozone measurement in question. The EPA concurrence or non-concurrence authority for flagging of ozone data for stratospheric in

- trusion is the responsibility of OAQPS upon review of the documentation submitted by the State or local agency flagging the ozone data.


### VOLCANIC ERUPTIONS (CO 3 S02., NOp, PM) Definition: The emission or ejection of volcanic materials at the Earth's surface from a crater or fissure. 9 Emissions from volcanic eruptions have a large-scale areawide impact on air quality. Excessive air quality concentrations resulting from volcanic eruptions should be flagged regardless of the frequency of eruptions. In most

15!



### ' cases, however, the eruptions and resulting impact on air quality would be

very infrequent. SANDBLASTING (PM) 

### Definition: Sandblasting or gritblasting refeirs to the temporary use of abrasive blasting with pressurizeci air for surface preparation purposes at a given location. Methods currently available are used tci control these operations to minimize their impact on air quality at fixed point sources where routine applications are part of the facilities' operations. Ambient air quality levels influenced by these activities shoulci not be fiagged. However, completely effective controi techniques are not necessarily available 

## or possible for portable sandblasting operatioris. Therefore, data collected at a site within a micro or middle scale distance from a temporary (generally 3 weeks or less) sandblasting operation may be flagged if all reasonable control measures have been employed to minimize adve!rse impacts on air quality. FOREST FIRES (CO 3 PM) 

### Definition: An uncontrolled fire in vegetation or associated flammable material that requires suppressive action to protect natural resources or values associated with natural resources or that is destructive to } natural resources. 10

[E.,

### Class Size, acres Class Size, acres

A <0.25 D 100 - 299
B 0.26 - 9 E 300 - 999 C 10 - 99 F 1000 - 4999 G >5000
Some forest fires are unpreventable and because uncontrollable emissions from Forest fire can adversely affect air quality concentrations ov.er a large area, forest fires should be considered an exceptional event for the purpose of flagging air quality data. In general, Class A and B fires tend to have a morz loca1ized impact; therefore, only data collected at downwind monitors within 3 miles of these type fires should be flagged. For Classes C through G, the impact of the fire is more widespread and the location with resppct to the monitor should be supported by receptor 11 , 12 , 13 , 14 or dispersion modeling. 15 , 16


### STRUCTURAL FIRES (CO 3 PM) Definition: Any accidental fire involving some kind of structure. In
' general, a structural fire involves a building having at least 600 square feet. The structural fire should be within a micro- or middle-scale distarrce (up to 500 meters as defined by 40 CFR 58, Appendix D) of a monitor in most instances for the data from that monitor to be flagged. However, a much greater distance may be appropriate for large fires such as a refinery, industrial, or commercial business area fire provided the causal relation is supported by receptor or dispersion modeling.

17

## HIGH POLLEN COUNT (PM) k Definition: A pollen count index above 25 grains/cm 2 or 1000 grains per 1

~ cubic meter. 17

The pollen count index is usually obtained by use of a coated slide mounted on a circular plate that is generally mounted on the top of a seven or eight-story building with an unobstructed'air flow. The index is in units of grains of pollen per cm. 2 Another method,of ineasuring the concentration of pollen is volumetric, i.e., counting the riumber of grains per cubic meter. Other recoqnized methods for measuring polleri levels may be used. For a high-pollen count to be flagged as an exceptional event, the pollen countindex should be greater than 25, or 1000 grains per cubic meter and the highvolume filters on which the samples were collected should be analyzed micro-

, scopically to ensure that significant amounts. of pollen (i.e., 50% or greater than the normal pollen count for a typical sa:mple) were collected on the day or days being considered for flagging. Where high pollen is considered to be a problem, State or local agencies should develop procedures for ascribing the effects of high pollen count on filters and should submit them to the respective Regional Office for approval.


### CHEMICAL SPILLS AND INDUSTRIAL ACCIDENTS (CO 3 S02, NO2, PM) Definition: Emissions that result from accident`s such as fire, explosions, power outages, train derailment, vehicular accidents, or combinations of these. 18 The spill or accident must, of course, n6t be a routine occurrence. Any of these situations that do occur routinely should be critically evaluated and

18stopped. Data from sites that can be unequivocally related to a non-rout'ine

accident or spill may be flagged. ' 

## UNUSUAL TRAFFIC CONGESTION (CO) Definition: A condition resulting frorn a major accident (rather than frequent minor accidents,) or short-duration obstruction, such as demolition or construction. During these conditions the level of traffic may increase until it exceeds the maximum capacity of a given street or highway. Speeds are reduced substantially and stoppages may occur for short or long periods 

### of time because of downstream congestion. In extreme cases, both speed and volume can drop to zero. 19 As a general rule of thumb, congestion must occur'within five hundred meters of a monitoring site (i.e., micro- to middle-scale) and not be a regular occurrence for the data from that site to be flagged. 

## CONSTRUCTION/DEMOLITION (PM) Definition: The building/destroying/renovation of any residential, institutional, commercial, or industrial building (including apartment buildings with more than four dwelling units), structure, facility, or installation that lasts for only a short period of time.and is reasonably controlled. The construction or demolition activity must take place within a reasonable • distance of the monitoring site and all reasonable control measures must be

19in use before the data from the site can be flagged. Flagged data should be

limited to sites classified as micro- or middie-scale (up to 500m) and downwind
' with respect to the construction activity.



### AGRICULTURAL TILLING (PM) Definition: The act of preparing dry soil for cultivation or for controlling the growth of weeds by the use of inechanical devices during periods with an hourly average windspeed of greater than 20 mph. Generally, agricultural tilling operat

- ions must occur within a reasonable distance (500 meters) of the monitoring sitE ~ and tilling must have occurred at the same relative location while the hourly average windspeed is greater than 20 mph for the monitoring data to be flaggeci. Flagged data must have been collected during or immediately after-the d<iy tilling occurred and should be limited to sites which would be classified <is micro- or middle-scale with respect to the tilling operations. 

### HIGHWAY CONSTRUCTION (PM) Oefinition: The act of building a new, or repairing an existing, highway, road or street. Particulate matter resulting from reascinably controlled highway construction for short time periods may be f'lagged provided that a microscopic r. analysis of the filter indicates that 85 per-cent of material on the filter is

~ related to construction activities and all reasonable control measures have

been utilized. . ~



### 20 m

### REROUTING OF TRAFFIC (CO)

Definition: A temporary deviation or detour of vehicular traffic A because of an accident, construction, or demolition. The detour must be for no more than 1 week. The rerouting of traffic should be within a reasonable distance of a monitoring site and last for no more than 1 week for the monitoring data

- to be flagged. Flagged data should be limited to sites classified as micro- or middle-scale (within 500 meters) with respect to the detour. 

### SALTING/SANDING OF STREETS (PM) Definition: The application of salt and/or sand to the road surface to increase traction and/or prevent the surface water from refreezing after it has melted. The salting and sanding must occur within a reasonable distance (up to 500 meters) of the monitoring site if the data from the site are to be flagged. Flagged data should be limited to sites classified as inicro- or middle-scale with respect to the salting/sanding operations and microscopic examination shows that 85 percent of the ► naterial on the filter is salt and/or sand. Data collection is not limited to the date of salting or sanding of the street. A11 reasonable control measures must be taken to minimize the adverse air quality impact of the salting or sanding operations in order for the data to be flagged. In general this type of data should not be flagged in areas , which experience a significant use of salt and/or sand.

21i



### . 

## INFREQUENT LARGE GATHERINGS (CO 3 PM)

Definition: A gathering of more than 10,000 people (5000 cars) at any one time and at a single iocation. Unusual traffic congestion must be associated with the event. A large gathering in and of itself wit'out the associated traffic congestion would not qualify as an unusual e!vent i`or the purpose of flagging.(See discussion of unusual traffic congestion for more details on the criteria for flagging data because of unusual traffic congestion). The event would also be expected to occur less than once per year, and the event should be at a location not regularly used for such purposes. Flagged data should be limited to sites classified as micro- or middle-scale with respec.t 'to the gathering.


### ROOFING OPERATIONS (PM, S02) Definition: The process of building, repairing, or recoating the external upper covering of a house or building that involves the application of a petroleum-based materia] (usually heavy residuals from a refining operation) to a roof. The material is heated and then sprayed or rolled onto the surf ace. Generally, a roof so covered wouldbe resurf aced or treated no more than once every 3 to 5 years. Uniess major damage has occurred, some surfaces would r

~ 

### equire treatment oniy every



### „ 5 to 10 years.

22Roofing operations must occur within a micro-scale distance and upwind

of the monitoring site, and all reasonable control measures must be applied . for the data to be flagged. 

### PRESCRIBED BURNING (PM, CO) Definition: A controlled fire of vegetative material that is used to improve range lands, agricultural or forestry resources, or associated values. Prescribed burning is generally a controlled activity that is 9imited to those days or periods when the meteorological conditions are conducive to good dispersion. Thus, the emissions which affect air quality are dispersed to the extent possible. However, the resulting emissions occasionally adversely affect air quality concentrations over a large area. In areas of the country-where prescribed burning is used regularly and extensively for agricultural and/orforestry land management, prescribed burning may not be considered an exceptional event for the'purposes of flagging air quality data. Prescribed burning in these areas is usually subject to rules and regulations, inclucling smoke management plans, under which a regulatory agency permits burning ai'ter deciding where, and to what extent, the smoke will be allowed to impact air quality. However, in many areas of the country, prescribed burning for agricultural, forestry land management, or other purposes is an infrequent but necessaryactivity and may be iinpractical to fully control. These practices may be conri sidered an exceptional event for the purposes of flagging air quality dat<i.

23However., it must be demonstrated through reci'2ptor or dispersion modeling, A that the burning operations have a substantial impact on the monitored air

quality data. 

## CLEAN UP ACTIVITIES AFTER A MAJOR DISASTER (PM, CO, SO?)
Definition: 

### For the purposes of flagging, majoi ~ 

### disasters are serious public misfortunes for which Statelor Federal relief has been granted. PM, CO 3 S02 or other pollutant data affected by and collected during, or for a reasonable period after, the clean up <ictivities following a major disaster may be flagged.


## 4.2 DEMONSTRATION OF CAUSAL RELATION Excluding the use of valid air quality clata from regulatory purposes is a serious action. Accordingly, a clear•demonstration of the relationship between the exceptional event and the measurEtd air quality must be provided. As a minimum, this demonstration should: (a) inciude all relevant raw data (e.g., air quality data, meteorological data„ traf

- Fic counts, etc.); (b) show that the monitor did not record high concentrations before and after the

~ period of the exceptional event; (c) show th<<t the local wind direction was such that the monitored pollutant was transpcirted from the exceptional event

### source to - tiie" moni tor duri ng the peri od i n questi on'; ( d) i nci ude as appropriate receptor 11 , 12 , 13 , 14 or dispersion mode;ling 15 , 16 connecting the monitored

> concentrations with the exceptional source erriissions; (e) include, as appropriate, microscopic filter analyses (for part,iculate emissions); and (f)
Y include documentation supporting the existence of the exceptional event.

~

24

~t

~ ~ !



### 4.3 APPLICATION OF DEFINITIONS AND/OR CRITERIA



### ._ As noted earlier, the purpose of this guideline is to provide guidance and direction for flagging air quality data associated with exceptional I events and thus promote national consistency in the flagging of such data. Having established general definitions for the exceptional events arid the criteria for applying flags to the data, the State or local agency should consider flagging of any data meeting the criteria of this guideline and prepare adequate evidence to clearly demonstrate the causal relationship between the exceptional event and the flagged data. The flagged data with adequate documentation of the causal relationship should be submitted to the appropriate Regional Office following the procedures outlined in Sections 2.1 and 2.2. The Regional Office, after review, should notify the State or local agency of any disagreements, their reasons for disagreeing, and seelc to resolve the conflict. Following their•determination (concurrence or non-concurrerice), the Regional Offices should notify AIRS and the State or local agency of their action so that the appropriate notation may be made to the AIRS data*base 

### and/or the Annual SLAMS Report. The only exception to this policy is the flagging of stratospheric olone intrusion. 3ecause of the technical complexity of determining stratospher•ic ozone intrusion, OAQPS will, upon request by the State or local agency tnrough th°e°Regional Office, either concur or non-concur based on documentation submitted by the requestor. The criteria (definitions) presented in this guideline will serve as the

1 

### basis for reviewing determinations associated with exceptional events. If a State or local agency chooses to apply criteria that are less stringent than

~ 

### those contained in the guideline, such recommendation should be subjected

25~

to public review. The recommendation, aloncj with the summary of comments,

should then be submitted to the respective F;egional Office for review and
' approval. OAQPS will have final approval auithority and, if approval is granted,

wili include the alternative criteria in a supplement to this national guideline.

4.4 DOCUMENTATION A11 decisions regarding the flagging of` data because of exceptional events must be documented so that the EPA and the public can review these decisions. The documentation may take sever-al forms. It may include reports from the National Weather Service; a copy of' a newspaper clipping or news report indicating that a chemical spill or i,ndustrial accident has occurred; a report from the local health department on the pollen count for a given day,supported by fiiter analyses; special reports prepared by the State or a consultant; or special statistical analyses of 'the air quality data and other key parameters associated with the event. The actual form of the documentation depends on the event and the extent of publicly available reports or documents that would support the determination of its',occurrence. As appropriate, theState or local agency is encouraged to rely on available reports and documentation. When such documentat7on is not available 9 the State or local agency must prepare the necessary material sufficient (see Section 4.2) to support its decision regarding the flagged data. The State or local agency should retain' copies of the necessary supporting materiai or documentation in its offices for review upon request. Copies of this material will have to be available in the record during the public review process and must be provided to EPA for concurrence. It is not intended that a public review process (comment period or public hearing) be conducted



### 26

### solely for the purpose of determining whether data should or should not be

,



### . flagged. Instead, the public review process referred to in this guide1ine refers to the public review process which is otherwise required for regulatory
. actions taken in accordance with the Clean Air Act. Although the main purpose of the documentation is to support the decision to flag a given piece of data, it also provides air quality analysts with background and supporting information regarding the events associated with the-data on which the analyst can rely if and when the data are needed to make a particular air quality decision. Theair quality analyst will also be aware of any limitations that should be considered in the use of such data.

.

~ f

27

### APPENDIX DEVELOPMENT OF CRITERIA FOR EXCEPTIONAL EVENTS
The purpose of this appendix is to summ

~ 

### irize the development history of this guide1ine and to assist users in understanding the information contained herein. The Standing Air Monitoring Work Group I;SAMWG) first addressed the issue of exceptional values and data flagging in DE

, ~ 

### cember 1981. Subsequent to that time, SAMWG solicited input from EPA Regiona'I Offices and State and local agencies to identify those exceptional events, that could have any adverse effect on air quality values measured during their otcurrence. The SAMWG also solicited input on how air quality measured during the exceptional event should be flagged. An initial list of possible excESptional events was compiled based on comments by selected,Regional Offices and State and local agencies for further consideration.

I. IDENTIFICATION OF EVENTS In general, the events given further coiisideration were grouped into three major categories: (1) natural events (meteor°ological and other natural events), (2) unintentional anthropogenic events, and (3) intentional anthropogeriic events. The events within each major category were as follows: 1. Natural Events (a) Meteorological Events o Sustained high windspeeds (PM) 

### o Stagnations/inversions (all pollutants) ` o Unusual lack of precipitation (PM) o Stratospheric ozone intrusion (03) x

:.' ~ • ' ~

(b) Other Natural Events o Volcanic eruption (CO 3 S02, PM)
. o Forest fires (CO 3 PM)

., o High pollen count (PM) 2. Unintentional Anthropogenic Events o Large accidental structural fires (CO 3 PM) o Major traffic congestion due to accident or nonrecurring obstruction (CO) o Chemical spills (S02, NO2, PM, CO) o Industrial accidents (S02, NO2, PM, CO) 3. Intentional Anthropogenic Events o Short-term construction/demolition (PM) o Sandblasting (PM) o High-sulfur oil refining (S02Y o Roofing operations (PM, S02) p Salting or sanding of streets (PM) o Infrequent large gatherings (PM, CO) o Soot blowing from ships (PM) o Agricultural tilling (PM) o Prescribed burning (CO 3 PM) o Noncompliance--point source (CO 3 S02, NO2, PM) Those whose comments and suggestions were solicited generally agreed thatnatural events, other than meteorological events, and unintentional anthropogenic events are, by their very nature, exceptional events. The control of , emissions from such events is usually not included in the general control

, strategy for a given pollutant, although it is sometimes handled as part of an

29~ s

a

' emergency response action immediately after the event has occurred to minimize

possible adverse health impacts on local res

- idents. Reasonable precautions would not guarantee against recurrence or that the air quality would not be 

### affected by these events in the future. Some disagreement was expressed with regard to intentional anthropogenic events. Some argued that these events occur routinely and the data therefore should not be flagged. Others argued that, although intentional anthropogenic events occur routinely, they are exceptional with respect to normal activities around a particular monitoring site. Still t,3thers argued that intentional anthropogenic events can and should be controlled; they f urther argued that, unless these events or activities occur within the immediate vici

- nity of a monitoring site, they should not be considered as exceptional and the data collected during their occurrenceshould not be flagged. Finally, some strong disagreement was expressed with respect to two meteorological events--stagnations and inversions. Many argue that these two events routinely occur. They further argue 'that because these events are climatological factors rather than exceptional events, pollutant levels measured during their occurrence should not be flagged. The list of suggested exceptional events was reviewed and evaluated to determine whether each of the events listed shouid be considered exceptional and whether other events should be added. The review indicated that this list was comprehensive and that no additional events should be considered at this time.
T Af ter considerable discussion over an extended period of time, a general

consensus was reached that 15 of the events ;initially considered for designation
V did generally satisfy the criteria for defining an exceptional event. Six of

the events initially considered {implementing transportation controls,



### 3014



### stagnation/inversions, high-sulfur oil refining, sootblowing from ships, noncompliance--local sources, and unusual lack of precipitation) however, were ' finally rejected. The rationale for rejecting these events is summarized t 

### below.
II. EVENTS NOT CONSIDERED EXCEPTIONAL FOR DATA FLAGGING PURPOSES 1. Implementing Transportation Controls Transportation control measures are not considered exceptional, and clata collected during the implementation of transportation controls should not beflagged. If, however, traffic must be temporarily rerouted during the implementation of the transportation control measures or some congestion occurs due to initial startup of the transportation plan, the data collected at monitors near the rerouted traffic or congestion may be flagged. 2. Stagnations/Tnversions Stagnations and inversions are frequent climatological occurrerices that mtjst be considered in evaluating whether a control program is adequate to attain and maintain the NAAQS. An inversion is said to occur at a point, or through a layer, where temperature increases with increasing height. 20 , 21 Surface-based inversions are those that extend vertically from the surface to some altitude aloft. One study found that surface-based inversions generally occur about 32 percent of the time. 22They are usually short-lived and disperse shortly after sunrise. Because inversions are expected to occur frequent1y and are part of weather patterns, they are not considered exceptional events 'for the purpose of flagging data. Stagnation episodes are periods of 4 or more days with surface wind speeds of generally 4 m/sec or less and no precipitation or frontal passage. In some "

31~ 

# •

parts of the United States stagnations usuallly persist for an extended period

of time, and they can affect an entire air Eiasin5 therefore, they are not generally considered exceptional for the purpose of flagging data. 

### 3. Pligh-Sulfu r Oil Refining High-sulf ur oil refining refers to the,process of refining crud e oil with a sulfur content that is 20 percent or greater than the design capacity of the refining operation. Because this is a common practice at many refineries, and procedures and control methods are used to minimize S02 emissions, it is not considered to be an exceptional event for the purpose 

### of fl aggi ng data. 4. Sootblowing from Ships Sootblowing f rom ships is a method in which air is used to remove deposits that may build up on the walls of the vessel's boiler tubes. This is a common practice that is either controlled or limited (in many areas of the country) by establishing opacity limits. Betause these activities are common and steps can be taken to minimize associated emissions, sootblowing f rom ships (like general sootblowing from utility and industrial boilers) is not considered an exceptional event for the purpose of flagging data. 

### 5. Noncompliance--Local Sources Limited noncompliance of local sources (:an be expected from time to time as a result of process upsets or malfunction

- ing control equipment. These 

### events are usual ly classified as "upsets" or, "malfunctions" as defined by

, the applicable State or local agency regulations, or they may be considered

a violation of applicable emission or opacity limits. If these events are caused by upsets or malfunctions, they shoulcl be so noted and reported to the appropriate control agency. If they constitute a violation, the appropriate


### 32~



### legal remedies will be taken. If legal action is taken, the air quality da.ta collected in the vicinity of the source will in all likelihood be used in the 

### legal proceedings, and any appropriate limitations associated with the data

~ . 

### would be reviewed and evaluated as part of the legal process. Because data collected during noncompliance conditions have special uses and the source is required to notify the State of the upset or malfunction, noncompliance of local sources is not considered an exceptional event for the purpose of flagging data. 6. Unusual Lack of Precipitation Lack of precipitation in and of itself would not be considered an exceptional event because it has very little impact on PM air quality leve'Is. Lack of precipitation or drought conditions combined with high winds, however,would be considered an exceptional event. Therefore, unusual lack of precipitation is not considered an exceptional event for the purpose of flagging 

## data.

3

33

### REFERENCES

1. "Guideline for Interpretation of Air Quality Standards," U. S. Environmental Protection Agency, Office of Air Quality Planning and Standards, Research Triangle Park, N.C. OAQPS No. 1.2-008 (revised February 1977). 2. 40 CFR 51.12d, Code of Federal Regulations, July 1, 1984. 3. Federal Register, Vol. 49, March 20, 1984 pp. 10433-10435. 4. Clean Air Act as amended August 1977. 5. Byers, H. R. Generai Meteorology. McGr!aw Hill, New York, New York, 1974. 6. Anthes, R. A., et al. The Atmosphere. Charles E. Merril Publishing Co., Coiumbus, Ohio, 1975. 7. Federal Meteorological Handbook No. 1, Surface Observations. Washington, D.C. 1976. 8. Dorn, W. L. Meteorology. Third edition. McGraw Hill, New York, New York, 1965. j 9. Bates,• R. L..., and J. A. Jackson. Glossary of Geology. Second edition. American Geological Institute, Fall-s Church, Virginia, 1980. 10. Personal Communication with Linda Farnsworth of the USDA Forest Service, Aviation and Fire Management Division, Fire Department, November 1983. 11. Receptor Model Technical Series, Volume I, Overview of Receptor Model Application to Particulate Source Apportionment, U.S. Environmental Protection Agency, Office of Air Quality Planning and St andards, Research Triangle Park, N C. EPA Publication No. EPA-450/4-81-016a. July 1981. 12. Receptor Model Technical Series, Volume II, Chemical Mass Balance, U.S.Environmental Protection Agency, Office of Air Quaiity Plannirig and Standards, Research Triangle Park, N C. EPA Publication No. EPA-450/4-81-016b. July 1981. 13. Receptor Model Technical Series, Volume III, User's Manual for Chernical Mass Balance Model, U.S. Environmental Protection Agency, Office of AirQuality Planning and Standards, Research Triangle Park, N C. EPA Publication No. EPA-450/4-83-014. July 1983.

, 14. Receptor Model Technical Series, Volume :[V, Sunmary of Particle Identification Techniques, U.S. Environmental Protection Agency, Office of Air Quality Planning and Standards, Research Triangle Park, N C. EPA Publica-

. 

### tion No. EPA-450/4-83-018. June 1983.

34

### 15. Guideline on Air Quality Models. OAQPS, U.S. Environmental Protection

Agency, Research Triangle Park, N C. EPA Publication No. EPA-450/2-78- 027 (NTIS PB 288-783). April 1978, or subsequent revisions. ' 16. Regional Workshops on Air Quality Modeling: A Summary Report, U.S. Environmental Protection Agency, Office of Air Quality Planning and " Standards, Research Triangle Park, N C. EPA Publication No. EPA-450/4- 82-015, (NTIS PB 83-150573), April 1981. (NTIS documents include 1982 and 1983 addendums) 17. Air Pollution Aspects of Aeroallergens (Pollens). National Air Pollution Control Administration Consumer Protection and Environmental Health Services, Department of Health, Education, and Welf are, September 1969. 18. Sonti, R. S. Practical Design and Operation of Vapor-Depressuring Systems. Chemical Engineering, 91(2):66, January 23, 1984. 19. An Introduction to Highway Transportation Engineering. Institute of Traffic Engineering, 1978. 20. McIntosh, D. H. Meteorological Glossary. Chemical Publishing, New York, 1972. 21. Huschke, R. E. Glossary of Meteorology. American Meteorological Society, 1959. 22. Geiger, R. The Climate Near the Ground. Harvard University Press. 1966.

r



### 35s `

TECHNICAL REPORIr DATA .0 (Please read lnstructfons on the reverse bejore completing) 1. REPORT NO. 2. 3. RECIPIENT'S ACCESSION NO. 

### EPA 450/4-86-007 4. TITLE AND SUBTITLE 

### Guideline on the Identification and Use of Air Qtiality 5. REPORT DATE July 1906 

### Data Affected by Exceptional Events 6.PERFORNNNG ORGANIZATION CODE

7. AUTHOR(S) S. PERFORMING ORGANIZATION REPORT NO. 

### EPA 450/4-36-007 9. PERFORMING ORGANIZATION NAME AND ADDRESS 10. PROGRAM ELEMENT NO. 

### U.S. Environmental Protection Agency Monitoring and Data Analysis DlvlSlon 11.CONTRACT/GRANT NO. 

### Monitoring and Reports Eranch Monitoring Section, RTP, iJC 27711
12. SPONSORING AGENCY NAME AND ADDRESS 13. TYPE OF REPORT AND PERIOD COVERED 

### Technical guideiine Same as 9. 14. SPONSORING AGENCY CODE

15. SUPPLEMENTARY NOTES

16. ABSTRACT 

### This guideline is intended to provide information to•State and iocal air pollution control agencies concerning the flagging of air quality data affected by exceptional events. The guidance defines exceptional events, establishes unifo.rm criteria and procedures for flagging air quality data, and provides a mechanism for allowing consideration of excludirng flagged data.

17. KEY WORDS AND DOC-UMEN'T ANALYSIS --- a. DESCRIPTORS b.IDENTIFIERS/OPEN ENDED TERMS C. COSATI E • ield/GtOup 

### Exceptional events Data flag Air quality data Excluding flagged data

18. DISTRIBUTION STATEMENT 19. SECURITY CLASS (TItlsReport) 21. NO. OF PAGES 

### Unlimited Unc'lassified 20. SECIJFIITY CLASS (This page) 22. PRICE 

### Unc• lassif 

### ied EPA Form 2220-1 (Rav. 4-77) PREVIOUS EDITtON 15 OBSOLETE' i