Ambient Air Quality Surveillance Siting Criteria for Open Path Analyzers

Federal RegisterAug 18, 1994

Ask Donna

What actually matters in this document.

Text

ENVIRONMENTAL PROTECTION AGENCY

40 CFR Part 58

[FRL-4842-4]

Ambient Air Quality Surveillance Siting Criteria for Open Path

Analyzers

AGENCY: Environmental Protection Agency (EPA).

ACTION: Proposed rule.

-----------------------------------------------------------------------

SUMMARY: The EPA proposes to amend provisions of part 58 of chapter I

of title 40 of the Code of Federal Regulations to define the

appropriate ambient air monitoring criteria for open path (long-path)

analyzers. The proposed revisions to the Ambient Air Quality

Surveillance regulations would define the siting requirements for open

path analyzers used as State and Local Air Monitoring Stations (SLAMS),

which includes both National Air Monitoring Stations (NAMS) and

Photochemical Assessment Monitoring Stations (PAMS), as well as the

quality assurance procedures for this technology. These changes will

allow the ambient air monitoring community to effectively use open path

monitoring data for regulatory purposes.

DATES: Comments must be received on or before September 19, 1994.

Requests for public hearing must be received by September 2, 1994. If a

hearing is held, comments must be received on or before 30 days from

the conclusion of the hearing.

ADDRESSES: Comments should be submitted (in duplicate, if possible) to:

Air Docket (LE-131), Attention: Docket Number A-93-44, U.S.

Environmental Protection Agency, room M-1500, 401 M Street, SW.,

Washington, DC 20460.

Public hearing: A public hearing will be held, if requested, in

accordance with information provided in the DATES section of this

proposal, to provide interested parties an opportunity for oral

presentation of data, views, or arguments concerning the proposed

revisions. If anyone contacts EPA requesting a public hearing, it will

be held at the EPA's Environmental Research Center, Research Triangle

Park, North Carolina. Persons interested in attending the hearing or

wishing to present oral testimony should notify Ms. Lee Ann B. Byrd,

Monitoring and Reports Branch (MD-14), U.S. Environmental Protection

Agency, Research Triangle Park, North Carolina 27711, telephone number

(919) 541- 5367. Specific dates and other pertinent details of this

public hearing will be published in a separate Federal Register notice.

Docket: Docket Number A-93-44, containing supporting information

used in developing these revised regulations, is available for public

inspection and copying between 8:30 a.m. and 12 noon, and between 1:30

p.m. and 3:30 p.m., Monday through Friday, at EPA's Air Docket Section

at the address noted above. As provided in 40 CFR Part 2, a reasonable

fee may be charged for copying.

FOR FURTHER INFORMATION CONTACT: Ms. Lee Ann B. Byrd at telephone (919)

541-5367 concerning this action. The address is Monitoring and Reports

Branch (MD-14), U.S. Environmental Protection Agency, Research Triangle

Park, North Carolina 27711.

SUPPLEMENTARY INFORMATION:

Table of Contents

I. Authority

II. Background of Proposed Rule

III. Discussion of Proposed Revisions to Regulation

A. Section 58.1 Definitions

B. Appendix A--Quality Assurance Requirements for State and

Local Air Monitoring Stations (SLAMS)

C. Appendix B--Quality Assurance Requirements for Prevention of

Significant Deterioration (PSD) Air Monitoring

D. Appendix E--Probe and Path Siting Criteria for Ambient Air

Quality Monitoring

IV. Comments and the Public Docket

V. Administrative Requirements

A. Administrative Designation.

B. Reporting and Recordkeeping Requirements

C. Regulatory Flexibility Act

I. Authority

Authority: sections 110, 301(a), 313, and 319 of the Clean Air

Act as amended 42 U.S.C. 7410, 7601(a), 7613, 7619.

II. Background of Proposed Rule

The Clean Air Act, as amended in 1990, requires, in sections

181(b)(2), 185A, and 186(b)(2)(A), ambient air quality monitoring for

purposes of defining areas of nonattainment with the National Ambient

Air Quality Standards (NAAQS), evaluating progress toward achievement

of the NAAQS pursuant to State implementation plans (SIP's), and

reporting air quality data to the EPA to document the status and trends

of the Nation's air quality. These are nontrivial activities, and to

achieve the aforementioned objectives, the EPA must ensure that the

ambient air monitoring networks consist of high quality instruments

that produce accurate concentration measurements. As new monitoring

techniques are developed, the EPA evaluates the new methodology and, as

appropriate, determines how to effectively incorporate it into the

existing air quality monitoring program. To assess new ambient air

monitoring instruments for those pollutants with established NAAQS, the

EPA currently uses the Ambient Air Monitoring Reference and Equivalent

Method regulatory procedures detailed in title 40, chapter 1, part 53.

The EPA does not formally regulate the performance testing of ambient

air monitoring instruments, which measure pollutants without

established NAAQS. Methodology for collected ozone (O3) precursor

data (specified in the Photochemical Assessment Monitoring program as

volatile organic compounds and oxides of nitrogen) is reviewed in the

``Technical Assistance Document for Sampling and Analysis of Ozone

Precursors,'' and any subsequent revisions, EPA/600-8-91/215, October

1991. Supplementing the part 53 performance requirements and the

aforementioned ``Technical Assistance Document,'' the part 58 Ambient

Air Quality Surveillance regulation specifies how to most appropriately

conduct routine ambient air monitoring through pollutant-specific

monitor siting criteria, operation schedules, monitoring network

design, and data reporting. Under the part 58 provisions, each SLAMS

must employ reference or equivalent methods, as determined according to

part 53, and meet all applicable siting requirements as contained in

part 58, before its data can be used for regulatory purposes.

Specifically, these regulatory actions include comparison with the

NAAQS and other SIP-related activities. It is important to note that

the NAMS and the PAMS are subsets of the SLAMS networks; therefore,

provisions for the SLAMS also apply to both the NAMS and PAMS, as

included in this proposal.

A new technique for monitoring pollutants in ambient air has been

developed and introduced to the EPA. Instruments based on this new

technique, called open path (or long-path) analyzers, use ultraviolet,

visible, or infrared light to measure nitrogen dioxide (NO2),

O3, carbon monoxide (CO), sulfur dioxide (SO2), and other

gaseous pollutant concentrations over a path of several meters up to

several kilometers. The concentration measurements obtained by these

open path analyzers are path-integrated, or path-averaged, values.

Traditional fixed point analyzers measure pollutant concentrations at

one specific point by extracting an air sample from the atmosphere

through an inlet probe. A list of all EPA-approved reference and

equivalent ambient air monitoring methods is available through the

docket. Due to the fundamental difference in the measurement principles

of open path and point analyzers, there may be trade-offs in using each

type of instrument for certain applications. Because of the ability of

open path analyzers to measure pollutant concentrations over a path,

these new techniques are expected to provide better spatial coverage,

and thereby a better assessment of a general population's exposure to

air pollutants for certain applications. However, due to this same

path-averaging characteristic, open path analyzers could underestimate

high pollutant concentrations at specific points within the measurement

path for other ambient air monitoring situations. The applicability of

either technique to a particular monitoring scenario is dependent on a

number of factors including plume dispersion characteristics,

monitoring location, pollutant of interest, population density, site

topography, and monitoring objective. The EPA has considered these

factors in evaluating the advantages and disadvantages of using open

path analyzers for the various ambient air monitoring applications

detailed in 40 CFR part 58. Additionally, several studies of the

comparability of data collected with point and open path analyzers have

been conducted by the EPA and by other organizations. The most recent

EPA study of these two methodologies was completed during the summer of

1993 in Baytown, Texas. Results from this study and others are

available in the docket for public review. The EPA solicits comment on

these studies and on the comparability of using path-averaged and point

measurements in the Nation's ambient air monitoring programs.

The EPA is currently assessing the performance of an open path

analyzer as a candidate method under part 53 to determine if it should

be designated as an equivalent method for one or more of those

pollutants. In parallel with this effort, the EPA has developed the

appropriate part 58 siting and quality assurance criteria for open path

analyzers, which are contained in this proposal.

The existing part 58 monitoring network design criteria define the

monitoring objectives for a particular site in terms of measurement

scale. More specifically, each ambient air monitoring station is

located in such a way that it represents a particular air parcel or

volume. The regulation uses six measurement scales to describe the size

of these air parcels. These six scales are: microscale (dimensions of

several meters to approximately 100 meters), middle scale (100 to 500

meters), neighborhood scale (500 meters to 4 kilometers), urban scale

(4 to 50 kilometers), regional scale (tens to hundreds of kilometers),

and national or global scales. (National and global scales are

generally not applicable for a single air monitoring station. National

and global averages are more appropriately determined by networks of

various monitoring stations.) Within each of these measurement scales,

it is assumed that the pollutant concentrations are relatively

homogeneous; therefore, a monitor placed at any point in the area,

within the tolerances of this siting regulation, measures a

concentration representative of that area.

Depending on the objective for a particular SLAMS, each pollutant

can be monitored on a particular measurement scale as defined in Table

5 of appendix D in part 58. The applicability of the first five scales

to monitoring the four pollutants referenced in this proposal, CO,

NO2, O3, and SO2, follows:

Summary of Spatial Scales for Selected SLAMS

------------------------------------------------------------------------

Ozone

Measurement Scale CO NO2 O3 SO2 precursors\1\

------------------------------------------------------------------------

Micro-....................... Yes.. No... No... No... No.

scale........................

Middle scale................. Yes.. Yes.. Yes.. Yes.. No.

Neighborhood scale........... Yes.. Yes.. Yes.. Yes.. Yes.

Urban scale.................. No... Yes.. Yes.. Yes.. Yes.

Regional..................... No... No... Yes.. Yes.. No.

------------------------------------------------------------------------

\1\Ozone precursors, as defined in the PAMS program, include volatile

organic compounds, oxides of nitrogen, and selected carbonyls.

Existing regulations in part 58 state that the pollutant

concentration within a particular measurement scale is nearly

homogeneous, and that a point measurement collected in this same scale

generally represents any other point within that scale. This basic

provision defines how ambient air monitoring data can be used to

represent the air quality in a neighborhood, city, or other geographic

region. Based on these current provisions, it is reasonable to accept

that a path-averaged measurement taken within the dimensions and other

siting specifications of that measurement scale would provide a value

descriptive of that same geographic region. In order to maintain data

comparability between open path and point analyzers, the revisions

contained in this proposal are based on the siting criteria currently

being used with conventional fixed point ambient air monitoring

networks. The most obvious difference between the proposed and existing

siting criteria is that the new requirements are defined in terms of a

``probe'' (applicable to point analyzers), a ``monitoring path''

(applicable to open path analyzers), or both. Some minor flexibility in

siting criteria was added for open path analyzers to compensate for the

additional difficulties in locating suitable sites for the various

equipment used with an open path analyzer, such as retroreflectors,

receivers, and transmitters. Nonetheless, these criteria should still

provide a concentration representative of the area to be monitored.

It is important to note that criteria for open path measurement of

CO in a street canyon scenario, typically defined in terms of

microscale dimensions (up to 100 meters), is not included in this

proposal. The siting criteria currently used for microscale CO

monitoring is unique and narrow in scope in comparison to other

monitoring scenarios. Adapting the existing siting criteria to

accommodate path measurement techniques, as this proposal does for

other types of monitoring scales, would unduly restrict the usage of

open path analyzers for this particular application. In order to fully

address more appropriate siting criteria for microscale CO monitoring

using open path analyzers, the EPA must more fully evaluate the effects

of measuring path-averaged CO concentrations across roadways,

intersections, and at locations other than those currently defined in

the part 58 regulation. The EPA specifically solicits comments from the

public regarding the use of open path analyzers for measuring CO in

microscale applications.

III. Discussion of Proposed Revisions to Regulations

A. Section 58.1 Definitions

Today's proposal would amend the definitions section of part 58 by

adding several new definitions that are necessary to clearly define the

proposed new requirements for open path analyzers. Definitions for

``point analyzer'' and ``open path analyzer'' would be added to define

these two types of automated instruments and to clarify the distinction

between them, since the various new and existing requirements may apply

to one or the other or both types of analyzers. A new definition for

``probe'' is proposed to specify the inlet where an air sample is

extracted from the atmosphere for delivery to a sampler or point

analyzer. This definition would clarify that location requirements

applicable to point analyzers apply to the analyzer's probe and not to

the analyzer (or sampler) itself, which could be located some distance

from the probe. Similarly, a new definition is proposed for

``monitoring path'' to describe the path in the atmosphere over which

an open path analyzer measures and averages a pollutant concentration.

Closely associated with the term ``monitoring path'' are new

definitions for ``monitoring path length,'' to describe the scalar

length of the monitoring path, and ``optical measurement path length,''

to describe the actual length of the optical beam of an open path

instrument. The length of the optical beam may be two or more times the

length of the monitoring path when one or more mirrors are used to

cause the optical beam to pass through the monitoring path more than

once.

To help describe the new requirements for data quality assessment

procedures, the term ``effective concentration'' is proposed. It would

refer to the ambient concentration of a pollutant over the monitoring

path that would be equivalent to a much higher concentration of the

pollutant contained in a short calibration cell inserted into the

optical beam of an open path analyzer during a precision test or

accuracy audit. Specifically, effective concentration is proposed to be

defined as the actual concentration of the pollutant in the test cell

multiplied by the ratio of the optical measurement path length of the

test cell to the optical measurement path length of the atmospheric

monitoring path. Also, when a calibration cell is inserted into the

actual atmospheric measurement beam of an open path analyzer for a

precision or accuracy test, the resulting measurement reading would be

the sum of the pollutant concentration in the calibration cell and the

pollutant concentration in the atmosphere. The atmospheric pollutant

concentration must be measured separately and subtracted from the test

measurement to produce a ``corrected concentration,'' which would be

the true test result. Thus, the term ``corrected concentration'' is

proposed to define the result of such a precision or accuracy

assessment test after correction of the test measurement by subtracting

the atmospheric pollutant concentration.

Finally, a formal definition of ``monitor'' is proposed to clarify

its use in the regulations as a generic term to refer to any type of

ambient air analyzer or sampler that is acceptable for use in a SLAMS

monitoring network under Appendix C of this part. A monitor could thus

be a point analyzer, an open path analyzer, or a sampler.

B. Appendix A--Quality Assurance Requirements for State and Local Air

Monitoring Stations (SLAMS)

Appendix A sets forth both general quality assurance requirements

applicable to SLAMS air monitoring as well as specific procedures for

assessing the quality of the monitoring data obtained in SLAMS

monitoring networks. While the general quality assurance requirements

(in section 2) would be directly applicable to open path analyzers

without change, the more specific data quality assessment procedures

(in section 3) must be modified somewhat to apply to open path

analyzers. Accordingly, changes to these procedures are proposed to

incorporate appropriate data quality assessment tests applicable to

open path monitoring instruments. To the extent possible, the new

requirements are similar or parallel to the existing requirements for

point analyzers.

For both the precision test (Sec. 3.1) and the accuracy audit

(Sec. 3.2), the proposed new requirements specify that an optical

calibration or test cell containing a pollutant concentration standard

must be inserted into the optical measurement beam of the open path

analyzer. Both theory and testing indicate that the use of such a

calibration or test cell is equivalent in accuracy to measurement of

the equivalent pollutant concentration in air over the entire

monitoring path of an open path analyzer. Each concentration standard

must be selected such that it produces an ``effective concentration''

equivalent to a specified ambient concentration over the monitoring

path. As noted previously, effective concentration is defined as the

actual concentration of the pollutant in the test cell multiplied by

the ratio of the optical measurement path length of the test cell to

the optical measurement path length of the atmospheric monitoring path.

The effective concentrations specified for the precision and accuracy

tests for open path analyzers would be the same as the test

concentrations currently specified in these procedures for point

analyzers.

Ideally, precision and accuracy assessments should test a

monitoring instrument in its normal monitoring configuration.

Therefore, the proposed test procedures require that the test or

calibration cell containing the test pollutant concentration standard

be inserted into the actual atmospheric measurement beam of the open

path analyzer. The resulting test measurement of the pollutant

concentration would thus be the sum of the test concentration in the

cell and the pollutant concentration in the atmosphere, because the

measurement beam would pass through both the test cell and the

atmospheric monitoring path. Accordingly, a correction for the

atmospheric concentration is required to obtain the true test result.

In the proposed procedures, the atmospheric pollutant concentration

would be measured immediately before and again immediately after the

precision or accuracy test, and the average of these two measurements

would be subtracted from the test concentration measurement to produce

a ``corrected concentration,'' which would be reported as the test

result.

The corrected concentration reported for a precision or accuracy

test may not be accurate if the atmospheric pollutant concentration

changes during the test. When the ambient concentration is variable,

the average of the pre- and post-test measurements may not be an

accurate representation of the ambient pollutant concentration during

the test. The proposed test procedures recommend that these tests

should be carried out, if possible, during periods when the atmospheric

pollutant concentration is low and steady. The lower the atmospheric

pollutant concentration, the steadier the concentration is likely to be

and the better the pre- and post-test measurements will represent the

actual atmospheric concentration during the test measurement. Further,

the procedures propose that if the pre- and post-test measurements of

the atmospheric concentration differ by more that 20 percent of the

effective concentration of the test standard, the test result would be

discarded and the test repeated.

It is recognized that the proposed tests for precision and accuracy

for open path analyzers, as well as the existing tests for point

analyzers, are described in very general terms, and that additional,

more detailed information and guidance is usually necessary for an

analyzer operator to carry out these tests properly. Accordingly,

section 3 of appendix A is proposed to be amended by adding an explicit

indication that supplemental information and guidance to assist the

analyst in conducting these tests may be available in the publication,

``Quality Assurance Handbook for Air Pollution Measurement Systems,

Volume II'' (EPA-600/4-77-027a, identified as Reference 3 at the end of

Appendix A), or in the operation or instruction manual associated with

the particular monitor being used.

The proposed techniques for precision and accuracy assessment of

open path analyzers are based largely on consultations with the

manufacturer, along with EPA tests, of the differential optical

absorption spectrometer that is currently under consideration by EPA

for possible designation as equivalent methods under 40 CFR part 53.

However, it is desirable that the techniques be generic in nature, if

possible, so that they would be applicable to other types of open path

monitoring instruments as well. In addition, for some types of open

path instruments or for some installations or configurations, there may

be technical reasons why the proposed techniques for precision and

accuracy assessment may not be feasible, appropriate, or advisable. The

procedures, as currently proposed, allow for the use of an alternate

local light source or an alternate optical path that does not include

the normal atmospheric monitoring path, if such alternate configuration

is permitted by the operation or instruction manual associated with the

analyzer. Since the analyzer operation or instruction manual would be

subject to approval as part of the requirements for EPA designation of

an open path analyzer as an equivalent method, EPA would thereby have

control over the alternate configurations that would be allowable for

the precision and accuracy assessment tests.

In view of these issues regarding the precision and accuracy

assessment techniques, EPA specifically solicits comments on: (1) The

suitability of the proposed techniques; (2) the advisability of a

technique that requires correction of the test result for the

atmospheric pollutant concentration versus a technique that does not

require that correction but does not test the normal atmospheric

measurement components and configuration; (3) the proposed technique

for correcting test measurements for the atmospheric pollutant

concentration, if required, and the 20 percent limit on the difference

between the pre- and post-test measurements of the atmospheric

concentration; and (4) whether the proposed techniques are sufficiently

generic in nature to apply to various other types of open path

analyzers that might be applicable to SLAMS monitoring, or how the

techniques could be made more generic.

C. Appendix B--Quality Assurance Requirements for Prevention of

Significant Deterioration (PSD) Air Monitoring

Appendix B sets forth both general quality assurance requirements

for PSD monitoring as well as specific procedures for assessing the

quality of the monitoring data obtained in PSD monitoring networks. The

amendments and procedures proposed for Appendix B to extend the

existing requirements to open path analyzers are essentially identical

to the changes proposed for Appendix A.

D. Appendix E--Probe and Path Siting Criteria for Ambient Air Quality

Monitoring

This proposal would amend Appendix E by adding new siting criteria

applicable to open path analyzers for monitoring of SO2, O3,

NO2, CO, and O3 precursors (defined in the PAMS program as

volatile organic compounds, oxides of nitrogen, and selected

carbonyls). Because of the substantial similarity in the siting

criteria for SO2, O3, and NO2 (both the existing

criteria for point monitors and proposed new criteria for open path

analyzers), the siting requirements for these three pollutants are

proposed to be combined, consolidated, and set forth in section 2 of

appendix E. The existing criteria for SO2, O3, and NO2

in sections 3, 5, and 6 would be deleted, and those sections would be

reserved. As noted below, the criteria for CO monitoring are somewhat

different, so they would be retained in a separate section 4. Siting

criteria for measuring O3 and its precursors as part of a PAMS

network are included in section 10. In all cases, the new open path

provisions would be incorporated into the existing provisions, as

appropriate.

The proposed new open path siting requirements largely parallel the

existing requirements for point analyzers, with the revised provisions

applicable to either a ``probe'' (for point analyzers), a ``monitoring

path'' (for open path analyzers), or both, as appropriate. Accordingly,

criteria for the monitoring path of an open path analyzer are proposed

for horizontal and vertical placement, spacing from minor sources,

spacing from obstructions, spacing from trees, and spacing from

roadways. The open path requirements would apply to most of the

monitoring path--generally 80 or 90 percent--but not to the entire

monitoring path, to allow some needed flexibility in siting open path

analyzers. For example, using the proposed 80 percent requirement, a

monitoring path may be sited across uneven terrain, where up to 20

percent of the monitoring path may not fall within the proposed 3 to 15

meter specification for height above ground.

In addition to the criteria common to both point and open path

analyzers mentioned above, two new provisions, applicable only to open

path analyzers, would limit the maximum length of the monitoring path

and the cumulative interferences on the path. The maximum monitoring

path length limit would help to ensure that open path monitoring data

represent the air volume that they are intended to measure according to

the monitoring objectives of the spatial scale identified for the site.

Similarly, the limit for the cumulative interferences on the monitoring

path would control the total amount of interferences from minor

sources, roadways, obstructions, and other factors that might unduly

influence the monitoring data collected by an open path analyzer. This

limit is necessary because a long monitoring path presents a much

greater opportunity to be affected by multiple interferences. It is

also recognized that State or local air monitoring agencies may

encounter difficulties in locating atmospheric monitoring equipment due

to vandalism, scarcity of available sites, and other considerations;

therefore, certain provisions are included in both the existing and the

proposed new provisions of the regulation to accommodate these

difficulties.

In the consolidation of current sections 3, 5, and 6 to section 2,

Tables 2 and 3, which list the minimum separation distance between

O3 and NO2 stations and nearby roadways, would be combined

and redesignated as Table 1. As a result, Table 1 (in section 3), Table

4 (in section 7), Table 5 (in section 10), and Table 6 (in section 12)

would be renumbered as tables 2, 3, 4, and 5, respectively. Finally,

the summary of all the general siting requirements in renumbered Table

5 would be modified to include the new criteria for monitoring paths.

IV. Comments and the Public Docket

The EPA welcomes comments on all aspects of this proposed

rulemaking, specifically: (a) The appropriateness of using open path

(long-path) analyzers to measure CO, O3, SO2, NO2, and/

or O3 precursors (defined in the PAMS program as volatile organic

compounds, oxides of nitrogen, and selected carbonyls); (b) the ability

of a monitoring agency to use an open path analyzer in a manner

consistent with these siting criteria; (c) using open path analyzers to

measure CO in microscale scenarios; (d) the precision and accuracy

assessment techniques as described in the proposed Appendix A and

Appendix B regulations; (e) using open path analyzers to measure

SO2 in source-oriented ambient air monitoring networks,

particularly in micro- and middle-scale applications; and (f) all

available and relevant study information on the comparability of open

path and point ambient air monitoring. All comments, with the exception

of proprietary information, should be directed to the EPA Air Docket

Section, Docket No. A-93-44.

Those who wish to submit proprietary information for consideration

should clearly separate such information from other comments by:

Labeling proprietary information ``Confidential Business

Information,'' and;

Sending proprietary information directly to the contact

person listed (see FOR FURTHER INFORMATION CONTACT) and not to the

public docket.

This will help ensure that proprietary information is not

inadvertently placed in the docket. If a commenter wants the EPA to use

a submission labeled as confidential business information as part of

the basis for the final rule, then a nonconfidential version of the

document, which summarizes the key data or information, should be sent

to the docket.

Information covered by a claim of confidentiality will be disclosed

by the EPA only to the extent allowed and by the procedures set forth

in 40 CFR part 2. If no claim of confidentiality accompanies the

submission when it is received by the EPA, the submission may be made

available to the public without notifying the commenters.

V. Administrative Requirements

A. Administrative Designation

Executive Order 12866

Under Executive Order 12866 (58 FR 51735 (October 4, 1993)) the

Agency must determine whether the regulatory action is ``significant''

and therefore subject to Office of Management and Budget (OMB) review

and the requirements of the Executive Order. The Order defines

``significant regulatory action'' as one that is likely to result in a

rule that may:

(1) Have an annual effect on the economy of $100 million or more or

adversely affect in a material way the economy, a sector of the

economy, productivity, competition, jobs, the environment, public

health or safety, or State, local, or tribal governments or

communities;

(2) Create a serious inconsistency or otherwise interfere with an

action taken or planned by another Agency;

(3) Materially alter the budgetary impact of entitlements, grants,

user fees, or loan programs or the rights and obligations or recipients

thereof; or

(4) Raise novel legal or policy issues arising out of legal

mandates, the President's priorities, or the principles set forth in

the Executive Order.

It has been determined that this rule is not a ``significant

regulatory action'' under the terms of Executive Order 12866 and is

therefore not subject to OMB review.

B. Reporting and Recordkeeping Requirements

All of the information collection requirements contained in part 58

have been approved by the OMB under the Paperwork Reduction Act of

1980, 44 U.S.C. 3501 et seq., and have been assigned OMB Control Number

2060-0084. This proposed amendment to Part 58 does not add any new

information collection requirements.

C. Regulatory Flexibility Act

Pursuant to section 605(b) of the Regulatory Flexibility Act, 5

U.S.C. 605(b), the Administrator certifies that this rule will not have

a significant economic impact on a substantial number of small

entities. This rulemaking package does not impose any additional

requirements on small entities, rather, it is this proposal's intent to

provide all entities with the option to choose the most suitable

ambient air method for their particular application. This proposal

provides the appropriate siting and quality assurance criteria for a

new ambient air monitoring technology (open path analyzers) as they are

used in various applications. All of the criteria listed in this

rulemaking package parallel existing requirements and vary only as

necessary due to technological differences between measurement

techniques. It is possible that a beneficial impact may be encountered

by some small entities that use this new technology in certain

scenarios.

List of Subjects in 40 CFR Part 58

Air pollution control, Ambient air monitoring, Ambient air

monitoring networks and siting criteria, Intergovernmental relations,

National ambient air monitoring program, Quality assurance

requirements, Reporting and recordkeeping requirements, State and local

agency ambient air monitoring programs.

Dated: August 4, 1994.

Carol M. Browner,

Administrator.

For reasons set forth in the preamble, title 40, chapter I, part 58

of the Code of Federal Regulations is proposed to be amended as

follows:

PART 58--[AMENDED]

1. The authority citation for part 58 continues to read as follows:

Authority: 42 U.S.C. 7410, 7601(a), 7613, and 7619.

2. In Sec. 58.1, the following definitions are added:

Sec. 58.1 Definitions.

* * * * *

(z) Point analyzer is an automated analytical method that measures

pollutant concentration in an ambient air sample extracted from the

atmosphere at a specific inlet probe point and that has been designated

as a reference or equivalent method in accordance with part 53 of this

chapter.

(aa) Probe is the actual inlet where an air sample is extracted

from the atmosphere for delivery to a sampler or point analyzer for

pollutant analysis.

(bb) Open path analyzer is an automated analytical method that

measures the average atmospheric pollutant concentration in situ along

one or more monitoring paths having a monitoring path length of 5

meters or more and that has been designated as a reference or

equivalent method under the provisions of part 53 of this chapter.

(cc) Monitoring path for an open path analyzer is the actual path

in space over which the pollutant concentration is measured and

averaged.

(dd) Monitoring path length of an open path analyzer is the length

of the monitoring path in the atmosphere over which the average

pollutant concentration measurement is determined. See also, ``optical

measurement path length.''

(ee) Optical measurement path length is the actual length of the

optical beam over which measurement of the pollutant is determined.

Generally, the optical measurement path length is:

(1) Equal to the monitoring path length for a (bistatic) system

having transmitter and receiver at opposite ends of the monitoring

path;

(2) Equal to twice the monitoring path length for a (monostatic)

system having a transmitter and receiver at one end of the monitoring

path and a mirror or retroreflector at the other end; or

(3) Equal to some multiple of the monitoring path length for more

complex systems having multiple passes of the measurement beam through

the monitoring path.

(ff) Effective concentration pertains to testing an open path

analyzer with a high-concentration calibration or audit standard gas

contained in a short test cell inserted into the optical measurement

beam of the instrument. Effective concentration is the equivalent

ambient-level concentration that would produce the same spectral

absorbance over the actual atmospheric monitoring path length as

produced by the high-concentration gas in the short test cell.

Quantitatively, effective concentration is equal to the actual

concentration of the gas standard in the test cell multiplied by the

ratio of the path length of the test cell to the actual atmospheric

monitoring path length.

(gg) Corrected concentration pertains to the result of an accuracy

or precision assessment test of an open path analyzer in which a high-

concentration test or audit standard gas contained in a short test cell

is inserted into the optical measurement beam of the instrument. When

the pollutant concentration measured by the analyzer in such a test

includes both the pollutant concentration in the test cell and the

concentration in the atmosphere, the atmospheric pollutant

concentration must be subtracted from the test measurement to obtain

the corrected concentration test result. The corrected concentration is

equal to the measured concentration minus the average of the

atmospheric pollutant concentrations measured (without the test cell)

immediately before and immediately after the test.

(hh) Monitor is a generic term for an instrument, sampler,

analyzer, or other device that measures or assists in the measurement

of atmospheric air pollutants and is acceptable for use in ambient air

surveillance under the provisions of appendix C to this part, including

both point and open path analyzers that have been designated as

reference or equivalent methods under part 53 of this chapter and air

samplers that are specified as part of a manual method that has been

designated as a reference or equivalent method under part 53 of this

chapter.

Appendix A [Amended]

3. Appendix A is amended as follows:

a. The fourth paragraph of section 3 introductory text is revised.

b. Section 3.1 is revised.

c. The text preceding the table in the second paragraph, and the

seventh, and eighth paragraphs of Sec. 3.2 are revised; and a new

paragraph is added between the seventh and eighth paragraphs.

d. Table A-1 is revised.

Appendix A--Quality Assurance Requirements for State and Local Air

Monitoring Stations (SLAMS)

* * * * *

3. Data Quality Assessment Requirements

* * * * *

Assessment results shall be reported as specified in section 4.

Concentration and flow standards must be as specified in Secs. 2.3

or 3.4. In addition, working standards and equipment used for

accuracy audits must not be the same standards and equipment used

for routine calibration. Additional information and guidance in the

technical aspects of conducting these tests may be found in

Reference 3 or in the operation or instruction manual associated

with the analyzer or sampler. Concentration measurements reported

from analyzers or analytical systems (indicated concentrations)

should be based on stable readings and must be derived by means of

the same calibration curve and data processing system used to obtain

the routine air monitoring data (see Reference 1 and Reference 3,

section 2.0.9.1.3(d)). Table A-1 provides a summary of the minimum

data quality assessment requirements, which are described in more

detail in the following sections.

3.1 Precision of Automated Methods

A one-point precision check must be carried out at least once every

2 weeks on each automated analyzer used to measure SO2, NO2,

O3, and CO. The precision check is made by challenging the

analyzer with a precision check gas of known concentration (effective

concentration for open path analyzers) between 0.08 and 0.10 ppm for

SO2, NO2, and O3 analyzers, and between 8 and 10 ppm for

CO analyzers. To check the precision of SLAMS analyzers operating on

ranges higher than 0 to 1.0 ppm SO2, NO2, and O3, or 0

to 100 ppm for CO, use precision check gases of appropriately higher

concentration as approved by the appropriate Regional Administrator or

the Regional Administrator's designee. However, the results of

precision checks at concentration levels other than those specified

above need not be reported to the EPA. The standards from which

precision check test concentrations are obtained must meet the

specifications of Sec. 2.3.

Except for certain CO analyzers described below, point analyzers

must operate in their normal sampling mode during the precision

check, and the test atmosphere must pass through all filters,

scrubbers, conditioners, and other components used during normal

ambient sampling and as much of the ambient air inlet system as is

practicable. If permitted by the associated operation or instruction

manual, a CO point analyzer may be temporarily modified during the

precision check to reduce vent or purge flows, or the test

atmosphere may enter the analyzer at a point other than the normal

sample inlet, provided that the analyzer's response is not likely to

be altered by these deviations from the normal operational mode.

If a precision check is made in conjunction with a zero or span

adjustment, it must be made prior to such zero or span adjustments.

Randomization of the precision check with respect to time of day,

day of week, and routine service and adjustments is encouraged where

possible.

Open path analyzers are tested by inserting a test cell

containing a precision check gas concentration into the optical

measurement beam of the instrument. If possible, the normally used

transmitter, receiver, and, as appropriate, reflecting devices

should be used during the test, and the normal monitoring

configuration of the instrument should be altered as little as

possible to accommodate the test cell for the test. However, if

permitted by the associated operation or instruction manual, an

alternate local light source or an alternate optical path that does

not include the normal atmospheric monitoring path may be used. The

actual concentration of the precision check gas in the test cell

must be selected to produce an ``effective concentration'' in the

range specified above. Generally, the precision test concentration

measurement will be the sum of the atmospheric pollutant

concentration and the precision test concentration. If so, the

result must be corrected to remove the atmospheric concentration

contribution. The ``corrected concentration'' is obtained by

subtracting the average of the atmospheric concentrations measured

by the instrument immediately before and immediately after the

precision check test from the precision test concentration

measurement. If the difference between these before and after

measurements is greater than 20 percent of the effective

concentration of the test gas, discard the test result and repeat

the test. If possible, open path analyzers should be tested during

periods when the atmospheric pollutant concentrations are relatively

low and steady.

Report the actual concentration (effective concentration for

open path analyzers) of the precision check gas and the

corresponding concentration measurement (corrected concentration, if

applicable, for open path analyzers) indicated by the analyzer. The

percent differences between these concentrations are used to assess

the precision of the monitoring data as described in Sec. 5.1.

3.2 Accuracy of Automated Methods

* * * * *

The audit is made by challenging the analyzer with at least one

audit gas of known concentration (effective concentration for open

path analyzers) from each of the following ranges that fall within

the measurement range of the analyzer being audited:

* * * * *

For point analyzers, the audit shall be carried out by allowing

the analyzer to analyze the audit test atmosphere in its normal

sampling mode such that the test atmosphere passes through all

filters, scrubbers, conditioners, and other sample inlet components

used during normal ambient sampling and as much of the ambient air

inlet system as is practicable. The exception given in Sec. 3.1 for

certain CO analyzers does not apply for audits.

Open path analyzers are audited by inserting a test cell

containing the various audit gas concentrations into the optical

measurement beam of the instrument. If possible, the normally used

transmitter, receiver, and, as appropriate, reflecting devices

should be used during the audit, and the normal monitoring

configuration of the instrument should be modified as little as

possible to accommodate the test cell for the audit. However, if

permitted by the associated operation or instruction manual, an

alternate local light source or an alternate optical path that does

not include the normal atmospheric monitoring path may be used. The

actual concentrations of the audit gas in the test cell must be

selected to produce ``effective concentrations'' in the ranges

specified in this Sec. 3.2. Generally, each audit concentration

measurement result will be the sum of the atmospheric pollutant

concentration and the audit test concentration. If so, the result

must be corrected to remove the atmospheric concentration

contribution. The ``corrected concentration'' is obtained by

subtracting the average of the atmospheric concentration measured by

the instrument immediately before and immediately after the audit

test (or preferably before and after each audit concentration level)

from the audit concentration measurement. If the difference between

the before and after measurements is greater than 20 percent of the

effective concentration of the test gas standard, discard the test

result for that concentration level and repeat the test for that

level. If possible, open path analyzers should be audited during

periods when the atmospheric pollutant concentrations are relatively

low and steady.

Report both the audit test concentrations (effective

concentrations for open path analyzers) and the corresponding

concentration measurements (corrected concentrations, if applicable,

for open path analyzers) indicated or produced by the analyzer being

tested. The percent differences between these concentrations are

used to assess the accuracy of the monitoring data as described in

Sec. 5.2.

* * * * *

Table A-1.--Minimum Data Assessment Requirements

----------------------------------------------------------------------------------------------------------------

Method Assessment method Coverage Minimum frequency Parameters reported

----------------------------------------------------------------------------------------------------------------

Precision:

Automated Methods Response check at Each analyzer........ Once per 2 weeks..... Actual

for SO2, NO2, concentration concentration\2\

O3, and CO. between .08 & .10 and measured

ppm (8 & 10 ppm for concentration.\3\

CO)\2\.

Manual methods Collocated samplers.. 1 site for 1-5 sites; Once per week........ Two concentration

including lead. 2 sites for 6-20 measurements.

sites; 3 sites > 20

sites; (sites with

highest conc.).

Accuracy:

Automated Methods Response check at: 1. Each analyzer. 2. 1. Once per year. 2. Actual

for SO2, NO2, .03-.08 ppm,12 .15- 25% of analyzers (at Each calendar concentration\2\

O3, and CO. .20 ppm;12 .35-.45 least 1). quarter. and measured

ppm;12 .80-.90 (indicated)

ppm;12 (if concentration\3\

applicable). for each level.

Manual methods Check of analytical Analytical system.... Each day samples are Actual concentration

for SO2 and NO2. procedures with analyzed, at least and measured

audit standard twice per quarter. (indicated)

solutions. concentration for

each audit

solution.

TSP, PM-10....... Check of sampler flow 1. Each sampler. 2. 1. Once per year. 2. Actual flow rate and

rate. 25% of samplers (at Each calendar flow rate indicated

least 1). quarter. by the sampler.

Lead............. 1. Check sample flow 1. Each sampler. 2. 1. Include with TSP. 1. Same as for TSP.

rate as for TSP. 2. Analytical system. 2. Each quarter. 2. Actual

Check analytical concentration &

system with Pb audit measured

strips. (indicated)

concentration of

audit samples

(g Pb/

strip).

----------------------------------------------------------------------------------------------------------------

\1\Concentration times 100 for CO.

\2\Effective concentration for open path analyzers.

\3\Corrected concentration, if applicable, for open path analyzers.

* * * * *

Appendix B [Amended]

4. Appendix B is amended as follows:

a. The first paragraph of section is revised.

b. Section 3.1 is revised.

c. The text preceding the table in the first paragraph, and the

third, and fourth paragraphs of section 3.2 are revised; and a new

paragraph is added between the third and fourth paragraphs.

d. Table B-1 is revised.

Appendix B--Quality Assurance Requirements for Prevention of

Significant Deterioration (PSD) Air Monitoring

* * * * *

3. Data Quality Assessment Requirements

All ambient monitoring methods or analyzers used in PSD

monitoring shall be tested periodically, as described in this

section 3, to quantitatively assess the quality of the data being

routinely collected. The results of these tests shall be reported as

specified in section 6. Concentration standards used for the tests

must be as specified in section Sec. 2.3. Additional information and

guidance in the technical aspects of conducting these tests may be

found in Reference 3 or in the operation or instruction manual

associated with the analyzer or sampler. Concentration measurements

reported from analyzers or analytical systems must be derived by

means of the same calibration curve and data processing system used

to obtain the routine air monitoring data. Table B-1 provides a

summary of the minimum data quality assessment requirements, which

are described in more detail in the following sections.

3.1 Precision of Automated Methods

A one-point precision check must be carried out at least once

every 2 weeks on each automated analyzer used to measure SO2,

NO2, O3, and CO. The precision check is made by

challenging the analyzer with a precision check gas of known

concentration (effective concentration for open path analyzers)

between 0.08 and 0.10 ppm for SO2, NO2, and O3

analyzers, and between 8 and 10 ppm for CO analyzers. The standards

from which precision check test concentrations are obtained must

meet the specifications of section 2.3. Except for certain CO

analyzers described below, point analyzers must operate in their

normal sampling mode during the precision check, and the test

atmosphere must pass through all filters, scrubbers, conditioners

and other components used during normal ambient sampling and as much

of the ambient air inlet system as is practicable. If permitted by

the associated operation or instruction manual, a CO point analyzer

may be temporarily modified during the precision check to reduce

vent or purge flows, or the test atmosphere may enter the analyzer

at a point other than the normal sample inlet, provided that the

analyzer's response is not likely to be altered by these deviations

from the normal operational mode.