Federal Register / Vol. 53, No. 163 / Tuesday, August 23, 1988 / Proposed Rules

authority in the Federal Aviation Act of

1958, as amended (49 U.S.C. 1301, et

seq.), which statute is construed to

preempt state law regulating the same

subject. Thus, in accordance with

Executive Order 12612, it is determined

that such regulations do not have

federalism implications warranting the

preparation of a Federalism

Assessment.

For these reasons, the FAA has

determined that this document (1)

involves a proposed regulation which is

not major under Executive Order 12291

and (2) is not a significant rule pursuant

to the Department of Transportation

Regulatory Policies and Procedures (44

FR 11034; February 26, 1979); and it is

further certified under the criteria of the

Regulatory Flexibility Act that this

proposed rule, if promulgated, will not

have a significant economic impact,

positive or negative, on a substantial

number of small entities because few, if

any, Model 727 airplanes are operated

by small entities. A copy of a draft

regulatory evaluation prepared for this

action is contained in the regulatory

docket.

List of Subjects: 14 CFR Part 39

Aviation safety, Aircraft.

The Proposed Amendment

Accordingly, pursuant to the authority

delegated to me by the Administrator,

the Federal Aviation Administration

proposes to amend Section 39.13 of Part

39 of the Federal Aviation Regulations

(14 CFR 39.13) as follows:

PART 39--[AMENDED]

1. The authority citation for Part 39

continues to read as follows:

Authority: 49 U.S.C. 1354(a), 1421 and 1423;

49 U.S.C. 106(g) (Revised Pub. L 97-449,

January 12, 1983); and 14 CFR 11.89.

2. By adding the following new

airworthiness directive:

Boeing: Applies to all Model 727 series

airplanes listed in Boeing Service

Bulletin 727-53-149, Revision 2, dated

March 20,1981, certificated in any

category. Compliance required as

indicated, unless previously

accomplished.

To detect cracking of the main landing gear (MLG) wheel well pressure floor adjacent to

body stations (BS) 880,890,930. and 940, accomplish the following:

A. Prior to the accumulation of 30,000

flights or within the next 2.500 flights, whichever occurs later, and thereafter at

intervals not to exceed 4,000 flights, perform a close visual, eddy current, or dye penetrant inspection for cracks in the pressure floor, in

accordance with Boeing Service Bulletin 727-

53-149, Revision 2, dated March 20,1981.

B. If cracks are detected that do not exceed

the limits listed in Table 11 in Section III of

Boeing Service Bulletin 727-53-149, Revision

2, dated March 20,1981, prior to further flight,

repair in accordance with the interim repair

described in paragraph C. of Section I, or

the permanent repair described in paragraph

D. of Section III of the service bulletin. The

interim repair must be replaced within 600

flights with the permanent repair.

C. If cracks are found that exceed the limits

listed in Table II, of Section III of Boeing

Service Bulletin 727-53-149, Revision 2, dated

March 20, 1981, prior to further flight,

accomplish the permanent repair described in

paragraph D. of Section III of the service

bulletin prior to further flight. A repair

accomplished using blind fasteners must be

reinspected at intervals not to exceed 2,000

flights until the blind fasteners are replaced

with the fasteners specified in paragraph 4. of

Section ImI of the service bulletin.

D. Incorporation of the repairs in

accordance with paragraph B. or C., above,

terminates the repetitive inspection

requirements of paragraph A., above, for that area. Incorporation of the preventative

modification in paragraph E. of Section III of

Boeing Service Bulletin 727-53-149, Revision

2, dated March 20, 1981, terminates the

repetitive inspection requirement of

paragraph A., above.

E. An alternate means of compliance or

adjustment of the compliance time, which

provides an acceptable level of safety, may

be used when approved by the Manager,

Seattle Transport Airplane Office, FAA,

Northwest Mountain Region.

Note.-The request should be forwarded

through an FAA Principal Maintenance

Inspector (PMI), who may add any comments

and then send it to the Manager, Seattle

Transport Airplane Office.

F. Special flight permits may be issued in

accordance with FAR 21.197 and 21.199 to

operate airplanes to a base in order to

comply with the requirements of this AD.

All persons affected by this directive

who have not already received the

appropriate service documents from the

manufacturer may obtain copies upon

request to Boeing Commercial

Airplanes, P.O. Box 3707, Seattle,

Washington 98124. These documents

may be examined at the FAA,

Northwest Mountain Region, 17900

Pacific Highway South, Seattle,

Washington, or Seattle Transport

Airplane Office, FAA. Northwest

Mountain Region, 9010 East Marginal

Way South, Seattle, Washington.

Issued in Washington, DC, on August 16,

1988.

Thomas B. McSweeny,

Acting Director, Office of Airworthiness.

[FR Doc. 68-19024 Filed 8-22-88; 8:45 am]

BILLING CODE 4910-1".

ENVIRONMENTAL PROTECTION

AGENCY

40 CFR Ch. I

(AD-FRL-3433-5; Docket No. A-88-041

Conference on Air Quality Modeling

AGENCY: U.S. Environmental Protection

Agency (EPA).

ACTION: Notice of conference.

SUMMARY: The EPA announces the

Fourth Conference on Air Quality

Modeling. Such a conference is required

by section 320 of the Clean Air Act

(CAA) to be held every 3 years. The

purpose of the fourth conference is to

advise the public on new modeling

techniques and to solicit comments to

guide EPA's consideration of any

rulemaking needed to revise the

"Guideline on Air Quality Models

(Revised)", EPA-450/2-78-027R (1986)

and Supplement A (1987). A more

detailed discussion of these new

modeling techniques will be given by

EPA during the conference.

DATES: The fourth conference will be

held on October 12 and 13, 1988, from

9:00 a.m. to 5:00 p.m. Requests to speak

at the conference must be submitted to

the individuals listed below by October

3, 1988. All written comments must be

submitted by December 15, 1988.

ADDRESSES: Conference: The conference

will be held in the Thomas Jefferson

Auditorium, South Agriculture Building,

14th Street and Independence Avenue,

SW., Washington, DC.

Comments: Written statements or

comments not presented at the

conference should be submitted (in

duplicate if possible) to: Central Docket

Section (South Conference Center, Room

4), Attention: Docket A-68-04, U.S.

Environmental Protection Agency, 401 M

Street, SW., Washington, DC 20460.

Documents referenced in this notice as

well as comments received may also be

inspected at this address. A reasonable

fee may be charged for copying. This is

a new docket established for the

conference and for consideration of any

further revision of the "Guideline on Air

Quality Models (Revised)" and

Supplement A. Prior material relevant to

the development of the modeling

guideline and Supplement A may be

found in Docket A-80-46.

FOR FURTHER INFORMATION CONTACT.

Joseph A. Tikvart. Chief, Source

Receptor Analysis Branch (MD-14),

Office of Air Quality Planning and

Standards, U.S. Environmental

Protection Agency, Research Triangle

Park, North Carolina 27711; telephone

I

32M81
Federal Register / Vol. 53, No. 163 / Tuesday, August 23, 1988 / Proposed Rules

(919) 541-5562 or Jawad S. Touma,

telephone (919) 541-5381.

SUPPLEMENTARY INFORMATION:

Background

Section 320 of the CAA states that a

conference on air quality modeling is to

be held every 3 years to address

appropriate air quality modeling

necessary for carrying out prevention of

significant deterioration (PSD)

requirements, thereby fostering the

standardization of air quality modeling

practices. Such models are also used for

evaluating State implementation plans

for existing sources, making new source

reviews, and otherwise estimating

source receptor relationships. The first

conference, held in December 1977,

addressed EPA's proposed modeling

guideline. The result was the "Guideline

on Air Quality Models" (EPA-450/2-78-

027) which provides guidance on the

selection and application of air quality

models. The second conference in

August 1981 was an open forum to

address model accuracy and the

incorporation of model uncertainty in

regulatory decision-making. The third

conference, held in January 1985,

provided a forum for public review and

comment on proposed revisions to the

modeling guideline. As a result of public

comment during that conference EPA

issued the "Guideline on Air Quality

(Revised)", EPA-450/2-78-027R, (51 FR

32176). Revisions responding to issues

raised during that conference are

included in Supplement A to the

guideline (53 FR 392).

The Fourth Conference on Air Quality

Modeling will address EPA's modeling

guidance. Substantial new knowledge

concerning modeling analyses has

become available since the guideline

and Supplement A were issued. Future

revisions to the guideline are needed to

improve the basis for air quality impact

assessments and to insure that it reflects

the state-of-the-art with respect to air

quality models and data bases. As a

basis for possible revisions of the

modeling guideline and for holding this

fourth conference, EPA has assembled a

list of recent developments in modeling

techniques and related methods

developed by EPA, other Federal

agencies, or the private sector. These

techniques and related methods are

briefly described below. Topics are

arranged to coincide with the

organization of the modeling guideline.

The EPA requests comments on the

general issues of technical validity,

relevant accuracy, merits and

limitations of the models and methods

listed here compared to current

techniques in the modeling guideline,

and comments on other more specific

issues listed below. Comments related

to air quality modeling of general

interest to the public may also be made.

The issues raised at the conference and

in the comment period will be

considered in development of a notice

proposing to revise the "Guideline on

Air Quality Models (Revised)" and

Supplement A.

Modeling Activities

A. Complex Terrain Dispersion Model

(CTDM)

The EPA has completed the CTDM

project, EPA/600/3-88/006 (Docket Item

11-1-2). One major output is the

development and evaluation of the

CTDM. This is a refined air quality

model for determining pollutant

concentrations from sources in "complex terrain" areas (where the

height of the nearby terrain exceeds the

height of the source being modeled). The

CTDM is designed for situations where

plume impingement on the windward

side of terrain features during stable to

neutral atmospheric conditions is

believed to cause air quality problems.

The user's guide documenting the

scientific assumptions used in CTDM is

available as EPA/600/8-87/058a and

058b (Docket Item 11-l-1). Because

CTDM was designed for neutral to

stable flow conditions, the model does

not predict concentrations during

unstable atmospheric conditions when a

plume is within the mixed layer. Thus, in

order to adequately estimate

concentrations during all averaging

periods of concern for regulatory

applications, it will be necessary to

merge the output from CTDM with

output from another model that can

handle the convectively unstable

atmospheric conditions. Other issues

that need to be resolved for any

regulatory application include

meteorological data requirements,

receptor grid spacing, the choice of

model options, and a consistent

approach to terrain characterization.

The EPA is currently studying the

performance of CTDM and has

completed several additional model

evaluation and sensitivity studies

(Docket Items 11-1-3 and 4). The EPA

solicits comments on: (1) Whether

CTDM is a technically valid model; (2)

whether use of an additional algorithm

for modeling convective atmospheric

conditions is suitable; (3) whether the

validation and sensitivity studies

warrant the adoption of CTDM as a

refined model in complex terrain; (4)

how data requirements should be

specified given that CTDM requires an

extensive set of meteorological data

input not routinely collected in most

current measurement programs; (5)

whether EPA should recommend the use

of CTDM in a screening mode with

assumed "worst case" meteorological

conditions if more sophisticated on-site

data are not available; and (6) whether

limitations should be placed on the use

of CTDM for regulatory applications.

The CTDM does not address all

situations involving complex terrain

where concentrations of possible

concern can occur, e.g., on the lee side

of hills. During the public comment

period on the supplemental proposal

(Docket A-80-46, Item VI-G-1), several

commenters suggested that high

concentrations may result at such

locations and that the highly

conservative nature of the existing

complex terrain screening models

compensates to some extent for not

addressing any of these phenomena. The

EPA solicits public comment on how to

take such situations into account in

setting emission limits for sources which

use CTDM.

B. Ozone Precursor Point Source

Modeling

The EPA's regulations require a

demonstration that a proposed source

(or modification) will not cause or

contribute to a violation of any National

Ambient Air Quality Standards. The

modeling guideline does not, however,

recommend a technique for predicting

the impact on ambient ozone

concentrations due to point sources of

ozone precursor emissions, i.e., volatile

organic compounds or nitrogen oxides.

The EPA has developed a screening

technique based on the Reactive Plume

Model (RPM-II), (Docket Item 11-1-5)

and solicits comments on the technical

validity of this screening technique.

C. Mobile Source Modeling at

Signalized Intersections

The EPA is reviewing the most

appropriate traffic and emissions

components of intersection models for

air quality analyses because high carbon

monoxide concentrations occur near

signalized intersections. In addition, the

EPA guidance contained in Worksheet 2

of the "Guideline for Air Quality

Maintenance Planning and Analysis,

Volume 9", EPA-450/4-75-01, cannot

adequately model overcapacity

situations at these intersections. The

EPA has been working with the Federal

Highway Administration (FHWA) to

determine how an intersection analysis

should be performed and what

emissions/traffic model to use. As a

result of this joint effort

recommendations on these issues and a

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Fgo'rrn!1 RAUI~tAI I Vnl. 53. No. 163 I Tuesday. Aumst 23, 1988 I Proposed Rules323

workplan for accomplishing them have

been developed (Docket Items 1-1-6 and

7). The EPA solicits comments on the

adequacy of the technical approaches in

the recommendations and workplan.

D. Emissions and Dispersion Modeling

System for Airports

The U.S. Air Force and the FAA are

jointly developing the Emissions and

Dispersion Modeling System (EDMS) to

provide an integrated assessment of

pollution from multiple sources (e.g.,

aircraft, motor vehicles, and power

plants) at airports and air bases. The

model makes use of a modern

microcomputer data base system

through which an inexperienced

layperson can enter data and initiate an

emissions or dispersion modeling

activity. This model has been submitted

to EPA in accordance with EPA

provisions for soliciting new models (45

FR 20157). A description of the model

and a User's Guide have been prepared

(Docket Item 1-1-8).

The EPA solicits comments on: (1)

Whether EDMS is a technically valid

model; (2) whether the performance

evaluations warrant the adoption of this

model as a preferred model to estimate

pollutant concentrations at airports; and

(3) whether any limitations should be

placed on the use of the EDMS model for

regulatory applications.

E. Long-Range Transport Models

The EPA has been evaluating the

performance of several long-range

transport models. These models are

needed to estimate pollutant

concentrations at distances beyond

about 50 kin, the conventional limit for

straightline Gaussian models. Estimates

of concentrations at distances greater

than 50 km may be required in certain

applications, e.g., Class I PSD areas.

Eight long-range transport models,

submitted to EPA in accordance with

EPA provisions for soliciting new

models (45 FR 20157), have been

evaluated by testing the models against

two sets of field data. The eight models

submitted can be used to predict shortterm averages (3 to 24 hours) of SO, and

primary partculates over distances of

20-2,000 km from single or a cluster of

multiple sources. The study is described

in the document titled "Evaluation of

Short-Term Long-Range Transport

Models", Volumes I and 2, EPA-450/4-

86-016a and 016b (Docket Item 11-1-9).

The American Meteorological Society

has completed a peer review report for

this study (Docket Item 11-1-10).

The EPA solicits comments on: (1)

Whether EPA should adopt one of these

eight models as a preferred long-range

transport model; (2) whether any

limitations should be placed on model

use for regulatory applications; (3)

whether the model estimates are

appropriate for averaging times and

source receptor distances of regulatory

concern; (4) whether the model use

should be limited to concentrations of

S02 and primary particulates; (5)

whether consideration should be given

to availability, complexity and the

detail/content of input data bases in

determining which model is

recommended; and (6) how data

collection and processing requirements

could be minimized.

The modeling guideline currently

states that selection of a long-range

transport model is on a case-by-case

basis. The EPA is developing an

example guidance protocol to illustratehow to apply a long-range transport

model to regulatory problems. This

document contains recommendations for

model input and options and an

example application (Docket Item H-I11). The EPA solicits comments on the

technical approach used therein.

F. Models for Estimating Visibility

Impact of Specific Sources

The modeling guideline lists two

models which may be used on a caseby-case basis for refined analysis to

estimate short-term impact assessment

of the type of visibility impairment

known as "plume blight" which can be

attributed to a specific source. The EPA

Office of Research and Development

has provided recommendations of

acceptable plume blight models (Docket

Item 11--12). The EPA solicits comments

on whether to adopt the

recommendations of this document and

whether any limitations shoud be placed

on the use of these models for regulatory

applications.

The modeling guideline also

references a document titled "Workbook

for Estimating Visibility Impairment",

EPA-450/4-80-031. A revision of this

document has been prepared to reflect

current technical information and

experience (Docket Item 11-1-13]. It

contains procedures and a visibility

model that can be used for screening

purposes to estimate visibility

impairment from specific sources. The

EPA solicits comments on the technical

validity of the revised visibility

workbook, and whether to adopt the

techniques in this document.

G. Model for Shoreline Dispersion

The modeling guideline recommends

the Offshore and Coastal Dispersion

model for simulating plume dispersion

and transport from offshore point

sources to receptors on land or water.

The modeling guideline also indicates

the need for predicting plume dispersion

and fumigation under the unique

meteorological conditions that affect

elevated sources located on the

coastline. There, a convective boundary

layer capped by an inversion, becomes

established when winds are onshore

and sufficient overland heat flux and

land-water temperature differences

exist. Although models have been

developed to address this problem,

previous evaluations were not sufficient

to allow EPA to recommend a specific

technique. The EPA has not completed a

performance evaluation entitled

"Analysis and Evaluation of Statistical

Coastal Fumigation Models", EPA-450/

4-87-002, (Docket Item 1-1-14). The EPA

has also developed a method to

incorporate shoreline dispersion

conditions in EPA regulatory models

using readily available data (Docket

Item 1-1-15).

The EPA solicits comment on: (1)

Whether the performance evaluation

study warrants the adoption of a

preferred model for predicting plume

dispersion and fumigation for elevated

sources located on the coastline; (2)

whether the methods to approximate

certain input parameters from readily

available data are adequate; and (3)

whether any limitations should be

placed on the use of the model in

regulatory applications.

H. Valley Stagnation

The modeling guideline addresses the

issues of wind stagnation but does not

recommend any specific modeling

techniques. Concerns about PMto

violation violations in valley basins

have led many State and local agencies

to request a simple modeling technique

for simulating stagnation and wind

recirculation conditions. Stagnation

conditions tend to occur more frequently

and persist for a longer time in well

defined valleys; however, periods of

persistent very low winds can also

occur in broad shallow velleys. Simply

Gaussian models are not adequate

during these conditions. The

WYNDvalley model (developed by

WYNDsoft, Inc.) appears to have

technical merit and to be relatively

simple to apply. However, model

evaluation results based on a

comparison between model estimates

and air quality data are limited (Docket

Item 11--16).

The EPA solicits comments on: (1)

Whether WYNDvalley is a technically

valid model; (2) whether additional data

bases exist to evaluate this model; (3)

what guidance EPA should provide for

users of the model; (4) whether any

limitations should be placed on its use

Federal Re ster / Vol 53 No. 163 / Tuesday, August 23, 1988 / Proposed Rules

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Federal Register / Vol. 53, No. 163 / Tuesday, August 23, 1988 / Proposed Rules

for regulatory applications; and (5)

whether there are any other models

applicable to these stagnation

conditions.

I. On-Site Meteorological Program

Guidance

The use of on-site meteorological data

to support air quality impact analyses

has grown steadily over recent years.

The EPA has published a document

titled "On-site Meteorological Program

Guidance for Regulatory Modeling

Applications", EPA-450/4-87-013

(Docket Item 11-1-17). The purpose of

this document is to consolidate into a single document specific guidance on the collection and use of on-site

meteorological data for air quality

modeling analyses. While this document

has undergone extensive external peer

review by State agencies,

meteorological instrument

manufacturers, and other Federal

agencies, it has not been subject to

formal public comment. The EPA,

therefore solicits comments on the onsite meteorological guidance document

and on whether to adopt the

recommendations of this document.

In response to the need for

consistency in the processing of on-site

meteorological data, EPA has developed

a Meteorological Processor for

Regulatory Models (MPRM), Docket

Item 11-1-18). This computer algorithm is

designed to process on-site

meteorological data following the

procedures recommended in the on-site

meteorological guidance document and

produces output necessary to run the

EPA regulatory dispersion models. The

MPRM can also process National

Weather Service surface and upper air

data. It is designed to provide

considerable flexibility to users in terms

of imput data formats, and also is

structured to be easily expanded to

accommodate data requirements of

future models. The EPA. therefore, also

solicits comments on whether to adopt

MPRM as the standard processor of

meteorological data imput for modeling

applications.

.Method for Evaluating Models

The modeling guideline describes a number of actions to be taken to allow a judgment to be made as to what model

is most appropriate for a given

application and specifically refers to the

document titled "Interim Procedures for

Evaluation Air Quality Models", EPA450/4-84-023. The Agency continues to

work on refining these methods and has

made advances in the statistical

methodology needed for determining

which model performs better than other

competing models. With this newer

methodology, it is feasible to combine

results from different averaging periods

and different data bases into a

probabilistic framework. This

methodology is described in an EPA

report titled "Protocol for Determining

the Best Performing Model" (Docket

Item 11--19). An Appendix to this report

provides examples of applying the

protocol to compare the performance of

two rural air quality models. The EPA

solicits comments on the technical

approach used in this report and

whether to adopt the procedure in

judging the best performing models for

regulatory applications.

K. Other Issues The modeling guideline references a

document titled "Guidelines for Air

Quality Maintenance Planning and

Analysis, Volume 10 (Revised)", EPA450/4-77-001. This document has been

revised to incorporate additions to the

technical approach and changes so that

the techniques now can easily be

executed on an IBM-PC compatible

microcomputer (Docket Item 11--20).

The EPA solicits comments on the

technical validity of these screening

techniques.

The EPA has under development and

evaluation two regional scale models:

the Regional Oxidant Model and the

Regional Acid Deposition Model

(Docket Items 11-1-21 and 22). These

models can treat complex chemical

interactions associated with emissions

from a large number of widely

distributed sources (e.g., a metropolitan

area) and can account for

comprehensive physical and chemical

processes important in the transport,

transformation, and deposition of

pollutants on a regional scale. These

models are designed to evaluate policy

implications of alternative control

strategies for groups of sources

encompassing a region. They are not

designed to set emission limits for

specific sources. The EPA solicits

comments on the potential usefulness to

regulatory programs of regional scale

models to assess transport, chemical

interactions and dispersion of multiple

pollutants.

Finally, air quality dispersion models

are taking on increasing importance as

tools for analyzing air emissions in

connection with toxics and hazardous

waste pollutants. The EPA solicits

comments on what modeling techniques

to consider in developing air pathway

analyses for such pollutants.

Public Participation

The Fourth Conference on Air Quality

Modeling will be open to the public; no

admission fee is charged. The morning

of the first day will include briefings by

EPA officials and others on the modeling

issues discussed above. In the

afternoon, the conference will continue

with statements from representatives of

APCA's Meteorology Committee, the

American Meteorological Society, the

National Academy of Sciences,

appropriate Federal agencies including

the National Science Foundation, the

National Oceanic and Atmospheric

Administration, the National Bureau of

Standards, the FAA, and others. The day

will conclude with statements by

representatives of State and local air

pollution control agencies.-On the

second day, the conference will be

opened to statements and comments

from the general public.

Persons wishing to speak at the

conference should contact EPA at the

address given in the "FURTHER

INFORMATION" section no later than

10 days prior to the conference date.

Such persons should identify the

organization (if any) on whose behalf

they are speaking and the length of

presentation. If a presentation is

projected to be longer than 15 minutes,

the presenter should also state why a

longer period is needed. Persons failing

to submit a written notice but desiring to

speak at the conference should notify

the presiding officer immediately before

the conference and will be scheduled on

a time-available basis.

The conference will be conducted

informally and chaired by an EPAofficial. There will be no sworn

testimony or cross examination. A

verbatim transcript of the conference

proceedings will be made and placed in

the docket. Speakers should bring extra

copies of their presentation for inclusion

in the docket, for the convenience of the

reporter and the Agency panel. Speakers

will be permitted to enter into the record

any additional written comments that

are not presented orally. Additional

written statements or comments should

be sent to the Central Docket Section

(see ADDRESSES section). A transcript

of the proceedings and a copy of all

written comments will be maintained in

Docket A-88-04 which will remain open

for 60 days following the conference for

the purpose of receiving additional

comments.

Date: August 15, 1988.

Don R. Clay,

Acting Assistant AdministratorforAir and

Radiation.

[FR Doc. 88-18951 Filed 8-22-88; 8:45 am]

BILLING CODE 6560-60-M

I

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