EPA-450/4-91-011

EMISSION INVENTORY

REQUIREMENTS FOR

CARBON MONOXIDE

STATE IMPLEMENTATION PLANS

By

Emission Inventory Branch

Technical Support Division

And

Radian Corporation 

Research Triangle Park, NC 27709

Office of Air Quality Planning and Standards

Office of Air and Radiation

U.S. Environmental Protection Agency

Research Triangle Park, NC 27711

March 1991 
ii

DISCLAIMER

This report has been reviewed by the Office of Air

Quality Planning and Standards, U. S. Environmental Protection

Agency, and has been approved for publication. Any mention of

trade names or commercial products does not constitute

endorsement or recommendation for use.

EPA-450/4-91-011
iii

PREFACE

This document describes the emission inventory

requirements related to the preparation and submission of carbon

monoxide (CO) State Implementation Plans (SIPs) for those areas

required to revise their plan as a result of provisions contained

in the 1990 Clean Air Act Amendments (CAAA). This document

represents a revision and an update to the document entitled

Emission Inventory Requirements for Post-1987 Carbon Monoxide

State Implementation Plans (EPA-450/4-88-020) issued in December

1988 in response to the proposed Post-1987 Ozone/CO Policy. 

As with the previous requirements document, the primary

focus of this document and its requirements discussion is base

year emission inventories. Other CO SIP inventories required or

necessitated by the CAAA, including periodic and modeling

inventories, are also identified and requirements for these

inventories are briefly discussed. Because both base year

inventories and attainment demonstrations for CO nonattainment

areas above 12.7 ppm are due in final form by November 15, 1992,

the importance of early submittal of base year inventories and

preparation of modeling inventories is emphasized. More detailed

guidance on these inventories will be issued by the U. S.

Environmental Protection Agency (EPA) in subsequent guidance

documents (see Section 6.0).

Guidance herein provides details of the 1990 CAAA CO

SIP emission inventory requirements beyond those discussed in

Guidance for Initiating Ozone/CO SIP Emission Inventories

Pursuant to the 1990 Clean Air Act Amendments, February 1991. 

While discussions in this document are consistent with the

February 1991 guidance, one change concerns the temporal basis

for CO emissions reporting. In the base year and periodic

inventories, States will be required to report CO emissions on a
iv

daily basis, rather than an 8 hour basis, as was discussed in the

February guidance.

Another change concerns the schedule for submittal of

Inventory Preparation Plans, which describe how and when the

inventories will be prepared and reported to EPA. The plan shall

present a blueprint for the methods and data sources a State

plans to use to compile and document its inventories. The IPP

shall also contain a specification of the intended quality

assurance program for each inventory compilation and a schedule

for preparation and submittal of each inventory. In the February

guidance document, a date was listed (October 1, 1991) by which

the plans must be agreed upon by EPA and in final form. However,

no initial submittal date was mentioned. Guidance herein

includes the October 1 date for a final Inventory Preparation

Plan and adds a requirement for submittal of the initial

Inventory Preparation Plan by July 31, 1991 (see Section 3.1).

The most significant changes incorporated into this

guidance from that provided to support the proposed Post-1987

Policy are summarized below. 

! As mentioned above, inventory preparation plans

(IPPs) shall be developed for each nonattainment

area that describe how and when the required

emission inventories for the area will be prepared

and submitted to EPA. IPPs were not required

under the proposed Post-1987 Ozone/CO policy

guidance. Each IPP must be submitted to EPA no

later than July 31, 1991, for review and approval. 

IPPs must be agreed upon with EPA and in final

form by October 1, 1991. EPA will not accept for

review any submitted CO SIP inventory for which

there is not an approved IPP.

! The MOBILE4 model, required under the proposed

Post-1987 Policy guidance for estimating on-road

mobile source emission factors, is being revised

and updated by EPA. The revised model, MOBILE4.1

(to be issued in May 1991), must be used to

estimate on-road vehicle emissions for CAAA SIP
v

inventories. The majority of the changes to the

model are internal such that there are essentially

no added requirements placed on the user, with the

possible exception of generating emissions on an

hourly basis. Specific guidance on the updated

model will be issued in May 1991.
vi

! Computerized data management and reporting

requirements for CAAA SIP inventories have been

significantly expanded beyond those found in the

guidance accompanying the previous policy. All CO

SIP emission inventory data must be provided to

EPA in an AIRS (Aerometric Information Retrieval

System) compatible format or directly into AIRS.

The data elements States must input into AIRS for

SIP inventories are discussed in the document. 

EPA will be issuing additional guidance in 1991 on

the use of AIRS and its subsystems.

! Written inventory documentation requirements have

been clarified and expanded for the purpose of

providing EPA with a better basis to perform

inventory quality review assessments. A specific

outline has been provided to States to indicate

the content and organization of the information

that States shall provide to EPA.

! EPA's Office of Mobile Sources (OMS) is actively

engaged in research to develop new methodologies

for estimating CO emissions from several mobile

source categories. Interim research results which

have been provided and which are recommended for

States' use in CO SIP inventory development are

discussed. The source categories principally

affected are non-road mobile sources such as

airplanes and trains. Work has also been

performed on revising the methods for deriving

vehicle-miles-traveled (VMT) estimates for on-road

mobile sources emissions. 

! States with SIP emission inventories prepared

under the proposed Post-1987 Policy that have

1987, 1988, or 1989 base years and that have been

determined by the EPA Regional Offices to be

complete, comprehensive, and accurate will be

allowed to update certain portions of these

inventories to a 1990 base year instead of having

to totally redevelop the inventories with 1990

data. Criteria for determining which inventories

can be updated and which can not have been

developed by EPA and will be applied on an

inventory-specific basis by the EPA Regional

Offices. Some specifications for updating are

provided in this document.

! CO SIP revisions under the CAAA must include

certain inventories that go beyond requirements in
vii

the proposed Post-1987 Policy. States shall

prepare periodic and modeling inventories that are

associated with tracking required emission

reductions and demonstrating attainment. 

Overviews of these inventories and their

requirements are presented, and schedules are

provided to indicate when detailed development

guidance will be forthcoming.
viii

TABLE OF CONTENTS

Page

DISCLAIMER ......................... ii

PREFACE ........................... iii

LIST OF TABLES ...................... viii

1.0 OVERVIEW OF DOCUMENT ................ 1

1.1 Purpose .................... 1

1.2 Summary of Document Contents .......... 1

2.0 INTRODUCTION TO INVENTORY REQUIREMENTS ....... 3

2.1 Nonattainment Classifications ......... 3

2.2 Summary of Inventory Types ........... 5

3.0 EMISSION INVENTORY REQUIREMENTS ........... 7

3.1 Inventory Preparation Plans .......... 7

3.2 Base Year Emissions Inventories ....... 11

3.2.1 AIRS Compatible Reporting ..... 14

3.2.2 Geographic Area to be Inventoried . 14

3.2.3 Pollutants to be Inventoried .... 15

3.2.4 Applicable Source Categories .... 15

3.2.5 Updated Mobile Emissions Model

(MOBILE4.1) ......................... 15

3.2.6 Updating from 1987/1988/1989 to 1990 16

3.3 Temporal Basis of Emissions ......... 20

3.3.1 Peak CO Season ........... 20

3.3.2 Typical Operating Day Emissions . . 21

3.4 Spatial Allocation of Emissions ....... 21

3.5 Temperature ................. 22

3.6 Rule Effectiveness (RE) and Rule Penetration . 23

3.7 Point Sources ................ 25

3.8 Area Sources ................. 27

3.9 Mobile Sources ................ 28

3.10 Periodic Emission Inventories ........ 29

3.11 Modeling Inventories ............. 30

3.12 Quality Assurance .............. 31

3.13 References .................. 31
ix

TABLE OF CONTENTS

Page

4.0 COMPUTERIZED DATA MANAGEMENT AND REPORTING .... 33

4.1 Point Source Inventory ............ 34

4.2 Point Source Data Elements .......... 37

4.3 Area and Mobile Source Inventory ....... 42

4.4 Area and Mobile Source Data Elements ..... 44

4.5 Format for Area and Mobile Source Data .... 47

5.0 DOCUMENTATION OF THE INVENTORY .......... 48

6.0 BIBLIOGRAPHY ................... 56

APPENDIX A - SUMMARY OF REQUIRED CARBON

MONOXIDE SIP INVENTORIES BY NONATTAINMENT

AREA CLASSIFICATION ................ A-1

APPENDIX B - POINT, AREA, AND MOBILE SOURCE

CATEGORIES NECESSARY FOR CONSIDERATION IN

CO SIP INVENTORIES ................ B-1
x

LIST OF TABLES

Page

3-1 Topics to be Included in Inventory Preparation Plans 12

5-1 Outline for EPA Recommended Format/Contents for CO SIP 

Emission Inventory Reports ............ 50
1

1.0 OVERVIEW OF DOCUMENT

1.1 Purpose

This document describes the emission inventory

requirements that are contained, either explicitly or implicitly,

in the 1990 Clean Air Act Amendments (CAAA) for those areas that

are required to revise their State Implementation Plan (SIP) for

attainment of the National Ambient Air Quality Standard (NAAQS)

for carbon monoxide (CO). The purposes of the document are to

identify the types of inventories required, to describe the

objective and ultimate use of the inventories, and to define

specifications for what data elements must be contained in the

inventories and how these elements must be developed.

1.2 Summary of Document Contents

As noted above, this section presents the purpose of

the document and also provides an overview of the document

organization and contents. The key points and format of the

material presented in the remaining sections of this document are

outlined below.

Section 2.0 presents an introduction to CO SIP emission

inventory requirements under the CAAA. It summarizes the

different CO nonattainment classifications and the general

emission inventory requirements applicable to each

classification.

The specific details of inventory development and

compilation requirements are provided in Section 3.0. The

majority of the discussion is focused on the base year inventory. 

Topics such as AIRS (Aerometric Information Retrieval System)

compatible data reporting, geographic areas of inventory
2

coverage, pollutants of interest, source categories of interest,

inventory updating, and newly developed tools for inventory

development are discussed. EPA requirements for a new feature,

inventory preparation plans, are presented and fully explained. 

In addition, requirements regarding the temporal and

spatial allocation of emissions, the selection of ambient

temperatures, the application of rule effectiveness, and the

definitions of point, area, and mobile sources are discussed. 

Section 3.0 also addresses requirements relating to periodic and

modeling inventories and quality assurance provisions.

Section 4.0 discusses the computerized data management

and reporting requirements that have been established by the

Environmental Protection Agency (EPA) for SIP inventories

compiled under the CAAA. These data management provisions apply

to point, area, and mobile data. Section 4.0 details State

requirements relating to the use of AIRS for reporting all SIP

emissions data.

Section 5.0 specifies the manner in which States shall

provide written documentation for their emission inventories. 

Requirements for both documentation format and content are

discussed. 

Section 6.0 provides bibliographic citations of

currently existing EPA guidance materials for the development of

CO SIP inventories. The list of guidance is divided into four

categories: CO SIP inventory guidance/requirements, quality

assurance/inventory review guidance, emission factors/models, and

general inventory guidance.
3

2.0 INTRODUCTION TO INVENTORY REQUIREMENTS

This section of the document summarizes the different

classifications, found in the CAAA of 1990, by which carbon

monoxide (CO) nonattainment areas are delineated. The types of

SIP inventories that are either explicitly or implicitly

contained in the CAAA, according to nonattainment classification,

are also identified in this section. These different types and

their requirements are specified in greater detail in 

Section 3.0. 

2.1 Nonattainment Classifications

Two classifications are contained in the CAAA for CO

nonattainment areas. These two groupings, known as moderate and

serious, are defined as follows [Section 186(a)(1)].

CO Nonattainment Classifications

Area Class Design Value (ppm) Attainment Date

Moderate 9.1 to 16.4 December 31, 1995

Serious 16.5 and above December 31, 2000

Even though they are classified as moderate areas, CO

nonattainment areas with design values greater than 12.7 ppm have

more stringent overall requirements than do moderate areas with

values in the 9.1 up to 12.7 range (Section 187). The extra

requirements include compiling additional vehicle miles travelled

(VMT) projections [187 (a)(2)(A)], preparing contingency plans if

projected VMT levels are not met and attainment is not achieved

[187 (a)(2)(B)(3)], establishing enhanced vehicle inspection and

maintenance (I/M) programs [187 (a)(2)(B)(6)], and preparing
4

specific plans to demonstrate that attainment and necessary

annual emission reductions will be met [187 (a)(2)(B)(7)]. 

Specifically, States that have serious CO areas or

moderate CO areas with a design value greater than 12.7 ppm must

comply with the following additional requirements per the CAAA

(unless a waiver is granted through Section 187(c)). 

1. The SIP revision shall contain a forecast of VMT for

each year before the year in which the plan projects

attainment will be reached. The forecast must be based

on guidance to be issued by the EPA Administrator. 

Annual updates of the forecasts have to be submitted

together with annual reports regarding the extent to

which such forecasts proved to be accurate. The annual

reports must contain estimates of actual VMT in each

year for which a forecast was required [Section 187

(a)(2)(A)].

2. The SIP revision plan must provide for the

implementation of specific measures to be undertaken if

any estimate of VMT submitted in an annual report (as

required in No. 1 above) exceeds the number predicted

in the most recent prior forecast, or if the area fails

to attain the NAAQS by the specified date. The

measures shall be included in the plan as contingency

measures to take effect without further action by the

State or the Administrator if the prior forecast has

been exceeded by an updated forecast or if the NAAQS is

not attained by the deadline [Section 187

(a)(2)(B)(3)].

3. The SIP revision plan must contain provisions for an

enhanced vehicle I/M program as required under CAAA
5

Section 182 (c)(3) as it pertains to CO [Section 187

(a)(2)(B)(6)].

4. The SIP revision must demonstrate that attainment will

be met by the applicable date and that required annual

emission reductions will be met [Section 187

(a)(2)(B)(7)].

Two 1-year extensions for reaching CO attainment are

available to States if: 1) all SIP requirements and commitments

for an area were met and 2) no more than one exceedance of the CO

NAAQS occurred in the year preceding the extension year [Section

181 (a)(5) and Section 186 (a)(4)].

2.2 Summary of Inventory Types

For CO nonattainment areas, States must generally

compile three types of inventories. The exception to this

requirement would be moderate CO areas with a design value equal

to or less than 12.7 ppm. These areas are required to compile

only two types of inventories, a base year inventory and periodic

inventories. Moderate areas above 12.7 ppm and serious areas are

required to develop a base year inventory, periodic inventories,

and modeling inventories to comply with CAAA provisions [Section

187 (a)(1), (a)(5), (a)(7), and 187 (d)(1)].

The base year inventory is the primary inventory from

which all other CO inventories are derived. Thus, all

inventories should be consistent with data provided in the base

year inventory. It establishes the basis for determining rate of

progress requirements, and is used as the basis for periodic

inventories and attainment demonstrations. The base year

inventory must reflect actual CO emissions during the 1990 base
6

year. More details on the requirements States must meet for the

base year inventory are provided in Section 3.2.

Periodic CO inventories essentially require the same

information as the base inventories. The primary difference

between them is the basis year for the emissions. Modeling

inventories are required for moderate areas above 12.7 ppm and

serious areas because CAAA provisions require such areas to make

attainment demonstrations using air quality dispersion models

[Section 187 (a)(7) and 187 (d)(1)]. Base year and projected

modeling inventories must be developed. The base year modeling

inventory shall address actual emissions, while the projected

modeling inventory shall be based on allowable emissions, where

they exist. 

More detailed specifications of the requirements States

must adhere to for periodic and modeling inventories are provided

in Sections 3.10 and 3.11, respectively. A summary of the

inventory requirements by CO nonattainment classification is

provided in Appendix A.
7

3.0 EMISSION INVENTORY REQUIREMENTS

As discussed in Section 2.0, revised carbon monoxide

(CO) SIPs under the CAAA shall include base year, periodic, and

modeling inventories. Emission estimates shall be determined to

the extent possible using source specific information in

conjunction with methodologies described in the inventory

guideline references listed in Section 6.0. One such reference,

Procedures for the Preparation of Emission Inventories for

Precursors of Ozone - Volume I , is recommended for inventorying 1

base year CO emissions from stationary sources. A revised and

updated version of this document is scheduled to be issued by EPA

in May 1991 and will address issues specific to CO inventories. 

Another reference, Procedures for Emission Inventory Preparation,

Volumes IV: Mobile Sources should be referred to for 2

inventorying base year CO emissions from mobile sources. A

revised and updated version of the mobile sources document is

also scheduled to be issued by EPA in May 1991.

More specifically, States shall be guided by the

requirements described in this section of the document for SIP

inventory preparation under the CAAA. The nature and

requirements of each inventory type are presented and discussed. 

Base year inventory requirements and their relation to other

inventories' requirements are discussed in Section 3.2. Specific

requirements for periodic inventories are discussed in Section

3.10, and modeling inventories in Section 3.11. Inventory

elements common to all inventory types (e.g., temporal basis of

emissions, temperature, rule effectiveness, etc.) are discussed

in other parts of Section 3.0. Quality assurance (QA)

requirements for all SIP inventory submittals are discussed in

Section 3.12.

3.1 Inventory Preparation Plans
8

Under the previously proposed Post-1987 Ozone/CO

Policy, States were not required to tell EPA how they planned to

prepare, document, and submit their base year emission

inventories prior to the actual submittal of the materials. For

the purposes of the CAAA and their emission inventory

requirements, EPA is adopting a new approach. For CAAA base year

inventories, EPA is requiring that States prepare a brief

Inventory Preparation Plan (IPP) that specifies to EPA how they

intend to develop, document, and submit their inventories. The

plans will give States the chance to tell EPA how they plan to

compile the required inventories, and will allow EPA to provide

feedback to avoid having States use approaches that are not

consistent with EPA requirements. With the use of IPPs, EPA can

help guide the preparation of inventories and attempt to ensure

that emission estimates are of higher quality and are consistent

with the CAAA requirements. States shall submit IPPs to EPA

Regional Offices and EPA Headquarters no later than July 31,

1991. IPPs are due in final form (i.e., agreed upon by EPA) by

October 1, 1991.

In addition to technical data, the IPPs shall contain

schedules for when the States plan to submit draft and final

inventories or inventory components to EPA. If the State plans

to submit an inventory in component pieces (e.g., point source

component, area source component, etc.), the IPP shall clearly

make this distinction and indicate a draft and final submittal

date for each component. The final submittal dates shall be

consistent with the ultimate inventory delivery dates specified

in the CAAA and presented in Section 3.0 of this document. 

Multi-State nonattainment areas shall define how they will

coordinate preparation and submittal of the inventories.

Each States shall submit its IPP to its EPA Regional

Office (RO) for review no later than July 31, 1991. Each State
9

should also send EPA Headquarters a copy of the document and any

correspondence relating to the plans. EPA Headquarters copies

should be sent to: Chief, Inventory Guidance and Evaluation

Section, Emission Inventory Branch (MD-14), Technical Support

Division, U.S. Environmental Protection Agency, Research Triangle

Park, North Carolina, 27711.

States shall prepare an IPP for each specific

nonattainment area for which a base year inventory is required by

the CAAA, to the extent that different approaches will be used. 

If a State has multiple nonattainment areas but plans to use the

same overall approach for each, the State can submit a single IPP

that details that approach and the areas to which it will apply. 

States need to be aware that EPA will not accept a base year

inventory for review from a State until EPA has received,

reviewed, and approved an IPP for that inventory. EPA approval

of an IPP does not, however, signify that EPA unconditionally

accepts all of the information to be contained in the actual

inventory. The inventory will be reviewed separately and on its

own merits regardless of how well or how poorly the IPP was

assembled. In approving an IPP submitted, EPA will accept the

intended approach for inventory compilation. The results

produced by these approved approaches will have to undergo a

separate review and approval process. 

An IPP shall address how a State plans to inventory all

sources (regardless of size) of CO for CO nonattainment areas. 

Separate discussions shall be used to address stationary point,

stationary area, on-road mobile, and non-road mobile sources. If

an inventory started under other programs will be utilized (e.g.,

under the proposed Post-1987 Policy), this should be stated. 

Generally, the State's starting point for the base year inventory

effort should be summarized. 
10

For point sources, States shall define how all

pertinent emission sources will be identified and located. 

States shall describe how point source activity levels and

associated parameters will be developed, and how these data will

be used to calculate emission estimates. States must describe

any source surveys that are planned, and if they intend to use

existing data contained in systems such as SAMS (SIP Air

Pollutant Inventory Management System), AIRS (Aerometric

Information Retrieval System), individual State EIS (Emissions

Inventory System), or State permitting files. The extent to

which a State plans to use EPA's AIRS and PC-SAMS data base

management systems to compile their point source inventory shall

be explained. 

For stationary area and non-road mobile sources, the

plan shall explicitly state which source categories will be

addressed and which will not be addressed (with justification for

exclusion). For those categories to be included, the plan shall

indicate what calculational method will be used to calculate

emissions. If a State plans on using EPA's inventory guidance

for all categories, it should report that it will be applying the

EPA-recommended approaches. If the EPA guidance has alternative

methods for a category, the IPP should clearly indicate which

method the State intends to use in its inventory. Particular

emphasis should be given to categories for which the State plans

to use an approach other than that recommended in EPA's guidance. 

Any major assumptions that will be used that affect the

development of emission estimates in a category shall be clearly

stated.

For on-road mobile sources, the IPP shall provide a

clear indication of how the State intends to develop VMT (vehicle

miles traveled) estimates and mobile source emission factors. 

Any predictive models that will be applied shall be identified
11

and key assumptions in the use of the models shall be stated. 

Other items that shall be addressed include specifications of the

vehicle classes that will be covered, the fuel RVP (Reid vapor

pressure) level to be used or method used to determine RVP, and

inspection/maintenance (I/M) and anti-tampering programs that are

in place.

The IPP must clearly describe how the State plans to

present document, and submit the inventory to EPA. The general

kinds of documentation that will be provided and the form of this

documentation shall be described to the extent that EPA can judge

if it would be satisfactory for inventory review purposes. The

IPP shall specify the written and computerized methods that a

State plans to compile and submit its data, keeping in mind that

States must submit their final SIP inventory data in AIRS or in

an AIRS-compatible format. States must clearly delineate whether

and how State data base/data systems will be used and how data

will be input into the AIRS Facility Subsystem (AFS) and the AIRS

Area and Mobile Source (AMS) Subsystem.

One component that must be contained in an IPP is the

QA plan for the inventory. This plan shall describe the overall

QA program that the State intends to use during the compilation

of the inventory. The QA plan shall be constructed according to

the guidance provided in Section 3.12 of this discussion. 

Generally, EPA envisions that the IPPs will be brief. 

It is EPA's intent that they be concise and to the point, and

only provide as much detail as is necessary to communicate to the

Agency how the State intends to develop and present its

inventory. However, the document must contain sufficient

information to enable EPA to make a judgment that the intended

State inventory approach is sound and consistent with EPA's
12

requirements. Although no specific IPP format is required, the

discussion should include the topics listed in Table 3-1.

3.2 Base Year Emission Inventories

The base year inventory is the primary inventory from

which other CO inventories are derived. It establishes the basis

for determining rate of progress requirements, and is used as the

basis for periodic inventories and attainment demonstrations. 

The base year CO inventory is defined in the 1990 CAAA to be a

"current inventory." EPA interprets this to mean an inventory

for 1990 (year of enactment). The inventory shall address actual

CO emissions during the peak CO season for the area. All

stationary point and area sources and on-road/non-road mobile

sources are to be included in the compilation. Peak CO season

shall reflect the three consecutive months when peak CO air

quality concentrations occur. For many, but not all, areas of

the country, the peak CO season will be in the wintertime months. 

For areas where winter is the peak CO season, the 1990 base year

inventory shall include the winter months beginning in 1989 and

extending into 1990 (e.g., December 1989 and January-February

1990). Emissions shall be determined for a typical operating day

during the designated peak CO season. 

States are required to submit the final base year

inventory for each of their CO nonattainment areas to EPA no

later than November 15, 1992. Attainment demonstrations for

areas above 12.7 ppm are also due by November 15, 1992. In order

to meet this schedule and allow sufficient time for EPA review

and State incorporation of EPA comments, draft base year

inventories should be submitted as soon after January 1, 1992 as

is feasible, but no later than to May 1, 1992.
13

TABLE 3-1. TOPICS TO BE INCLUDED IN 

 INVENTORY PREPARATION PLANS

 

 

IPP Topics

A. Introduction

- define what nonattainment area the plan is for, whether

attainment for CO only, or both CO and O3,

classification(s) of the area.

- background/basis for the inventory (i.e., previous

efforts that are viable and related), starting point

- define how the plan is structured, what does it contain

- specify who is responsible for the inventory and who is

actually compiling it (air agency, consultants, etc.)

B. Point Sources Approach

- how will sources be identified and located

- how will minor sources be identified

- define role of existing data (AIRS, NAPAP, permitting

data, etc.)

- identify data collection methods to be used (e.g.,

surveys, etc.)

- basis for activity level data and emission estimates

- basis for control efficiencies

- application of rule effectiveness

- basis for rule penetration and rule effectiveness

levels

C. Area and Non-Road Mobile Sources Approach

- what categories will be addressed and why

- what categories will be excluded and why

 

 
14

TABLE 3-1. Continued

 

 -

what estimation methods will be used (e.g., AP-42,

Procedures Document, site-specific surveys, etc.)

- methods for collecting activity/commodity level data 

- application of rule effectiveness

- basis for rule penetration and rule effectiveness

levels

 

D. On-Road Mobile Sources Approach

- specification of how VMT are to be determined

- specification of the mobile source emissions model used

(will be an updated version of MOBILE4)

- specification of key assumptions for the emissions

model involving parameters such as temperature, speeds,

existence of I/M and anti-tampering programs,

incorporation of vehicle refueling losses, etc.

 

E. Documentation Approach

- written presentation and documentation

- computerized compilations and documentation

- use of AIRS online, PC-SAMS and PC-AMS

- submission of data in AIRS-compatible format

 

F. Quality Assurance Plan

- description of QA program

- how QA program will affect and benefit inventory

- description of adherence to previously issued QA

guidance

 

 
15

The remainder of Section 3.2 presents base year

inventory requirements pertaining to factors such as AIRScompatible reporting (3.2.1), inventory geographic area (3.2.2),

pollutants to be inventoried (3.2.3), source categories to be

inventoried (3.2.4), an updated version of MOBILE4 (3.2.5), and

inventory updates from 1987/88/89 to 1990 (3.2.6). 

3.2.1 AIRS Compatible Reporting

The AIRS will be the official repository for all

emission inventory data. Therefore, all SIP data must be

submitted in an AIRS compatible format in order to be accepted.

The EPA will provide PC software packages for States to perform

preliminary inventory preparation activities (see Section 4.0). 

Point source data transfer from the SAMS PC package to the AFS

will be possible beginning in January 1992. Area source data

transfer from the new area and mobile source PC package to the

AIRS Area and Mobile Source Subsystem (AMS) will be available in

May 1992. Specifications for AIRS reporting are detailed in

Section 4.0 of this document.

3.2.2 Geographic Area to be Inventoried

Most geographic areas for CO nonattainment designations

will be defined by EPA by July 13, 1991. These designations will

be made under the provisions of the CAAA, which require each

State to submit to EPA a list of all areas in the State

indicating designations (attainment, nonattainment,

unclassifiable) for CO (or affirming existing designations) and

describing their boundaries. The designations will be published

in Part 81 of the Code of Federal Regulations. All point, area

and mobile sources of CO within the designated nonattainment area

shall be included in the base year emission inventory as well as

the periodic and modeling inventories.
16

Modeling demonstrations need to be performed in

designated nonattainment areas with a CO design value that

exceeds 12.7 ppm. This modeling demonstration shall include both

areawide and hot spot modeling. The areawide model shall be

either the RAM or the UAM (Urban Airshed Model). The model

currently proposed for hot spot demonstrations is CAL3QHC. The

hot spot model and its use are described in detail in References

3 and 4.

3.2.3 Pollutants to be Inventoried

Carbon monoxide (CO) is the only pollutant that needs

to be included in the CO SIP emission inventories compiled under

the 1990 CAAA. The inventory shall contain CO emission estimates

and other required data (see Section 4.0) from stationary point

and area, on-road mobile, and non-road mobile sources.

3.2.4 Applicable Source Categories

The types of sources to be included in base year

inventories under the CAAA are essentially the same as those

found in the proposed Post-1987 Policy. Base year inventories

are required to address all stationary point and area sources,

non-road mobile sources, and on-road mobile sources. A tentative

listing of the point, area, and mobile source categories that

must be evaluated for inclusion in the inventory are listed in

Appendix B. Table B-1 lists individual point source categories. 

Area and mobile source categories are listed in Table B-2. A

final listing will be included in the revised version of the

Procedures Document.1

Formats for reporting 1990 emission inventory data will

differ from previous requirements. Information and requirements
17

on formats and systems for base year inventory data reporting are

contained in Section 4.0. 

3.2.5 Updated Mobile Emissions Model (MOBILE4.1)

In May of 1991, EPA plans to issue an updated version

of its mobile source emissions estimation model, MOBILE4. The

updated version of MOBILE4 will be known as MOBILE4.1 and will

replace and supersede its predecessor. States are required to

use MOBILE4.1 in determining highway mobile source emissions for

all of their base year emission inventories under the CAAA. 

California shall consult with EPA Region 9 in determining the

mobile model to be used. The overall application of MOBILE4.1

for base year inventory purposes is generally the same as that

used for MOBILE4 with the exception of an option to run hour by

hour. The majority of the enhancements in the revised model are

internal to the model and do not directly impact the user for

base year inventory emission factor generation purposes. 

Specific guidance on the scope of the model changes and their

impacts, and on the use of the model for base year inventories

will be issued in May 1991.

3.2.6 Updating from 1987/1988/1989 to 1990

Several ozone and CO nonattainment areas that received

SIP calls in 1988 or 1989 have prepared or have begun preparation

of base year emission inventories per the requirements and

guidance in the proposed Post-1987 O3/CO Policy (52 FR 45044,

November 24, 1987). These inventories have either 1987, 1988, or

1989 as their base year. For the purposes of the CAAA, these

inventories have to be either updated to 1990, the year of

enactment of the CAAA, or redone totally to reflect a 1990 base

year. States which have fully completed portions of their base

year inventories for 1987, 1988, or 1989 that they desire to
18

update and have received EPA approval of these portions will be

considered for approval to update. Otherwise, States shall

prepare a completely new inventory for base year 1990. For the

purposes of accuracy and providing an inventory that will meet

the goals of the CAAA, EPA encourages all areas to prepare new

1990 base year inventories even if they assembled base year

inventories for 1987/1988/1989.

States shall work with their respective EPA RO to

determine if they can perform updates to 1987/1988/1989

inventories that have been prepared, and to determine how these

updates should be performed. Regional Office questions will be

resolved by EPA air headquarters staff [Office of Air Quality

Planning and Standards (OAQPS)]. Before any updating can be

performed on 1987/1988/1989 inventories, States shall receive

written authorization from the appropriate EPA Regional Office

allowing them to do so. EPA will not accept any updated

inventories in cases where this prior authorization is not

received. For nonattainment areas that meet the above stated

conditions, States shall request from their EPA Regional Office

as soon as possible approval to perform an update if the State

does not desire to reconstruct a 1990 base year inventory from

the start. In their petition, States should clearly document the

case for why they should be allowed to perform an update of the

1987/1988/1989 inventory. Once approval to perform an update is

received, the State shall complete and submit an IPP as required

by EPA under the CAAA (see Section 3.1 for details on the IPP

requirements). 

For States that are able to perform updates to the

1987/1988/1989 base year inventories, the updating process will

likely be split along the lines of point, area, non-road mobile,

and on-road mobile sources. EPA plans to issue more direct

formal guidance for performing updates (e.g., specific growth
19

factors to use on an individual source category basis) in May

1991. However, for the purposes of this guidance discussion, the

following general guidance should be followed. 

3.2.6.1 Point Sources

All stationary point sources of CO with emissions of

100 tons/yr or greater shall be re-inventoried completely and not

simply updated. Existing point source guidance in the Procedures

Document (revised version to be issued in May 1991) shall be used

to inventory the major sources. Sources with emissions less than

100 tons/yr can be adjusted to the 1990 base year using scaling

factors based on industrial growth for the category generally or

the plant specifically. The intended approach and source of the

growth factors must be fully explained in the IPP. Such an

approach negates having to resurvey each small CO point source;

however, States are encouraged to re-inventory these sources if

feasible. A new inventory of this type should give more accurate

current emissions data than could be obtained by adjusting older

data with growth factors. 

In the one to three year span since the previous base

year inventories were compiled, it is possible that new point

sources could have come into being that need to be added to the

1990 base year inventory. Once new sources are identified, they

should be inventoried according to the updated guidance in the

revised Procedures Document due to be issued in May 1991. For

major sources, additions should be well known to the State/local

agencies. Similarly, major plant shutdowns or curtailments

should be well documented. Other methods that States should use

to identify possible new sources or identify source shutdowns

include reviewing current industrial directories, reviewing

recent permitting records for new plants and existing plant

changes, and reviewing nationally-oriented data bases such as the
20

Toxic Release Inventory System (TRIS) for SARA 313 reporting

records.

3.2.6.2 Area and Non-Road Mobile Sources

Practically all of the emission estimates for area and

non-road mobile sources are based on the use of an emission

factor and some activity/commodity level(s) (e.g., population,

employment, equipment counts, etc.) that is a surrogate indicator

of emissions. States can perform updates for these source types

by examining how the surrogate activity levels have changed over

the period to 1990. For most of the source categories, changes

over the one to three year span will not have been large. For

each area and non-road mobile source category, States must

investigate the key emissions surrogate parameters and determine

how they have changed since the previous base year inventories

were developed. The 87/88/89 inventory should be reviewed to

determine what the key emission surrogates are. They will

generally be expressed in the emission factor itself (e.g., lbs

CO/capita) or in a multi-step calculation process (e.g., pieces

of equipment x hours of operation per piece x lbs CO/hr of

operation). In some cases, the extrapolation to 1990 will be

very easy to perform because the surrogate statistics are readily

available (e.g., population). In other cases, the State must

determine new data that are very site-specific (e.g., airplane

takeoff/landing cycles at an airport) to the point that the

category is actually being reinventoried as opposed to being

updated.

States are reminded that EPA will be issuing new

inventory procedures guidance for some area and non-road mobile

source categories in May 1991 that may significantly affect how

emissions are to be determined. For these categories (railroads,

aircraft, solvent uses), it will likely not be possible to
21

perform updates from the previous estimates. Instead, new

emission estimates shall be prepared using the new methodology. 

Furthermore, updated inventories must meet the requirements for

coverage of source categories (Section 3.2.4), data reporting

(Section 4.0), and other basic requirements described herein and

in the revised Procedures Documents (References 1 and 2) to be

issued in May. 

3.2.6.3 On-Road Mobile Sources

On-road (highway) mobile source emission estimates must

be derived from scratch using a 1990 base year for all areas,

including those with 1987/1988/1989 base year inventories that

were allowed to update their overall inventory. There are

several reasons EPA is adopting this requirement. One relates to

the way that mobile source models calculate emission factors. 

Relatively significant changes occur in the factors with fleet

turnover from one model year to the next. Also, with new road

construction, VMT patterns change that significantly impact

mobile source emissions. These changes may involve not only more

roads, but also changes in speeds both higher and lower. For

example, in 1990, several interstate roads now have 65 mile per

hour speed limits instead of 55. Since the on-road mobile source

component of these inventories is often the major contributor to

total area emissions, it makes sense to reevaluate its emissions

from year to year. The planned release of a new version of the

mobile source emissions estimation model, MOBILE4.1, in May 1991

also provides additional justification for totally reevaluating

mobile source emissions as opposed to application of a growth

factor. [California shall consult with EPA Region 9 in

determining the mobile source model to be used.]

The planned May 1991 release of new guidance for

determining VMT further solidifies the need for States to re-
22

calculate on-road mobile source emissions for the purposes of the

1990 base year inventories under the CAAA. States should use the

updated version of MOBILE4 and VMT development guidance to be

issued in May 1991 to construct their 1990 on-road mobile source

inventories. State air agency staff should begin contacting

Metropolitan Planning Office (MPO) personnel (or their

equivalent) to become familiar with the MPO's VMT estimation

methods, base years of data, and overall capabilities, and to

explain to the MPOs the CAAA provisions.

3.3 Temporal Basis of Emissions

The temporal basis on which CO emissions must be

expressed for 1990 base year inventories under the CAAA is the

peak CO period of the year for each nonattainment area. 

Generally, emissions must be reflective of a typical operating

day during the peak CO season. More specific guidance is

provided below for determining peak CO season and typical daily

emissions.

3.3.1 Peak CO Season

Peak CO season should reflect the months when peak CO

air quality concentrations occur. States shall define their peak

CO season to be the three contiguous months when the highest CO

NAAQS exceedance episode days occur. This determination shall be

based on ambient data for the last three to four years. For

many, but not all, areas of the country, the peak CO season will

be in the wintertime months. For areas where winter is the peak

CO season, the 1990 base year inventory will include the winter

months beginning in 1989 and extending into 1990 (e.g., December

1989 and January-February 1990).
23

Source category activity data must be developed that

are correlated with the peak CO season as defined for each

nonattainment area. States should determine their peak CO season

prior to assembling their IPP. The peak CO season shall be

defined in the IPP and a brief documentation given for the period

selected.
24

3.3.2 Typical Operating Day Emissions

For CO nonattainment area base year inventories,

emissions must be determined and expressed on the basis of an

average operating day during the peak CO season. A typical

operating day shall consist of a 24-hour period. Additional

procedural guidance on how to determine operating day emissions

will be provided in the updated procedures document guidance to

be issued in May 1991. For those CO nonattainment areas required

to do modeling, operating day emissions must be further allocated

to an hourly basis, as discussed below.

If the CO design value for the nonattainment area is

less than 12.7 ppm CO, a 24-hour daily CO emissions estimate is

acceptable. However, if the design value is greater than 12.7

ppm, hourly CO emission estimates are required for modeling

purposes. The required techniques for control strategy

demonstrations for areas exceeding the 12.7 ppm design value are

the RAM Model or the UAM. Guidance on deriving hourly emission 5 6

estimates for the representative operating day in the peak CO

season can be obtained from the dispersion modeling guidance

document Procedures for the Preparation of Emission Inventories

for Volatile Organic Compounds, Volume II: Emission Inventory

Requirements for Photochemical Air Quality Simulation Models.

7

Although this document was prepared specifically for temporally

allocating VOC emissions, this is generally applicable to CO

emission sources as well. The revised version to be issued in

May 1991 will address CO modeling specific issues.

3.4 Spatial Allocation of Emissions

If the nonattainment area has a design value less than

or equal to 12.7 ppm CO, a countywide emissions inventory is

acceptable. If the design value of the area is greater than 12.7
25

ppm CO, then the control strategy demonstration must be performed

with the RAM Model or the UAM. If the RAM Model is used for

control strategy demonstrations, mobile and area sources need to

be allocated to square grid cells within the modeling domain that

covers the geographic area of the inventory discussed in Section

3.2.2 of this document. The size of the grid cells used in the

RAM Model can vary over the modeling domain. The recommended

grid square sizes are from 1 to 5 kilometers (km), with a 1 km

grid square recommended for the central business district (CBD)

of urban areas and larger grid squares recommended for areas

outside the CBD. Dispersion models such as the RAM model require

that point sources be allocated to the exact location in

Universal Transverse Mercator (UTM) coordinates and that stack

parameters (e.g., height, diameter, exit velocity, and exit

temperature) be specified for input.

Guidance on preparing a spatially resolved emissions

inventory for dispersion modeling is contained in Procedures For

The Preparation Of Emission Inventories For Volatile Organic

Compounds, Volume II: Emission Inventory Requirements For

Photochemical Air Quality Simulation Models. Again, although 7

this document was prepared specifically for spatial allocation of

VOC emissions, the guidance is generally applicable to CO

emissions.

The spatial allocation requirements for the UAM are the

same as those for the RAM Model with one difference. The

difference is that the grid square size for allocation of mobile

and area sources needs to remain constant over the modeling

domain for the UAM. The recommended grid square size for UAM is

from 2 to 5 kilometers. The choice of grid square size depends

on the size of the area being modeled, the resources available

for modeling, and the degree of resolution needed to determine

the effects of a particular control strategy.
26

3.5 Temperature

The MOBILE4.1 model requires that temperature be

entered as a key variable to the model's estimation of CO

emission factors for mobile sources. States must determine the

temperatures, for calculational purposes, that are appropriate

for the peak CO season they have defined. Furthermore, hourly

temperatures are required for input to the UAM for episode day

modeling. Guidance concerning temperature determinations will be

issued in the updated procedures guidance documents in May 1991.

3.6 Rule Effectiveness (RE) and Rule Penetration

Past inventories have assumed that regulatory programs

would be implemented with full effectiveness, achieving all of

the required or intended emission reductions and maintaining that

level over time. However, experience has shown regulatory

programs to be less than 100 percent effective for most source

categories in most areas of the country. The concept of applying

rule effectiveness in the SIP emission inventory has evolved from

this observation. In short, RE reflects the ability of a

regulatory program to achieve all the emission reductions that

could be achieved by full compliance with the applicable

regulations at all sources at all times.

Several factors should be taken into account when

estimating the effectiveness of a regulatory program. These

include: (1) the nature of the regulation (e.g., whether any

ambiguities or deficiencies exist, whether test methods and/or

recordkeeping requirements are prescribed); (2) the nature of the

compliance procedures (e.g., taking into account the long-term

performance capabilities of the control); (3) the performance of

the source in maintaining compliance over time (e.g., training

programs, maintenance schedule, recordkeeping practices); and (4)
27

the performance of the implementing agency in assuring compliance

(e.g., training programs, inspection schedules, follow-up

procedures).

Rule effectiveness shall be applied for stationary

sources that are affected by a regulation and for which emissions

are determined by means of emission factors and control

efficiency estimates. No rule effectiveness factor is needed in

cases where no control is applied or there is no applicable

regulation.

In the proposed Post-1987 Ozone/CO policy, it was

stated that a factor of 80 percent should be used to estimate RE

in the base year inventories for most point and area sources. 

For the purpose of base year CO inventories under the CAAA, EPA

will allow the use of the 80 percent default value, but will also

give States the option to derive local category-specific RE

factors according to guidance contained in Reference 8.

The RE factor shall be applied to the estimated control

efficiency in the calculation of emissions from a source. An

example of the application is given below.

Uncontrolled emissions = 50 lbs/day

Estimated control efficiency = 90%

Rule effectiveness = 80%

Emissions after control = 50 [1 - (0.90)(0.80)]

 = 50 [1 - (0.72)]

 = 14 lbs/day

Thus, the application of RE results in a total emission reduction

of 72 percent.
28

Fuels programs, such as local controls on volatility,

should be adjusted for effectiveness because of a number of

assumptions regarding market penetration, compliance, etc.

associated with implementation of such programs. States should

contact their EPA Regional Office for guidance on how to adjust

the base year inventory for the effectiveness of these programs.

In addition to RE, another important regulatory

consideration is the extent to which a regulation may cover

emissions from a source category. When estimating emissions

using methodologies for source categories where a rule or

regulation applies, agencies shall incorporate an estimate of the

amount of rule penetration by means of the following formula:

 Rule Uncontrolled emissions

 Penetration = covered by the regulation x 100 percent

 Total uncontrolled emissions
29

Once uncontrolled emissions and rule penetration are

determined, RE should be applied as discussed above. An example

of how to incorporate both penetration and RE in the same source

category follows.

Uncontrolled emissions = 100,000 tpy

Control efficiency required by the regulation = 95

percent

Rule penetration = 60 percent

Rule effectiveness = 80 percent

Emissions from the category =

 (100,000)[1 - (0.60)(0.95)(0.80)] = 54,400 tpy

Further discussions of the use of rule effectiveness and rule

penetration are included in Reference 8.

3.7 Point Sources

Although a revised version of the procedures document

for CO is scheduled for release in May of 1991, the guidance for

inventorying point sources of CO has essentially not been changed

from what was contained in the document Procedures for the

Preparation of Emission Inventories for Precursors of Ozone,

Volume 1 (EPA 450/4-88-021, December 1988). For this reason, 1

States should immediately begin data gathering for the

development of the point source component of their base year

inventories. There is no reason to postpone data gathering and

development because no new guidance is planned for point sources

that will significantly affect States' 1990 base year inventory

efforts. Some refinements and enhancements may be issued to the

previous guidance for selected source categories, but this

information will not affect the basic activity data that States

need to be collecting on individual point sources. States are
30

encouraged to submit the point source portion of the inventory to

EPA as early as January 1, 1992.

As under the previously proposed Post-1987 Policy, the

point source emissions cutoff definition for CO sources is 100

tons/yr. While sources with emissions at these levels and above

must be inventoried as individual point sources, States are

encouraged to inventory sources below these cutoffs on an

individual point source basis as well. Smaller CO sources may

either be inventoried as individual point sources or aggregated

in the area source component of the base year inventory. 

Detailed process and emissions data shall be collected and

reported for each CO point source that emits 100 tons per year or

more. A summary listing of plant names, locations and total

plant emissions (tons/day) is required for sources of CO that

emit at least 100 tons per year.

The 100 ton/yr cutoff level is not necessarily

consistent with the "major source" delineations given in the CAAA

for CO sources. This is because the two types of cutoffs are to

be used for different purposes. In several cases, the CAAA have

established other major source cutoff definitions for purposes

such as the application of RACT (reasonably available control

technology), for new source review, and for Emissions

Statements. For example, in serious CO nonattainment areas,

major sources are defined as those with the potential to emit 50

tons/yr CO. However, because these other lower cutoffs do exist,

States should consider the benefits of going ahead and

inventorying sources of CO below 100 tons/yr if possible.

New point sources that have come into being since the

previous base year inventory was compiled need to be included in

this base year inventory. For major sources, additions should be

obvious and well known to the State/local agencies. Similarly,
31

major plant shutdowns or curtailments should be well documented. 

Other methods that States may use to identify possible new

sources or identify source shutdowns include reviewing current

industrial directories, reviewing recent permitting records for

new plants and existing plant changes, and reviewing nationallyoriented data bases such as the TRIS for SARA 313 reporting

records. Again, the methodologies to be used should be specified

in the IPP.
32

3.8 Area Sources

Area sources include those emissions from stationary

and non-highway sources that are too small and/or too numerous to

be included in the point source inventory, but which can

contribute collectively to CO nonattainment. One such source

category is residential fuel combustion, including woodstoves and

fireplaces. For source categories such as this, all sources may

be addressed as area sources in the inventory because of the

difficulty in identifying the few operations that may be major

emitters.

In a number of previous SIP submittals, emissions from

many small sources have been left out of inventories because of a

lack of available procedures or lack of emphasis on this portion

of the inventory. Existing methodologies can be used to estimate

emissions from the various area source categories. Detailed

procedures are discussed in Reference 1. However, some of these

techniques are briefly described herein for emphasis.

Emissions from certain area source categories may be

estimated on a per capita basis. This procedure may be necessary

when the availability of other area source estimating

methodologies is limited. Population estimates used in making

such emission estimates should be documented. Specific

information on per capita factors is contained in Reference 1.

Another area source procedure essentially uses

nationally derived emissions-per-employee factors to calculate

emissions from sources in an area based on areawide employment

data. The procedure is best utilized for those source categories

where (a) total employment in the source category is known for

the area, and (b) where there are numerous sources whose

emissions are typically less than the cutoffs mentioned above for
33

point sources, but whose collective emissions represent a

significant total.

When compiling their area source inventories, States

should also be aware that EPA's JEIOG has identified some new

area source categories that were previously uninventoried for CO

emissions. These area sources must be addressed in the 1990 base

year inventories. The new area source guidance material will be

issued in May 1991 as a part of the updated procedures guidance

document.

3.9 Mobile Sources

Mobile sources consist of two types, on-road mobile

sources (e.g., automobiles, trucks, motorcycles) and non-road

mobile sources (e.g., trains, airplanes, agricultural equipment,

industrial equipment, construction vehicles, off-road

motorcycles, marine vessels, and other site-specific vehicles). 

Guidance on this issue can be found in Reference 2.

The on-road mobile sources portion of the inventory

must include a detailed accounting of vehicle emissions in the

designated nonattainment area. Emissions from local traffic, as

well as emissions from traffic on major highways, must be

included in the analysis. On-road mobile source emissions shall

be derived by multiplying VMT by MOBILE4.1 emission factors. The

base year for the VMT shall be 1990. Specifications on the

required use of MOBILE4.1 variables such as temperature, speed,

etc. will be provided in the May 1991 procedures guidance. 

States must determine VMT by the procedures specified

by EPA. In May 1991, EPA will be issuing new inventory

procedures guidance that contains updated methods for determining

on-road vehicle VMT. States shall be required to use the new
34

procedures to produce their 1990 base year inventories under the

CAAA. The new VMT guidance to be issued in May represents an

update to that contained in Reference 2 for deriving on-road

vehicle VMT. 

States shall present on-road mobile source CO emissions

by individual county (or other equivalent basis) within the

nonattainment area, as well as by vehicle class and by roadway

type. States shall also report MOBILE4.1 input and output data

and a discussion of how VMT estimates were developed (see Section

4.0 and 5.0). For modeling inventories, mobile source data (as

well as point and area source data) such as VMT, temperature and

emissions, must be developed on a gridded, hourly basis.

Emissions from most non-road mobile sources are

determined based on a source activity variable that is a

surrogate indicator of emissions. Activity levels for each

non-road category shall be developed using revised guidance to be

issued in May 1991 (Reference 2).

In May 1991, as a part of EPA's updated procedures

guidance, new inventorying procedures will be presented that

States shall use to develop non-road emissions estimates for

trains and airplanes. The new procedures for trains and

airplanes are required for the 1990 base year inventories. 

3.10 Periodic Emission Inventories

As identified in Section 2.0, States are required to

develop and submit to EPA periodic CO emission inventories. 

Periodic CO inventories shall require essentially the same

information as the base year CO inventory. The primary

difference between them is the basis year for the inventory. The

first periodic inventory must be based on 1993 emission rate and
35

activity level information [Section 187 (a)]. It is due in final

form to EPA no later than September 30, 1995, and subsequent ones

no later than the end of each 3-year period thereafter, until the

area is redesignated to attainment [Section 187 (a)(5)]. 

Periodic CO inventories must address actual CO emissions during

the CO season on a typical daily basis. Emission estimates shall

be prepared according to the general procedures for base year

inventories outlined in Section 3.2. 
36

3.11 Modeling Inventories

Modeling inventories are necessary for CO because of

CAAA provisions that require Attainment Demonstrations to be made

for certain CO nonattainment areas [Section 187 (a)(7) and

187(d)(1)]. Moderate areas exceeding a design value of 12.7 ppm

must submit an attainment plan before November 15, 1992 that

projects how attainment will be achieved by December 31, 1995. 

The same requirement exists for serious areas except that

attainment must be demonstrated by December 31, 2000. Base year

and projected modeling inventories will be needed. Base

inventories are used for evaluating model performance while

projected inventories are used as "future base cases" upon which

additional control strategies are superimposed in an attainment

demonstration.

This modeling demonstration shall include both areawide

and hot spot modeling. The areawide model should be either the

RAM or the UAM. The model currently proposed for hot spot

demonstrations is CAL3QHC. The hot spot model and its use are

described in detail in References 3 and 4. EPA will provide more

direction to States on areawide modeling in the near future.

The CO base year modeling inventory shall represent

actual emissions representative of the base year episodes

selected for modeling. Emissions would be determined for an

average 24-hour operating day during the peak CO season. See

Sections 3.3 and 3.4 for a discussion of temporal and spatial

reporting of emissions for modeling inventories. All stationary

point and area sources and all mobile source types must be

included in the inventory. Activity levels and production data

used to calculate emissions should represent actual data. 

Conversely, the projection modeling inventory would be based on

allowable emissions dictated by regulatory limits, and not actual
37

emissions. The emission levels in effect will represent the

results that State expects from its SIP control strategies. 

Activity levels used to estimate emissions should be those

expected in the future attainment year (i.e., 1995 for moderate

areas or 2000 for serious areas).
38

3.12 Quality Assurance

States are required to design and implement a quality

assurance (QA) program to enhance the overall reliability and

accuracy of the CO SIP emission inventories prepared in response

to the CAAA. States must design a QA program and prepare a QA

plan that is consistent with the previously issued guidance

document: Guidance for the Preparation of Quality Assurance

Plans for O3/CO SIP Emission Inventories (EPA 450/4-88-023). 9

States are required to submit QA plans as an initial step in

their inventory development work and receive EPA approval on

their plans early on in the process. The QA plans must be

submitted no later than July 31, 1991, as a part of a State's IPP

which is a new requirement for the 1990 base year inventories.

The full provisions and requirements of the IPPs are explained in

Section 3.1. The content and general form of QA plans must be

consistent with the previously issued guidance.

As an aid to States in the preparation and checking of

their inventories prior to submittal to EPA, the Agency has been

preparing a set of quality review guidelines. These guidelines

will contain what is essentially a checklist of items that an

inventory must contain or address in order for the inventory to

be considered acceptable for review by EPA. The guidelines will

address whether inventories meet developed specifications for

completeness, consistency (both internal and with national

trends), reasonableness of emission values, and emissions

documentation. EPA is planning to issue the final review

guidelines in July 1991.

3.13 References

1. Procedures For The Preparation Of Emission Inventories

For Precursors Of Ozone, Volume I, EPA-450/4-88-021,

Third Edition, U. S. Environmental Protection Agency,

Office of Air Quality Planning and Standards, Research
39

Triangle Park, NC, December 1988. Revised version to

be issued May 1991, will supersede this guidance.
40

2. Procedures For Emission Inventory Preparation, Volume

IV: Mobile Sources, EPA-450/4-81-026d, U. S.

Environmental Protection Agency, Office of Air Quality

Planning and Standards, Research Triangle Park, NC,

July 1989. Revised version to be issued May 1991, will

supersede this guidance.

3. User's Guide to CAL3QHC - A Modeling Methodology for

Predicting Pollutant Concentrations Near Roadway

Intersections. Parsons Brinckerhoff Quade and Douglas,

Inc., New York, NY. September 1990.

4. Guideline for Modeling Carbon Monoxide from Roadway

Intersections (Draft Report). Schewe, G. J., et al. 

PEI Associates, Cincinnati, Ohio. October 1990.

5. User's Guide for RAM - Second Edition. 

EPA-600/8-87-046. U. S. Environmental Protection

Agency, Research Triangle Park, NC. October 1987.

6. User's Guide for the Urban Airshed Model - Volume I: 

User's Manual for UAM (CB-IV). EPA-450/4-90-007a. 

Systems Applications, Inc., San Rafael, CA, and U. S.

Environmental Protection Agency, Research Triangle

Park, NC. June 1990.

7. Procedures For The Preparation Of Emission Inventories

For Volatile Organic Compounds, Volume II: Emission

Inventory Requirements For Photochemical Air Quality

Simulation Models. EPA-450/4-79-018, U. S.

Environmental Protection Agency, Research Triangle

Park, NC, September 1979. Revised version to be issued

May 1991, will supersede this guidance and will address

CO specific issues.

8. Procedures For Estimating And Applying Rule

Effectiveness In Post-1987 Base Year Emission

Inventories For Ozone And Carbon Monoxide State

Implementation Plans, U. S. Environmental Protection

Agency, Office of Air Quality Planning and Standards,

Research Triangle Park, NC, 

June 1989.

9. Guidance For The Preparation Of Quality Assurance Plans

For O3/CO SIP Emission Inventories, EPA-450/4-88-023,

U. S. Environmental Protection Agency, Office of Air

Quality Planning and Standards, Research Triangle Park,

NC, December 1988.
41

4.0 COMPUTERIZED DATA MANAGEMENT AND REPORTING

Emission inventory information for base year, periodic,

and modeling inventories under the CAAA shall be provided to EPA

in both written and computerized formats. Computerized

submittals of emissions data and documentation must meet the

specifications set forth by EPA's National Air Data Branch

(NADB). The computerized submittals are discussed in this

Section, while the written reporting/documentation requirements

are summarized in Section 5.0.

Computerized submittals must be input to the Aerometric

Information Retrieval System (AIRS), with point source data on

the AIRS Facility Subsystem (AFS) and area and mobile source data

on the Area and Mobile Source Subsystem (AMS). If States do not

input State Implementation Plan (SIP) inventory data directly to

AIRS, then they must submit data in a computer-readable

AIRS-compatible format. Methods for providing AIRS-compatible

formats are discussed in this section. AIRS transactions

submitted by States will be updated to AIRS by EPA Regional

Offices which will then provide the States with printed reports. 

States will review these reports and correct any errors before

final EPA confirmation of inventory completeness is given. 

States are advised to establish internal coordination

procedures to eliminate potential conflicts between the

submittals of their SIP data to AFS and their other regular

submittals of compliance and emissions data to AFS. Some SIP

data elements will be uniquely "owned" by SIP emission inventory

users who submit data to AFS. Other data elements in AFS will be

shared in common with other State or local agency users who

submit other emissions or compliance data to AFS. The AFS

security procedures will permit only authorized users to update

the data base. Where data element ownership is shared by SIP
42

emission inventory users, and other emissions and compliance

users, the updating of a data element by different users is

possible at different times. Effective internal coordination by

States is necessary to insure that data reported to meet a SIP

requirement do not conflict with or inappropriately change data

that have been reported to AFS by other State personnel. For

emissions data, the data elements contained in the previous

National Emissions Data System (NEDS) can be reported to AFS as

batch data updates. States who are direct users of AFS may also

perform online updates to the AFS database. The SIP submittals

made by States using SAMS (SIP Air Pollutant Inventory Management

System) or AFS batch transactions (see following subsection)

should not contain transactions that change emissions data values

for pollutants not required for the SIP inventory (such as PM10

or SO2, for example) unless the submittal of such data has been

coordinated with and approved by the persons who normally submit

such data. Similarly, changes to other shared emissions data

elements such as latitude/longitude or UTM coordinates, stack

parameters and common point general and segment general level

data elements should be coordinated with other emissions

inventory personnel to insure that SIP data updates do not

improperly change their data. 

For compliance data, the only data elements that are

shared by SIP inventory and compliance users are the plant name,

street address, city code and city name, ZIP code and SIC codes

on the plant general level. SIP inventory personnel must

coordinate with compliance personnel to insure that inappropriate

changes to these data elements do not occur as the result of a

SIP inventory data submittal to AFS. 

Various submittal mechanisms will be available for the

States to fulfill their inventory requirements. The information
43

below addresses inventory data management issues for point, area,

and mobile sources. 

4.1 Point Source Inventory

States submitting point source inventories can choose

one of four basic options to submit their data: 
44

Option When Available

(1) SAMS Version 3.1 Now 1

(2) SAMS Version 4.0 Now 2

(3) AFS Batch Transaction

Format Available May 17, 1991 3 

(4) Interactive direct entry 

to AFS December 31, 1991

NOTES: (1) SAMS Version 3.1 (used for the Post-87 SIP

inventories). If currently using Version 3.1,

States should update to SAMS Version 4.0 to

achieve compatibility of data format with AFS (see

discussion below).

(2) SAMS Version 4.0 which includes additional data

elements (Stack-ID and Segment-ID) and edits to

ensure compatibility with AFS. A later version of

SAMS, Version 4.1, will include the capability to

generate an AFS formatted transaction file

(available mid-July 1991).

(3) This format must be used by States submitting data

electronically from their own computer system

directly to EPA's mainframe.

Option (1)

States may have already begun work to update their

inventories to 1990 by using SAMS Version 3.1. However, prior to

uploading to AFS, reconciliation of SAMS 3.1 data with the AFS

data structure at the stack and segment levels of related

SAMS/AFS facilities will be required. SAMS Version 4.0 allows

entering this additional information thereby reducing to a

minimum the data conversion process from SAMS to AFS. 

Information relative to the required data elements for the

inventory is also provided in this guidance document. 
45

If States are currently using SAMS Version 3.1, please

contact John Ackermann of NADB at (919) 541-5687 (FTS 629-5687)

to discuss the data reconciliation process and issues. 

Option (2)

SAMS Version 4.0 can be installed on a PC so that it

can be used to update a SAMS data base prepared with an earlier

version. By using the new data elements and AFS-edit routine in

Version 4.0, the SAMS user can prepare 1990 SIP data on SAMS (PC)

that will be consistent with their State's files on AFS

(mainframe). The National Air Data Branch has developed

AFS computer printout reports that can assist State and local

agencies in the identification of AFS stack and segment ID

numbers for input to SAMS Version 4.0. These reports (AFS Quick

Look reports) may be obtained from EPA Regional Office AFS

Emissions Contacts or by contacting Jerry Husketh of NADB at

(919) 541-5449 (FTS 629-5449). Names and phone numbers for the

Regional Office contacts can be obtained by calling Jerry Husketh

at the number above.

There will be a later release of SAMS Version 4.1,

available in mid-July 1991. This newer version will provide a

capability to generate AFS-acceptable transactions as an output

from SAMS. The AFS-formatted transaction data from SAMS will be

uploaded to the EPA IBM mainframe and then updated to AFS. EPA

will review the submitted inventory prior to updating the AFS

files. The updating of AFS will begin in January 1992. 

Option (3)

States submitting an AFS formatted transaction file to

EPA (format definitions will be provided in May 1991) can either

mail a magnetic non-labeled tape or transmit a data set (if State
46

has appropriate connectivity and technical resources) to the

National Computer Center. Tape submitted data should be

structured in IBM extended binary coded decimal interchange code

(EBCDIC). The loading of the transaction files to AFS will begin

in January 1992. Contact Jerry Husketh of NADB at (919) 541-5449

(FTS 629-5449) for more information.

Option (4)

In the long-term, the preferred option is to enter the

SIP inventory point source data directly into AFS. However, this

option will not be available to users until January 1992. 

Contact John Ackermann at (919) 541-5687 (FTS 629-5687) or Jerry

Husketh at (919) 541-5449 (FTS 629-5449), NADB, if States plan to

use this approach. 

4.2 Point Source Data Elements

Applicable data elements that will be supported by AFS

are as follows. Data elements required for the ozone/CO

inventories are shaded. These data elements are more explicitly

defined in documentation for SAMS Version 4.0 and will be further

defined with the specification of AFS batch transaction formats

to be provided in May 1991. 

 

List of Data Elements for Plant General Level:

Description

**FIPS state code1

**FIPS county code1

 *year of record for emissions

**plant ID from AFS (or NEDS)

 *plant name

 *street address

 *city name2

 *zip code

 local plant ID

 *FIPS city code1,2
47

 *plant latitude3

 *plant longitude3

 *UTM zone3

 *UTM easting3

 *UTM northing3

 township/modeling grid

 *primary SIC code

 secondary SIC code

 tertiary SIC code

 principal product

 number of employees

 plant area

 plant contact

 contact telephone number

 type of inventory

 plant comment

 * Mandatory for AFS format, for Adds.

 ** Mandatory for both Adds and Changes to AFS.

Note for FIPS codes: While SAMS currently uses SAROAD 1

codes, these will be converted to FIPS codes by SAMS

software when AFS transactions are created by SAMS

users. States that generate AFS transactions from

other software must use FIPS codes.

Note for city: enter data for either city name or 2

FIPS city code but not both. If city code is reported

to AFS, this will be used to generate a city name and

the city name field entry will be ignored. SIP

inventory users in New England States are requested to

report the FIPS city code if possible. This will

permit AFS to generate the appropriate Metropolitan

Statistical Area (MSA) codes for those States. Except

for New England States, the MSA code can be generated

from county codes so that city code is not necessary.

Note for plant location: enter data for either 3

lat/long or UTM, but not both. For cases where both

are reported, UTM data will be used to update AFS and

lat/long data will be ignored.

 List of Data Elements for Point General Level:

Description

**FIPS state code

**FIPS county code

**plant ID from AFS (or NEDS)
48

**point ID from AFS

 local point ID

 hours per day

 days per week

 hours operated per year

 start time (each workday)

 end time (each workday)

 percent throughput - Dec. thru Feb.

 percent throughput - March thru May

 percent throughput - June thru Aug.

 percent throughput - Sept. thru Nov.

 boiler capacity

 space heat percentage

 point comment

 ** Mandatory for both Adds and Changes to AFS.

 List of Data Elements for Point Pollutant Level:

Description

**FIPS state code

**FIPS county code

**plant ID from AFS (or NEDS)

**point ID from AFS

**pollutant code or CAS code

 measured emissions at point

 emission measurement method code

 measured emissions units

 SIP regulation in place for point

 compliance year for point

 emission limitation for point

 emission limitation value

 emission limitation units

 ** Mandatory for both Adds and Changes to AFS. 

 List of Data Elements for Stack Level:

Description

**FIPS state code

**FIPS county code

**plant ID from AFS (or NEDS)

**stack ID from AFS

 *stack height (ft)1,3

 *stack diameter (ft)1,3

 *plume height (vent height, ft)1,3

 latitude for stack2,3
49

 longitude for stack2,3

 UTM easting for stack2,3

 UTM northing for stack2,3

 temperature of exit gases (F)

 exhaust gas flow rate (ACFM)

 exit gas velocity (ft/sec)

 * Mandatory for AFS format, for Adds.

 ** Mandatory for both Adds and Changes to AFS. 

Note: required either to enter stack height and 1

 stack diameter or to enter plume height (vent

height).

Note: for Stack location (if different from Plant), 2

 enter either lat/long or UTM, but not both. 

Note: required for AFS only if a stack exists and 3

stack 

 ID has been entered; for SIP inventories, this

parameter is

 not required if no stack exists or if photochemical

modeling 

 is not required for an attainment demonstration.

 List of Data Elements for Segment General Level:

Description

**FIPS state code

**FIPS county code

**plant ID from AFS (or NEDS)

**point ID from AFS

**segment ID from AFS

 *SCC number

 sulfur percentage

 ash percentage

 heat content

 confidentiality

 process rate units

 actual annual process rate2

 maximum design rate2

 O3 season process rate (daily)2

 CO season process rate (daily)2

 stack ID related to this segment1

 segment comment

 * Mandatory for AFS format, for Adds.
50

 ** Mandatory for both Adds and Changes to AFS.

Note: required for AFS only if a stack exists; for 1

SIP inventories, 

 this parameter is not required if no stack exists or

if photochemical

 modeling is not required for attainment demonstration.

Note: these parameters must be provided unless they 2

are deemed to

 be confidential or their reporting is prohibited by

State law.

 List of Data Elements for Segment Pollutant Level:

Description

**FIPS state code **FIPS county code

**plant ID from AFS (or NEDS)

**point ID from AFS

**segment ID from AFS

**pollutant code or CAS code

 primary control device code1

 secondary control device code1

 control efficiency1

 SIP regulation in place for segment

 compliance year for segment

 emission limitation description for segment

 emission limitation value

 emission limitation units

 emission estimation method

 emission factor2

 seasonal adjustment factor

 annual nonbanked emissions (estimated actual)

 annual banked emissions

 rule effectiveness3

 O3 season emissions (lb/day)

 CO season emissions (lb/day)

 ** Mandatory for both Adds and Changes to AFS.

Note: required for SIP inventories only when a 1

control device exists.

Note: required for SIP inventories only when the 2

emission estimation

 method code indicates that an emission factor was used

(i.e., method

 codes 3 and 5 for SAMS reporting or method code 9 for

AFS batch
51

 format reporting). For other method codes, an

emission factor does not

 apply and is not required.

Note: required for SIP inventories only when rule is 3

in place that affects

 emissions of the pollutant.

4.3 Area and Mobile Source Inventory

The NADB is developing a new AIRS subsystem to handle

the area and mobile source inventories. The new mainframe

software is called AMS and will facilitate State data entry,

update, and access to area source data. Since AMS will not be

able to upload State data in formatted transactions until May

1992 (AMS "National" capability by November 1992), AMS data entry

software is being developed on a personal computer (PC).

States have three basic options to submit their area

source data. However, please note that option 3 will not be

available in time for the draft area and mobile source inventory

submittals but could be used for final base year submittals or

periodic inventory updates.

Option When Available

(1) AMS-PC Version 1.0 June 28, 1991

(2) AMS Batch Transaction

Format Available July 31, 1991

(3) AMS Mainframe Interactive

Direct Entry May 29, 1992

Option (1)

The AMS-PC package will be available to the States by

June 28, 1991. States may use the AMS-PC package to submit their
52

1990 base-year inventory for area and mobile sources. The AMS-PC

Version 1.0 will be a basic data-entry system for State-prepared

emissions values, and will have only minimal calculation

capabilities. The AMS-PC package will be compatible with the

mainframe AIRS AMS in categories, codes, and edits, and will be

consistent with EPA's guidance for SIP 1990 base-year

inventories. Note that SAMS Version 4.0 and Version 4.1 will not

provide the appropriate categories and formats to develop the

1990 area source or mobile source inventory; therefore, SAMS

cannot be used for the purpose of submitting AMS inventory data. 

Option (2)

States planning to transmit a computer generated data

set or magnetic tape file will need to supply data in EPA's AMS

batch transaction format. This format will be defined and

distributed to the States in July 1991. Tape submitted data

should be structured in IBM EBCDIC. 

AMS transactions generated from the AMS-PC and AMS

batch transactions generated and submitted from State computers

will be updated to the AMS mainframe data base. The capability

to update this SIP data to the mainframe is scheduled for May

1992. During the period of January through May, 1992, the

Technical Support Division will provide assistance with basic

edits and review of draft inventories submitted as AMS batch

transactions from State computers. The Regions and the States

will receive additional information and guidance regarding area

and mobile source procedures in the near future. State personnel

should contact John Ackermann or Sue Kimbrough of NADB to

indicate what type of approach will be used for their area and

mobile source inventories. 

Option (3)
53

The AMS mainframe data entry capability for area and

mobile source data will be available in May 1992. States will be

able to do corrections, updates or projections interactively to

base year data existing or imported into AMS. States planning

to use this approach will need AMS training and should coordinate

their submittal plan with Sue Kimbrough of NADB, at (919) 541-

5457 (FTS 629-5457). 

4.4 Area and Mobile Source Data Elements

Area and mobile source data should be reported either

using AMS or in a computer readable format compatible with AMS,

as stated previously. A tentative list of data elements to be

supported by AMS is included below. This list does not cover the

bulk of the on-road mobile source data elements (e.g., inputs to

and outputs from the MOBILE model) that will be required with the

inventory submittal. AMS data elements and formats (including

on-road mobile source data) will be defined more explicitly in

AMS documentation to be finalized by July 31, 1991. Shaded data

elements are required for SIP emission inventories.

List of Data Elements for Source Category Level:

Provider (EPA or State)

Inventory Type (Base Year, RFP Projection, etc)

Base Year

State Code

County Code

City Code

Zone (for City or County Subdivision)

Source Category (from valid EPA AMS Source Classification Codes)

Activity Level (annual quantity consumed, produced, etc. -

associated with emissions)

Activity Level Units (units of measure for activity level - e.g.,

cubic feet, tons, employees, VMT)

Activity Level Process (burned, produced, consumed, etc.)

Activity Level Method (EPA SIP, State, etc.)

Activity Level Origin (Input by user, calculated, etc.)

Activity Level Limit (maximum activity allowed by regulation)1

Activity Level Limit Units1
54

Activity Level Limit Process1

Ash Content Percent

Sulfur Content Percent

Comment

Note: Required for SIP inventories only when the 1

activity level is limited by regulation.

List of Data Elements for Pollutant Level:

Provider

Inventory Type

Base Year

State Code

County Code

City Code

Zone

Source Category

Pollutant Code

Emission Factor

Emission Factor Decimal

Emission Factor Units

Emission Factor Limit (maximum factor allowable by regulation)1

Emission Factor Limit Decimal1

Emission Factor Limit Units1

Emission Factor - QA 

Emission Factor - QA Decimal

Emission Factor - QA Units

Percent Reactivity

Days Per Week

Weeks Per Year

SIP Rule in Place

Year Regulated

Year Last Modified

Rule Penetration

Rule Effectiveness

Control Equipment

Control Efficiency

Percent Usage

Comment

Note: Required for SIP inventories only when the 1

emission rate is limited by regulation.

List of Data Elements for Period Level:

Provider

Inventory Type

Base Year

State Code
55

County Code

City Code

Zone

Source Category

Pollutant Code

Period Code (Typical Winter Day, Peak Ozone Season, etc.)

Period Begin Month

Period End Month

Period Throughput

Interval Code (1 HR, 3 HR, 8 HR, etc.)

Hour 00 .. Hour 23 Throughput

Start Hour

Weekday Adjustment Factor

Saturday Adjustment Factor

Sunday Adjustment Factor

Emission Factor

Emission Factor Decimal

Emission Factor Units

Emission Factor Limit

Emission Factor Limit Decimal

Emission Factor Limit Units

List of Data Elements for Emissions Level:

Provider

Inventory Type

Base Year

State Code

County Code

City Code

Zone

Source Category

Pollutant Code

Emissions Type (Actual, Allowable, Uncontrolled)

Annual Emissions

Annual Emissions Decimal

Annual Emissions Units

Period Code

Daily Emissions

Daily Emissions Decimal

Daily Emissions Units

Interval Code

Interval Emissions

Interval Emissions Decimal

Interval Emissions Units

Note: If EPA or State default values are used, the origin (EPA or

State) and level (National, State or County) are required to be

indicated each time a default is used. 
56

4.5 Format for Area and Mobile Source Data

Previously, the SIP guidance documents and the SAMS

system provided for a series of source categories that ranged

from the detailed level to a very aggregated level. However, the

source category codes developed for use within AMS have been

designed to encourage the user to submit data at a more detailed

level. Therefore, the AMS source categories are significantly

different from the manner in which source categories have been

designated in past SIP guidance. A tentative listing of major

AMS source categories is included in Appendix B. A detailed

listing of the final AMS source category codes and descriptions

will be provided in AMS guidance to be issued by July 1991.
57

5.0 DOCUMENTATION OF THE INVENTORY

Base year emission inventory information under the

Clean Air Act Amendments (CAAA) shall be provided to EPA in both

written and computerized formats. The written presentation has

to contain documentation that is extensive enough for the Agency

to reproduce the emission estimates that are submitted in the

inventory. Written reporting/documentation requirements are

summarized in this section. The use of AIRS may alleviate the

need for detailed hard copy data reporting because of the ability

of AIRS to generate the necessary reports. However, this does

not eliminate the need for certain documentation of the inventory

such as the specification of how applicable sources were

identified, where activity data were derived, and how rule

effectiveness levels were determined. The parallel

specifications for computerized submittals are presented in

Section 4.0.

Under the CAAA, EPA is requiring that States prepare

written inventory documentation reports according to a more

standardized set of guidelines. Inventory reports that are not

prepared according to the guidelines will be harder for EPA to

review and are more likely to be deemed unacceptable by the

Agency. This does not mean that every State inventory report

must be organized precisely the same and look identical. EPA's

primary interest is that all inventories address the crucial

elements inherent in a good inventory and provide summary data

and documentation that allow the quality of the inventory effort

to be effectively judged. Therefore, the emphasis is on the

types of data that need to be reported and not the specific

format they are reported in. Inventories not meeting the minimum

data reporting and documentation standards established in this

discussion shall, however, be deemed unacceptable and returned to
58

the States for modification before any further technical quality

review will be performed.

EPA has already published a detailed guidance document

on this issue that States need to consult before preparing their

written reports. This document is entitled Example Emissions

Inventory Documentation for Post-1987 Ozone State Implementation

Plans (EPA 450/4-89-018). The full reference for the document is

given in citation 

No. 4 of the Section 6.0 bibliography. If a State does not have

the report, copies can be obtained from the Emission Inventory

Branch of OAQPS. As the title implies, the guidance document

provides a complete example of how an inventory should be

compiled and documented. The kinds of summary tables and

graphics that States need to provide to EPA for their base year

inventories are clearly shown. The examples cover point, area,

and mobile sources, and they address quality assurance aspects of

the inventory. Even though the guidance was prepared for ozone

inventories, the examples are equally applicable and

transferrable to CO inventories. It also provides States

guidance on how to summarize quality assurance activities that

need to be carried out in the compilation of the inventory. 

EPA's recommended outline for the organization and

content of a State's inventory report is given in Table 5-1. The

combination of the Table 5-1 outline with the Example Emissions

Inventory Documentation report should provide States with all of

the guidance necessary to prepare an inventory documentation

report that will satisfy EPA and the intent of the CAAA.

The introduction to an inventory report shall contain a

description of the nonattainment area that has been inventoried;

a listing of the counties covered; a map of the area including

the 25-mile boundary outside of the nonattainment area; an
59

identification of who prepared the inventory and who are the

respective contacts for major inventory components; a description

of major inventory problems or deficiencies; and a discussion of

how the remainder of the report is organized. After the

introduction, the report must contain a thorough summary of the

emissions data by pollutant, source type (point, area, mobile),

and geographic area. The Example Emissions Inventory

Documentation report provides several examples of tables and

graphics that can be presented for point, area, and mobile

sources. At a minimum, the report must include summary emissions

tables by pollutant and by source type; summary emissions tables

by
60

TABLE 5-1. OUTLINE FOR EPA RECOMMENDED FORMAT/CONTENTS FOR

CO SIP EMISSION INVENTORY REPORTS

 

 

 I. Cover and Title Page

A. Title (geographic area, type of inventories,

pollutants, base year)

B. Responsible agency [e.g., NC Dept of Health and

Natural Resources]

C. Report date (date completed/distributed)

D. Preparer (if different from responsible agency -

e.g., contractor)

 II. Table of Contents

A. Contents

B. Tables

C. Figures

III. Introduction

A. Reason for report being prepared, purpose

[For example, In response to letter from to

 , dated requesting preparation of

a SIP for demonstration of attainment of ozone

NAAQS in (geographic area), beginning with an

emission inventory for base year 1990. Base year

emission inventory serves as the basis for

emissions modeling and projections for future

years.]

B. Geographic area covered, base year, type of

inventory (O3 SIP, CO SIP), pollutants included

(VOC, NOx, CO)

C. Brief discussion of contents of report

[Note: Include a paragraph or less describing

each major report section. For example, Section 2

summarizes stationary point, area and mobile

source emissions by county. Section 3 describes

stationary point source emissions and includes a

discussion of methods used to gather data,

calculate annual and seasonal emissions, and

presents a summary of emissions by plant. 

Detailed point source emissions data are presented

in Appendix F. Section 4 discusses...]
61

D. Discussion of automated data systems used (SAMS,

AIR AFS, AMS-PC, State system)

 

 
62

TABLE 5-1. Continued

 

 

E. Major problems, deficiencies, portions of

inventory not included

F. List of primary guidance documents and references

used (EPA guidance documents, AP-42, etc.)

G. List of contacts for each distinct portion of the

inventory

 IV. Summary

A. Emissions (annual and seasonal) of each pollutant

by major category (point, area, mobile - broken

down by non-road sources and on-road vehicles;

brief discussion in footnote, etc. to clarify what

each includes - point sources above cutoff, area

sources excluding non-road mobile sources?,

non-road sources include aircraft, trains,...)

B. See example tables and graphics given in Example

Emissions Inventory Documentation for Post-1987

Ozone State Implementation Plans (EPA-450/4-89-

018).

 V. Documentation of Emissions Methods/Data/Estimates*

A. Stationary Point Source Emissions*

1. discussions of procedures and methodologies

2. example surveys/questionnaires

3. list of plants by primary product and total

emissions

4. detailed data for each plant (can put in

appendix instead)

5. point source emissions summary

B. Stationary Area Source Emissions*

1. discussion of procedures and methodologies

2. list of source categories and emissions

3. calculations and discussion for each source

category

4. area source emissions summary

C. Mobile Source Emissions*
63

 

 
64

TABLE 5-1. Continued

 

 

1. Non-Road Mobile Sources

a. same information as for stationary area

sources

2. On-Road Vehicles

a. mobile model inputs and outputs

b. VMT estimates

c. emission estimates

d. documentation (can put all or part in

Appendices)

e. mobile source emissions summary

f. discussion of procedures and

methodologies

 VI. Quality Assurance/Quality Checking (QA/QC)

A. QA/QC plan - discussion of QA/QC methodologies

used

B. Results

C. QA procedures can also be discussed in individual

source category sections

VII. Appendices

A. Lengthy data, calculations, documentation of

methodologies/models

 

 

Notes: Both annual (except for on-road mobile sources) and

seasonal emissions (CO - CO season typical weekday emissions)

should be presented in the summary and sections describing

emissions.

All pages in the report (including appendices) should be

numbered. All reports shall be bound except computer printouts. 

Sources of information should be referenced throughout. Include

complete list(s) of references within body of report (preferably

at end of each section).

Margins of report should be adequate so that copying of report

will not lose text, page numbers, or other important information.

In addition to hard copy reporting requirements for *

emissions data, data must be reported in a computerized AIRS
65

compatible format (Section 4.0). To the extent that data

have been successfully loaded onto AIRS and reports can be

generated from AIRS for nonattainment areas, this may

alleviate transmittal of portions of the hard copy inventory

that contain the detailed emissions data.
66

county; and graphics illustrating the contribution to areawide

emissions by source type. States are required to report

emissions data both on an annual (except on-road mobile sources)

and CO season daily basis. Separate discussions must be

presented to describe inventory development procedures and

results for point, area, non-road mobile, and on-road mobile

sources. In addition to the specific parameters germane to

point, area, and mobile source types, each source type discussion

needs to explain how emissions were temporally allocated to a

daily basis and how rule effectiveness was incorporated into each

emission estimate. 

 The point source discussion shall include a description

of how the list of sources to be inventoried was identified. The

discussion shall address the issue of completeness of source

coverage (i.e., how did you ensure that all 100 ton/yr sources

were identified). Data collection methods and tools shall be

thoroughly explained and documented. All information surveys

that may have been conducted must be discussed and the results

provided (probably in an appendix). All sources inventoried

shall be listed according to their source category type (e.g.,

refinery, power plant, 

steel mill, etc.). The methodology by which activity levels and

emissions were determined for each plant or source category (when

applicable) shall be succinctly but explicitly explained. Large

volumes of detailed data shall be put into appendices but clearly

linked to the text discussion in terms of how they were used to

determine emissions. Summary tables and graphics shall be

prepared to address just point source emissions (e.g., summary

table on CO point source emissions ranked by source category

type).

The area source discussion shall cover stationary area

sources, with off-highway mobile sources included in the mobile
67

source discussion. The report must state if any source

categories were not considered in the inventory and why. All of

the source categories covered shall be listed and the method used

to determine emissions identified. If the EPA-recommended

approach in the Procedures Document (EPA-450/4-88-021) was used,

but a different emission factor was used, this must be noted. 

For all approaches used (EPA or otherwise), the derivation of

activity/commodity level data shall be thoroughly discussed. As

needed, supporting data can be put into appendices but the

appendices shall be fully explained and clearly linkable back to

the text discussion and emission estimates. Like point sources,

emission summaries shall be developed for area sources. The

summaries must reflect emissions by county and for the entire

nonattainment area. Examples for these types of sources are

found in the Example Emission Inventory Documentation report.

In the mobile sources section of the inventory report,

States shall clearly describe how non-road mobile emissions were

calculated, how on-road vehicle emission factors were determined,

and how vehicle miles traveled (VMT) estimates were determined. 

For on-road vehicle emission factors, the States must fully

report how they used the updated MOBILE4 model to help determine

emissions. The values used for all input parameters required by

the model shall be presented and their basis discussed. The

emission factors produced by the model shall be presented by

vehicle class. For VMT, the State must describe the methodology

employed to generate VMT data, key assumptions and inputs to the

process, and the group responsible for the estimates. The VMT

data determined shall be presented by road type classification

and by vehicle class. States must explicitly describe the

derivation of VMT. It is not acceptable to simply state that the

Department of Transportation ran a transportation planning model

and provided the air agency with VMT numbers. Simply providing a

computer printout of a transportation modeling run, without any
68

explanation, is also not acceptable. The agency that is

responsible for the overall inventory must ensure that sufficient

documentation is provided to fully explain how VMT and mobile

source emission factors were derived. 

The report shall fully describe how the VMT data were

combined with the emission factors to produce mobile source

emission estimates. The calculated estimates must be provided in

summary form by vehicle class, by pollutant, and by county. 

Simple examples of how these summaries can be provided are given

in the Example Emissions Inventory Documentation report

referenced previously. 

The inventory report shall have a separate section that

describes the implementation of the State's QA plan and the

results achieved by the QA program. For all source category

types, the QA discussion shall address the completeness of the

inventory (e.g., are all of the EPA-recommended area source

categories accounted for), reasonableness of the emission

estimates (e.g., are estimates for a category consistent with

some other related parameter for the area), and relative accuracy

of the data (e.g., do all of the individual county emission

figures total to the sums given for the whole area). The QA

discussion must show the range of quality review that was

performed and how this review benefitted the inventory. The

Emission Inventory Branch will be issuing additional quality

review guidance in July 1991 to help States perform many of these

quality checks and provide the kinds of QA feedback deemed

necessary by EPA. 
69

6.0 BIBLIOGRAPHY

The purpose of this section is to identify and provide

bibliographic citations of currently existing EPA guidance

materials for the development of CO emission inventories. The

list of existing guidance is divided into four categories: CO

inventory guidance/requirements, quality assurance/inventory

review guidance, emission factors/models, and general inventory

guidance. If updates to an existing document are planned in

response to the Clean Air Act Amendment (CAAA), this is indicated

in the guidance citation.

CO Inventory Guidance/Requirements

 1. Procedures For The Preparation Of Emission Inventories

For Precursors Of Ozone, Volume I, EPA-450/4-88-021,

Third Edition, U. S. Environmental Protection Agency,

Office of Air Quality Planning and Standards, Research

Triangle Park, NC, December 1988. [Revised version to

be completed in May 1991 and will specifically address

CO issues in addition to ozone.]

 2. Procedures For The Preparation Of Emission Inventories

For Volatile Organic Compounds, Volume II: Emission

Inventory Requirements For Photochemical Air Quality

Simulation Models, EPA-450/4-79-018, U. S.

Environmental Protection Agency, Office of Air Quality

Planning and Standards, Research Triangle Park, NC,

September 1979. [Revised version to be completed in

May 1991 and will specifically address CO issues in

addition to ozone.]

 3. Procedures For Emission Inventory Preparation, Volume IV: 

Mobile Sources, EPA-450/4-81-026d, U. S. Environmental

Protection Agency, Office of Air Quality Planning and

Standards, Research Triangle, Park, NC, July 1989 (also

listed below under General Inventory Guidance). [Revised

version to be completed in May 1991.]

 4. Example Emission Inventory Documentation For Post-1987

Ozone State Implementation Plans (SIPs), EPA-450/4-89-

018, U. S. Environmental Protection Agency, Office of Air

Quality Planning and Standards, Research Triangle Park,

NC, October 1989.
70

 5. Procedures For Estimating And Applying Rule Effectiveness

In Post-1987 Base Year Emission Inventories For Ozone And

Carbon Monoxide State Implementation Plans, U. S.

Environmental Protection Agency, Office of Air Quality

Planning and Standards, Research Triangle Park, NC, June

1989.

 6. SIP Air Pollutant Inventory Management System (SAMS)

Version 4.0 and SAMS User's Manual, U. S. Environmental

Protection Agency, Office of Air Quality Planning and

Standards, Research Triangle Park, NC, March 1991. 

Quality Assurance/Inventory Review Guidance

 7. Guidance For The Preparation Of Quality Assurance Plans

For O3/CO SIP Emission Inventories, EPA-450/4-88-023, U.

S. Environmental Protection Agency, Office of Air Quality

Planning and Standards, Research Triangle Park, NC,

December 1988.

 8. Quality Assurance Program For Post-1987 Ozone And Carbon

Monoxide State Implementation Plan Emission Inventories,

EPA-450/4-89-004, U. S. Environmental Protection Agency,

Office of Air Quality Planning and Standards, Research

Triangle Park, NC, March 1989.

 9. Quality Review Guidelines For Post-1987 State

Implementation Plan (SIP) Base Year Emission Inventories

(Draft), U. S. Environmental Protection Agency, Office of

Air Quality Planning and Standards, Research Triangle

Park, NC, February 1990. [Final version to be completed

in July 1991.] 

10. Guidelines For Review Of Highway Source Emission

Inventories For 1982 State Implementation Plans, EPA450/12-80-002, U. S. Environmental Protection Agency,

Research Triangle Park, NC, December 1980. [This

document will be superseded by the Quality Review

Guidelines document above, to be completed in July 1991.] 

General Inventory Guidance

11. Procedures For Emission Inventory Preparation, U. S.

Environmental Protection Agency, Office of Air Quality

Planning and Standards, Research Triangle, Park, NC:
71

a. Volume I: Emission Inventory Fundamentals, EPA450/4-81-026a, September 1981.
72

b. Volume II: Point Sources, EPA-450/4-81-026b,

September 1981.

c. Volume III: Area Sources, EPA-450/4-81-026c,

September 1981.

d. Volume IV: Mobile Sources, EPA-450/4-81-026d

(Revised), July 1989. [Updated version to be

completed in May 1991.] 

e. Volume V: Bibliography, EPA-450/4-81-026e,

September 1981.

Emission Factors/Models

12. Compilation of Air Pollutant Emission Factors, Volumes I and

II and its supplements, Fourth Edition, AP-42, U. S.

Environmental Protection Agency, Office of Air Quality

Planning and Standards, Research Triangle Park, NC, September

1985.

13. AIRS Facility Subsystem Source Classification Codes (SCCs) And

Emission Factor Listing For Criteria Pollutants, U. S.

Environmental Protection Agency, Office of Air Quality

Planning and Standards, Research Triangle Park, NC, September

1989.

14. User's Guide to MOBILE4 (Mobile Source Emission Factor Model),

EPA-AA-TEB-89-01, U. S. Environmental Protection Agency,

Office of Mobile Sources, Ann Arbor, MI, February 1989. 

[Revised version of MOBILE4 and documentation to be completed

in May 1991.]

To obtain copies of any of these documents, contact Mary Ann

Stewart at (919) 541-4340 or FTS 629-4340.
A-1

APPENDIX A 

SUMMARY OF REQUIRED CARBON MONOXIDE SIP INVENTORIES

BY NONATTAINMENT AREA CLASSIFICATION
A-2

The type of inventories that are required (either explicitly

or implicitly) to be compiled under the Clean Air Act Amendments

(CAAA) of 1990 for each different carbon monoxide nonattainment

classification are delineated below. The timing of each inventory

is also denoted.

CO Nonattainment Areas

Moderate Areas:

a) Base Year Inventory -- Required by November 15, 1992, base

year is 1990, only pollutant inventoried is CO, represents

actual emissions on a typical daily period basis in the

peak CO season

b) Periodic Inventory -- A revised base year inventory is

required to be submitted no later than September 30, 1995,

and every 3 years thereafter until the area is

redesignated to attainment, represents actual emissions.

c) Modeling Inventory -- Areas exceeding a design value of

12.7 must submit an attainment demonstration plan by

November 15, 1992 that demonstrates attainment by December

31, 1995. To make the Attainment Demonstration, base year

and projected modeling inventories are needed. The level

of inventory detail is dictated by whether proportional

rollback or gridded dispersion modeling is required. The

base year modeling inventory will have a base year

consistent with the CO season, while the projected

modeling inventory will have a 1995 base year. The

projected modeling inventory will be used to determine if

the proposed SIP control strategies are adequate to reach

attainment by the designated date.

Serious Areas:

a) Base Year Inventory -- Same requirements as Moderate Areas

b) Periodic Inventory -- Same requirements as Moderate Areas
A-3

c) Modeling Inventory -- Serious areas must submit an

attainment demonstration plan by November 15, 1992 that

demonstrates attainment by December 31, 2000. To make the

Attainment Demonstration, base year and projected modeling

inventories are needed. The level of inventory detail is

dictated by whether proportional rollback or gridded

dispersion modeling is required. The base year modeling

inventory will have a base year consistent with the CO

season, while the projected modeling inventory will have a

2000 base year. The projected modeling inventory will be

used to determine if the proposed SIP control strategies

are adequate to reach attainment by the designated date.
B-1

APPENDIX B 

POINT, AREA, AND MOBILE SOURCE CATEGORIES

NECESSARY FOR CONSIDERATION IN CO SIP INVENTORIES
B-2

TABLE B-1. INDIVIDUAL POINT SOURCE CATEGORIES

 

 

External Fuel Combustion

 Utility Boilers

 Industrial Boilers

 Commercial/Institutional Boilers

 Other External Fuel Combustion

Stationary Internal Combustion

 Reciprocating Engines

 Gas Turbines

Waste Disposal

 Municipal Waste

 Combustion

 Refuse Derived Fuel

 Mass Burn

 Co-fired

 Other

Industrial Processes

 Iron And Steel Manufacture

 Coke Production

 Coke Pushing

 Coke Oven Doors

 Coke Byproduct Plant

 Coke Charging

 Coal Preheater

 Topside Leaks

 Quenching

 Battery Stacks

 

 
B-3

TABLE B-1. Continued

 

 

 Sintering

 Electric Arc Furnaces

 Other Process Units (specify)

 Petroleum Refineries

 Mineral Products

 Cement

 Glass

 Other

 

 
B-4

TABLE B-2. AREA AND MOBILE SOURCE CATEGORIES

 

 

Stationary Source Fuel Combustion

Electric Utility

Industrial

Commercial/Institutional

Residential

Waste Disposal, Treatment & Recovery

On-Site Incineration

Industrial On-Site Incineration

Commercial/Institutional On-Site Incineration

Residential On-Site Incineration

Open Burning

Industrial

Commercial/Institutional

Residential

Miscellaneous Area Sources

Other Combustion

Forest Wildfires

Managed (Slash/Prescribed) Burning

Charcoal Grilling

Structure Fires

Firefighting Training

Aircraft/Rocket Engine Firing & Testing

Mobile Sources

On-Road Vehicles

Light Duty Gasoline Vehicles (LDGV)

Light Duty Gasoline Trucks 1 (LDGT 1)

 

 
B-5

TABLE B-2. Continued

 

 

Light Duty Gasoline Trucks 2 (LDGT 2)

Heavy Duty Gasoline Vehicles (HDGV)

Motorcycles (MC)

Light Duty Diesel Vehicles (LDDV)

Light Duty Diesel Trucks (LDDT)

Heavy Duty Diesel Vehicles (HDDV)

Non-Road Vehicle Gasoline

Recreational Vehicles

Construction Equipment

Industrial/Commercial Equipment

Lawn & Garden Equipment

Farm Equipment

Non-Road Vehicle Diesel

Construction Equipment

Industrial/Commercial Equipment

Farm Equipment

Aircraft

Military Aircraft

Commercial Aircraft

Civil Aircraft

Unpaved Airstrips

Marine Vessels

Coal

Diesel Fuel

Residual Oil

Gasoline

Railroads

Coal

Diesel