United States
               Environmental Protection
               Agency
Air and Energy Engineering
Research Laboratory
Research Triangle Park, NC 27711
               Research and Development
EPA/600/SR-95/004  February 1995
EPA       Project Summary
               The  Development  and
               Improvement  of Temporal
               Allocation Factor  Files

               Theresa Moody, J. David Winkler, Terry Wilson, and Sharon Kersteter
                Emissions inventories have tradi-
              tionally been  developed to produce
              estimates  of  annual or daily emis-
              sions. To be used as input to photo-
              chemical  and other  atmospheric
              simulation models, hourly emissions
              estimates  are usually required.  Ide-
              ally, hourly emissions would be mea-
              sured or calculated directly at the
              emissions source; however, this ap-
              proach is normally impractical due to
              technical and  resource  restraints. As
              an alternative, hourly emissions esti-
              mates can be obtained using surro-
              gate temporal allocation factors from
              "temporal  profiles" assigned to spe-
              cific emissions source categories.
              Hourly emissions may  then be esti-
              mated  by applying the appropriate
              temporal allocation factors to avail-
              able annual, seasonal, or daily emis-
              sions values. This approach has been
              followed in  previous  air  pollution
              studies, including the National Acid
              Precipitation  Assessment Program
              (NAPAP) and the Northeast Corridor
              Regional Modeling Project. Since the
              performance of atmospheric simula-
              tion models is dependent  upon the
              availability of accurate, temporally
              resolved emissions values, suitable
              methodologies and databases  must
              be available to personnel responsible
              for developing the daily emissions es-
              timates  needed for model inputs.
                The purposes of this project were to
              evaluate the quality and  completeness
              of data  and methods being used for
              temporal allocation of emissions data,
              to identify and prioritize needed im-
provements to the current methods for
developing temporal allocation factors,
and to collect and use data to improve
an existing temporal allocation factor
(TAP) file. The TAP file will be used as
a source of national default allocation
factors by the emissions  model pro-
cessing systems that calculate tempo-
rally resolved emissions estimates for
model input.
  This Project Summary was developed
by EPA's Air and Energy Engineering
Research Laboratory, Research Triangle
Park, NC, to announce key findings of
the research project that is fully docu-
mented in a separate report of the same
title (see Project Report ordering infor-
mation at back).

Methodology
  Relevant literature references were iden-
tified, acquired, and reviewed to evaluate
the quality and completeness of data and
methodologies being used for temporal
allocation  of emissions data. The most
comprehensive set of temporal factors de-
veloped to date was found to be those for
the NAPAP effort. Major limitations of the
NAPAP factors are that they were devel-
oped only for the NAPAP point and area
source categories and were incompletely
documented. To augment these data, the
following data sources were identified:
     Business and labor statistics data
     Department of Energy data pertain-
     ing to production/consumption from
     various energy industries
     California  Air Resources  Board
     (CARS) AB-2588 "Hot Spots"
     pooled source test reports

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      Texas Air  Control  Board (TACB)
      stationary source operating sched-
      ule data
      Southern Oxidant Study (SOS) data
      Lake  Michigan  Ozone  Study
      (LMOS) data
      Continuous  Emissions  Monitoring
      (CEM) data
      Other data sources,  including
      wastewater data  from  publicly
      owned treatment works;  operating
      schedule/parameter data from  re-
      source recovery  facilities;  acid-
      modes field  study data;  and Urban
      Airshed Model Emissions Prepro-
      cessor System temporal profiles

Source Category Prioritization
  Emissions source  categories were  pri-
oritized to ensure attention for categories
that are major national contributors  to air
pollution. The prioritization reflected only
point source data available from the Aero-
metric Information Retrieval System (AIRS)
Facility  Subsystem.  National  area and
mobile source emissions  data were  not
available at  the time  of  this  study.  To
check for consistency with previous U.S.
Environmental Protection  Agency  (EPA)
efforts, high priority source categories listed
in the September 24, 1992, Federal Reg-
ister notice  were  reviewed. This  notice
listed  industry groups and source catego-
ries targeted for Maximum Achievable Con-
trol Technology standard development.
The comparison demonstrated consistency
with the earlier prioritization effort.
Temporal Allocation Factor  File
Development
  Data were collected for the high priority
source categories. To  process and  com-
bine these data, a number of intermediate
data processing steps were required. The
product of this effort was a single TAP file
in a flat ASCII format. Figure 1  shows  the
final TAP file format. Key fields for this file
are AIRS  Source Classification Category
(SCC) code, season  (winter,  spring,  sum-
mer, fall), and a day code (weekday, Sat-
urday, or Sunday). For each  record in  the
file, day and seasonal scenario fractions
are given, along with flags to identify  the
sources of these data. The TAP file also
includes hourly allocation factors for hours
00 through 24, along  with a flag to identify
the source of these  data. The final TAP
file resides on EPA's  mainframe computer
at  the  National Computer Center in Re-
search Triangle Park, NC.
  A three-tiered approach was  used to
produce  the final  TAP file  data. Tier  1
provided  a baseline TAP file, covering all
source  categories,  but  including  only
monthly data.  Tier 1 data are useful for
constructing seasonal allocation profiles.
These profiles were constructed predomi-
nantly using monthly labor statistics and
energy consumption data. Tier 1 data were
used  only for sources not included in Tier
2 or 3. Tier 2 data provide increased tem-
poral  resolution for a large number of cat-
egories. Tier 2 data were created  based
on  information from  TACB, SOS,  and
LMOS for specific  sources.  These  files
provided hourly profiles. Tier 2 data were
used  for emissions sources  not  included
in Tier 3. Tier 3 data were developed from
CARS reports, CEM data, and other data
sources. The data in the Tier 3 files repre-
sent efforts focused on improving the de-
fault operating profiles for a few important
emissions sources. Tier 3 data are the
most  detailed and  desirable data avail-
able in the final TAP file.

Analysis and Conclusions
  This  project created  comprehensive,
well-documented, representative national
default allocation profiles that may be used
to  generate hourly emissions estimates
from annual estimates. The  methodology
used  to create the TAP file  is well-docu-
mented, allowing future updates and im-
provements. TAP  profiles are based on
Variable Name
                  Field
                 Format
             Field
             Width
                          activity,  rather  than emissions, making
                          them valid for allocating the emissions of
                          any pollutant. Still, there are many source
                          categories for which further improvements
                          would be desirable. Detailed, Tier 3 level
                          data could be collected  and analyzed for
                          high priority categories.
                            A plan for analyzing the TAP file data
                          was developed  for this  project. A limited
                          implementation  of the plan for the highest
                          priority SCC categories revealed inconsis-
                          tent and unexpected data for some SCC
                          categories.  Resources available for this
                          project did not  permit review of all SCC
                          categories.  Inconsistencies  in TAP  pro-
                          files for electric utility boiler categories were
                          traced to CEM  data.  It was  determined
                          that the CEM data obtained for this project
                          were inappropriate for the calculation of
                          TAP profiles. The CEM data, consisting of
                          only concentration measurements,  were
                          found not to be  accurate  indicators of
                          source activity levels. The CEM data were
                          removed  from the final TAP  profiles for
                          electric utilities.
                            This project  focused  primarily  on im-
                          proving  temporal  profiles for  stationary
                          point sources. TAP profiles for many point
                          source categories were improved  as the
                          result of this effort.  A  number of  other
                          data sources are  available that could be
                                                  Description/Validation
SCC

DAY_CODE


SEA CODE
Numeric

Numeric


Numeric
DAY FRAC       Real
SEA FRAC       Real
SEA_FLAG



DAY_FLAG


HOUR  FLAG
Character



Character


Character
HOUR1-HOUR24   Real
10          Source Classification Code (Point area or mobile)

 1          Day scenario identifier
            (1=Weekday, 2=Saturday, 3=Sunday)

 1          Season scenario identifier
            1=Spring, 2=Summer, 3=Fall, 4=Winter)

 7.5a       Day scenario fraction
            (65 x weekday fraction) + (13 x Saturday fraction)
             + (13 x Sunday fraction) = 1.0

 7.5 a       Seasonal scenario fraction
            (Spring fraction + Summer fraction + Fall fraction
             +Winter fraction = 1.0)

 4          Seasonal profile data source or combination
            method identifier
 4          Daily profile data source or combination method
            identifier

 4          Hourly profile data source or combination method
            identifier

 7.5         Diurnal profile
  Field width for field type real is defined as X. Y, where X represents the field width and Y represents
  the allowable number of digits to the right of the decimal.
                                          Figure 1. Final TAF file format.

                                                             2

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used  to  improve point  source data for
additional categories and to expand the
geographic base for point source tempo-
ral  data. The report  lists recommenda-
tions for additional data sets that could be
examined. On the other hand, only  one
existing source of area  source temporal
data could be obtained for this study. To
improve temporal profiles for area source
categories, it may be necessary to collect
new information through surveys  of the
most  important  source  categories.  This
approach was beyond  the scope of this
project and would  require additional cal-
endar time and resources to design  the
surveys, obtain Office of Management and
Budget clearance,  and perform the sur-
veys.  One product of this study was sta-
tistical methods for the analysis of temporal
data. The application of these methods to
quality assure the TAP  file data would be
appropriate.  In addition, the development
of computer software to access and ana-
lyze the TAP file data was recommended.
The availability of  an improved TAP file
does  not  eliminate the need  to  collect
actual data for temporally resolved emis-
sions when these data are needed for an
emissions inventory. Whenever inventory
development resources permit, actual data
should still be collected and quality as-
sured for  inventory projects where  sea-
sonal, daily, or hourly emissions estimates
are needed.  The  TAP file  provides an
improved database of default values that
should be used when actual data  cannot
be collected.

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  Theresa Moody, J. David Winkler, Terry Wilson, andSharon Kersteterare with TRC
    Environmental Corp., Chapel Hill, NC 27514.
  Charles O. Mann is the EPA Project Officer (see below).
  The complete report, entitled "The Development and Improvement of Temporal
    Allocation Factor Files," (Order No.  PB95-166153; Cost: $52.00; subject to
    change)  will be available only from
         National Technical Information Service
         5285 Port Royal Road
         Springfield, VA 22161
         Telephone: 703-487-4650
  The EPA Project Officer can be contacted at
         Air and Energy Engineering Research Laboratory
         U. S. Environmental Protection Agency
         Research Triangle Park,  NC 27711
United States
Environmental Protection Agency
Center for Environmental Research Information
Cincinnati, OH 45268

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