y Planning and Standards
U.S. Environmental Protection Agency
MD-10
Research Triangle Park, NC 27711
Dear John:
On behalf of STAPPA and ALAPCO, we wish to apprise you of some serious concerns state
and local air agencies have concerning Section 11.19.2 (Crushed Stone Processing) of AP-
42, EPA's Compilation of Air Pollutant Emission Factors. AP-42 is a respected reference
and state and local air pollution agencies calculate 80 percent or more of their overall air
emissions using the information contained in it. As such, it is important that AP-42 contain
up-to-date information that is presented in an unbiased, scientific manner. Unfortunately,
Section 11.19.2 does not contain the most current emission factor information related to
calculating total particulate. Based on the following information, STAPPA and ALAPCO
request that EPA revise Section 11.19.2 of AP-42 to include all scientifically appropriate
emission factor adjustments related to calculating particulate matter emissions for the
crushed stone processing industry.
To understand STAPPA and ALAPCO's concerns and desire to revise Section 11.19.2 of
AP-42, it is important to understand the recent history of that section. The 1977 Clean Air
Act Amendments identified total suspended particulate (TSP) as a criteria pollutant for
which EPA was required to adopt a National Ambient Air Quality Standard (NAAQS). TSP
represents that portion of the total measurable particulate matter fraction with nominal
diameters of 30 microns or less. In response to EPA's adoption of a TSP NAAQS, most state
and local agencies developed rules incorporating this new standard into their regulations.
Subsequently, in 1987, EPA identified PM10 as a criteria pollutant and, at the same time,
abolished its TSP standard. After EPA adopted a PM10 NAAQS, state and local agencies
revised their regulations accordingly. Many agencies, however, continued their TSP
regulations as a surrogate for PM10 and/or to address nuisance complaints against sources
emitting a high percentage of large particles (i.e., greater than 10 microns) for which the new
PM10 standard provided no regulatory authority. Over the years, state and local agencies
have relied on EPA to develop emission factors for sources with large-particle emissions.
In July 1994, EPA revised Section 11.19.2, including new emission factor information for
certain equipment used by the nonmetallic mining industry. EPA and the National Stone
Association (NSA), which is the trade organization affiliated with the nonmetallic mining
industry, worked cooperatively to complete the emissions testing necessary for the
development of the crushed stone processing emission factors contained in AP-42. Section
11.19.2 summarized relevant emission factors for PM10, as well as emission factors for particles measuring 50 microns or less (i.e., filterable particulate matter), that were contained
in Table 11.19.2-1. EPA acknowledged that its particulate matter emission testing had not
addressed TSP, but suggested that TSP could be calculated by multiplying the filterable
particulate matter by an adjustment factor of 0.80. Thereafter, state and local agencies
calculated particulate matter emissions for their nonmetallic mining sources using EPA's
suggested adjustment factor.
About six months later, however, EPA published its Fifth Edition of AP-42 in January 1995,
which gave rise to our current concerns about Section 11.19.2. Without explanation, EPA
eliminated from the Fifth Edition of AP-42 the information related to the filterable
particulate matter emissions that had been listed in Table 11.19.2-1 of the 1994 Edition of
AP-42 and inserted in a footnote to Table 11.19.2-1 that "relative ratios in AP-42 Sections
13.2.2 [Unpaved Roads] and 13.2.4 [Aggregate Handling and Storage Piles] indicate that
TSP emission factors may be estimated by multiplying PM-10 by 2.1." Significantly, EPA
made this change even though measurements of filterable particulate matter were obtained as
part of the testing conducted for the 1995 revisions to Section 11.19.2, and that data shows
filterable particulate emission levels up to 20-times greater than would be estimated using
the PM10 and 2.1 adjustment factor introduced in the Fifth Edition. Thus, AP-42 no longer
provided state and local agencies with support for using the 0.8 emission factor adjustment
for calculating total particulate contained in the 1994 edition of AP-42, and instead
suggested that total particulate should be calculated by multiplying the PM10 emission factor
by 2.1, even though summary testing information indicated that using the new adjustment
factor was most likely inaccurate. After EPA changed Section 11.19.2 in 1995, nonmetallic
mining sources in affected states insisted that state and local air agencies use the 5th Edition
of AP-42 when calculating total particulate, arguing that it was based on the most current
information issued by OAQPS for calculating these air emissions. Moreover, application of
the 1995 adjustment factor has produced significantly different total particulate matter
emissions calculations compared to both the 1994 adjustment factor and specific source
emissions testing data being collected across the country.
Recently, EPA revised AP-42 Section 13.2.2, which contains emission factor information
related to the unpaved road source category. Significantly, the recent revisions to that section
changed the equation for estimating particulate matter emissions for unpaved roads creating
a variable between filterable particulate matter and PM10 emissions. As a result of the
change to Section 13.2.2, EPA's citation in Table 11.19.2-1 (discussed above), which cites
Section 13.2.2 and the use of PM10 times 2.1 as a relative ratio for calculating total
particulate for crushed stone processing sources, no longer applies and leaves state and local
air agencies without an adequate basis for calculating total particulate from crushed stone
processing sources.
STAPPA and ALAPCO believe that EPA's recent change to Section 13.2.2 and the
availability of filterable particulate matter emissions information from 1995 testing
necessitates that Section 11.19.2 be revised to reflect the most current information regarding
how to calculate total particulate emissions for crushed stone processing facilities. Therefore,
the associations strongly recommend that EPA immediately begin appropriate reviews
and/or scientific estimations of existing emissions data that may be used to calculate total particulate matter emissions from crushed stone processing sources and revise Section
11.19.2 of AP-42 accordingly. This approach will help ensure that AP-42 contains the most
current emissions estimation information on which to calculate emissions from crushed stone
processing facilities.
Thank you for considering this request and we welcome the opportunity to work with EPA to
improve AP-42. If you have any questions or desire additional information related to our
request, please contact either of us or Dave Wallenberg of STAPPA/ALAPCO.
Sincerely,
(original signed)
Roger Westman
ALAPCO Chair
Emissions and Modeling Committee
(original signed)
Herb Williams
STAPPA Chair
Emissions and Modeling Committee
cc: David Mobley