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AIR EMISSIONS REPORTING REQUIREMENTS RULE 

EPA Comment Summary and Response Report 

1. Harmonizing Report Due Dates 

Comments: Many commenters (0026, 0028, 0029, 0035, 0036, 0039, 0041, 0044, 0045 and 

0046) supported the concept of harmonizing report due dates. However, some of the commenters 

in this group felt that harmonizing the report due dates by reducing the reporting timeline for 

point sources to 12 months might compromise the integrity and accuracy of data, which must be 

quality assured and urged EPA to harmonize the report due date at 17 months for all emission 

sectors (point, nonpoint and mobile). 

One commenter (0028) supported a 12-month reporting schedule for point sources for the 2008 

triennial year since his State had met this annual timeline for the last three years. Another 

commenter (0036) did not object to the 12-month schedule proposed for 2008 for point and 

nonpoint source emission inventories but did object to shortening the reporting time for mobile 

sources due to resource restrictions. One commenter (0030) expressed support for efforts by EPA 

and/or State agencies to streamline reporting requirements and reduce reporting burdens on States 

and sources but thought it should not be at the expense of sources. 

Two commenters (0014 and 0032) thought that a 12-month timeline for reporting point source 

emissions was achievable but preferred retaining the existing 17-month reporting timeline. One 

commenter (0043) noted that the existing 17-month timeline is used to review and enter a large 

volume of point source data. The commenter indicated that additional time is needed to collect 

Highway Performance Monitoring System Vehicle Miles Traveled estimates which are not 

available until August for the inventory year. The commenter believed that the 12 month 

reporting due date proposed for 2008 would pose reporting problems, but thought it was 

preferable to the 6 month timeline proposed for 2011. Two commenters (0044 and 0046) thought 

the 17-month timeline for reporting nonpoint and mobile source emissions should be retained due 

to unavailability of data needed to develop the emission estimates. 

 

One commenter (0042) did not support EPA-mandated reporting dates and believed that States 

should have the flexibility to establish reporting dates that meet State administrative needs. 

Response: 

In the AERR rulemaking, EPA proposed to shorten the timeline of 17 months for reporting under 

the CERR to be consistent with the 12 months for reporting under the NOx SIP Call. A second 

alternative requiring 12 months for reporting of point sources and 17 months for nonpoint and 

mobile sources was also proposed. Most commenters expressed support for the concept of 

consolidating the reporting requirements under the NOx SIP Call and the CERR, but were 

concerned about the alternative of using the 12-month timeline for some or all sources for the 

2008 inventory year. 

EPA agrees with the concerns of the commenters regarding the proposal to tighten the timeline to 

12 months for the 2008 inventory year and in this rulemaking has decided to implement the 

shorter timeline for reporting under the AERR starting with the 2009 inventory year. Since the 
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2009 and 2010 inventory years require reporting for Type A (large point) sources only, one 

impact of this action is to delay implementing a 12-month timeline for reporting of all sources 

until the 2011 inventory year, which is the next 3-year comprehensive emission inventory year. 

For the 2008 inventory year, the 17-month timeline under the CERR will remain in place. This 

will provide additional stability for States using the new data submittal and operating procedures 

for the Emission Inventory System (EIS), which will be available for the 2008 inventory year. 

Maintaining the 17-month timeline will allow State agencies to adapt to the new data reporting 

and system requirements without introducing additional uncertainty to the process. It will also 

provide time for EPA to correct any problems with the new system procedures before attempting 

to adjust the timeline for data submittals. EPA believes that completing the 3-year cycle emission 

inventory for the 2008 inventory year using a 17-month timeline will allow States to become 

sufficiently familiar with the new procedures to implement a 12-month timeline to report data 

from Type A sources for the 2009 and 2010 inventory years and to implement a 12-month 

timeline to report data from all sources for the 2011 inventory year as part of the comprehensive 

3-year cycle inventory. 

EPA did not propose to extend the existing 12-month timeline for reporting under the NOx SIP 

Call. Thus, the NOx SIP Call 12-month timeline will be retained for the 2008 inventory year and 

harmonized reporting under the NOx SIP Call and AERR will be delayed until the 2009 inventory 

year. 

It should be noted that although the timeline for data reporting by State agencies will be 

unchanged for the 2008 inventory year, EPA’s internal procedures for data handling will be 

updated with the goal of releasing the final 2008 National Emission Inventory (NEI) on a 

schedule that is considerably shorter than the 3 years that has historically been required. 

EPA disagrees with the commenter who did not support EPA-mandated reporting dates. State 

reporting of emissions data by specified dates is essential to developing national emission 

inventories that are fundamental to understanding air quality problems and supporting national 

level rules to reduce emissions. EPA will continue to work with its partners to ensure that the 

timelines for data submittal are achievable and meet the purposes of developing timely and high 

quality emissions data. 

Comment: One commenter (0048) requested that states not be required to submit emissions 

data for sources subject to the NOx SIP Call or acid rain rules and have CEMs for NOx, SO2 and 

CO (and estimate emissions for CO2). The commenter stated that the acid rain program 

provides data to the NEI for these sources. In addition, the commenter wanted EPA to accept 

complete data sets from states that would include these sources but asked that EPA not subject 

data for these sources to rigorous quality assurance procedures used for other sources. 

Response: EPA has tried to address the commenter’s concern that States not be required to 

report data that are directly reported to EPA under trading programs. Section 51.30 (a) (6) of the 

AERR (as proposed) allows States to not provide annual data to EPA for sources participating in 

a trading program under Sections 51.123 and 51.124 (CAIR). Because CAIR was vacated and 

remanded to EPA by the U.S. Court of Appeals on July 11, 2008, the final rule eliminates all 

references to Sections 51.123 and 51.124. States are still required, however, to provide complete 

triennial emission inventories to EPA for all point, nonpoint and mobile sources. 

EPA will be prepared to accept complete data sets from States to meet the requirements of the 

AERR. However, new data transmittal procedures being developed as part of the new EIS will 

impose quality assurance and data integrity checks prior to acceptance of data by EPA. Data 
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accepted by EPA will be considered a submittal under the AERR and may be subjected to the 

same quality assurance procedures as other data, regardless of whether the data are used to 

support the NEI or are used for other purposes. 

2. Accelerating Report Due Dates 

EPA asked for comments on two alternatives for tightening the timeline for submittal of data for 

the 2011 inventory year: (1) 6 months for submittal of data from point sources and 12 months for 

nonpoint and mobile sources and (2) 6 – 12 months for submittal of data from point sources and 

12 – 17 months for nonpoint and mobile sources. 

Comments: Most commenters (0005, 0007, 0014, 0021, 0026, 0028, 0029, 0032, 0036, 0037, 

0038, 0041, 0042, 0043, 0044, 0045, 0046 and 0048) were concerned with or opposed to the 

proposed 6-month timeline for States to submit point source data for the 2011 inventory year. 

Commenters generally indicated that the accelerated schedule would make for a very short time 

for point sources to gather the data needed to report to States and for States to process and quality 

assure the data. They believed this would result in incomplete and inconsistent data quality, due 

to the lack of time for entry and quality assurance of the data. One commenter (0009) supported 

EPA’s proposal to further accelerate the reporting schedule starting with the 2011 inventory year 

by requiring that point sources be reported within 6 months from the end of the inventory year. 

Several commenters (0021, 0028, 0032, 0036, 0037, 0042, 0043 and 0044) who expressed 

concerns about the proposed 6-month point source reporting timeline for the 2011 inventory year 

thought that tightening the timeline for point sources to 12 months would be possible. Some of 

the commenters (0028, 0032, 0037, 0042 and 0044) thought that 17 months would continue to be 

needed for the nonpoint and mobile source inventory sectors due to the unavailability of data on a 

shorter schedule from other agencies that is needed to develop the emission estimates. One 

commenter (0036) thought that 17 months would continue to be needed for mobile sources but 

that nonpoint data could be submitted within 12 months. 

Two commenters (0027 and 0038) expressed concerns with the proposed 6-month timeline but 

thought that a 9-month schedule for submittal of point sources data would be possible. 

Many commenters (0006, 0007, 0015, 0017, 0018, 0019, 0022, 0023, 0024, 0025, 0030, and 

0031) thought the proposed 6-month timeline for States to submit data to EPA would result in 

States imposing shorter timelines for sources to submit their data to States. These commenters 

believed that the shorter timelines would affect the cost and accuracy of the reports provided by 

regulated businesses to States. Two of these commenters (0006 and 0031) noted that other 

reporting requirements such as those under Title V and the Toxics Release Inventory (TRI) help 

create efficiency in the system since these reports are due at approximately the same time. The 

commenters were concerned that requiring States to submit data to EPA on a 6 month timeline 

would require sources to submit data to States on a more compressed schedule and eliminate the 

efficiency gained by having State emission reports due at approximately the same time as TRI 

reports. One commenter (0028) pointed out that companies now complying with the Emission 

Statement requirements of the Clean Air Act (which require reporting within 6 months) must 

submit their estimates to their State by March 1 and the data are certified by June 30. A 6-month 

submittal schedule would require moving the certification step to mid-May to include the 

additional step of submitting the data to EPA by June 30. The commenter did not think that 

moving the certification step to mid-May would be possible since many companies would still be 

reviewing preliminary emission estimates at that time. 
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Two commenters (0026 and 0035) wanted to retain the existing 17-month timeline for reporting 

point, nonpoint and mobile source data. One of the commenters (0035) expressed concerns that 

were based primarily on having to conduct a similar data collection and compilation effort within 

California. The commenter thought that the time to conduct the California data collection effort 

made accelerating the timeline to less than 17 months unrealistic and could compromise data 

quality. The other commenter (0026) expressed opposition to the concept of a bifurcated 

reporting system which would require submittal of point and nonpoint/mobile source sector data 

on separate dates. 

One commenter (0039) strongly opposed shortening the existing time frame of 17 months for data 

collection from point sources and thought that web-based submittal tools needed to move beyond 

the developmental stage before it might be possible to shorten the timeframe to 12 months. The 

commenter also thought that much of the activity data needed to develop the nonpoint source 

estimates was not available for 12 – 15 months after the end of the inventory year and EPA 

should consider using previous year data as a surrogate for the inventory year. 

Another commenter (0030) suggested that EPA encourage State agencies to implement online 

reporting systems to speed up the efficiency of reporting before finalizing the AERR. One 

commenter (0031) indicated that they already used a web-based reporting system to report their 

air emissions to the State of North Carolina. 

Response: EPA agrees with the concerns expressed by most of the commenters regarding the 

proposed 6-month timeline for submittal of point source data by the 2011 inventory year. When 

EPA developed the proposed rulemaking, a project known as the “Rapid Inventory Development 

Pilot” was initiated. EPA has now evaluated the results of the project and believes that 6 months 

for development and submittal of inventory data is not yet achievable on a consistent basis with 

application of proper quality assurance procedures for all emission inventory source sectors. 

However, the project did demonstrate that a timeline shorter than the existing 17 months is 

possible since a number of States were able to submit data to EPA 10 months after the emission 

inventory year. 

EPA understands that some difficulties were encountered by several of the participating States 

which indicated that additional time is needed for refinement of electronic tools and procedures to 

support, on a consistent basis, development and submittal of emissions data on an expedited 

timeline. To allow additional time for technological improvements, EPA will retain the existing 

17-month reporting timeline for point, nonpoint, and mobile sources for the 2008 inventory year 

(data due June 1, 2010) under the CERR. The 12-month timeline under the AERR will be 

implemented starting with the 2009 inventory year. 

3. Reporting Biogenic Emissions 

EPA proposed to remove a requirement in the existing CERR for reporting annual and typical 

ozone season day biogenic emissions. 

Comments : All commenters (0009, 0026, 0028, 0029, 0035, 0036, 0042, 0044, 0045, 0046 and 

0048) on the biogenic emissions reporting requirement supported EPA’s proposal to not include 

biogenic emissions reporting in the AERR. 

Response: EPA agrees with the commenters and will implement this part of the AERR as 

proposed by removing the existing reporting requirements (under the CERR) for annual and 

typical ozone season day biogenic emissions. 
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4. Reporting Emission Model Inputs

EPA proposed an option for States to provide emission inventory estimation model inputs in lieu 

of actual emission estimates. This option would start with the 2005 inventory year. The Agency 

also invited comment on whether States, in addition to providing emissions data, should be 

required to provide model inputs where they have used a widely available emissions model. 

Comments: Several commenters (0004, 0026, 0028, 0029, 0032, 0035, 0036, 0045 and 0046) 

expressed support for the option of providing emission inventory estimation model inputs in lieu 

of actual emission estimates. One commenter (0042) supported States being able to submit inputs 

in lieu of emission estimates, but believed that States should retain the ability to develop their 

own emission inventory data. Another commenter (0043) indicated a willingness to submit the 

inputs, but thought that EPA should maintain the option of allowing States to report emission 

estimates. One commenter (0028) supported the option for States to submit model inputs in lieu 

of emissions data and suggested that EPA develop emissions summaries based upon the 

submitted modeling inputs for use by States. 

Several commenters (0026, 0029, 0036, and 0045) supported the option of providing model 

inputs in lieu of emissions data but were concerned that EPA would make the option a 

requirement. Some of the commenters also noted that EPA has, in the past, overridden Statesubmitted model inputs and urged that EPA not do so in the future. 

Two commenters (0035 and 0044) supported the option of reporting model inputs in lieu of 

emission estimates but did not support the proposal to require States to report model inputs. One 

commenter (0035) believed that requiring States to report model inputs would remove their 

option of reporting emissions using independent models or using differing classifications or 

categories of emission sources. The other commenter (0044) encouraged reporting of model 

inputs in addition to actual emission estimates to provide data for EPA strategy analyses and 

allow States to retain the ability to submit actual estimates to the NEI. 

Other commenters (0042 and 0043) indicated they had no problem with States submitting inputs 

in lieu of emissions and relying on EPA to develop emission estimates utilizing those inputs but 

were concerned that such a shift could limit their ability to calculate their own emissions. One of 

the commenters (0042) utilized EPA models in developing their emission inventory and modified 

a number of default model parameters to more accurately reflect their emissions. The commenter 

believed that States should retain the ability to develop their own emission inventory data 

utilizing local data when available and hoped that EPA would continue to consider States that 

develop their own emission inventories as EPA moved forward with development of new tools. 

The other commenter (0043) was concerned that submitting only the model input data to the EPA 

would make emission estimates calculated by EPA inconsistent with their onroad and nonroad 

mobile inventories, since post-processing was performed on these inventories to improve the 

spatial and temporal allocation of the emissions data. 

One commenter (0046) supported allowing States to report model inputs rather than emission 

estimates but only if EPA made the model outputs available to the States (e.g., typical summer 

day emissions needed for State Implementation Plans) and the steps used by EPA in developing 

the emission estimates were transparent. 

One commenter (0037) had no problem with including the input files with their inventory 

submittal but felt strongly that EPA’s focus should be on quality assurance and quality control 
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(QA/QC) of the data and not on compiling it. This commenter was against submitting input files 

in lieu of emissions data for mobile and nonroad sources and preferred to run the models since 

this allowed the commenter to understand the results. 

One commenter (0048) questioned the adequacy of providing model inputs in lieu of emissions to 

EPA. The commenter believed that EPA should complete development of the new Emission 

Inventory System (EIS) before establishing an alternate reporting requirement. The commenter 

cited concerns with (1) compatibility between the EIS and NIF, (2) how the States will access and 

provide data to EIS without substantial new expenditures, disruptions and confusion and (3) the 

ability of a third party, lacking specific information and knowledge about facilities, to properly 

calculate emissions. 

Response: EPA agrees with the majority of commenters who supported the option of submitting 

input data in lieu of emission estimates and will make this an option under the AERR. Although 

the proposed rule indicated this option would be available for reporting emissions for the 2005 

inventory year, EPA intends to delay implementation of this option until the 2008 inventory year 

since the final rule was not published before the due date for data from the 2005 inventory year 

(June 1, 2007). Although EPA encourages States to submit model inputs where they have used a 

widely available model to develop emission estimates, States will not be required to submit input 

data when they provide emission estimates.Submitting model inputs to EPA will assist EPA in 

adjusting assumptions used in inventories when conducting analyses necessary for national-level 

rule development.

EPA does not believe that States should be concerned about limitations to their ability to develop 

their own emission estimates. Since the option of submitting inputs to models includes use of 

input values adjusted by States to reflect local conditions, use of those same inputs by EPA will 

not impact State efforts and will tend to enhance the consistency of estimates developed by the 

State and EPA. The concerns of one commenter regarding differences that emerge when EPA 

and States conduct spatial and temporal allocations of emissions during post-processing of 

emission inventories for air quality modeling are no different than those that now exist. These 

differences are inevitable as independent operations are performed by States and EPA on similar 

inventories and will not be exacerbated by States submitting input data to EPA. 

The concerns expressed by several commenters regarding EPA developing requirements to 

submit input data in lieu of emissions data are unfounded. The proposal offered States the option 

of submitting input data in lieu of emissions data , but did not propose to make it a requirement. 

With regard to the comment that the focus of EPA activities should be directed toward QA/QC of 

the data rather than on compiling it, EPA notes that it is often involved in both activities in 

developing the NEI.EPA does not believe that QA/QC procedures are compromised by its efforts 

to develop data. 

In addition, EPA does not believe that offering the option of submitting model inputs will 

significantly affect development of the EIS. The models primarily in question estimate nonroad 

and onroad mobile source emissions and were developed by EPA. Although models are updated 

and inputs can change, the inputs and the interface with the new EIS will be required regardless 

of whether EPA or States operate the models. EPA does not believe that substantial new 

expenditures, disruptions and confusion will be created by the new EIS. Rather, EPA expects that 

the new system, through use of standardized procedures developed with State input, will help 

address some of the problems that have long existed in developing data for submittal to EPA. 

The ability of a third party to estimate emissions from facilities also has little bearing on the 

question of submitting model inputs since the models at issue concern mobile sources. This is 
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supported by the language under Section 51.15 (e), which states that “EPA may allow States to 

submit comprehensive input values for models capable of estimating emissions from a certain 

source type on a national scale....” Models such as TANKS, Landfill, Chemdat, etc. are used by 

States for estimating individual point source emissions and therefore are not subject to the 

provisions of Section 51.15 (e).. 

With regard to the comments about availability and transparency of modeling data, EPA notes 

that improving “transparency” is one of the goals of the new EIS. Accordingly, EPA intends to 

make model input and model output data available to States as well as provide documentation on 

the steps used to develop emission estimates.

5. Reporting Summer Day Emissions 

EPA proposed to retain the requirement for reporting of summer day emissions from all sources 

(except biogenic sources) at 3-year intervals, but to restrict it to States with ozone nonattainment 

areas or States covered by the NOx SIP Call or CAIR. The summer day emissions reporting 

requirement would be restricted to VOC and NOx emissions. Comments were invited on whether 

CO emissions should be required also. 

Comments: Several commenters (0026, 0028, 0029, 0036 and 0044) supported EPA’s proposal 

to retain the requirement for reporting of summer-day emissions (NOx and VOC) from all 

sources at 3-year intervals but to limit it to States with ozone nonattainment areas or sources 

covered by the NOx SIP call or Clean Air Interstate Rule. 

Two commenters (0042 and 0043) thought that ozone season day NOx, VOC and CO emissions 

should be reported for all areas. One of the commenters (0042) believed that limiting the 

reporting requirement to ozone nonattainment areas would create gaps in the inventory which the 

CERR attempted to resolve. The other commenter (0043) cited regional haze “episodes” that 

tend to occur with ozone episodes as a reason for continued reporting for all areas. 

Two commenters (0046 and 0048) questioned the value of reporting summer day VOC and NOx 

emissions. One commenter’s (0046) experience was that summer day emissions were not used 

for attainment demonstrations which generally involved atmospheric modeling of episodic 

conditions. The commenter stated that summer day emissions were not used to evaluate control 

strategies presented in the SIP and believed that inventory products that do not directly support 

the SIP should not be required. Another commenter (0028) thought that requiring ozone season 

and daily emissions for point, nonpoint and nonroad sources was redundant since the temporal 

parameters needed to calculate these emissions were required. 

One commenter (0036) thought that summer day emissions of CO should not be reported while 

two other commenters (0028 and 0029) believed that reporting CO summer day emissions was 

necessary only for CO nonattainment areas. 

One commenter (0045) requested that in the proposed rule or in guidance, EPA specify exactly 

what it is requesting when it asks for summer day emissions. 

Response: EPA agrees with the majority of the commenters that the reporting requirements for 

summer day emissions from all sources (except biogenic sources) at 3-year intervals should only 

include States with ozone nonattainment areas (VOC and NOx) and States covered by the NOx 

SIP Call (NOx only). However, EPA believes that it is also appropriate to include summer day 

emissions reporting for sources in attainment counties that are covered by the modeling domain 
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used to demonstrate reasonable further progress (RFP). EPA’s current guidance requires the RFP 

calculations to be done on an “average summer weekday emissions” basis. If the State takes 

credit for reductions from outside the nonattainment area, the requirement would be to determine 

whether there were reductions (in average summer week day emissions) from those sources. 

EPA believes that reporting of CO summer day emissions is not necessary since, as noted by one 

commenter, other data elements already reported allow summer day emissions to be derived and 

CO emissions, unlike VOC and NOx emissions, are not used for tracking RFP. Therefore, 

reporting of CO summer day emissions will not be a requirement under the AERR, regardless of 

ozone attainment status. 

The AERR proposal indicated that “We are proposing to retain the requirement for summer day 

emissions....” However, the CERR requires reporting of “work weekday emissions” for point 

sources and “summer work weekday emissions” for nonpoint and mobile sources. Although we 

did not receive comments on the work weekday versus summer day emissions issue, we realized 

that the preamble language indicated that no changes would be made to the summer day 

emissions definition contained in the CERR (beyond the proposal to restrict the requirement to 

ozone nonattainment and NOx SIP Call areas), but the proposed AERR regulatory language made 

additional changes to the definition of "summer day emissions." Accordingly, in recognition of 

the conflicting language and as indicated in the preamble to the proposed rule, the final AERR 

will retain the definition of and requirement to report “work weekday emissions” for point 

sources and "summer work weekday emissions" for nonpoint and mobile source reporting in the 

CERR, revised only to the extent that it will restrict the requirement to ozone nonattainment areas 

(including sources in counties that are covered by the modeling domain used to demonstrate RFP) 

and NOx SIP Call areas. In addition, the definition for summer day emissions has been revised to 

require the use of work weekday emissions (as required under the CERR) when estimating 

summer day emissions for reporting. 

6. Reporting Winter Work Weekday Emissions 

EPA proposed to delete the existing requirement that all States report emissions for a winter work 

weekday. 

Comments: Most commenters (0009, 0026, 0028, 0033, 0036, 0042, 0044, 0045 and 0048) 

supported EPA’s proposal to delete the reporting requirement for winter work weekday 

emissions. One commenter (0029) opposed EPA’s proposal to eliminate the existing reporting 

requirement, citing a need by States for this data in CO maintenance plans. 

Response: Although most of the commenters agreed with EPA’s proposal to delete the reporting 

requirement for winter work weekday emissions, EPA finds the comment that CO reporting is 

needed for CO maintenance plans to be compelling. As noted by the commenter, CO 

maintenance plans require tracking of emission reductions to ensure continued maintenance of the 

CO NAAQS. While it is not necessary to follow the requirements of the AERR to report 

emissions to EPA, doing so will aid in standardizing the data reported and facilitate review of the 

data by interested parties. 

A concern not raised by commenters relates to requests from States to discontinue monitoring of 

ambient CO concentrations in certain areas that have been redesignated to attainment for CO. 

EPA’s approval of such requests is conditioned on the expectation that emissions will not 

increase and areas will continue to maintain the CO NAAQS. To provide a means of ensuring 
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that the CO NAAQS are maintained in areas that no longer have ambient CO monitors, emissions 

reporting becomes even more critical. 

The AERR proposal indicated that EPA could work on a case-by-case basis with the few 

remaining CO nonattainmment areas regarding reporting of winter work weekday emissions. 

However, in the final rule, EPA has determined that for those areas in which EPA determines that 

reporting is still needed, reporting emissions using the AERR requirements will ensure that CO 

emissions are reported periodically and that the data are in a standardized format that will 

facilitate data review and thus help ensure attainment and maintenance of the CO NAAQS. 

Therefore, to monitor progress toward attaining and maintaining the CO NAAQS, EPA will 

retain the requirement for reporting of winter work weekday emissions of CO, but will limit it to 

CO nonattainment areas and areas with CO maintenance plans. 

7. New Data Elements 

EPA proposed to add several data elements: contact name, contact phone number, emission 

release point type, control status, emission type and method accuracy description (MAD) codes. 

Comment: Three commenters (0026, 0029 and 0044) supported EPA’s proposal to add new data 

elements to the Air Emissions Reporting Requirements (AERR) rule. 

 

Response: EPA agrees with the supportive comments on the proposed new data elements. 

However, the need for one new data element (Control Status) has been reconsidered by EPA. 

Comments and responses specific to this proposed data element are addressed later in this section. 

Comment: Several commenters (0028, 0042, 0045, 0046, and 0048) indicated they were already 

reporting many of the new data elements and did not understand why they were being proposed 

for addition to the AERR. Three commenters (0028, 0045 and 0048) believed that the new data 

elements should be added to the NIF or guidance documents rather than the AERR. One of the 

commenters (0045) suggested that a Federal-State task force be established to review, revise, 

finalize and implement changes in code details. The commenter was concerned that many 

changes resulted in significant impacts upon data collection and storage programs used by States, 

with significant resulting impacts on resources and timing issues for individual States. To limit 

the impacts, the commenter thought that identification of extensive lists of mandatory data 

elements should be limited to guidance documents developed in collaboration with state, local 

and tribal (S/L/T) agencies. The commenter urged that discussion of data elements and data 

formatting procedures and code tables be excluded from the rule. 

Response: EPA believes that both data reporting rules and data reporting formats are needed for 

effective data reporting. Although the AERR and NEI Input Format (NIF) address many 

common data elements for reporting to EPA, their purposes are somewhat different. Data 

reporting rules such as the AERR identify data elements and timelines for reporting. Data 

reporting formats such as the NIF address the details of how the data are to be reported to 

facilitate handling of the data by EPA. 

EPA does not believe that using a data formatting protocol such as the NIF is an effective way to 

communicate data needs with State agencies. EPA has long codified data reporting requirements 

since States need to understand what will be required and when it will be required by EPA to 

implement programs under the Clean Air Act. EPA continues to believe that codifying data 

elements for reporting and timelines for submittal of data are appropriate levels of detail to be 

addressed through the rulemaking process. This process allows for all affected parties to review 
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the basic requirements for submittal of data to EPA and provide comments for EPA review. The 

rulemaking process is a means of providing assurances to affected parties that their concerns will 

be heard and considered. 

In response to the one commenter’s concerns regarding discussion of the NIF and code tables in 

the proposed rulemaking, EPA discussed these materials in the preamble to impart additional 

clarity to requirements for data reporting. It was not EPA’s intent to include these materials by 

extension in the rulemaking notice. Text in the regulatory portion of the rulemaking notice does 

not reference the NIF or associated code tables. The commenter suggested that a Federal-State 

task force be established to review, revise, finalize and implement changes in code details. Such 

a task force has been established to help with developing the new EIS. EPA expects the task 

force to update tools and guidance materials for data reporting and periodically review data 

elements and reporting codes for use by State agencies. 

Comment: One commenter (0042) currently collected a contact name and phone number with 

each emission statement submission for point source emissions but did not track emission release 

point type, control status, emission type and MAD codes. The commenter was not opposed to 

collecting the additional data elements, but indicated a state rulemaking and modifications to their 

integrated data system will be required and urged EPA to provide sufficient lead time for the state 

to complete its rulemaking process. 

Another commenter (0046) indicated that they already reported contact and release point 

information where provided by facilities. The commenter thought that it was difficult to report 

control information for point sources in a manner that supported automated projection of control 

strategy impacts and believed the problem was a lack of clear information on how the data 

elements were to be populated and how the data would be used. The commenter recommended 

that EPA clarify and encourage proper use of currently available data elements before requiring 

additional data. 

One commenter (0028) questioned the inclusion of a data field for emission release point type 

since state quality assurance programs were more concerned with emission estimates than quality 

assuring stack characteristics necessary for air quality modeling. 

Response: We understand that States need lead time to respond to changing data reporting 

requirements. Accordingly, EPA has retained the 17-month timeline for reporting under the 

CERR for the 2008 inventory year to provide states additional time to transition to the new 

reporting requirements under the AERR. The AERR reporting requirements will be effective 

beginning with the 2009 inventory year. Data submittals for the 2009 inventory year will be due 

to EPA by December 31, 2010, which should provide states sufficient lead time to adjust to the 

new reporting requirements under the AERR.. 

As discussed earlier in this section, EPA and the National Association of Clean Air Agencies 

(NACAA) have recently formed a workgroup to address issues during development of the EIS. 

Developing better guidance materials is one of the focus areas and EPA is hopeful that the 

workgroup efforts will help address the commenter’s needs for clarity on procedures for 

populating data elements. 

Regarding the concern with quality assuring emissions rather than stack parameters, EPA 

encourages States to do both since it is important for EPA to locate stack emissions and use other 

data provided by States to conduct accurate air quality simulations for support of air quality 

analyses and national rules. 
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Comment: One commenter (0009) expressed support for the option of States having a code 

indicating "don't know" if the information needed for the method accuracy description (MAD) 

codes is not available. Another commenter (0035) noted that the proposal indicated that the code 

“don’t know” was included in the domain for method accuracy description codes but was not sure 

if similar codes were available for other proposed data elements such as emission release point 

type and control status. The commenter suggested that “N/A” be included in the domains for 

these elements. 

Response: As discussed earlier in this section, the data element for control status will not be 

added to the AERR. EPA believes that “don’t know” or “N/A” codes for the proposed emission 

release point type data element are not needed since States should have these data.. However, in 

the event that data do not exist for emission release point type, States have the option of not 

selecting a code 

Comment: One commenter (0028) thought that EPA should provide additional information on 

the need for method accuracy description (MAD) codes and suggested that if these codes were 

added, only the coordinate data source code (State, facility, etc.) and the horizontal collection 

method code (map, global positioning system, etc.) be included. 

Response: EPA understands that agencies may not be able to provide the data requested under 

the method accuracy description (MAD) codes. As explained in the preamble of the proposed 

AERR rule, where States do not have the requested data, no additional work will be required 

since they will be able to use a code for “don’t know.” The codes are required to meet EPA’s 

latitude/longitude data standard which applies to many EPA programs. 

Comment: One commenter (0028) was concerned that some of the data elements appeared to be 

proposed only for point sources and thought that EPA should clarify in the final rule what was 

intended. 

Response: The preamble in the proposal did not discuss if the new data elements were specific 

to inventory categories. However, Tables 2A, 2B and 2C in the regulatory portion of the rule 

were specific to each inventory category (point, nonpoint, nonroad mobile, and onroad mobile) 

and did list all data elements proposed for each under the AERR. 

Comment: One commenter (0048) thought that in order for the proposed emission release point 

type and related data to be submitted, EPA needed to revise the NIF and the manner in which the 

data are transferred. The commenter noted that EPA’s system does not currently allow reporting 

of “many-to-many” relationships that are necessary to maintain the integrity of State data for 

facilities that have complex exhaust flow situations among several stacks. Currently, North 

Carolina must simplify data and lose the many-to-many relationships reported by some facilities 

in order to submit the data to EPA. 

Response: The “many-to-many” data relationship issue is outside the scope of the AERR which 

is concerned only with the data reporting requirements. However, EPA understands the concerns 

of the commenter and agrees with the need to add the “many-to-many” data relationship 

capability to the new EIS. 

Comment: One commenter (0048) thought that the AERR needed to make a distinction between 

control devices and changes in process. The commenter asserted that many “control strategies” 

utilize means to reduce emissions that are actually process changes or redesigns (e.g. VOC 

coating changes, or low-NOx burners) and are not properly described in control device codes, but 
12

should be redefined as a separate source classification code (SCC) or process 

definition/description. 

Response: EPA does not believe the AERR needs to make distinctions between process changes 

or use of control equipment. Both reduce emissions, and appropriate data source codes are 

available to indicate what process change or type of control equipment is responsible for the 

resultant emission reduction. 

Comment: One commenter (0048) noted that the proposal appeared to differentiate between 

primary and secondary controls with reference to control of a single pollutant. The commenter 

indicated that the efficiency of the final control device is what determines the control efficiency 

or percent reduction. In the case of particulate matter controls where a cyclone is used prior to a 

bag filter, the function of the cyclone is to condition the gas stream before the bag filter and has 

little to no effect on the net control efficiency resulting from the bag filter. The commenter 

thought that the data elements associated with controls should be part of the NIF requirements 

and not included in the AERR. 

Response: EPA agrees with the commenter that a primary control for particulate matter may 

have little impact on the overall or net control efficiency. However, EPA did propose a data 

element for “total capture and control efficiency (percent)” which will address the commenter’s 

concerns regarding the net control efficiency. The data elements associated with controls will be 

part of the NIF requirements, but as explained earlier in this section, EPA believes it is 

appropriate to include data reporting requirements and timelines in data reporting rules to provide 

States with an opportunity to comment on the basic requirements of what data will be reported 

and when it will be required. 

Comment: One commenter (0032) believed that the existing fields for control equipment and 

efficiency were adequate, but thought that EPA needed to improve and update the code options 

with the latest technologies and control devices (e.g., regenerative thermal oxidizer, etc.). The 

commenter also noted that although the current list does include a few options for control 

methods that involve operational changes rather than physical devices (e.g. process change, low 

solvent coating, etc), perhaps a more expansive list of nonphysical-device control methods could 

be developed. 

Response: EPA believes the current code tables are adequate for most applications, but agrees 

that the tables need to be reviewed and updated periodically. This task is being conducted as part 

of the new Emission Inventory System now under development by EPA. 

Comment: Two commenters (0033 and 0034) thought that the addition of a control status code 

would not make the status of a facility any more clear and believed that the control status of a 

facility could be determined from other data elements already required for reporting under the 

CERR and proposed under the AERR (e.g., control device codes and control efficiency). 

One of the commenters (0033) thought that accurate assessments of future emissions could not be 

made without the more detailed information already required by the CERR regarding the specific 

control techniques in use and their efficiency. The commenter went on to state that EPA’s 

detailed reporting instructions have long provided for the "control device" data element to specify 

such nonphysical equipment control techniques as "low solvent coatings", "water-borne 

coatings", "process change", and several varieties of combustion modifications. The commenter 

thought that the NIF format provided more detail regarding control types and efficiencies than the 

current proposal seeks to add and EPA should more carefully evaluate what is really needed and 

then provide guidance on how the existing data elements can be utilized to meet those needs. 
13

Response: Control status was the only new data element proposed under the AERR that was not 

already in the NIF Version 3.0 and thus was perceived as a new data reporting requirement by 

several commenters. This new data element would require States to indicate if a source is 

controlled or uncontrolled. EPA agrees with the concerns expressed by the commenters. The 

data reporting requirements proposed under the AERR for control types and efficiencies in 

combination with reporting codes for those data elements will be sufficient to discern whether 

sources are uncontrolled or controlled and to what extent. Therefore, EPA has decided not to 

include the control status data element in the final AERR. 

Comment: One commenter (0034) thought that the existing requirements and data fields needed 

to be better explained and noted that the current fields for point sources do not ask for the total 

capture/control efficiency, which is required for nonpoint sources. The commenter thought that 

the capture efficiency along with the total capture/control efficiency should be required for point 

sources since the current requirements for primary and secondary control efficiencies do not 

provide a way to determine the overall control efficiency. In addition, the commenter did not 

believe that “Rule Effectiveness” had ever been adequately explained and said it was not apparent 

how or if it could be used without knowledge of how it relates to the other terms. 

Response: EPA agrees with the commenter’s suggestion to add capture efficiency as a data 

element for point sources. The following new data fields were proposed in the AERR: “Primary 

capture and control efficiencies (percent)” and “Total capture and control efficiency (percent)” 

and will be included in the final rule to provide for determining the overall control efficiency for 

a source. 

EPA disagrees with the commenter’s concerns that Rule Effectiveness (RE) has not been 

adequately explained. Section 51.50 of the rule contains definitions for RE (a rating of how well 

a regulatory program achieves all possible emissions reductions) and Rule Penetration (a term 

used to quantify the percentage of a nonpoint source category covered by an applicable 

regulation). EPA notes that during the Spring of 2004, EPA convened a workgroup consisting of 

emission inventory staff from State, local and EPA offices to review existing RE guidance and 

develop a consensus recommendation for improvements to this guidance. The revised Rule 

Effectiveness guidance developed by the workgroup is found in Appendix B of the document 

titled Emissions Inventory Guidance for Implementation of Ozone and Particulate Matter 

National Ambient Air Quality Standards (NAAQS) and Regional Haze Regulations – EPA-454/R05-001. (August 2005, updated November 2005). EPA believes the workgroup presented a clear 

rationale regarding development and implementation of the new approach to adjusting emission 

inventories to address RE, explaining how RE can be used to adjust the control efficiency from 

what could be realized under ideal conditions to what is actually emitted in practice due to less 

than ideal conditions. Accordingly, EPA has expanded the regulatory definition of RE to explain 

how it is used in making these adjustments 

Comment: Several commenters (0017, 0018, 0019, 0020, 0022, 0023 and 0031) were opposed 

to any additional reporting requirements for States that would be passed on to businesses but 

offered no specific concerns with individual reporting requirements. 

Response: The reporting requirements of the AERR will apply to States and not to sources. 

However, we recognize that in some cases, States will need to modify their data reporting rules to 

meet the requirements of the AERR for data elements to be reported and the new timelines for 

reporting. EPA notes that the burden estimate from the Supporting Statement for the Information 

Collection Request (ICR) indicates that the AERR will not increase the reporting burden on 
14

States and will impose no additional burden on sources although starting in the 2009 inventory 

year timelines for reporting will be shortened. 

8. Identification of New Emissions Related Data Requirements 

EPA invited comment on whether or not additional emissions related data should be required. 

 

Comment: Several commenters (0026, 0039 and 0048) encouraged EPA to include a specific 

requirement in the AERR for reporting hazardous air pollutant (HAP) emissions data for Title V 

facilities. Another commenter (0044) encouraged EPA to include requirements for reporting of 

HAPs from all emission sources. One commenter (0039) noted that States are attempting to 

provide HAP data to EPA by relying on data collected from facilities largely on a voluntary basis. 

These data are then supplemented by EPA with data from other sources. The commenter thought 

that collecting quality HAP data for use in modeling efforts such as the National Air Toxics 

Assessment (NATA) would require an EPA directive. 

Response: EPA is not including requirements for reporting of HAPs in this final rule. However, 

EPA has developed national level inventories of HAP emissions on a 3-year cycle since 1990. 

These inventories have provided support for development of HAP control programs, helped 

assess HAP air quality trends and provided a means to track EPA progress under the Government 

Performance Results Act. The success of EPA’s efforts rests in large measure on the cooperation 

of States in submitting HAP data to EPA to support the development of national HAP emission 

inventories. Each emission inventory cycle has benefited from increased State agency 

participation in submitting HAP data. EPA believes it will be possible to continue developing 

and improving national level HAP inventories using the cooperative approach employed to date 

but intends to closely monitor the participation of State agencies in this effort. EPA understands 

the concerns of some State agencies regarding the need for a HAP data reporting rule and may, 

should the need arise, revisit this issue in the future. 

Comment: One commenter (0035) thought that data element 41, “SIC/NAICS at the facility and 

unit levels,” in Table 2A, Data Elements for Reporting on Emissions from Point Sources should 

be separated into two fields: one for the facility and one for the unit. Another commenter (0037) 

thought that reporting NAICS at the unit level was not necessary since these codes are used for 

PSD applicability and in many cases there is only one SIC/NAICS that describes the source. The 

commenter thought that reporting these codes at the unit level had little to do with emission 

inventories. 

Response: The CERR included a data element for reporting of SIC/NAICS codes for point 

sources but did not specify whether the codes should also be reported at the unit level. Table 2A 

to subpart A of part 51 in the AERR proposal clarified this requirement by including data element 

#41 for reporting of “SIC/NAICS at the facility and unit levels.” Guidance from the Census 

Bureau, which develops the SIC/NAICS codes, indicates that they are designed to reflect the 

primary economic activity of a source, which also brings into question the reporting of these 

codes at the unit level. Based upon this information, EPA has reconsidered the need for reporting 

these codes at the unit level and revised data element #41 to require the reporting of “SIC/NAICS 

at the facility level.” 

One additional revision concerns the reporting of SIC codes as an alternative to NAICS codes. 

Since the January 3, 2006 proposal, users of SIC codes have transitioned to the new NAICS 

codes, and EPA finds that retaining the reference to “SIC” as a reporting alternative is no longer 

necessary. Therefore, data element #41 has been revised to require the reporting of “NAICS at 
15

the facility level” and the definition for “SIC/NAICS” has been revised to reference only NAICS 

codes. 

Comment: One commenter (0035) stated that data elements 49, 33 and 34 (emission release 

point type, X stack coordinate and Y stack coordinate), and stack parameters are all associated 

with point source stacks and recommended that these fields be grouped closely together. The 

commenter also thought that all process related data such as SIC/NAICS, SCC, heat content, ash 

content, activity, and temporal data should be grouped together with the process ID code. 

Response: EPA has attempted to group like-data elements together to the degree possible in the 

AERR. However, it is important to remember that how the data elements are grouped in the 

proposed AERR is unrelated to the groupings for data reporting using the NIF or XML schema. 

As an example, the NIF has an Emission Release Point table that includes data elements 49, 33 

and 34. Temporal data elements for seasonal, weekly and daily emissions are found in the 

Emission Process table, while the Emission Period table contains data elements for hours per day, 

days per week and weeks per year. While data elements may not be listed sequentially in the 

proposed AERR, for purposes of data reporting, the data elements have been logically grouped in 

tables as recommended by the commenter. 

9. Revisions to Specific Data Elements 

EPA proposed deleting or revising data elements that have been grouped into the following areas: 

a. Data Elements from NOx SIP Call 

Comments: Several commenters (0026, 0028, 0029 and 0039) agreed with EPA’s proposal to 

combine the separate lists of required data elements for the Consolidated Emissions Reporting 

Rule (CERR) and the NOx SIP Call into a single new list of required data elements, eliminating 

several requirements from the NOx SIP Call: area designation, Federal ID code (plant), Federal 

ID code (point), Federal ID code (process) maximum design rate, work weekday emissions, 

secondary control efficiency, source of fuel heat content data, source of activity/throughput data, 

source of emission factor and source of emissions data. Three commenters (0039, 0045 and 

0048) suggested that the list of data elements be maintained in the NIF rather than in the rule to 

allow for changes in required data elements without the need for rulemaking. 

One commenter (0032) expressed support for deleting several of the data elements as proposed: 

Area designation, Federal ID code (process), Maximum design rate, Work weekday emissions, 

Secondary control efficiency, Source of fuel heat content data, Source of activity/throughput data, 

Source of emission factor and Source of emissions data. The commenter thought that data 

elements for Federal ID code (plant), Federal ID code (point) and Federal ID code (stack/number) 

should be retained since plant identification codes were necessary for identifying the facilities, 

especially during air dispersion modeling. 

Another commenter (0036) supported retaining the “currently required data elements” but 

identified only the data elements not related to the NOx SIP Call. 

One commenter (0045) thought that data elements related to the NOx SIP Call should be retained 

but included in guidance rather than in the AERR. In a separate paragraph, the commenter stated 

that the data elements should be eliminated as proposed. 
16

One commenter (0048) thought that the data element for “Maximum design rate” should be 

retained since it may be required for classifying facilities as subject to Clean Air Act Title V 

requirements and will need to be recorded within the NIF as the basis for facility classification. 

Response: EPA agrees with the commenters expressing support for the proposed deletion of data 

elements related to the NOx SIP Call. The data elements for Federal ID Codes (Plant, Point, 

Process and Stack Number) were assigned to sources subject to the NOx SIP Call and perform 

similar ID functions to the data elements in the proposed AERR for Facility ID code, Unit ID 

code, Process ID code and Stack ID code. EPA believes the NOx SIP Call ID codes are 

redundant and can be deleted without compromising the identity of sources and emissions. 

The concern about deleting the NOx SIP Call data element for “Maximum design rate” is not well 

founded since the AERR retains a data element under point source reporting requirements for 

“Design capacity” which is defined as “a measure of the size of a point source, based on the 

maximum continuous throughput or output capacity of the unit...” Therefore, EPA believes that 

the data of concern will continue to be collected under the data element for “Design capacity” in 

the AERR. 

b. Data Elements from Earlier Systems – Comments on Usefulness and Sufficiency 

One commenter (0009) thought that the all the data elements that had been carried forward from 

earlier systems – heat content (fuel), ash content (fuel), sulfur content (fuel) for fuels other than 

coal, activity/throughput, hours per day in operation, days per week in operation, weeks per year 

in operation, and start time in the day – should be deleted. Three commenters (0036, 0037 and 

0042) thought that the data element for start time should be deleted since it did not appear to be 

useful. Another commenter (0032) supported deleting the data element for ash content (fuel). 

Several commenters (0026, 0029, 0036, 0039 and 0042) indicated that data elements for heat 

content (fuel), ash content (fuel), sulfur content (fuel) for fuels other than coal, 

activity/throughput, hours per day in operation, days per week in operation, weeks per year in 

operation and start time in the day were used for a variety of applications and should be retained. 

Three commenters (0028, 0032 and 0048) recommended retaining the data elements since they 

were used for a variety of applications. One of the commenters (0028) cited "heat content (fuel)", 

"ash content (fuel)", "sulfur content (fuel) for fuels other than coal", "activity/throughput" as 

needed to check emission calculations. The commenter also thought that "hours per day in 

operation", "days per week in operation" and "weeks per year in operation" were needed to 

calculate average ozone season day emissions and should be retained. Another of the 

commenters (0032) thought the data elements should be retained since they were used for 

calculating daily ozone precursor emissions, air dispersion modeling, estimating emissions and 

for developing alternative emission reduction strategies. 

One commenter (0004) recommended retaining the data element for activity/throughput since this 

information could be used as a surrogate for projection of emissions or for development of 

growth factors. 

Response: EPA agrees with the majority of commenters that data for elements for heat content 

(fuel), ash content (fuel), sulfur content (fuel) for fuels other than coal, activity/throughput, hours 

per day in operation, days per week in operation, weeks per year in operation should be retained 

since these elements are used for a variety of applications. Start time (hour) was specifically 

identified by three commenters as not being useful and EPA agrees that this data element should 
17

be deleted since it is either not applicable to the operation of sources or not used since temporal 

profiles developed to prepare emission inventories for air quality modeling provide similar 

information. 

c. Data Elements for Point Source Stacks 

EPA invited comment on which, if any, of these data elements for point source stacks should be 

deleted: stack diameter, exit gas velocity and exit gas flow rate. Any one of these can be 

calculated from the other two. 

Comment: Several commenters (0026, 0029, 0044 and 0045) recommended that we delete one 

of the point source stack data elements since having data on any two of the elements will allow 

the third to be calculated. The commenters did not indicate a preference for which one of the data 

elements should be deleted. One of the commenters (0029) suggested that EPA make a 

distinction between reported and calculated data elements in the NEI. 

Several other commenters (0004, 0028, 0032 and 0036) thought that exit gas velocity should be 

deleted as a data element since their States collected data on stack diameter and exit gas flow rate. 

A number of commenters (0039, 0042, 0043, 0046, and 0048) thought that all three data elements 

should be retained for a variety of reasons. Three of the commenters (0039, 0042 and 0048) 

believed that all three data elements should be reported to make sure that the data were in 

agreement and to provide a means for checking data entry errors. Another commenter (0043) 

indicated that they would continue to meet the needs of their end users who are accustomed to 

having all three data elements reported and requested that EPA handle any data reporting changes 

as modifications to its software until States can develop modified reports to extract only the data 

that EPA requests. 

One commenter (0046) thought that allowing States the option of which two stack parameters to 

report among flow rate, velocity and diameter would require having all three available for use and 

suggested that no changes be made to the reporting format. 

Response: The commenters were largely divided into three categories: (1) continue to report all 

three data elements, (2) delete any one of the three data elements and (3) delete the exit gas 

velocity data element. 

The stack diameter can be calculated by dividing the gas flow rate by the gas velocity, however, 

no commenters suggested deleting the stack diameter from the list of data elements. EPA 

believes it is appropriate to report stack diameter data since it can be readily determined and has 

the least amount of uncertainty of the stack-related data elements. 

One commenter (0046), who stated that all three data elements would be required to be reported 

if States were able to choose two out of the three for reporting to EPA, apparently interpreted the 

proposal in the broadest sense as allowing States to select data elements on a source-specific 

basis. EPA was proposing to select data elements for reporting based upon preferences of the 

States and apply them universally to all point sources. 

EPA believes that given the variety of practices among State agencies, flexibility in reporting 

should be included in the AERR for stack-related data elements. Several States indicated a 

preference for deleting one of the data elements and others specifically asked that exit gas 

velocity be deleted. One commenter indicated their State collected stack diameter and exit gas 
18

velocity data which may be the practice in other States. EPA therefore believes it is appropriate 

to also offer several options for reporting of stack-related data elements and will allow States to 

report all three data elements but also offer the option of reporting either stack diameter and exit 

gas flow rate or stack diameter and exit gas velocity. 

Modified 3-Year Cycle Reporting Requirements 

A provision of the CERR (section 51.35) allows States the option of developing their triennial 

inventories over three years and submitting them annually in piecemeal fashion as they are 

completed. EPA proposed to allow States to continue the option of obtaining estimates from 

point sources and/or prepare one-third of their nonpoint or mobile source emission estimates each 

year on a rolling basis and but would limit data submissions to a single package on the required 

3rd year submission date. 

Comments: One commenter (0032) supported EPA’s proposal to submit triennial data as one 

single submission because his agency historically provided data as one submission. One 

commenter (0042) stated that his agency had always developed a single year’s inventory and 

submitted it as a single package and would prefer to continue this practice. Another commenter 

(0048) thought that the proposal was not practical due to staff turnover and EPA’s changing 

requirements. The commenter went on to suggest that a 5 year rolling basis be used to be 

consistent with the cycle his State uses for smaller sources. 

Response: This proposal did not generate much interest. The few comments received suggest 

that the existing provision of the CERR which allows triennial emission inventory development 

over a three year period is impractical and is not utilized by the States. However, all commenters 

were supportive of the change to require one submission for triennial inventories. EPA agrees 

with the commenters that the change to require one submission under section 51.35 is appropriate 

and is modifying this provision as proposed. EPA notes that States may use the provisions of 

section 51.35 to equalize workloads but are not required to do so. 

10. Point Source Reporting Definition 

EPA proposed to expand the definition of what sources must be reported in point source format, 

so that fewer sources would be included in nonpoint source emissions. The requirement for point 

source format reporting would be based on whether the source is a major source under 40 CFR 

part 70 for the pollutants for which reporting is required. 

Comment: Many commenters (0026, 0029, 0036, 0039, 0044 and 0045) expressed support for 

the agency’s proposal to use the definition in 40 CFR Part 70 for determining major source status 

to establish which sources should be reported as point sources. One of the commenters (0045) 

was concerned about the resources needed to report additional point sources under the AERR and 

thought that data quality and availability could be impacted. 

Response: Many comments were received in support of the proposal to change the reporting 

criterion from actual emissions to the 40 CFR part 70 definition for applicability which is based 

upon “potential to emit.” Since only one commenter expressed concerns about resources for 

reporting additional sources using the point source format but was still supportive of the change, 

EPA intends to implement this change as proposed. 
19

Comment: Several commenters (0026, 0029 and 0039) expressed support for the proposal to 

continue reporting actual emissions under the AERR as was required under the CERR.

Response: EPA agrees and will continue to require reporting of actual emissions. In limited 

situations, States may report model inputs in lieu of reporting source emissions and EPA will use 

the inputs to estimate actual emissions. 

Comment: Three commenters (0004, 0045 and 0048) noted that the proposed definition for 

major source reporting would not include sources that have a Federally Enforceable State 

Operating permit (FESOP) in place to maintain their nonmajor status. The commenters thought 

that the definition for major point source reporting should be expanded to include sources with 

FESOPs. 

Response: The commenters did not present arguments for why the point source reporting 

definition should be revised to include FESOPs. States with lower reporting thresholds for point 

sources than those included in the AERR proposal may report emissions from sources subject to 

those thresholds as point sources. This would include sources with FESOPs. 

Comment: One commenter (0048) thought that the table (untitled) listed under the definition for 

Point sources (page 81 of the FR notice) was inconsistent with the proposed reporting 

requirements using the Title V (and non-Title V) definitions. The commenter believed that the 

effect of the lower reporting threshold would be small especially if sources now reported as point 

sources were previously reported as nonpoint sources. The commenter noted that the definition 

for Type A source seemed inconsistent with the proposed change from actual emissions to 

“potential to emit” when determining sources that meet Title V requirements and thus would 

report their emissions as point sources. The commenter also thought that the Table 1 to Subpart 

A of Part 51 (Emission Thresholds by Pollutant for Treatment of Point Sources as Type A Under 

40 CFR 51.30) did not “appear to retain any relevancy.” 

Response: EPA agrees with the commenter that there are some inconsistencies in the notice for 

the proposed rule. The preamble for the proposal stated that EPA is “proposing to base the 

requirement for point source format reporting on whether the source is a major source under 40 

CFR part 70 for the pollutants for which reporting is required....” This indicated that reporting 

thresholds for all point sources would be based upon the 40 CFR part definition of “potential to 

emit” (PTE). However, we further stated that “we are proposing to expand the definition of what 

sources must be reported in point source format so that fewer sources would be included in 

nonpoint source emissions.” Later in the preamble, we stated that “this change may require more 

sources to be reported as point sources every 3rd year.” Both sentences imply that the change 

would apply only to Type B sources. Application of the 40 CFR 70 point source definition to all 

point sources would likely require some existing Type B point sources to be reported each year as 

Type A sources, which was not identified as a likely change in point source reporting. 

EPA used the definition for “Point source” to establish that use of the 40 CFR 70 major source 

definition would begin with the 2008 inventory year. Point source reporting for inventory years 

prior to 2008 would continue to be based upon use of “actual emissions.” However, the Point 

source definition referenced the table for reporting Type A and B sources and that table indicated 

that the reporting thresholds in the table were “in tons per year of actual emissions.” While EPA 

intended that the emissions reported would continue to be actual emissions, PTE was to be used 

to determine point source reporting requirements, and no consideration of this change was 

included in the table. 
20

The proposed definition for Type A sources requires use of “actual annual emissions” to 

determine reporting requirements. However, the use of actual annual emissions to determine 

Type A sources appears to conflict with the Point source definition (applicable to both Type A 

and B point sources), which indicated that emission reporting for the 2008 inventory year and 

later inventory years will be determined using the 40 CFR 70 definition of major source, which 

uses PTE. 

Given the confusing preamble language and apparent conflict in the text of the regulation, EPA 

will accept use of either approach to determine Type A and Type B point source reporting 

requirements prior to and including the 2009 inventory year. For the inventory years following 

2009, EPA will expect States to use the 40 CFR 70 major source definition for all point sources to 

simplify reporting requirements, as discussed in the proposal preamble. Accordingly, EPA has 

revised the definition of Type A sources and Table A to make clear that the 40 CFR part 70 

definition of major source will be used to determine point source reporting requirements 

following the 2009 inventory year. 

As noted by the commenter, the effect of using the 40 CFR part 70 definition for reporting of 

Type B sources may be small. In terms of total emissions from sources, there should be little 

effect since emissions previously reported as nonpoint will now be reported as point. The 

Supporting Statement prepared to estimate the burden associated with the point source reporting 

change estimated that the number of point sources reported by states would increase from 7,385 

to 17,316. This is still well below the total of 52,277 point sources reported by states under the 

existing definition of major sources for the 1999 inventory year. 

The commenter stated that Table 1 to Subpart A of Part 51 (Emission Thresholds by Pollutant for 

Treatment of Point Sources as Type A Under 40 CFR 51.30) did not “appear to retain any 

relevancy.” It is not entirely clear what is meant by this statement, but the table does repeat some 

of the information presented earlier in the notice under the definitions (Section 51.50) and 

therefore is redundant. Despite that, the information presented in both tables is consistent. 

Comment: One commenter (0004) noted that the language in the preamble of the proposed rule 

states that EPA is “proposing to base the requirement for point source format reporting on 

whether the source is a major source under 40 CFR part 70 for the pollutants for which reporting 

is required, i.e. for CO, VOC, NOX, sulfur dioxide (SO2), PM2.5, PM10, and ammonia but 

without regard to emissions of hazardous air pollutants.” The commenter noted that lead 

emissions were not identified as a criterion in determining major source status under 40 CFR part 

70, however, a table on Page 81 of the FR notice lists Type B point sources with a 5-ton threshold 

of lead emissions. The commenter thought that the language in the two cited sections 

contradicted each other. 

Response: EPA agrees that the preamble language should have included a reference to lead 

emissions since the table on Page 81 of the FR notice includes a point source threshold level for 

sources emitting lead. This reporting requirement remains in the AERR and is unchanged from 

the CERR. 

Comment: One commenter (0048) thought that Section 51.122 further “re-defined” the 

reporting requirements after having just re-defined them according to the Title V definition and 

recommended that the distinctions being made should be consolidated so they are clear. 

Response: Section 51.122 presents reporting schedules for affected NOx sources that are 

consistent with subpart A requirements. It does not redefine reporting requirements for any 

sources. The consolidation effort under the AERR for the NOx SIP Call consisted of moving 
21

data elements for emissions reporting under Section 51.122 to subpart A. Further consolidation 

of reporting requirements is possible but was not attempted under the AERR. 

Comment: One commenter (0028) suggested that the AERR not limit point source reporting to 

major sources under 40 CFR part 70. The commenter was concerned that his State inventoried 

sources below the point source reporting thresholds in the AERR as point sources and that it 

would be necessary to discard this data before submittal to EPA. Another commenter (0004) 

noted that States are able to report sources that are below the point source reporting thresholds 

and thought this flexibility would avoid a burden on States of only reporting sources subject to 

the point source reporting thresholds.

Response: Section 51.20 (c) of the proposed AERR addresses the commenter’s concern as 

follows: “If your State has lower emission reporting thresholds for point sources than 

paragraph.(b) of this section, then you may use these in reporting your emissions to EPA.” This 

provision is discussed in the preamble under B. Proposed Emissions Reporting Requirements. 

As noted by the second commenter, it has always been possible for States to submit data to EPA 

in point source format for sources with emissions below the point source reporting thresholds. 

Therefore, no reason exists to discard data for point sources with emissions below the reporting 

thresholds in the AERR. These data should be included with other point source records reported 

to EPA. 

11. Burden Estimates 

Comments: One commenter (0016) indicated the proposed changes would consolidate data on 

form A, harmonize data points and eliminate the inconsistent definitions that currently exist 

between the two forms (A and R) currently used for reporting. The commenter noted that these 

changes would reduce the reporting burden, eliminate confusion caused by differing definitions, 

and improve data accumulation but thought that having triennial emission reports would deprive 

data users of accurate and timely information. 

Response: The commenter appears to have confused emission reporting requirements for the 

Toxics Release Inventory (TRI) with the proposed reporting requirements in the AERR. Forms A 

and R are used for TRI reporting and address emissions of hazardous air pollutants (HAPs). 

Reporting of HAP emissions was not proposed in the AERR 

The commenter was concerned about proposed triennial reporting under the AERR. 

Comprehensive emissions reporting on a triennial basis under the proposed AERR is similar to 

the existing triennial CERR emissions data reporting requirements. Again, EPA believes that the 

commenter has confused the triennial reporting requirements under the AERR, which remain 

largely unchanged from the CERR, with a recent EPA proposal to reduce the TRI reporting 

burden. 

Comment: One commenter (0048) thought the estimate of 13 labor hours of reductions from 

104 respondents was speculative. The commenter stated that no studies had been conducted to 

obtain data on the actual hours required and that rule changes can require modifications to data 

systems in use by the States and facilities which can cost hundreds of thousands of dollars to 

implement. Associated costs of tracking, training, etc. would also need to be included. 

Response: The burden hour estimate developed by EPA for the Information Collection Request 

(ICR) is an estimate but is based upon information from a small sampling of State agencies to 

“ground-truth” the numbers. EPA believes that burden estimate reduction is reasonable since it is 
22

based upon the elimination of some reporting requirements and consolidation of reporting dates 

to create efficiency in reporting. EPA notes that the burden reduction estimate is an average 

number and therefore, will vary from State to State. 

EPA understands the commenter’s concerns that changes to data reporting rules can require 

changes to State agency data reporting systems and procedures. The ICR notes that Capital and 

Operations and Maintenance Costs estimated under the supporting ICRs for the CERR and NOx 

SIP Call are believed to be sufficient to accommodate the modest changes in reporting burden 

under the AERR. Although there are several new data elements and some that have been deleted 

which will require programming changes, no fundamental system requirements have been altered 

that will require changes to State funding for capital and operations and maintenance of State data 

systems. EPA believes the costs of reprogramming to meet the new AERR requirements should 

be accommodated within existing State budgets for maintenance of data systems. 

12. Miscellaneous 

Comment: Three commenters (0021, 0045, and 0048) supported consolidating all emission 

inventory reporting requirements into a central federal rule for all emission inventories needed by 

the U.S. EPA. One of the commenters (0021) also supported the idea that only emissions data 

that are needed be required and recommended that this be reflected in the NEI data entry interface 

with the elimination of all data fields that are not required. 

Response: While the concept of consolidating all emission inventory requirements in one data 

reporting rule has advantages, EPA does not believe this is advisable due to differing regulatory 

requirements among air programs. As an example, emission inventories developed to support 

State Implementation Plans may have specialized nonattainment area data needs which are 

difficult to determine a priori. Attempting to include all possible requirements in a national air 

emissions reporting rule would lead to inefficiencies as States report data to EPA that are not 

needed. EPA believes the AERR will be most consistent with the comment recommendation that 

only emissions data that are needed be required if the rule does not attempt to include all possible 

data elements that might be required for SIP inventories. 

Comment: One commenter (0009) thought that changing the terminology from “area source” to 

“nonpoint source” reduced confusion when referring to a stationary source that is part of an 

aggregated source category rather than an individual facility. Several commenters (0026, 0032, 

0034, 0036 and 0048) recommended that EPA continue to use the term “area source” and not 

replace it with “nonpoint source” as discussed in the proposal. Their specific concerns are 

summarized as follows. 

One commenter (0026) thought that EPA’s proposal was confusing and recommended that if a 

change was to be made, the term “minor point source” be used. 

Another commenter (0032) felt that “area source” was a better descriptor of the types of smaller, 

aggregated emission sources than the term “nonpoint source” since mobile sources would also be 

included in the proposed term. The commenter thought that the “area source” term had a similar 

meaning in the HAP program since it included smaller emission sources and should be retained 

for emission inventory purposes. 

One commenter (0034) argued that the rationale offered of avoiding confusion with the “area 

source” term as used in section 112 of the CAA was not appropriate since the AERR did not 

address hazardous air pollutants. The commenter noted that the “nonpoint source” term is 
23

commonly understood in the water programs with a different meaning and suggested that EPA 

maintain the historical use of the term “area source” for air emission inventories. 

Another commenter (0036) thought that replacing the term "area sources" with "nonpoint 

sources" to distinguish this category from area sources of hazardous air pollutants would create 

confusion. The commenter thought another classification would serve no useful purpose since 

the term "nonpoint sources" referred to onroad mobile, nonroad mobile and biogenic sources and 

not point sources that emit below the point source reporting levels. 

The final commenter (0048) in this group thought that changing terminology from “area source” 

to “nonpoint source” was confusing and suggested using the “section 112 area source” to refer to 

the nonmajor or minor point sources of HAP, 

Response: EPA disagrees with the majority of commenters that using the term “nonpoint 

source” in place of “area source” will be confusing. A footnote on page 72 of the January 3, 

2006, proposal provided the following explanation for the change: We use the term “nonpoint 

source” to refer to a stationary source that is treated for inventory purposes as part of an 

aggregated source category rather than as an individual facility. In the existing subpart A of part 

51, such emissions are referred to as “area sources.” However, the term “area source” is used 

in section 112 of the CAA to indicate a nonmajor source of hazardous air pollutants, which could 

be a point source. As emissions inventory activities increasingly encompass both NAAQS-related 

pollutants and hazardous air pollutants, the differing uses of “area source” can cause confusion. 

Accordingly, EPA proposes to substitute the term “nonpoint source” for the term “area source” 

in subpart A and in section 51.122 to avoid confusion. 

EPA does not believe that substituting the term “minor point source” (as suggested by one 

commenter) will be any less confusing. The term “minor point source” is often used to denote 

sources that have agreed to limit their emissions through Federally Enforceable State Operating 

Permits (FESOPs) to avert applicability of the Title V permit program. Since these sources are of 

sufficient size to receive operating permits, they are often reported as point sources to EPA. 

Thus, using the term “minor point source” for an emission inventory category (nonpoint sources) 

that generally consists of sources too small to report individually would only lead to more 

confusion. 

Although the CERR and AERR (as proposed) do not include reporting requirements for HAP 

emissions, many State agencies voluntarily report HAP emissions to EPA which are used for 

developing the NEI. EPA expects this practice to continue under the final AERR. EPA believes 

that identifying HAP emissions reported in aggregate for source categories as “nonpoint sources” 

rather than “area sources” will serve to limit confusion over applicability of control programs 

under section 112 of the CAA. 

EPA does not believe that the term “nonpoint sources” is widely used when referring to the 

inventory categories designated “onroad mobile,” “nonroad mobile” and “biogenic sources.” 

EPA generally uses the terms “onroad mobile”, “nonroad mobile’ and “biogenic sources” as 

identified in the CERR and AERR proposal when referring to these other emission inventory 

categories and believes this usage to be the most common among emission inventory preparers. 

EPA agrees with one commenter who noted that the “nonpoint source” term is commonly 

understood in the water programs with a different meaning but disagrees that using it here will 

lead to confusion with the water program usage. EPA believes the potential for confusion is 
24

negligible since the data reporting and regulatory program requirements for air and water are 

distinctly separate requirements that are generally conducted by different staff within agencies. 

Comment: One commenter (0036) opposed replacing Source Classification Codes (SCCs) with 

Process Classification Codes (PCC). The commenter noted that the intention to make this change 

was found in the definition of Process Classification Codes (PCCs) in the proposal. 

Response: At the outset, EPA notes that it does not intend to replace SCCs with PCCs in the 

AERR rule. The language in the proposed rule referencing PCCs in addition to SCCs was 

included to provide flexibility in the event EPA decided to develop the new reporting codes. For 

several years, EPA has considered developing PCCs as a replacement for SCCs. There was no 

additional discussion of developing PCCs in the proposal since the replacement system had not 

moved beyond the concept phase. As of the final rule publication date, PCCs remain a concept. 

EPA wishes to assure the commenter that any decision to move ahead with development of PCCs 

as replacements for SCCs will be well coordinated with State agencies due to the considerable 

effort that will be required by all to embrace a new coding system for data reporting. At this 

time, EPA has no intention of developing a replacement system for SCCs and has removed 

references to PCCs from the final rule. 

Comment: One commenter (0004) noted that EPA was proposing the rule “in an effort to 

improve EPA’s ability to compile a national inventory of air pollutant emissions” and wondered 

if this meant that EPA would have the same NEI timetable for HAPs and criteria air pollutants 

(CAPs). The commenter stated that it was more difficult for States to meet the proposed emission 

reporting timeline for HAPs than for CAPs and cited several reasons for needing more time: 

1. Minnesota, like many other States, has a rule to mandate CAP emission reporting but not 

HAP emission reporting. The HAP emission inventory is established based on the CAP 

emission inventory and relies on voluntary data reporting from facilities, emission factor 

calculations, and data from the Toxics Release Inventory (TRI). 

2. The HAP emission inventory covers hundreds of pollutants while the CAP emission 

inventory only accounts for fewer than ten pollutants. 

3. The HAP emission inventory relies partially on TRI data. However, the due date for 

facilities to report TRI data is July 1 (6 months after the end of the year). Usually, State 

TRI data are available 11-12 months after the end of the year, but 2003 TRI data were not 

available until 15 months after the end of the year. 

The commenter suggested developing two separate NEI time tables for HAPs and CAPs and 

providing a later due date for the HAP emission inventory. 

Response: Although EPA encourages States to submit HAP data according to the requirements 

of the AERR, this is a voluntary action by States, while CAP data reporting is required under the 

rule. The commenter’s concerns regarding the timeline for developing HAP data appear based 

upon the proposed timelines for developing the NEI, which would require States to submit CAP 

data on an expedited schedule for the 2008 inventory year and on a shorter schedule starting with 

the 2011 inventory. EPA believes that the commenter’s concerns regarding the need for separate 

CAP and HAP reporting timelines will be addressed by maintaining the 17-month timeline from 

the existing CERR for the 2008 emission inventory and by implementing the 12-month timeline 

from the final AERR beginning with the 2009 inventory year. The 12-month reporting timeline 

under the final AERR that begins with the 2009 inventory will apply to CAP emissions only. 

Where States choose to submit HAP emission estimates voluntarily to EPA and they require 
25

additional time for developing and submitting those estimates, EPA will attempt to include the 

data submittals in the NEI development process. 

Comment: One commenter (0041) opposed EPA's proposed addition of a new, five-month 

ozone season reporting requirement for NOx emissions. The commenter stated that Florida had 

no ozone nonattainment areas and was not subject to the NOx SIP Call, but was subject to the 

ozone season reporting requirement under the Clean Air Interstate Rule (CAIR) because of the 

State's projected impact on the Atlanta, Georgia, hour ozone nonattainment area. As a result, 

EPA proposed adding to the 3-year reporting cycle, a requirement to report NOx emissions from 

all sources for the five-month ozone season. This requirement is in addition to the summer-day 

NOx and VOC emissions reporting requirement needed for regional-scale ozone modeling. The 

commenter did not understand the purpose of requiring the additional ozone season data for 

States such as Florida which were not required to develop five-month emissions projections for 

purposes of the NOx SIP Call and considered it unreasonable to burden all point sources (CAIR 

and non-CAIR) and the State with a third reporting requirement (annual, summer day, and ozone 

season), when the need for such data under CAIR was not apparent. 

Response: On July 11, 2008, the United States Court of Appeals for the District Court of 

Columbia Circuit vacated CAIR in its entirety. Accordingly, all references to CAIR and its 

reporting requirements have been removed from the final AERR. 

Comment: One commenter (0042) urged EPA to place more emphasis on emissions quality and 

less on the dates for States to submit emissions data. The commenter had concerns over the 

current quality of the PM2.5 and ammonia inventories because of the lack of federal emission 

factors and approved stack test methods. The commenter felt that EPA needed to assess the 

quality of its existing emission inventories, address deficiencies or inconsistencies between 

States, and make the information more readily available before it accelerated submission dates. 

Response: EPA agrees with the commenter’s recommendation that given a choice between 

improving the quality of emission inventories and accelerating submission dates, improving the 

quality of emission inventories is the correct choice. However, EPA does not agree that one must 

choose between one or the other. EPA believes that development of the new EIS will allow the 

quality of the NEI to be improved while the timeline for completion is shortened. This will be 

possible through the use of more automated data handling procedures which will not only speed 

the handling of data but will reduce data errors otherwise introduced through use of less 

automated procedures. It should be noted that EPA understands the need for caution with the 

new system until users become familiar with the new procedures and for this reason will not alter 

the reporting due date until the 2009 inventory year. This will provide for completion of two 

inventory cycles for Type A sources before the first comprehensive 3-year inventory cycle is 

conducted for the 2011 inventory year. 

Regarding the estimation of emissions for PM2.5 and ammonia, a similar comment was received 

on the proposed CERR. EPA’s response at that time is still applicable: We agree that 

improvements in many of the emission estimation techniques are highly desirable, particularly in 

some of the areas identified by the commenters. However, we know that there will always be the 

opportunity to improve emission estimation techniques and that this is an evolutionary process. 

The CERR does not require the use of any specific emission estimation technique. There are 

emission estimation techniques available for all of the required pollutants and their major 

sources. Therefore, we believe that State or local agencies should be able to make emission 

inventory submittals that will be acceptable to EPA using current state-of-the-art-techniques (67 

FR 39606, June 10, 2002). 
26

 

In the years that have passed since promulgation of the CERR, state-of-the-art techniques for 

estimating PM2.5 and ammonia emissions have improved. As with the CERR, the AERR does 

not specify use of any emission estimation technique. EPA continues to believe that State 

agencies should be able to estimate PM2.5 and ammonia emissions and thus meet the 

requirements of the AERR. 

Comment: One commenter (0044) observed that section 51.5 of the proposed rule highlighted 

guidance produced by the Emission Inventory Improvement Program (EIIP) as preferred tools for 

preparing emission inventories but noted that funding for EIIP has been discontinued and that 

other tools will emerge as methods of choice. The commenter thought section 51.5 should be 

revised to reflect the changing nature of emission estimation methodologies and allow use of 

other tools and methods for estimating emissions. 

Response: EPA agrees with the commenter. The language in section 51.5 from the proposal was 

unchanged from the CERR when EIIP was still an active program. EIIP has not been funded for 

several years and guidance materials produced by the program have not been updated to reflect 

advancements in state-of-the-science emissions estimation techniques. Despite that, many of the 

documents are still useful for estimating emissions so EPA believes it is appropriate to reference 

them as a starting point for estimating emissions. As noted by the commenter, other techniques 

may be available which represent methods of choice and EPA agrees that such methods should be 

used where they represent advancements over estimation techniques presented in EIIP 

documents. Therefore, EPA is revising the language under section 51.5 to also reference use of 

state-of-the-art techniques that have emerged subsequent to the guidance materials developed 

under EIIP. 

Comment: One commenter (0044) noted that the preamble of the CERR included the question, 

What Happens if EPA Doesn't Get My Agency's Emissions Data? and that EPA’s response was 

that it would develop preliminary estimates for nonpoint and mobile sources and give States the 

option of accepting all or part of these inventories as their own submission. The commenter 

observed that the proposed AERR did not include this language and thought that without this 

commitment, serious resource issues might emerge for States/locals/tribes relying on these 

estimates for all or part of their data submittals. The commenter thought that Regional Planning 

Organizations (RPOs) might be able to fill this gap. 

The commenter stated that many agencies receive funding for inventory development and thought 

it was important for the entire inventory community to collaborate early in the NEI process to 

ensure efficient use of' the available inventory resources. Examples of efficient uses of resources 

cited by the commenter included the proposal for EPA to calculate biogenic emissions and the 

proposal to allow model input reporting in lieu of emission estimates. Another efficient use of 

resources would be the elimination of low-emissions source categories from the NEI which the 

commenter thought EPA should consider. Finally, the commenter thought the EPA should take a 

leadership role in collaboration efforts. 

Response: When the CERR was promulgated and requirements for submitting complete 

emission inventories were first implemented, EPA felt the need to offer an alternative for State 

agencies that were developing and submitting statewide data for all inventory sectors for the first 

time. Under the AERR, EPA is deleting the reporting requirement for biogenic emissions and 

including an option for States to submit inputs for mobile source data in lieu of emission 

estimates. EPA believes that these changes, combined with the experience developed by State 
27

agencies since the CERR was first implemented, will enable agencies to comply with the 

requirements of the AERR to develop emission estimates for all emission inventory sectors. 

EPA agrees that there are efficiencies to be realized through collaboration and has embraced this 

approach in developing the new EIS, the database within which the NEI resides. We envision 

taking the lead on several source categories that would benefit from a national approach which 

should alleviate some of the resource concerns noted by the commenter. In addition, we will 

collaborate with State agencies on approaches for developing their NEI data submittals for the 

2008 inventory year and thus exert a leadership role as suggested by the commenter. 

EPA understands the commenter’s concerns regarding the treatment of low-emitting sources and 

source categories. It does make sense to focus limited resources on high-emitting sources and 

source categories. EPA has included a “de minimis percentage of total county and State 

emissions” under Section 51.20 of the rule which allows States to omit “low-emissions” nonpoint 

source categories. EPA trusts that States will utilize good judgment in evaluating whether or not 

nonpoint source categories qualify for this de minimis exemption and will efficiently utilize their 

resources to address the most significant sources and source sectors while striving to maintain a 

balance with inventory completeness. 

Comment: One commenter (0046) thought that states would need additional resources to meet 

the new due dates proposed by EPA for submittal of data and recommended that EPA adopt an 

iterative approach in developing the NEI to balance data quality and timeliness needs. 

Response: EPA believes that the current NEI development process already incorporates 

elements of the iterative approach recommended by the commenter. The new EIS will move the 

NEI even closer to the iterative concept through increased transparency which will allow data 

submitters to observe and react to adjustments that EPA might make to their data as well as track 

development of the NEI from start through completion. 

The timeline for implementation of the AERR will allow states to continue with their existing 

CERR inventory development efforts through the 2008 inventory year and thus will not require 

additional resources. The 12-month timeline for submittal of data under the AERR will begin 

with the 2009 inventory year and EPA believes that States will be able to meet the new timeline 

with minimal or no additional resourcesMany States are able to now meet the 12-month timeline 

for point sources, and the option of providing model inputs to EPA in lieu of emission estimates 

will provide additional resource savings for the onroad and nonroad mobile source sectors. EPA 

believes the automated routines in the new EIS will also provide additional resource savings to 

States by facilitating the development of emission estimates. No additional resources will be 

required for for 2011 since EPA has decided against implementing the more stringent 6-month 

timeline that was proposed based upon reviewer comments. 

Comment: One commenter (0048) reminded EPA of the CAA requirements under section 130 

regarding the development of emission factors for carbon monoxide (CO), volatile organic 

compounds (VOC) and oxides of nitrogen (NOX). The commenter stated that EPA budget cuts 

have affected EPA’s efforts to develop emission factors and that the quality of emission estimates 

generated by facilities and States using emission factors has eroded. 

Response: EPA is well aware of the requirements under section 130 of the CAA, which 

explicitly direct the Administrator to periodically review and revise emission factors for CO, 

VOC and NOX. EPA is attempting to satisfy the requirements of section 130, but must balance 

these needs with other CAA directives, while working within the limits of allocated resources to 
28

accomplish its mission. Despite the difficulties of satisfying competing priorities, EPA believes 

that the emission factors that are now available are sufficient to support development of data 

submittals and thus allow States to comply with the requirements of the AERR. EPA also notes 

that use of emission factors is only one method of estimating emissions from among a variety of 

approaches. 

Comment: One commenter (0048) thought that EPA’s regulations regarding Confidential 

Business Information (CBI) should be “referenced, summarized and endorsed for clarity and 

completeness, including a succinct repetition of statements regarding what emission inventory 

(point source) data are and are not considered CBI by EPA.” 

Response: Section 51.15(d) of the AERR indicates that we do not consider the data included in 

Tables 2A through 2C of the AERR proposal to include confidential data and advises States to 

consult with their regional offices regarding consistencies of federal and State requirements for 

handling confidential data. In general, States have adopted regulations for handling CBI that are 

consistent with EPA’s requirements that are in 40 CFR 70, part 2, Subpart B – Confidentiality of 

Business Information. 

EPA does not believe that referencing the requirements of part 2, Subpart B is needed in the 

AERR since States will use their own CBI regulations as guides for identifying data that should 

not be included in AERR submittals. In addition, EPA believes that little benefit would be 

derived from summarizing EPA CBI requirements within the AERR since misinterpretation of 

the part 2 requirements could result. Finally, EPA sees no need to endorse its own regulations 

since their very existence constitutes endorsement by EPA. 

Comment: One commenter (0048) suggested that each emission inventory requirement be 

constantly reviewed by EPA and revised to reflect changes to needs or uses of the data by the 

federal sector so that only those data actually needed and used are required. The commenter 

recommended that a requirements list be generated which summarized various parts of the 

legislation and regulations that it addressed and for which requirements are included. This would 

assist in integration of future reporting requirements. 

Response: EPA is conducting a review of emission inventory requirements as part of the EIS 

development process and has included its State partners in the review process through the 

formation of a NEI Task Force. Members of the task force are largely from the National 

Association of Clean Air Agencies (NACAA) although several EPA regional offices also 

participate. One of the task force’s goals is to ensure that the participants understand the purpose 

of each data element requested from States. 

The second request by the commenter would have EPA identify legislation and regulations that 

require each specific data element. Although doing this is possible, the connections in some 

cases are not direct and some data elements are needed to satisfy the requirements of a wide array 

of CAA requirements. In essence this request is being implemented through the NEI Task Force 

as it reviews the need for and application of each data element. EPA believes that attempting to 

formally identify all legislation and regulations that relate to each data element within the AERR 

would be cumbersome and not an efficient use of resources. 

Comment: One commenter (0048) believed that many data elements required by States to 

prepare emission inventories for State Implementation Plans (SIPs) may not actually be used or 

needed by EPA as a separate report. The commenter thought this process should be reworked to 

reduce redundancies and unneeded data to simplify data collection and reduce inefficiencies, 
29

costs and potential confusion created by having separate sources for the same information with 

different sources and timing. 

Response: The commenter appears to be endorsing a concept that EPA has followed in 

developing the CERR and AERR. The AERR does not attempt to address all the data 

requirements for SIP emission inventories although many will be addressed. The second part of 

the comment recommends that redundancies and differences in timing in data reporting should be 

resolved. EPA agrees with this goal. The CERR initiated this process and the AERR attempts to 

further consolidate data reporting requirements and resolve differences in reporting timelines. 

Comment: One commenter (0048) suggested that the specific purposes and uses of the data 

required under the AERR be carefully evaluated against the consequences of accelerating the 

reporting dates. The commenter thought that existing data could be used to project and 

extrapolate emissions if the purpose of accelerating the timeline was to develop a national 

summary-level report. The commenter suggested that each subsequent report developed by EPA 

could then be updated based on the later submittal of better and more quality assured data by the 

States. The commenter agreed with the concept of making environmental information available 

as soon as possible, but believed it was more important that data be quality assured which takes 

time. 

The commenter suggested that if the purpose of the data submittals was for modeling and as a 

modeling data clearinghouse, then the dates for which the States need the data for such modeling 

often will allow time for corrections. The commenter noted that data actually modeled for SIP 

development can often have significant differences and improvements after the required “raw” 

data were submitted to EPA and thought that effort should be applied where it makes the most 

difference such as on large point sources (e.g., electric generating units) which dominate the 

emissions for a given pollutant. 

Response: EPA has considered the consequences of shortening the timelines for submittal of 

data by States as suggested by the commenter and adjusted the timelines in response to comments 

received on the proposal (see preamble Section III.B., Harmonizing Report Due Dates and 

Section III.C., Accelerating Report Due Dates). The new timelines represent a balance between 

the need to develop data on a more expedited schedule and the demand for improving the quality 

of the emission estimates arising from increasing uses of inventory data. 

Data submitted by States to EPA are used for development of the National Emission Inventory 

(NEI). The NEI has several applications, one of which is to support analyses of emission trends 

in the U.S. EPA already utilizes a process similar to that described by the commenter to develop 

national-level emission estimates to depict recent year emission trends prior to completion of the 

NEI. EPA will consider using similar approaches for developing estimates for certain sectors of 

the NEI where there is reason to believe that emission estimates from earlier year inventories are 

relatively unchanged. 

The NEI is also used to support a variety of air quality modeling applications. As noted by the 

commenter, the process of preparing emission inventories for modeling independently by EPA 

and States may result in inventory differences since the application of inventories often results in 

additional questioning and adjustment of inventory values. The additional transparency that will 

be incorporated into the new EIS should help address some of these concerns since data suppliers 

will now be able to monitor and understand changes to the NEI prior to conducting emissions 

modeling, as the NEI is prepared for use in air quality modeling applications. 
30

EPA agrees with the commenter’s suggestion that efforts to improve inventories should be 

focused where they will make the most difference. This is especially true with limited resources 

and EPA has embraced this concept in developing the NEI. 

Comment: One commenter (0048) stated that area source emission factors were developed years 

ago and in many cases were matched to the Standard Industrial Code (SIC) employment 

classification system which has been replaced by the North American Industrial Classification 

System (NAICS). The commenter believed that methods and technology in the various source 

categories may have changed considerably and that it was important for EPA to update these 

emission factors for all the area source categories. 

Response: EPA periodically updates point and nonpoint source emission factors and will 

consider the impacts of the NAICS as it conducts this process. In many cases it is possible to 

directly correlate the older Standard Industrial Codes directly with the new NAICS codes, but in 

some cases the source groupings are slightly different and care will be needed to ensure that new 

factors are developed that correlate to groupings under the new codes. 

Comment: One commenter (0048) stated that rule effectiveness (RE) under “New Data 

Elements” was a problem that EPA should solve with new studies and recommendations. The 

commenter stated that 80% RE had long been EPA’s standard default and the value was 

apparently obtained from a dated Government Accountability Office (GAO) study that looked at 

compliance issues specific to bag houses and particulate matter. The commenter did not believe 

that the study was intended to set an RE number to apply to all industries, all pollutants, and all 

control devices and that it was not even clear that it was intended to develop an RE value to 

adjust emission inventory data for use of bag houses. The commenter thought that EPA should 

make it a priority to develop accurate default rule effectiveness values considering current 

enforcement practices and instrumentation and that RE should be by control device type and by 

industry process controlled. The commenter also thought that EPA should develop accurate 

default RE and Rule Penetration values based on current experience for area and nonroad sources 

since States generally do not have the resources to do this. 

The commenter believed that RE concepts should be used only to examine and develop new 

control strategies and that “basic” emission inventories should represent the best available 

information on what is actually happening at the facility. The commenter noted that start-up, shut 

down and malfunction emissions were excluded from Title V emission reporting requirements 

and were a departure from reality. 

Response: The rule effectiveness (RE) guidance cited by the commenter was updated by EPA in 

Appendix B to a document titled Emissions Inventory Guidance for Implementation of Ozone and 

Particulate Matter National Ambient Air Quality Standards (NAAQS) and Regional Haze 

Regulations – FINAL, November 2005. This guidance reflects the consensus of a workgroup that 

was formed in the Spring of 2004 to review and update the RE guidance. The workgroup 

included representatives of several EPA regional offices as well as State and local agency staff 

involved with development of emission inventories. 

The revised guidance removes the previous recommendation for use of an across the board 80% 

default value for RE. In its place, this new guidance provides inventory preparers with a listing of 

the factors that are most likely to affect RE, and ranks these factors in a priority order. Likely 

responses to evaluation of these factors were then grouped into RE ranges, such that more 

positive responses to a number of the factors will lead towards selection of a higher RE value, 

whereas more negative responses will direct one to select an RE value from a lower range. EPA 
31

believes the updated guidance addresses concerns identified by the commenter regarding use of 

an 80% default value for RE. 

One area of confusion noted by the commenter concerns the reporting of emissions from start-up, 

shut-down and malfunction conditions. EPA recognizes that some permits contain alternative 

conditions for use during periods of start-up, shutdown and malfunctions; however, to the extent 

that these emissions can be quantified and reported, they should be included in data submittals 

reported under the AERR to reflect “actual” emissions. EPA believes that accounting for 

emissions from start-up, shutdown and malfunctions is appropriate for “basic” emission 

inventories which are used for inventory projections since omitting such emissions will tend to 

underestimate actual emissions as the foundation for both the baseline and projection estimates. 

Similarly, EPA disagrees with the commenter’s belief that accounting for RE is not appropriate 

for “basic” emission inventories since RE is only applied when emission estimates are thought to 

deviate from what is actually emitted. 

Comment: One commenter (0048) noted that Section III.B. of the rule addressed requirements 

of the Paperwork Reduction Act and stated that “The information collection requirements in the 

proposed amendments are mandatory for all States and territories (excluding tribal 

governments).” The commenter believed that tribes were not excluded from federal requirements 

and should be subject to the requirements of the AERR. 

Response: EPA disagrees with the commenter’s assertion to the extent that it argues that the 

AERR applies to all tribes. EPA’s actions with respect to tribes are governed by the Tribal 

Authority Rule (Indian Tribes: Air Quality Planning and Management, 63 Fed. Reg. 7253 

(February 12, 1998), codified at 40 CFR part 49, subpart A). As prescribed by the Tribal 

Authority Rule, Tribes may elect to seek treatment as State (TAS) status and obtain approval to 

implement the requirements of rules such as the AERR through a Tribal Implementation Plan 

(TIP), but Tribes are under no obligation to do so. However, those Tribes that have obtained TAS 

status are subject to the AERR to the extent specified in their TIPs. Accordingly, to the extent a 

Tribal government has applied for and received TAS status for air quality control purposes and is 

subject to the AERR under an approved TIP, EPA has clarified that the use of the term State(s) in 

the AERR shall include that Tribal government. 

Comment: One commenter (0048) stated that “The emission data uses cited are redundant with 

the purposes of the State in submittal of a SIP. In those cases, the judgment and technical criteria 

should be to have adequate data to determine if the SIP will lead to attainment and maintenance 

of the ambient air quality standards. This encompasses PSD, NSR and other elements referred to 

in this section. EPA’s responsibilities include the evaluation of the SIPs, not the States.” 

Response:. Section III.B. of the proposal cites the following uses for the data: “The reported 

emissions data are used by EPA to develop and evaluate State, regional, and national control 

strategies; to assess and analyze trends in criteria pollutant emissions; to identify emission and 

control technology research priorities; and to assess the impact of new or modified sources within 

a geographic area.” 

The commenter appears to be concerned about the portion of the text which indicates that EPA 

will use the data to “develop... state... control strategies.” Although this could be interpreted to 

be redundant with State responsibilities and actions, EPA often needs to develop, through 

independent means, ways to evaluate the adequacy of State efforts to attain the NAAQS. In 

addition, EPA also has a responsibility to function as a safety net where States are unable or 
32

unwilling to fulfill their responsibilities under the CAA. In those cases, EPA must have the tools 

it needs to address air quality problems on a State or regional basis. Therefore, EPA disagrees 

with the commenter’s concerns regarding the redundancy of federal and State efforts. 

Comment: One commenter (0045) recommended that EPA consider including reporting 

requirements for emissions of carbon dioxide data for Title V facilities. Another commenter 

(0048) thought it would be appropriate to include greenhouse gases from point sources as an 

option for States to report under the AERR. 

Response: 

The FY-08 Omnibus Appropriations Bill included a requirement for “the Agency to use its 

existing authority under the Clean Air Act to develop and publish a rule requiring mandatory 

reporting of greenhouse gas emissions above appropriate thresholds in all sectors of the 

economy.” This was a new development that occurred following the close of the AERR 

comment period and EPA believes that it is most appropriate to consider all alternatives for 

reporting greenhouse gas emissions in implementing the new directive. The AERR will no doubt 

help inform development of the mandatory greenhouse gas rule and EPA will explore 

opportunities to consolidate state emissions reporting requirements which appeared to be the 

focus of the commenter’s recommendations. 

Comment: One commenter (0048) requested that emissions of nitrogen oxides (NOX) be 

reported on the basis of NO2. 

Response: The definition of nitrogen oxides (NOX) from the proposal reads as follows: 

“Nitrogen oxides (NOX) means nitrogen oxides (NOX) as defined in 40 CFR 60.2 as all oxides of 

nitrogen except N2O. Nitrogen oxides should be reported on an equivalent molecular weight 

basis as nitrogen dioxide (NO2).” 

EPA believes the definition from the proposal addresses the concerns of the commenter and will 

include this definition in the final rule. 

Comment: One commenter (0048) stated that there is no need for reporting PM filterable and 

condensable emissions because only the total PM is regulated. 

Response: EPA disagrees with the commenter based upon recent experience with attempting to 

understand the content of State data submittals under the CERR for primary PM2.5 and primary 

PM10. Primary PM includes filterable and condensable PM fractions. In some cases, it has not 

been clear if the primary PM reported included the condensable fraction and comparisons with 

earlier State data submittals have been conducted by EPA as a means of identifying the reported 

fractions. To address this uncertainty, the AERR was amended to include reporting of the 

component parts of PM which States need to develop primary (or total) PM. Reporting the 

fractions individually in addition to primary PM will ensure that EPA is able to identify where 

States have submitted filterable emissions only and efforts are necessary by EPA to augment 

State data submittals to account for the condensable PM fraction. This position is also 

supported by the recent PM2.5 final rule, in which EPA stated that “for purposes of 

emission inventories..., States should continue to describe the impacts of baseline

emissions and develop future air quality strategies using information available on primary 

PM2.5 emissions, including condensable PM2.5.” Clean Air Fine Particle 

Implementation Rule, 72 Fed. Reg. 20586, 20650 (April 25, 2007) (emphasis added). 
33

Comment: One commenter (0048) recommended that emissions of ammonia (NH3) be reported 

on the basis of NH3 equivalence. 

Response: There are several methods used for measuring ammonia emissions from stationary 

and mobile sources, one of which uses NH3 equivalence. EPA’s Conditional Test Method (CTM) 

027 (Procedure for Collection and Analysis of Ammonia in Stationary Sources) is a manual 

method for measuring concentrations of ammonia in parts per million (ppm). CTM 027 converts 

the ammonia to ammonia ion (NH4) for analysis by ion chromatography, and the ammonia ion 

concentration results are then converted to an ammonia equivalent in parts per million. 

The commenter's recommendation to report on the "basis of NH3 equivalence" could be 

interpreted to imply that compounds other than ammonia be included in the reported mass. If so, 

EPA disagrees with this recommendation, since NH3 is the pollutant identified in the AERR for 

reporting. In addition, to the extent that the comment could be interpreted to mean that NH3

equivalence should be the only method available for measuring and reporting ammonia emission, 

EPA does not agree, given the several methods presently available. 

Comment: One commenter (0048) requested that the requirements under section 51.15 (a) (7) be 

modified to define hazardous air pollutants “as listed in the Clean Air Act Section 112,” and to 

encourage submittal of these data at least on an every third (or fifth) year basis. The justification 

for including these compounds in the inventory would be to provide speciation information for 

use in photochemical modeling and to quality assure emissions. 

Response: As discussed earlier in this section, EPA does not intend to revise the AERR to 

include reporting of hazardous air pollutants listed under Title III of the CAA. The existing 

regulatory text allows States to report emissions of hazardous air pollutants on a voluntary basis. 

Given the voluntary nature of HAP pollutant reporting, EPA sees no need to qualify the HAPs for 

reporting under the AERR by adding language to reference Title III of the CAA. However, EPA 

has developed pollutant reporting codes only for CAA Title III pollutants so the effect of this will 

be for EPA’s data handling systems to recognize only CAA HAPs and thus is consistent with the 

commenter’s request. 

Comment: One commenter (0048) recommended that the regulatory text under section 51.20 (c) 

be revised to read as follows: “If your State has lower emission thresholds for point sources than 

paragraph (b) of this section, then you may use these in reporting your emissions to EPA as minor 

point sources to be reconciled with area source emissions as a whole to avoid gaps.” The 

commenter also recommended that the regulatory text under 51.20 (d) be revised to read: “All 

stationary sources that are not subject to reporting as point sources must be reported as area 

sources and avoid double counting.” 

Response: EPA does not believe that the suggested revisions to the regulatory text are necessary. 

The additional text suggested by the commenter related to gaps and double counting are terms of 

art used by emission inventory preparers but are not well defined. As discussed in an earlier 

response in this section, EPA does not agree that using the terms “minor point sources” and “area 

sources” will add clarity to the reporting requirements. 

During review of this comment, EPA became aware of the restrictive nature of the language 

under section 51.20 (d) which required sources that were not subject to the point source reporting 

requirements to be reported as nonpoint sources. Although section 51.20 (c) allows states to use 

the point source reporting format for other sources that are subject to lower state point source 

reporting thresholds, the effect of 51.20 (d) is to restrict use of the point source reporting format 
34

to sources subject to state or EPA point source reporting requirements. The revised regulatory 

language under section 51.20 (d) in the final rule allows states to also report sources using the 

point source reporting format that are below the EPA or state point source reporting thresholds. 

Comment: One commenter (0048) recommended that the regulatory text under section 51.30 be 

revised to read as follows: “All States are required to report two basic types of emission 

inventories to EPA: Every-year Cycle Inventory for Title V facilities; and Three-year Cycle 

Inventory for area and minor point sources” (suggested text additions are italicized).

Response: EPA believes the existing regulatory text for every-year cycle inventory reporting is 

sufficiently clear. Adding “for Title V facilities” includes a qualifier that could exclude sources 

that, for whatever reasons, have emissions that would subject them to the point source reporting 

requirements but do not have an operating permit issued under the Title V program. The 

additional qualifier also would add a new class of sources that are regulated under section 112 of 

the CAA, which EPA did not intend to include in reporting under the AERR. The suggested text 

revision for the Three-year Cycle Inventory is incorrect since it would omit point source data 

elements required by Table 2A of the AERR. 

EPA believes the annual and triennial reporting requirements presented in section 51.50 “What 

definitions apply to this subpart?” and the table that is included in the Point Source definition in 

this section provide an adequate description of what sources are to be reported as part of the 

annual and triennial reporting cycles. 

Comment: One commenter (0048) thought that the terms and definitions under section 51.50 

were misplaced. The commenter stated that if the purpose of the regulation was to be “allinclusive, it is inadequate. If the purpose is to prescribe to the States the general concepts and 

requirements to meet policy needs, it is much overdone, with much of these definitions and 

specific details belonging in the NIF technical requirements....” 

Response: The suggestion to include all technical details in the NIF data formatting guidance 

has been addressed in a response to earlier, similar comments in this section. The purpose of 

section 51.50 was to provide definitions for terms used in the rule to ensure that EPA and readers 

have a common understanding of many terms that inventory developers commonly use but in 

some cases have imprecise meanings. EPA believes that section 51.50 serves its intended 

purpose by providing an explanation of terms used in the rule that could otherwise be open to 

multiple interpretations. 

Comment: One commenter (0048) noted that Primary and Total PM are used for the same 

meaning at different places in the AERR proposal. 

Response: The commenter is correct. Under section 51.15, What data does my State need to 

report to EPA?, the terms “Primary PM2.5” and “Primary PM10 are used to indicate the 

pollutants for reporting while the term “total” is used to indicate the sum of the filterable and 

condensable fractions (Primary PM). EPA has revised the definitions for Primary PM2.5 and 

Primary PM10 under section 51.50 and removed references to total PM. 

Comment: One commenter (0048) thought that Rule Effectiveness and Rule Penetration 

belonged in “modeled inventories” rather than in base case data sets of emission inventory 

reports. The commenter believed that application of either of these concepts required the use of 

judgments and assumptions that escape the definition of “data” and were no longer appropriate 

parts of the emission inventory. The commenter suggested that if EPA needed adjustments to 

data, they were more appropriately reflected in the SIP approval process. 
35

Response: Rule Effectiveness (RE), which includes Rule Penetration when applying the concept 

to the effectiveness of rules for area sources, was first developed in 1980 and has been used in 

emission inventory development since that time. RE studies conducted during the early 1980’s 

demonstrated that sources rarely achieved full compliance with rules on a continuous basis and 

that some adjustment of emissions was appropriate to better reflect “actual” air emissions to the 

atmosphere. Since RE is associated with developing estimates of “actual” emissions, EPA 

believes it needs to be considered in all emission inventories that attempt to reflect “actual” 

emissions. Judgments and assumptions are applied in many aspects of emission inventory 

development due to the scale of inventories and application of state-of-the-art techniques to 

estimate emissions for many pollutants from a wide variety of stationary and mobile sources. 

EPA’s policy on RE encourages States to apply their knowledge of source operations to develop 

their best estimates of actual emissions and thus is consistent with the AERR requirements for 

reporting actual emissions. If States are able to demonstrate that sources are in full compliance 

with rules during the time period represented by the emission inventory, then no RE adjustment 

of the emissions is needed.