VI. A. 6.6 Comment: One commenter ( 605) contended that EPA Method 320 ( Extractive FTIR), CARB Method 430 ( in field DNPH derivatization), and EPA SW 846 Method 0011 ( similar to CARB 430) should not be cited in the proposed rule because they have not been validated for the sources and concentrations in questions.

Response: Although EPA disagrees with the commenters rationale, EPA agrees that CARB Method 430 and EPA SW 846 Method 0011 should not be cited in the final rule. Method 320 is a self validating performance based method, that is capable of being successfully implemented and is cited.

B. Performance Tests 1. Portable CO Monitor VI. B. 1.1 Comment: Two commenters ( 526, 579) stated that the proposed standards require continuous monitoring of pressure drop across the catalyst, catalyst inlet temperature and temperature rise across the catalyst, and setting operating limits of these parameters in reference to the initial performance test data. Since these operating parameters vary depending upon engine load, the initial performance test must be mapped over the entire operating range to establish the reference points. This is especially true of variably loaded engines such as those following diurnal sewage flow patterns. Upon changing as little as a single catalyst element, the same parameters must be re established. Hence extremely comprehensive and frequent source tests could result from the proposed rule. The commenters stated that the periodic monitoring provisions that have been relatively recently agreed to by EPA and States as part of the title V program should serve as the continuous compliance criteria of the proposed rule. The use of simple hand held CO 86 monitors using approved EPA protocols with results reported through the title V process are adequate and should be offered as an option to operators.

Response: The EPA disagrees and feels that some type of continuous monitoring is necessary to demonstrate continuous compliance. The EPA has removed the requirement to monitor and maintain the temperature rise across the catalyst for 4SRB engines using NSCR. The EPA has also adjusted the requirement for pressure drop monitoring to only require that the pressure drop across the catalyst be measured monthly. Finally, EPA has removed the requirement to monitor and maintain the operating load or fuel flow rate for sources complying with the alternative formaldehyde concentration emission limitation. The rationale for these changes are discussed elsewhere in this document.

VI. B. 1.2 Comment: Four commenters ( 542, 554, 556, 587) stated that quarterly emission testing with CO portable units should not be full performance tests. This provision is burdensome and unnecessary. The final rule should not require that the quarterly emission tests be full performance tests for the following reasons:

( 1) For full performance tests, engines in load following applications may need to conduct emissions testing at multiple operating conditions, in accordance with the General Provisions' requirement that performance tests be conducted for representative conditions;

( 2) Facilities with load following operations, such as natural gas transmission and storage, may not be able to operate the engines over the full range of operating conditions on a quarterly basis;

( 3) Full performance tests impose significant burden on the owner or operator to develop site specific test plans, provide notification to the permitting authority 60 days in advance of the test, and submit the full results within 60 days of completion of the testing; and ( 4) Review of other MACT standards indicates that full performance tests are not required more frequently than annually.

Response: The EPA agrees with the commenters that requiring full performance tests quarterly for sources complying with CO reduction requirement may impose significant burden on the owner or operator to develop site specific test plans, provide notification to the permitting authority 60 days in advance of the test, and submit the full results within 60 days of completion of the testing. The EPA now feels that quarterly testing for CO is unnecessary and inappropriate. In the final rule, EPA has specified that new 2SLB, new 4SLB, and new CI engines complying with requirement to reduce CO emissions must conduct semiannual performance tests for CO to demonstrate that the required CO percent reduction is achieved. Semiannual performance testing for CO in addition to monitoring and maintaining operating parameters will ensure, on an ongoing basis, that the applicable CO percent reduction requirement is being met. After demonstrating 87 compliance for two consecutive tests, the frequency can be reduced to annually. However, if an annual performance test indicates a deviation of CO emissions from the CO reduction requirement, you must return to semiannual performance tests.

VI. B. 1.3 Comment: One commenter ( 555) indicated that accurate measurements with portable emission monitors will be difficult. The portable the commenter is familiar with have a full range scale of 0 500 ppmvd and are not expected to be accurate at 10 ppmvd.

Response: That particular instrument arrangement would probably not meet Section 8.3.1 of ASTM D 6522 00 which requires the span gas concentration to be chosen such that the average stack gas reading for each run is greater than 25 percent of the span gas concentration and also meet the performance and design criteria of Section 9 and 10.4.11 as required by Section 7.2 of the method. However, there are portable monitors for sale that do meet ASTM D6522 00 and our monitoring requirements.

2. Other VI. B. 2.1 Comment: Five commenters ( 542, 554, 556, 565, 587) contended that additional performance tests should not be required when NSCR or oxidation catalysts are replaced with identical units.

Response: The EPA disagrees. Additional performance tests are required to be performed even though an emission control device is replaced with an identical unit. The performance of identical catalysts can vary significantly, and it is not guaranteed that the NSCR or oxidation catalyst will achieve the same performance levels.

VI. B. 2.2 Comment: One commenter ( 570) asked that EPA specify what is meant by the phrase " catalyst elements." The commenter requested that EPA specify within the rule what specifically is intended to trigger the requirement to conduct another performance test when replacing catalyst elements.

Response: Sources have to conduct another performance test when the catalyst is replaced.

VI. B. 2.3 Comment: One commenter ( 570) recommended that EPA eliminate Table 3 of the proposed rule and impose no testing requirements beyond the initial performance tests. One commenter ( 569) said that the requirements for subsequent performance tests in Table 3 of the proposed rule should be deleted from RICE equipped with catalyst. Subsequent performance tests, if any, should only be required on one RICE if a facility operates several RICE of the same design.

Response: The EPA disagrees with the commenters. Subsequent performance testing is needed for units in order to demonstrate continuous compliance with the applicable emission limitation beyond initial compliance demonstration. Subsequent performance tests must be 88 conducted on each RICE even though a facility operates several RICE of the same design. The performance of different stationary RICE can vary significantly, even if they are of the same design.

VI. B. 2.4 Comment: One commenter ( 552) suggested that EPA include a provision that performance tests be conducted within the manufacturer's recommended operating range, excluding idle. The EPA needs to identify reasonable engine operating and load conditions to be used during the initial and subsequent performance tests. Tables 5 and 6 of the proposed rule establishes requirements related to initial and subsequent performance tests. However, no direction is given in the tables or the text of the proposed rule regarding the operating load to be used during these tests. The EPA should revise the tables and the text of the proposed rule to clarify the engine conditions and loading requirements for these tests. Engine loads and operating conditions can vary significantly depending on specific applications and changing demands, and it is important that the final rule does not restrict nor confine the flexibility needed to successfully operate these engines. The commenter therefore suggested that EPA include a provision that performance tests be conducted within the manufacturer's recommended operating range. Since HAP emissions generally decrease with increasing engine load and operating temperature and catalytic removal efficiency improves with higher exhaust temperatures, the initial performance test should be conducted at the lower end of this range. Completing performance testing under the above specified conditions should result in the maximum expected generation of HAP from the engine. Consequently, the operator and EPA can be assured that HAP emissions will be lower across the remaining recommended operating range. In order to assure that RICE will be able to continue to operate, special provisions regarding start up, idle, and shutdown operation should be specified in the final rule, and the commenter stands ready to work with EPA to develop workable solutions and language.

Response: The EPA has removed the requirement to maintain an operating load or fuel flow rate equal to or greater than 95 percent of the operating load or fuel flow rate established during the initial performance test. This was discussed in response to comment V. B. 1.2. Furthermore, EPA has based the final emission limitations on test results from testing conducted at high loads only. Since the emission limitations are based on emissions data from high load tests, EPA has found it appropriate to require that performance test be conducted at high load conditions. This has been specified in the final rule. The EPA has defined high load conditions as 100 percent ± 10 percent. Sources are not required to meet the emission limitations at low load.

VI. B. 2.5 Comment: One commenter ( 549) expressed the opinion that the initial performance test period for 2SLB, 4SLB, and CI RICE should be increased from 4 to 24 hours to obtain results representative of the normal duty cycle.

Response: The EPA does not agree with this comment; it is believed that 4 hours is sufficient time to conduct the initial performance test. This was discussed in response to comment V. F. 3.

VI. B. 2.6 Comment: One commenter ( 549) asked that EPA include similar language as in 89 the Petroleum Refinery MACT for Catalytic Cracking Units which has the provision to make adjustments to one of the monitored operating parameters to acknowledge that it may not be possible to achieve worst case operation during the performance test. In this scenario, the testing of a similar unit should be allowed to serve as the basis for establishing acceptable inlet temperatures.

One commenter ( 569) remarked that initial performance tests should only have to be performed on one engine when an installation is provided with several identical engines.

Response: The EPA does not agree that it is appropriate to allow a facility with identical engines to conduct testing on only one of the units to establish operating parameters. Although the units are identical, operating parameters, as well as emissions, could vary significantly from unit to unit. The EPA does not agree that it is appropriate to allow a facility with identical engines to conduct performance tests on only one of the units to demonstrate compliance with the emission limits for all of the identical units. It is EPA's experience that emissions from identical units can vary significantly.

VI. B. 2.7 Comment: One commenter ( 569) stated that manufacturer's performance data should be allowable in lieu of an initial performance test.

Response: The EPA is not allowing manufacturer's performance data in lieu of an initial performance test. Performance data provided by the manufacturer may not be representative of how the engine will perform in the field and may overestimate the engine's performance.

VI. B. 2.8 Comment: One commenter ( 567) contended that the stack testing should be no more frequent than semiannual for CO. The stack testing for formaldehyde should be no more frequent than annual. The commenter added that both should also include the ability to go to even less frequent testing based upon good performance.

Response: The EPA agrees with the commenter and feels that it is appropriate to require semiannual performance tests for CO for sources meeting the CO percent reduction requirement. This has been specified in the final rule. The rationale for reducing the CO testing requirement was previously discussed. For CO stack testing, EPA also agrees with the commenter that it is appropriate to allow sources that demonstrate compliance for two consecutive tests, to reduce the frequency of subsequent performance tests to annually. However, if an annual performance test indicates a deviation of CO emissions from the CO reduction requirement, sources must return to semiannual performance tests. Regarding formaldehyde testing, EPA disagrees with the commenter and feels that it has appropriately set the testing requirements for formaldehyde at semiannual performance tests. Periodic stack testing for CO and formaldehyde will ensure, on an ongoing basis, that the source is meeting the emission limitation requirements. For formaldehyde stack testing, if you have demonstrated compliance for two consecutive tests, you may reduce the frequency of subsequent performance tests to annually. However, if the results of any subsequent annual performance test indicate that the stationary engine is not in compliance with the formaldehyde emission limitation, or you deviate from any of your operating limitations, you must 90 resume semiannual performance tests.

VI. B. 2.9 Comment: One commenter ( 565) was of the opinion that EPA should allow facilities complying with the formaldehyde emission limitation to use existing performance test data to demonstrate initial compliance with the emission limit.

Response: The EPA agrees with the commenter that existing performance test data can be used to demonstrate compliance with the emission limit. The facility must petition the Administrator for approval and demonstrate that the tests were conducted using the same test methods specified in the subpart, the test method procedures were correctly followed, no process or equipment changes have been made since the test, and the data is of good quality and is less than 2 years old. Existing test data can only be used to demonstrate initial compliance; after the initial compliance demonstration, facilities must then begin to follow the annual compliance test schedule.

VI. B. 2.10 Comment: One commenter ( 545) stated that if EPA does not exempt all limited use units from the rule, requirements for performance testing in Table 6 of the proposed rule should be amended to provide alternative performance testing requirements for infrequently operated or seasonally operated stationary RICE.

Response: The frequency of performance testing might be as low as once per year, if the source has demonstrated compliance for two successive tests. For 4SRB units complying with the requirement to reduce formaldehyde emissions and that are less than 5,000 HP, only an initial performance test is required. Owners and operators of seasonally or infrequently operated stationary RICE can schedule the performance test for when the unit will be operating. For these reasons, EPA does not feel it is necessary to establish alternative performance testing requirements for infrequently operated or seasonally operated stationary RICE. Infrequently operated units subject to emission limitations must follow the same performance testing requirements as other units.

VI. B. 2.11 Comment: One commenter ( 549) stated that EPA should define the number of test runs and duration of test runs for periodic CO monitoring using portable CO analyzer. The RICE MACT should stipulate the test duration for periodic testing of engines using the referenced portable monitoring protocol. While the protocol includes quality assurance/ quality control and test procedures, the duration of the test is not defined. Portable monitoring has been implemented in a number of States to address monitoring requirements for the title V operating permit program. From a limited review of State approaches, it is apparent that some States rely on Conditional Test Methods from the EPA Emission Measurement Center website, including CTM 030, which is the method from which the ASTM method was derived. In implementing these procedures, the duration for emissions data acquisition is as short as 2 minutes ( per CTM 034). Test runs on the order of 15 20 minutes are more common. For example, a Wyoming protocol based on CTM 030 defines the test duration as a minimum of 21 minutes, with the start of the emissions test period dependent upon analyzer response as defined in the protocol ( and consistent with CTM 030). We recommend that EPA follow a similar approach and define the sampling 91 period for acquisition of emissions data as a minimum of 15 minutes for portable analyzer testing. A single run would constitute a test.

Response: The EPA agrees with the commenter that for RICE a minimum 15 minute run time should be specified. However, the tester must additionally document conformance with the ASTM D6522 00 performance requirements of minimum sample points, and equal sample time per point, detailed in section 10 of the method which may require longer run times. If the three point option is used, then recording five 1 minute values ( after purging the greater of two times the response time or the stability time) at each point could minimally constitute a run. If the source can qualify for the single point sampling then recording 15 1 minute values ( after purging the greater of two times the response time or the stability time) would be accepted. The EPA disagrees with the commenter that a single run should constitute a test. The EPA wants to require the same number of runs in a test regardless of method followed. ( Section 63.7( e)( 3) of the General Provisions requires three unless the final rule specifies differently.)

VII. COST/ IMPACT VII. 1 Comment: One commenter ( 555) stated that NOx increases due to oxidation catalysts for 2SLB and 4SLB engines should be considered in evaluating the cost and benefits of the proposed rule. Test results for 2SLB and 4SLB engines ( Docket No. OAR 2002 0059 0049 ( A 95 35 II B 27)) equipped with oxidation catalysts indicate an increase of NOx emissions up to about 15 percent and 12 percent for 2SLB and 4SLB engines, respectively. It is not clear that the impacts of this NOx increase has been addressed with respect to the ability of sources to comply with State and local NOx limits or impacts on the environment.

Response: The EPA did consider NOx increases due to oxidation catalysts for 2SLB and 4SLB engines. However, the NOx increases resulting from 2SLB and 4SLB installing oxidation catalyst controls to comply with the final rule are far less than the NOx decreases resulting from 4SRB engines installing NSCR controls to comply with the final rule, resulting in a net decrease in NOx emissions due to the final rule and a benefit to the environment overall. In addition, oxidation catalysts are not specifically required by the final rule and as only new 2SLB and new 4SLB engines are affected by the final rule, sources that are concerned about NOx emissions can use other methods of HAP emission control that are less problematic from a NOx control perspective ( like in cylinder controls), or they can use NOx control to reduce NOx from engines using oxidation catalysts.

VII. 2 Comment: One commenter ( 569) expressed that the RICE MACT is not cost effective for existing 4SRB engines.

Response: In the development of MACT floors, EPA does not consider the cost effectiveness of implementing rule requirements. In developing options more stringent than the floor, the EPA can consider costs of achieving emissions reductions and base a decision on whether or not going beyond the floor is cost effective. 92 VII. 3 Comment: One commenter ( 570) stated that it may be possible for EPA to obtain the same level of HAP emissions reductions from stationary RICE in objectively and discretely defined high risk urban areas at significantly lower costs than will be realized in the proposed rule. The commenter offered a model which includes an operation and maintenance plan ( O& M Plan) for the control device, initial performance test, compliance with O& M represents compliance with emission standards, control device summaries and excess emission reports to be provided to the Administrator on an annual basis.

Response: It appears the commenter is suggesting that the rule cover high risk urban areas only. The EPA is unable to do so as EPA is required by the CAA to establish NESHAP and set MACT requirements for the source category and subcategories. In addition, the commenter's model suggests a case by case operating plan which would greatly increase the regulatory resources needed for the rule and could lead to significantly different requirements for similar sources. In addition, as discussed in response to several other comments, EPA feels that there are very good reasons to require periodic testing of all regulated sources.

VII. 4 Comment: One commenter ( 583) asserted that if EPA adopts the new MACT standards as proposed, the rule would adversely affect its members by increasing the cost to operate compressor engines on pipelines and at natural gas storage facilities, and by discouraging customers from using natural gas fired engines as distributed energy.

Response: The EPA does not agree with the commenter that the rule would adversely affect the regulated community. The economic impact analysis for the final rule, which is available in the public docket, shows that costs to industries and changes in prices of natural gas will be less than 1 percent overall. These impact estimates do account for the effect on consumers from the increase in natural gas prices, and account for the pass through of higher natural gas prices to consumers as well as the higher cost of operations to natural gas compressor engine operators and storage facilities. It should be also be noted that EPA is required by the CAA to regulate this source category.

VIII. RISK Note: All of the comments pertaining to risk are summarized below. There is a single response given at the end of this section for all of the risk comments.

VIII. 1 Comment: Three commenters ( 558, 564, 585) supported the use of risk based applicability criteria to remove sources that do not pose significant risk. VIII. 2 Comment: One commenter ( 565) stated that allowing the use of the CAA section 112( d)( 4) provision within the source category could provide substantial cost effectiveness benefits while, at the same time, providing protection to human health and the environment. However, the commenters believe that EPA must clarify in the final rule exactly how the provisions will be implemented. VIII. 3 Comment: One commenter ( 562) believes that there are ways to structure the rule 93 to focus on facilities that pose significant risks and avoid imposition of high costs on facilities that pose little risk. An appropriate approach would be to allow individual facilities to conduct a risk assessment to show that it poses insignificant risks to the public. Commenter 562 stated that such an approach would involve air quality modeling and the use of RfCs. VIII. 4 Comment: One commenter ( 570) believes that the proposed RICE MACT should be either withdrawn and stationary RICE de listed pursuant to 112( c) or the rule should be limited in scope to those sources where the social benefits resulting from the relatively small HAP emissions reductions can be demonstrated ( e. g., large urban areas). In this latter case, the rule should be greatly simplified. The commenter supported inclusion of the risk based approaches presented in the preamble but does not see how the RICE category fits into the risk based approach that EPA wants to use. VIII. 5 Comment: Three commenters ( 548, 560, 595) encouraged EPA to continue considering the establishment of a subcategory of RICE that would meet 112( c)( 9)( B)' s riskbased criteria for delisting, and support the use of 112( c)( 9)( B) to achieve the goals of the rule in a less costly manner. VIII. 6 Comment: One commenter ( 550) stated that they support focusing efforts on the greatest risks to public health, but suggested that the risk based approaches be presented to an appropriate scientific peer review group ( e. g., the CAA Advisory Committee or Science Advisory Board) before being placed in the preamble. VIII. 7 Comment: Three commenters ( 499, 572, 586) are opposed to the risk based exemptions. Commenter 499 noted that the proposal to include risk based exemptions is critically flawed and opposes adoption of the risk based exemptions into MACT. Commenter 586 is extremely concerned about the policy and technical implications of the risk based exemption proposal. Because of the flaws with the proposal, the commenter is opposed to the adoption of the risk based exemptions to MACT. Commenter 574 stated the belief that the use of risk based concepts to evade MACT applicability is contrary to the intent of the CAA and is based on a flawed interpretation of section 112( d)( 4) of the CAA. The commenter added that the CAA requires a technology based floor level of control and does not provide exclusions for risk or secondary impacts from applying the MACT floor. Commenter 574 stated that from a practical standpoint, the approaches ( to risk based exemptions) in the preamble are not appropriate. VIII. 8 Comment: One commenter ( 529) is opposed to risk based exemptions discussed in the preamble and recommends that EPA expeditiously propose and promulgate the rule without such exemptions. Commenter 567 is opposed to the risk based exemptions and called upon EPA to promulgate the remaining technology based MACT standards without the risk based exemptions. VIII. 9 Comment: Four commenters ( 499, 567, 572, 586) believe that the preambles of individual rule proposals were an inappropriate forum for introducing significant changes in the way that MACT standards are established. Precedent setting change of the magnitude that EPA has raised should be discussed openly and carefully with all affected parties instead of being buried in the preambles of individual standards. Commenter 574 stated the concern that other parties may miss commenting on the riskbased exemptions because they are contained within six separate proposals. The commenter added that to give the issue full consideration, the risk provisions should not be adopted within any of the final rules but should be addressed in one place, such as in revisions to the General 94 Provisions of 40 CFR 63 subpart A. VIII. 10 Comment: One commenter ( 586) stated that the preamble discussion of the riskbased approaches is not sufficient to allow for complete public comment and, therefore, it would not be appropriate for EPA to go directly to a final rule ( without reproposal) with any of the approaches outlined in the proposal. The commenter recommended that the risk based exemption proposal be dropped because it is unacceptable. Commenter 567 stated that the use of sub categorization and source category deletions under CAA section 112( c) have been implemented several times since the MACT program began. The commenters have been unable to comment on the technical merit of the risk analysis employed by the EPA. Until the residual risk analysis procedures have been implemented via the CAA section 112( f) process, risk analysis should not been used in making MACT determinations pursuant to CAA section 112( d)( 4) and, could never be used to establish a MACT floor. VIII. 11 Comment: Six commenters ( 499, 529, 567, 572, 586, 588) stated that the proposal to include risk based exemptions is contrary to the 1990 CAA Amendments ( CAAA) which calls for MACT standards based on technology rather than risk as a first step. Congress incorporated the residual risk program under CAA section 112( f) to follow the MACT standards ( not to replace them). The need for the technology based approach has been recently reinforced by the results of the National Air Toxics Assessment ( NATA), which indicates that exposure to air toxics is very high throughout the country in urban and remote areas. Commenters 586 and 499 added that risk based approaches will be used separately to augment and improve technology based standards that do not adequately provide protection to the public. Commenter 572 added that section 112( f) of the CAA was developed to address residual risks remaining after implementation of technology based MACT standards and was intended to provide additional protection, not replace technology controls. VIII. 12 Comment: Five commenters ( 499, 529, 567, 572, 586) stated that the proposal to allow risk based exemptions would divert back to the time consuming NESHAP development process that existed prior to the CAAA. Under this process, which began with a risk assessment step, only eight NESHAP were promulgated during a 20 year period. If the proposed approaches are inserted into upcoming standards, the commenters fear the MACT program ( which is already far behind schedule) would be further delayed. VIII. 13 Comment: Three commenters ( 499, 567, 586) stated that the risk based exemption proposal removes the " level playing field" that would result from the proper implementation of technology based MACT standards. Establishing a baseline level of control is essential to prevent industry from moving to areas of the country that have the least stringent air toxics programs, which was one of the primary goals of developing a uniform national air toxics program under section 112 of the 1990 CAA amendments. The risk based approaches would jeopardize future reductions of HAP in a uniform and consistent manner across the nation. Commenter 499 stated that the NATA data show that virtually no area of the country has escaped measurable concentrations of toxic air pollution. The NATA information indicates that exposure to air toxics is high in both densely populated and remote rural areas. VIII. 14 Comment: Four commenters ( 548, 560, 565, 595) believe that CAA section 112( d)( 4) provides EPA with authority to exclude sources that emit threshold pollutants from regulation. The commenters indicated that CAA section 112( d)( 4) allows for discretion in developing MACT standards for HAP with health thresholds. This is consistent with the plain 95 language of the statute, which states that: " With respect to pollutants for which a health threshold has been established, the Administrator may consider such threshold level, with an ample margin of safety, when establishing emission standards under this subsection." The use of CAA section 112( d)( 4) authority also is supported by CAA's legislative history, which emphasizes that Congress included § 112( d)( 4) in the CAA to prevent unnecessary regulation of source categories. Multiple commenters ( 548) referenced Sen Rep. 101 228, at 176 ( 1989), reprinted in 1990 U. S. C. C. A. N. 3385, 3560: "[ W] here some sources do emit more than the threshold amount, the Administrator is authorized by section 112( d)( 4) to use the no observable effects level or NOEL ( again with an ample margin of safety) as the emission limitation in lieu of more stringent " best technology" requirements. Following this scenario, only those sources in the category which present a risk to public health ( those emitting in amounts greater than the safety threshold) would be required to install controls, even though the general policy is " maximum achievable technology everywhere." Again, there is a means to avoid regulatory costs which would be without public health benefit." VIII. 15 Comment: Four commenters ( 547, 548, 560, 595) supported the use of § 112( d)( 4) applicability cutoffs for both threshold and non threshold pollutants. Commenter 548 stated that the plain language of 112( d)( 4) does not distinguish between carcinogens and non carcinogens. Commenter 595 stated that nothing in CAA section 112( d)( 4) limits it to non carcinogens, and EPA should consider 112( d)( 4) whenever it sets emission standards for HAP regardless of health endpoint. Commenters 548, 595, and 560 stated that advances in risk assessment science indicate that some carcinogens may be threshold pollutants. Commenter 547 believes that a health threshold of one in one million cancer risk is appropriate for non threshold pollutants. VIII. 16 Comment: One commenter ( 565) believes that EPA could implement a CAA section 112( d)( 4) emissions limitation under both the first and third scenarios discussed in the preamble ( scenario 1: exempt low risk facilities emitting only threshold pollutants, scenario 3: exempt emission points at facilities that emit only threshold pollutants). However, the commenters believe that the use of a CAA section 112( d)( 4) emissions limit as described under the third scenario in the preamble would provide the maximum benefit of the CAA section 112( d)( 4) provision. Under this scenario, facilities that emit both threshold and nonthreshold pollutants could achieve exemption from MACT controls for threshold HAP emission points based on their ability to meet the associated health threshold for those HAP. Another possible use of the CAA section 112( d)( 4) emissions limitation that EPA discussed would apply to both threshold and nonthreshold pollutants. VIII. 17 Comment: Two commenters ( 574, 575) disagreed that § 112( d)( 4) can be interpreted to allow exemptions for individual sources. The commenters believe that § 112( d)( 4) applies to categories of sources. Commenter 575 understood CAA section 112( d)( 4) to allow the Agency to reduce the stringency of a MACT standard applicable to an entire category or subcategory based on a health threshold for a particular pollutant. VIII. 18 Comment: One commenter ( 567) stated that the plain meaning of § 112( d)( 4) 96 does not allow EPA to make MACT standard exemptions for individual sources. Commenter 567 believes that EPA has misinterpreted the provision in 112( d)( 4). Section 112( d)( 4) of the CAA does not state that EPA can use applicability thresholds " in lieu of" the CAA section 112( d)( 3) MACT floor requirements. The commenters interpreted CAA section 112( d)( 4) to state that health based thresholds can be considered when establishing the degree of the MACT floor requirements, but it should not be used to supplant the requirements established pursuant to CAA section 112( d)( 3). VIII. 19 Comment: One commenter ( 574) stated that CAA section 112( d)( 4) does not apply for source categories that emit carcinogens. VIII. 20 Comment: One commenter ( 586) stated that the concept of cancer exposure below a threshold is untried, and Congress clearly intended that carcinogens be considered nonthreshold pollutants. VIII. 21 Comment: One commenter ( 565) believes that EPA could accomplish the same outcome as a CAA section 112( d)( 4) emissions limitation if it applied an emissions limitation on nonthreshold pollutants using its inherent de minimis authority instead of a limit based on CAA section 112( d)( 4). VIII. 22 Comment: Regarding the use of a concentration based applicability threshold, commenter 567 stated that this is not what Congress intended in the CAAA of 1990. Congress mandated that the MACT floor be established as initial level of control. VIII. 23 Comment: One commenter ( 565) stated that in the preambles, EPA expresses uncertainty over whether it has the authority to subcategorize source categories based on risk. The commenter believes that EPA has ample authority, based on CAA sections 112( c)( 1) and 112( d)( 1), to subcategorize based on risk. Section 112( c)( 1) of the CAA states: " Nothing in the preceding sentence [ relating to following the NSPS program categories and subcategories] limits the Administrator's authority to establish subcategories under this section as appropriate." Thus, Congress allowed EPA discretion to subcategorize previously created categories, regardless of the criteria that EPA used to create the category in the first place, and to do so at any time. Section 112( d)( 1) of the CAA provides that EPA " may distinguish among classes, types and sizes of sources" when establishing MACT standards. The broad terms " classes," " types," and " sizes" indicate that Congress intended that EPA have broad discretion in establishing subcategories and do not preclude EPA from subcategorizing based on risk, since low risk sources could be considered a " class" or " type" of source. The commenter added that the only case to clarify this statutory language recognized the broad discretion it confers on EPA to create subcategories with different emission standards. Sierra Club v. Costle, 657 F. 2D 298 ( D. C. Cir. 1981). The Court noted, "[ t] he required finding that must underlie a variable standard is much broader than a mere determination that uniformity is not achievable." Id. at 321. On this basis, the Court expressly upheld EPA's subcategorization of coal fired power plants based on the sulfur content of fuel. More generally, the Sierra Club decision confirms EPA's discretion to set differentiated emissions standards for subcategories of sources, even in instances where the strictest standard may be achievable by all sources. VIII. 24 Comment: One commenter ( 575) did not see legal basis for creating a subcategory based on risk alone. VIII. 25 Comment: One commenter ( 574) stated that the only option that appears consistent with the CAA, does not create excessive work for State and local agencies, and may be 97 able to be based on science, is the subcategorization and delisting approach. However, the commenter added that the subcategories should be based on equipment or fuel use, not risk. The commenter added that a subcategory based on site specific risk creates a circular definition and does not make sense. The commenter also stated that subcategory de listing should occur before the compliance date so that facilities do not put off compliance in the hope or anticipation of delisting VIII. 26 Comment: One commenter ( 575) urged caution in the effort to define a permissible subcategory based upon technological differences that would then be susceptible to delisting under the extremely stringent delisting requirements of CAA section 112. VIII. 27 Comment: One commenter ( 574) stated that the preamble discussion of a lowrisk subcategory on the MACT floors for the entire category sounds like another valid reason not to mix the risk based and technology based standards development. The commenter added that EPA does not address how the " once in, always in" policy would apply. VIII. 28 Comment: One commenter ( 565) supported the concept described in the preambles regarding the establishment of the MACT floor based on the controls for the entire source category. The commenter agreed that considering controls for low risk subcategories could maintain the appropriate stringency of the MACT floor. Once the floor is established, facilities could demonstrate their inclusion in the low risk category that is subsequently listed. VIII. 29 Comment: One commenter ( 605) agreed that the MACT floor could be established for the entire source category and then facilities could be allowed to become part of a low risk subcategory in the future, after MACT standards are established. This would allow low risk facilities to use CAA section 112( c)( 9) without affecting the MACT floor. VIII. 30 Comment: One commenter ( 579) stated that EPA should add the reference values for acute exposure to Table 2 on page 77848 of the proposed rule so that facilities will be able to more accurately calculate their hazard indices when the health risk assessment guidance is implemented. VIII. 31 Comment: One commenter ( 567) agreed with EPA's choice to derive their data from IRIS, CAL EPA and ATSDR for its documentation for establishing risk based threshold and non threshold values. The commenter added that almost all HAP are being reviewed and reevaluated on a regular basis, and it would be inappropriate to single out formaldehyde and acetaldehyde at this time. The EPA can only rely on what is currently published and underwent either peer review or agency review. The issue of changing health based guideline values will always be a concern once health based regulations are promulgated. VIII. 32 Comment: One commenter ( 574) stated that EPA should consider formaldehyde and acetaldehyde as carcinogens unless a reassessment classifies them as threshold pollutants. VIII. 33 Comment: One commenter ( 565) stated that making an allowance for other exposures under CAA section 112 is not necessary to protect public health. The commenter added that consideration of exposures from other sources places a disproportionate burden on major sources. Legislative history does not support the consideration of exposures from other source types when setting risk based criteria. The commenter stated that multi pathway risk assessment should be required only for those HAP that have the potential for causing significant multi pathway exposure. VIII. 34 Comment: One commenter ( 527) stated that there is some question about whether formaldehyde produced by natural gas engines can be considered as a significant direct 98 source of formaldehyde to which people are exposed. An EPA report by D. Luecken estimates that 85 99 percent of the aldehydes in the atmosphere are due to atmospheric formation, not emissions. Commenter 527 stated that the population density adjacent to major sources of HAP should be considered. A more reasonable rule for formaldehyde should also consider the location of the source relative to current population and possibly a reasonable expectation of future population in the area. VIII. 35 Comment: One commenter ( 565) stated that uncertainty is already considered in the establishment of reference concentrations from which the hazard index ( HI) is derived. The commenter stated that the uncertainty factors used in the NATA are large, and because of the considerable uncertainty adjustments that are already applied, it is highly unlikely that an ample margin of safety would ever have to include more uncertainties than are already incorporated in the RfCs. In some cases, the uncertainty corrections are too conservative. VIII. 36 Comment: One commenter ( 548) stated that EPA should use reference concentrations ( RfCs) and reference doses ( RfDs) as the threshold for deciding whether a MACT standard for a specific pollutant is warranted. The RfCs and RfDs are set conservatively by first determining a NOEL and then reducing that level by an uncertainty factor. This method of setting RfCs and RfDs assures that public health is protected by " an ample margin of safety." Commenter 548 added that, as EPA suggests, the ample margin of safety for nonthreshold pollutants is a cancer risk that does not exceed one in one million. VIII. 37 Comment: One commenter ( 565) stated that EPA should clarify that sources wishing to use the CAA section 112( d)( 4) emissions limit must only demonstrate compliance with risk based thresholds for those HAP listed in Table 2 of the RICE proposal preamble. VIII. 38 Comment: One commenter ( 565) stated that hazard quotients for chemical mixes should not be summed to determine the HI unless the primary effects are on the same organ by the same mechanism; otherwise the risk will be overestimated. VIII. 39 Comment: One commenter ( 565) stated that all risk related provisions of CAA section 112 should be guided by the purpose of the ample margin of safety determination  namely, to account for uncertainty in the underlying health value. A HI equal to or greater than one should account for uncertainty and provide an ample margin a safety. Commenter 565 stated that The Report of the Commission on Risk Assessment and Risk Management provides further guidance and supports the commenters' contention that a HI equal to or greater than 1 should provide an ample margin of safety for a threshold HAP. VIII. 40 Comment: One commenter ( 565) stated that adoption of the Drinking Water Program's concept of a HI of 0.2 is not supportable. The commenter added that, at a minimum, before EPA could import the drinking water policy into air programs, the agency would need to evaluate the available scientific data   for the HAP of concern in each individual rulemaking   to determine wether the data justify a conclusion that 80 percent of the exposures to those pollutants come from sources outside the source category. VIII. 41 Comment: One commenter ( 574) stated that the HI is useful in evaluating sitespecific impacts, but choosing a generic HI ( some multiple of 1) for application to a wide range of sites is inappropriate. The commenter added that selection of an arbitrary multiple of 1 is not science, does not conform with CAA section 112( d)( 4) and does not protect public health. The commenter added that using background concentrations from NATA and a HI of 1 is 99 inappropriate because NATA information includes warnings that the information is useful for large scale planning purposes and not for local area assessment. VIII. 42 Comment: One commenter ( 567) evaluated the four potential options that EPA proposed to ensure that a risk analysis under CAA section 112( d)( 4) considers the total ambient air concentrations of all the HAPs to which the public is exposed. Option 1, which requires that the HI for all pollutants be no greater than 1, does not consider additional sources or background and is unacceptable. Option 3, which uses existing data such as the National Scale Air Toxics Assessment ( NATA) to determine background and requires that the HI be no greater than 1, is also unacceptable. The EPA has clearly stated at public meetings that the NATA is not to be used to make regulatory decisions. The NATA relies on data submitted to EPA voluntarily and has been reported to consistently underestimate measured concentrations. Until EPA requires that HAP inventories be submitted as proposed in the CERR, and the NATA conducts refined modeling around stationary sources, the NATA should not be considered for estimating background concentrations. Option 4, which allows individual facilities to monitoring the HAP backgrounds for use in their own analysis, will require oversight and evaluation by the States to ensure proper site selections and analytical methods and should not be considered. The commenters believe Option 2, which requires that the HI be no greater than 0.2, would be the only viable option at this time using a conservative risk screening analysis. However, the commenters did not endorse using any of the proposed threshold limit applicability methods to exempt process sources from NESHAP requirements. VIII. 43 Comment: One commenter ( 586) stated that in the case of RICE and boilers/ process heaters, which emit acrolien, there appears to be no reasonable limit ( that would allow sufficient protection between the contribution of a potentially affected source and the existing background concentrations of non carcinogens) since exposure to acrolien is predicted to be high almost everywhere in the country ( based on NATA). Uniformly applied NESHAP are necessary to move this country toward lower exposures to irritants like acrolien. VIII. 44 Comment: One commenter ( 574) stated that the selection of a 0.2 HI as a rough screening tool seems reasonable, although it is unsupported by any analysis. The commenter added that if a default HI is used, EPA should include a provision that would disallow the use to exclude a facility from MACT, now or in the future, if better background information is available that suggests that the default does not protect public health. The commenter, however, believes that the interpretation that includes the use of such a default to allow exemptions for individual sources is not supported by the CAA, and the expansion of the interpretation to include nonthreshold pollutants is in direct conflict with section 112( d)( 4) of the CAA. VIII. 45 Comment: One commenter ( 567) stated that the use of NATA to determine background concentrations is unacceptable. The EPA has clearly stated at a number of public meetings that NATA is not to be used to make regulatory decisions. VIII. 46 Comment: One commenter ( 586) stated that the proposal is critically flawed because risk based exemptions ignore the cumulative risk that comes from exposure to multiple air toxics sources ( e. g., hundreds of combustion engines and boilers within a city) and do not protect public health. Although many individual sources may pose a risk below a designated threshold, the accumulation of these pollutants can be hazardous. Addressing this problem will require a general reduction in air toxics emissions across large and small sources, not just those sources for which a high local risk can be demonstrated. The commenter stated that NATA 100 indicates that air toxics exposures are already high throughout the country. Commenter 586 stated that, because background risk is already too high, the inhalation margin allowed for an individual source would be zero, which leads back to Congress' decision that all HAP sources should take reasonable ( i. e., MACT) steps to reduce emissions. VIII. 47 Comment: One commenter ( 574) stated that when persistent biological toxicant or metal emissions are significant, ingestion and other pathways should be considered in the risk screening. VIII. 48 Comment: One commenter ( 567) stated that analyses like the concentrationbased applicability threshold approach do not address non inhalation exposures or adverse effects on the environment. Commenter 567 stated that allowing individual facilities to monitor the HAP backgrounds for use in their own analysis would require oversight and evaluation by State and local agencies to insure proper site selections and analytical methods and would be costly to administer and, therefore, not acceptable. VIII. 49 Comment: One commenter ( 567) stated, in response to EPA's request for comment on subcategorizing RICE having a capacity utilization of less than 10 percent, that this class of RICE would operate mostly in the summer months when the public is more likely to be impacted by the emissions. Acetaldehyde, acrolein, and formaldehyde all have documented shortterm acute health effects. The EPA has failed to identify short term health effects throughout any of the risk analysis proposals. Any subcategorization of these engines without controls is not protective of public health. The commenter added that any subcategorization of these RICE should include a permit requirement that these units operate less than 876 hours per year, and that this class of RICE could have less onerous monitoring requirements as a way to lower costs. NOTE: This comment is also included under applicability emergency/ limited use. VIII. 50 Comment: One commenter ( 529) stated that the proposal does not address ecological risk that may result from uncontrolled HAP emissions, especially in those areas with sensitive habitats but few people nearby to be exposed. VIII. 51 Comment: One commenter ( 565) support EPA's proposed tiered modeling approach, which begins with simple " look up tables" and progresses to more refined facilityspecific risk assessments. Commenter 565 stated that an initial simplified tier of risk assessment, such as look up table, nomograph, or equivalent, should be embedded in individual rulemakings. The commenters added that a guidance document should address two additional tiers of assessment: a conservative screening approach, and a flexible refined approach. Commenter 565 stated that a risk assessment guidance document should not attempt to address policy and regulatory decisions. Rather, regulatory goals and policies should be put forth within individual notice and rulemakings. Appropriate risk assessment endpoints of concern will also be established within these rulemakings. Commenter 565 stated that refined risk assessments ( 3rd tier) should allow for more accurate estimates of maximum individual risk, and could accomplish this through: ( 1) modeling ambient exposures to an actual human receptor location; ( 2) use of exposure factors or models; ( 3) use of realistic exposure assumptions based on site specific data ( residential tenure, etc.); and, ( 4) use of probabilistic analysis of uncertainty and variability. Commenter 565 stated that rulemakings that use source conducted risk assessment should 101 appropriately focus the initial scope of the assessment on the HAP, sources, and other parameters of concern through applicability criteria specified with the individual rulemakings. VIII. 52 Comment: One commenter ( 579) agreed that a tiered approach, including lookup tables, is a good idea for the RICE source category. The commenter also suggested that, for 2nd tier modeling, facilities be allowed to use any industry approved models for evaluating emissions and the corresponding health risks, because EPA approved modeling procedures usually are too conservative and tend to over predict emissions. VIII. 53 Comment: One commenter ( 526) believes that EPA should establish risk based applicability cutoffs for RICE by including lookup tables. However, because of the conservative assumptions outlined in the preamble, the commenter believes that the lookup tables would be of very limited value. In addition, very few facilities could probably take advantage of cutoffs based on health risks since standards apply only to RICE at major sources. VIII. 54 Comment: One commenter ( 574) stated that the State of Wisconsin uses a tiered approach that first allows sources to demonstrate compliance if their potential emissions, stack height, and exhaust direction are within the ranges provided in conservative lookup tables. The second tier allows facilities to provide site specific modeling to demonstrate compliance with ambient air standards at the property line. In general, the tiered approach has worked well in Wisconsin. VIII. 55 Comment: One commenter ( 567) stated that if EPA decides to pursue an up front risk analysis approach, it should not be a tiered approach. The development of generic risk screening approach under the CAA section 112( d)( 4) framework will need to be conservative, and the use of a ( non tiered) conservative approach would represent the least cost to the regulated community and would be the least time consuming for States reviewing the facility's application. VIII. 56 Comment: Two commenters ( 564, 565) stated that any risk based approaches should be consistent with the policies in development for the residual risk rules. Commenter 585 added that because the approaches used in the MACT rulemaking may set a precedent ( that could apply to the residual risk program), it is important for EPA to identify and address all of the issues associated with the risk based approaches. Commenter 565 stated that EPA should specify many of the procedures for facility specific risk assessments in guidelines rather than in the rules, because procedures set in rules could be seen as precedent setting and could impact the residual risk program. For example, the commenters believe that EPA should specify the threshold levels by which a source would be excluded from a rule, as well as any tier 1 lookup tables, in each individual rule. In contrast, the specifics for how sources should carry out tier 2 and tier 3 risk assessments should be left flexible in guidelines now under development by EPA for the residual risk program. VIII. 57 Comment: Two commenters ( 586, 499) stated that the tools needed to identify sources eligible for the risk based exemption would be the same tools necessary for a CAA section 112( f) residual risk assessment. It is the commenters' understanding that these tools are not yet ready for general use. Commenter 567 has serious reservations with EPA's apparent attempt to conduct an adhoc risk analysis for specific source categories by seeking comments on the specific elements to be included in the risk analysis and do not believe these rulemakings are an adequate forum to develop this risk analysis process. The commenter believes that any risk analysis conducted by 102 the EPA must adhere to the risk assessment principles outlined in the Residual Risk Report to Congress. VIII. 58 Comment: Two commenters ( 499, 550) stated that the proposal will place a very intensive resource demand on State and local agencies to review source's risk assessments. State and local agencies may not have expertise in risk assessment methodology or the resources needed to verify information ( e. g., emissions data and stack parameters) submitted with each risk assessment. VIII. 59 Comment: One commenter ( 574) stated that they are concerned about the potential cost and workload that risk provisions would place on permitting authorities. The commenter added that the permitting authorities would need to either perform or verify the risk analyses, and that diverting State and local resources to focus on presumably insignificant sources would detract from efforts associated with significant sources. The commenter pointed out some of the specific items that would add burden to the State and local agencies, including data verification for background concentrations and ongoing assurance that low risk facilities remain low risk. VIII. 60 Comment: Because EPA understands the difficulty with risk assessments, commenter 572 found it perplexing that EPA believes such analyses at the State and local levels would be an efficient way to protect public health. VIII. 61 Comment: One commenter ( 567) noted that for EPA to conduct an up front risk analysis, the procedure would need to be conducted using the most conservative stack parameters, with a hypothetical facility fence line to satisfy the many impact scenarios that could occur. If EPA intends to have the affected industries conduct the analysis, then EPA must consider the cost incurred by States which may lack the necessary expertise to evaluate and review these analyses. The current proposal is silent on these implementation and cost issues. VIII. 62 Comment: Two commenters ( 586, 529) stated that the proposal is critically flawed because implementing the exemption program will require significant State resources to review risk assessments prepared by sources trying to exempt themselves from MACT. This review will require expertise in risk assessment methodology lacking in many States positioned to implement MACT standards through the title V permit program. It will also be necessary for States to verify extensive emissions and stack information used in the risk assessment to ensure that the assessment has been done properly. Because the procedures for preparing these risk assessments on a large scale basis and for assessing the potential adverse effects of the pollutants emitted ( e. g. taking into account existing background and looking for a threshold level for carcinogens) are untried and will require extensive debate and review to launch, even more time and resources will be needed. Commenter 586 expressed concern about exempting a facility based on limited emission data if EPA established a subcategory listing low risk sources. VIII. 63 Comment: One commenter ( 605) expressed concern that the risk based delisting would be resource intensive. VIII. 64 Comment: One commenter ( 567) stated that if EPA intends to have the affected industries conduct the analysis, then EPA must consider the additional cost incurred by smaller sources to do the analysis. VIII. 65 Comment: One commenter ( 574) stated that title V permits seem to be the obvious implementation tool, and that title V permits could provide enforceable limitations, appropriate recordkeeping requirements, and periodic review upon renewal. The commenter 103 added that since the rule would apply only to major sources, title V permits already are required and would not be an added burden. The commenter added that title V could be used to implement applicability cutoffs, but that the workload involved with the options requiring modeling, ambient monitoring, or other means to establish background concentrations would be a hindrance to any implementation mechanism. The commenter stated that with respect to potential risk based provisions, monitoring is more useful for demonstrating non compliance than compliance because the regulation would apply to potential emissions under any weather conditions, whereas monitoring reflects current weather and emission conditions. VIII. 66 Comment: One commenter ( 536) supported EPA efforts to determine alternative MACT setting methodologies but strongly recommended that these be pursued separately from this rulemaking. This will provide for timely issuance of final RICE and Boiler/ Process Heater MACT standards relative to the settlement deadline. VIII. 67 Comment: One commenter ( 499) stated that it is evident that the proposed approach to risk based exemptions would require extensive debate and review in order to launch, which will further delay promulgation of the remaining MACT standards. Commenter 499 stated that delays could be exacerbated by litigation following legal challenges to the rules, and such delays would trigger the MACT hammer, which would unnecessarily burden the State and local agencies and the industries. The commenter concluded that, obviously, further delay is unacceptable. VIII. 68 Comment: One commenter ( 586) stated that the risk assessment exemption could significantly delay compliance with MACT for sources trying unsuccessfully to opt out using the exemption. VIII. 69 Comment: One commenter ( 575) supported efforts to lower the costs to industry but expressed concern about the legal viability of the risk based approaches discussed in the proposal. The concerns are practical and acute, in that if the rules are invalidated the MACT " hammer" could fall, subjecting sources to case by case MACT determinations. Such a result would not serve the interests of industry or any other stakeholders. VIII. 70 Comment: Two commenters ( 529, 550) stated that the proposed approaches will jeopardize expeditious promulgation of remaining MACT standards. The commenters noted that according to a recently proposed EPA rule regarding CAA section 112( j), the regulated community and State and local agencies would have to proceed with part 2 permit applications, followed by case by case MACT, if EPA misses the newly agreed upon MACT deadlines by as little as 2 months. This would be time consuming, costly, and burdensome for both regulators and the regulated community. VIII. 71 Comment: One commenter ( 567) endorsed the comments submitted by commenter 499.

Response: The preamble to the proposed rule requested comment on whether there might be further ways to structure the rule to focus on the facilities which pose significant risks and avoid the imposition of high costs on facilities that pose little risk to public health and the environment. Specifically, EPA requested comment on the technical and legal viability of three risk based approaches: ( 1) an applicability cutoff for threshold pollutants under the authority of CAA section 112( d)( 4); ( 2) subcategorization and delisting under the 2 190 authority of CAA 2See 68 FR 1276 ( January 9, 2003) ( Plywood and Composite Wood Products Proposed NESHAP) and Docket ID No. A 98 44, Item No. II D 525 ( White papers submitted to EPA outlining the risk based approaches).

104 sections 112( c)( l) and 112( c)( 9); and ( 3) a concentration based applicability threshold. 2 The EPA indicated that it would evaluate all comments before determining whether either approach would be included in the final rule. As presented above, numerous commenters submitted detailed comments on these risk based approaches.

Based on EPA's consideration of the comments received and other factors, EPA has decided not to include the risk based approaches in the final rule. The risk based approaches described in the proposed rule and addressed in the comments EPA received raise a number of complex issues. In addition, EPA must issue the final rule expeditiously, because the statutory deadline for promulgation has passed and EPA has agreed to a binding schedule in a consent decree entered in Sierra Club v. Whitman, Civil Action No. 1: 01CVO1537 ( D. D. C.). Given the range of issues raised by the risk based approaches and the need to promulgate a final rule expeditiously, EPA feels that it is not appropriate to include any risk based approaches in the final rule. Nonetheless, EPA expects to continue to consider risk based approaches in connection with other proposed NESHAP where EPA has described and solicited comment on such approaches. Finally, while EPA is not including risk based approaches in the final rule, EPA has included a number of other measures that it expects will reduce the costs and burdens on the affected sources.

IX. EMISSIONS DATA A. CSU Testing IX. A. 1 Comment: One commenter ( 537) contended that data from testing of 2SLB and 4SLB should be disallowed. The commenter provided the following reasons:

( 1) The range of engine operating conditions in the testing of the 2SLB engine and quite probably the 4SLB engine are far leaner than the leanest engine in the pipeline RICE fleet. This is indicated by the extremely low NOx emissions.

( 2) Engines equipped with pre combustion chambers operating extremely lean are not typical examples of the 2SLB and 4SLB fleet.

( 3) The range of exhaust temperatures, air/ fuel ratios, and exhaust O 2 are not typical of 2SLB and 4SLB.

( 4) Engines were laboratory research engines. They were not equipped with turbochargers, but with turbocharger simulators that do not have the same traits as 105 a turbocharger.

( 5) Found no information in the piping diagrams of insulation on the ducting and manifolds leading from the engine to the catalyst. Certainly all ducting is insulated in industry. The EPA needs to determine if any insulation was in place.

( 6) The following excerpt from page 77840 of the proposed rule is not true: " In general, higher exhaust temperatures lead to better catalyst performance. This difference in temperatures is a function of the inherent design of these engine types and cannot be controlled by the operator." By controlling the air/ fuel ratio of the engine, the exhaust gas temperature, and thus the catalyst inlet temperature, can be precisely controlled.

( 7) If HAP data from the 2SLB and 4SLB testing is allowed to stand, then this testing must become the definitive work on all pollutants tested as well, including NOx. The NOx data should be forwarded to the criteria pollutant group.

One commenter ( 530) disagreed that the engine at CSU is representative of 2SLB engines in the industry due to low NOx levels, high levels of oxygen, and low exhaust temperatures. The 2SLB engine was running considerably leaner than similar model engines at similar conditions.

Response: The EPA compared these parameters to other 2SLB and 4SLB engines for which EPA has information in the Emissions Database. The NOx and oxygen levels and exhaust temperatures for the 2SLB and 4SLB engines tested at CSU are similar to those observed for other non CSU 2SLB and 4SLB engines in the Emissions Database. This analysis is presented in the memorandum entitled " Engine Operation at Colorado State University" available from EPA's Edocket Website ( Docket Number OAR 2002 0059 ( A 95 35)). The EPA feels that the 2SLB and 4SLB engines tested at CSU are representative of 2SLB and 4SLB engines in the industry. As far as insulation is concerned, the catalyst inlet temperature recorded should represent catalyst performance at that temperature regardless of insulation presence or absence. It should be remembered that the MACT standard for new sources under CAA section 112( d) is based on the level of control of the best controlled similar source.

IX. A. 2 Comment: One commenter ( 551) was concerned that the limited data used to establish the standard for new 4SLB engines using oxidation catalyst is not representative of typical engine operating conditions in the field for varied engine and catalyst manufacturers.

Response: The EPA agrees with the commenter that it had limited data but disagrees with the commenter that the testing was not representative. As explained in the preamble to the proposed rule, the testing conducted at CSU to obtain HAP and CO emissions data was a joint EPA industry effort. Prior to testing, EPA and industry developed a list of engine operating parameters that were known to vary throughout the U. S. for each type of engine. The engines and control devices were tested at typical engine conditions in which these operating parameters were varied. The variations in the emission reduction results for each engine type are due to the 106 variability of the engine and control system and include a representation of the performance of the best controlled source for new engines. Equipment manufacturers, catalyst vendors, owners and operators, and EPA agreed that the tests conducted at CSU were representative of typical engine operating conditions in the field for varied engine and catalyst manufacturers.

IX. A. 3 Comment: One commenter ( 530) stated that the testing did not include in its test protocol dynamic spiking that is required in Method 320 which leaves some question to the integrity of the sample measured in the test program.

Response: An alternative quality assurance procedure was proposed and followed resulting in data of sufficient quality. The entire FTIR sampling analysis system was validated on a 2SLB engine by a dynamic spiking of formaldehyde, acrolein, and acetaldehyde. The data were assessed following Method 301 criteria. Then, on a daily basis, the analyzer was checked for linearity and alignment, a diagnostic or transfer standard consisting of the CO was used to confirm accuracy, a second diagnostic standard consisting of CO 2, carbon monoxide, methane, and NOx was introduced using the same procedure. Then to check sampling system integrity, a formaldehyde standard was introduced directly into the instrument and a reading obtained, then it was introduced into the sampling system at the sample probe upstream of the filter and another reading obtained. The sampling system pass/ fail criterion was 100 percent ± 10 percent of the direct to the analyzer reading. Finally, the diagnostic and system integrity procedures were repeated at the end of each day testing. This procedure resulted in data of sufficient quality.

B. Other IX. B. 1 Comment: One commenter ( 552) recommended that EPA establish an optional demonstration program that would allow the regulated community to submit data demonstrating the actual relationship between formaldehyde emissions and CO reduction levels. The intent of this compliance option is to allow industry to demonstrate compliance with the proposed formaldehyde standard established in the rule and to validate a corresponding CO reduction percentage for a particular RICE system. The CO reduction percentage could then be used for monitoring and compliance purposes instead of the CO reduction percentage currently proposed in the rule. For example, an engine manufacturer should be allowed to demonstrate that a specific 4SLB engine model and associated emissions control device can meet the 14 ppmvd formaldehyde emissions limit at a corresponding CO reduction rate of 70 percent. With this demonstration, the 70 percent CO reduction would serve as a reliable and justified compliance emissions limit for all operators installing this engine system, and the operator could then monitor CO reduction to assure compliance.

Response: The EPA feels that the CO percent reduction may not be an appropriate measure for a source that complies with the formaldehyde concentration emission limitation. Carbon monoxide reduction may not correspond closely to formaldehyde concentration, depending on the circumstances, and should therefore not be allowed to show compliance with the formaldehyde concentration emission limitation. The reduction of CO does however relate to the reduction of HAP, which is why EPA has included a compliance option for lean burn and CI 107 engines in the final rule the option to comply with the CO percent reduction standard. Another reason why it would not be appropriate to allow sources to conduct their own demonstration program to demonstrate the relationship between formaldehyde emissions and CO reduction levels, is that such demonstration programs could lead to different requirements for different engines. In addition, in the proposed rule, EPA specified that 2SLB, 4SLB, and CI engines had to either meet the CO emission reduction requirement if using an oxidation catalyst, or the formaldehyde concentration requirement if using means other than an oxidation catalyst. In the final rule, EPA is allowing flexibility; sources can meet either emission limitation regardless of which control technique is applied. For lean burn and CI engines that means that anyone can comply with the CO percent reduction requirement or the formaldehyde concentration emission limitation. Sources must test the formaldehyde concentration and show that they meet the applicable formaldehyde concentration limit, if that is the emission limitation they wish to demonstrate compliance with.

X. OTHER A. General Provisions X. A. 1 Comment: One commenter ( 565) said that it is not clear whether § § 63.5( a), 63.5( b)( 3) and 63.5( b)( 4) applies to the construction or reconstruction of exempted RICE units under § 63.6590( b). There is a conflict in requirement indication between Table 8, item 5 of the proposed rule and § § 63.6590( b) and 63.6596( c). The commenter supported excluding exempted units from these requirements in the General Provisions.

Response: The units listed under § 63.9590( b) of the proposed rule are not exempted from the rule. The units listed in this section are stationary RICE with limited requirements in the rule, but these units are not exemptions. Stationary RICE less than or equal to 500 HP are not covered by the final rule. This was discussed in response to comment I. A. 2 and the final rule has been written accordingly. The EPA believes the commenter is referring to § 63.9595( c) and not § 63.6596( c), which is a section that does not exist. Sections 63.5( a), 63.5( b)( 3), and 63.5( b)( 4) apply to the units listed in § 63.6590 of the final rule.

X. A. 2 Comment: One commenter ( 565) stated that derivative General Provisions requirements that depend on a SSMP should be deemed " not applicable."

Response: The rule requires sources to develop and maintain a SSMP. Therefore, derivative General Provisions requirements that depend on a SSMP should not be deemed " not applicable."

X. A. 3 Comment: One commenter ( 565) requested that EPA clarify that applicability determinations are not required for exempted units. There is a conflict between the indications in Table 8, item 75 of the proposed rule and in particular § 63.10( b)( 3), and the recordkeeping exclusion in § 63.6590( b). Also, § 63.6595( c) may be in conflict with the exclusion in 108 § 63.6590( b).

Response: The EPA believes the commenter is referring to the units listed in § 63.6590( b). These engines are not exempted units, but are units with limited requirements in the rule. The EPA disagrees with the commenter. Applicability determinations are required for these units.

X. A. 4 Comment: One commenter ( 565) asked that EPA clarify retesting requirements on new sources. Section 63.6610 is ambiguous on the General Provisions requirement for some new sources to retest 3 years after promulgation in § 63.7( a)( 2)( ix). Table 8, item 24, of the proposed rule does not clarify the issue.

Response: Section 63.7( a)( 2)( ix) of the General Provisions discusses performance test dates if the promulgated standard is more stringent that the proposed standard. Sources that commenced construction or reconstruction between the proposal and promulgation have the option to demonstrate compliance with either the proposed or the promulgated standard. If the owner or operator chooses to comply with the proposed standard initially, the owner or operator must conduct a second performance test within 3 years to demonstrate compliance with the promulgated standard. Since the promulgated standard in some cases is more stringent than the proposed standard, EPA has specified in § 63.6610( c) of the final rule that sources that commenced construction or reconstruction between the proposal and promulgation have this option.

X. A. 5 Comment: One commenter ( 565) stated that § 63.1( b)( 2) is a reserved paragraph.

Response: The commenter is correct that § 63.1( b)( 2) is a reserved paragraph. However, EPA does not feel it is necessary to list all the individual sections of § 63.1 in Table 8 of the final rule, and has therefore not noted in Table 8 of the final rule that § 63.1( b)( 2) is a reserved paragraph.

X. A. 6 Comment: One commenter ( 565) provided comments on § 63.1( b)( 3): Except § 63.1( b)( 3) does not apply to exempted units per § § 63.6590( b)( 1) and ( 2). The commenter also noted conflict of § § 63.6590( b)( 1) and ( 2) with § 63.6595( c) that is created by this item in Table 8 of the proposed rule.

Response: The units listed under § 63.6590( b) are not exempted. These units are stationary RICE with limited requirements in the rule. Section 63.1( b)( 3) applies to the units listed in § 63.6590( b).

X. A. 7 Comment: One commenter ( 565) had a comment regarding § 63.1( c)( 1): Subpart ZZZZ should clarify the applicability of each paragraph of subpart A to sources subject to subpart ZZZZ. Section 63.1( c)( 2) regarding title V permit requirements for area sources should not apply to the subpart since area sources are not subject to subpart ZZZZ. Sections 63.1( c)( 3)( 4) are reserved paragraphs. 109 Response: The EPA does not think it is necessary to clarify the applicability of each paragraph in Table 8 of the final rule. The EPA feels the manner in which the sections are presented is sufficient.

X. A. 8 Comment: One commenter ( 565) referred to § 63.1( c)( 5) where the commenter stated that EPA should clarify § 63.1( c)( 5) does not apply if the affected source only includes exempt RICE units in § § 63.6590( b)( 1) and ( 2). A reference to this exclusion should also be added at § 63.6595( b). Otherwise, EPA should add § 63.1( c)( 5) as a required notification in § § 63.6590( b)( 1) and ( 2).

Response: The stationary RICE listed in § § 63.6590( b)( 1) and ( 2) of the final rule are not exempt units, but are units with limited requirements in the rule. The units listed in § 63.6590( b)( 3) of the final rule are covered by the rule but have no specific requirements. Section 63.1( c)( 5) therefore applies to these sources as well as to other affected sources with emission limitations and other requirements. The EPA has not made the change recommended by the commenter.

X. A. 9 Comment: One commenter ( 565) had several comments regarding the General Provisions table of the proposed rule and provided the following suggested revisions:

§ 63.4: EPA should clarify conversion of a rich burn RICE to a lean burn is not circumvention.

§ 63.5( a): Clarify " Except for exempted units in § 63.6590( b)."

§ 63.5( b)( 3): Clarify " Except for exempted units in § 63.6590( b)."

§ 63.5( b)( 4): Clarify " Except for exempted units in § 63.6590( b)."

§ 63.5( d): Clarify " HAP identification is required only for formaldehyde under subpart ZZZZ."

§ 63.5( e): Clarify " Note: Engine substitution does not constitute construction or reconstruction."

§ 63.6( c)( 5): The EPA should incorporate the default in this paragraph into the RICE rule ( 3 year compliance period).

§ 63.6( e)( 1)( 2): Clarify, " Yes, except there is no duty to comply with an emission limitation during SSM." Note that ( 2) is a reserved paragraph.

§ 63.6( e)( 3): Agrees but notes discrepancies with other proposal citations.

§ 63.7( e)( 2): OK. Note the label for this paragraph is the same as the preceding 110 paragraph.

§ 63.8( a)( 4): Subject should be changed to monitoring for control devices.

§ 63.8( c)( 1)( iii): This paragraph refers to SSMP for CEMS and points back to § 63.6( e)( 3) for which the answer above is No. The EPA should change answer here to " No."

§ 63.9( b)( 1)( 5): OK but ( 3) is reserved.

§ 63.9( h)( 1)( 6): OK but ( 4) is reserved.

§ 63.10( b)( 2)( i)( v): The EPA should clarify that SSMPs are not required and should clarify that § 63.10( b)( 2)( iv) and ( v) are not applicable.

§ 63.10( c): OK except ( c)( 2)( 4) and ( 9) are reserved and ( 15) is not applicable since it refers to an SSM plan.

§ 63.10( d)( 5): A No response to § 63.10( d)( 5)( ii) ( immediate reporting) should be indicated consistent with EPA's not requiring an SSMP.

§ 63.10( e)( 3): § 63.10( 3)( i)( C) is reserved. The commenter requests a No response to § 63.10( e)( 3) consistent with the comment to substitute work practice requirements for operating limitations.

Response: Rich burn is defined by the manufacturer's intent. A conversion of a rich burn engine to a lean burn engine would therefore not change the classification of the engine for purposes of the final rule, unless the conversion took place prior to December 19, 2002 and the engine was modified with passive emission control technology for NOx ( such as pre combustion chambers). The EPA has written the definition of a rich burn engine in the final rule as " any fourstroke spark ignited engine where the manufacturer's recommended operating air/ fuel ratio divided by the stoichiometric air/ fuel ratio at full load conditions is less than or equal to 1.1. Engines originally manufactured as rich burn engines, but modified prior to December 19, 2002 with passive emission control technology for NOx ( such as pre combustion chambers) will be considered lean burn engines. Also, existing engines where there are no manufacturer's recommendations regarding air/ fuel ratio will be considered a rich burn engine if the excess oxygen content of the exhaust at full load conditions is less than or equal to 2 percent."

As previously indicated, the units listed in § 63.6590( b) are not exempt units but are stationary RICE with limited requirements. These units are affected sources and are subject to the rule. Sections 63.5( a), 63.5( b)( 3), and 63.5( b)( 4) apply to the units listed in § 63.6590( b).

The EPA disagrees with the commenter that it should clarify that HAP identification is required only for formaldehyde under subpart ZZZZ in Table 8 of the final rule. Section 63.5( d)( 1)( ii)( H) 111 of the General Provisions requires that the type and quantity of HAP emitted by the sources, be included in the application for approval or construction or reconstruction. Sources should use the units and averaging times specified for formaldehyde for all HAP in the identification of HAP expected to be emitted. The requirement of section 63.5( d) is consistent with requirements implemented for other promulgated rules.

Regarding the comment on § 63.5( e), EPA contacted the commenter for clarification. The commenter stated that its suggestion for this clarifying note refers to its position, explained in comment I. A. 5, that it feels that an engine that was built before December 19, 2002 should be considered an existing source even though it may be installed after that date and could be deemed a new source. The commenter stated that the reason for suggesting that such units be considered existing sources, is that facilities may have ordered and assembled engines before December 19, 2002, that more closely resemble the technology EPA evaluated for setting the existing MACT floor, and thus these engines could become obsolete simply because they have been kept in reserve waiting to be used. The commenter used the word " engine substitution" as a way of avoiding the word reconstruction, which has a particular legal connotation. The EPA feels that this comment was sufficiently addressed in response to comment I. A. 5. The EPA also feels that any replacement engine needs to meet the full requirements of the final rule applicable to that engine, because even similar engines can have different emission characteristics.

The EPA agrees with the commenter regarding § 63.6( c)( 5) and feels it is appropriate to provide existing area sources that become major sources 3 years to comply with the final rule. This has been specified in the final rule in § 63.6595( b). Any new or reconstructed stationary RICE must be in compliance with the final rule when the area source becomes a major source of HAP.

Regarding § 63.6( e)( 1) the EPA agrees with the commenter but does not feel it is necessary to clarify this in Table 8 of the final rule. The EPA has noted in Table 8 of the final rule that § 63.6( e)( 2) is a reserved paragraph. The EPA acknowledges that § 63.6( e)( 3) was inconsistent with other citations in the proposal. However, EPA does not agree with the commenter that a SSMP is not required. The EPA has written Table 8 of the final rule to indicate that a SSMP is required. The subject in Table 8 of the final rule for § 63.7( e)( 2) is " Conduct of performance tests and reduction of data." The EPA agrees with the commenter regarding the subject of § 63.8( a)( 4), which will be " Monitoring for control devices." The EPA disagrees with the commenter that the answer to § 63.8( c)( 1)( iii) should be " No" instead of " Yes." As previously indicated, EPA has specified in the final rule that a SSMP is required. The EPA has therefore not made this change in Table 8 of the final rule.

The EPA has noted in Table 8 of the final rule under § 63.9( b)( 1)( 5) that § 63.9( b)( 3) is reserved. The EPA has also noted in Table 8 of the final rule under § 63.9( h)( 1)( 6) that § 63.9( h)( 4) is reserved.

A SSMP is required under the final rule. The EPA has therefore not made the change to § 63.10( b)( 2)( i)( v) that the commenter suggested. All sections of 63.10( c) are applicable since EPA is requiring a SSMP. The EPA has noted in Table 8 of the final rule that § 63.10( c)( 2)( 4) 112 and ( 9) are reserved. The EPA is requiring immediate SSM reports only when actions addressing the startup, shutdown, or malfunction were inconsistent with the SSMP. The EPA has made this notation in Table 8 of the final rule under § 63.10( d)( 5). The EPA assumes the commenter means that § 63.10( e)( 3)( i)( C) is a reserved paragraph and not § 63.10( 3)( i)( C). The EPA has noted in Table 8 of the final rule that § 63.10( e)( 3)( i)( C) is a reserved paragraph. The EPA disagrees with the commenter's request of a No response to § 63.10( e)( 3). The EPA has not made this change.

B. Other X. B. 1 Comment: Five commenters ( 542, 551, 554, 556, 587) asserted that the basis for any size threshold should be expressed in site rated HP as opposed to manufacturer's nameplate HP. One commenter ( 587) gave the following reasons:

( 1) The database used by EPA to determine the MACT floor provisions likely includes the site rated HP, based on the facility's air permit;

( 2) Stationary RICE are typically identified by site rated HP, rather than manufacturer's nameplate HP in the facility's title V permit and not all engines have HP on the nameplate; and ( 3) Federal Energy Regulatory Commission certified HP for natural gas transmission facilities are issued based on site rated HP.

Response: The EPA contacted one of the commenters who submitted this comment and also an engine manufacturer. Information received from both sources indicated that there may be differences between site rated HP and the manufacturer's nameplate rating. Factors such as altitude, temperature, fuel, etc. affect what the site rated HP will be for the engine at a specific location. Some manufacturers include the specific site rating on the nameplate of the engine, which is a HP rating which has been adjusted to account for the characteristics of the location the engine is installed at as well as other parameters affecting the engine rating. For these reasons, EPA agrees with the commenter that it is appropriate to use the site rated HP as opposed to the manufacturer's nameplate rating for the size applicability criteria, because relying on the manufacturer's nameplate rating may not be representative of the capability of the engine on site. The EPA has specified this in the final rule.

X. B. 2 Comment: Four commenters ( 542, 554, 556, 587) asked that EPA include nonaggregation provisions for transmission and storage facilities for the Transmission & Storage ( T& S) MACT.

Response: The EPA has incorporated this comment in the final rule. The nonaggregation provisions for transmission and storage facilities from the Natural Gas Transmission and Storage MACT ( 40 CFR part 63, subpart HHH), which are found in the definition of major source in that subpart, are as follows: 113 ( 1) Emissions from any pipeline compressor station or pump station shall not be aggregated with emissions from other similar units, whether or not such units are in a contiguous area or under common control; and ( 2) Emissions from processes, operations, and equipment that are not part of the same natural gas transmission and storage facility, as defined in this section, shall not be aggregated.

The non aggregation provisions in ( 1) above were already included in the proposed definition of major source for the RICE NESHAP and have been retained in the final rule. The non aggregation provisions in ( 2) above have also been added to the definition of major source for the RICE NESHAP.

X. B. 3 Comment: Five commenters ( 542, 549, 554, 556, 587) requested that EPA include the provisions to calculate potential emissions for storage facilities from the T& S MACT.

Response: The EPA agrees with the commenters and has incorporated their comment in the final rule by modifying the definition of potential to emit in the final rule to include the following:

" For oil and natural gas production facilities subject to subpart HH of this part, the potential to emit provisions in § 63.760( a) may be used. For natural gas transmission and storage facilities subject to subpart HHH of this part, the maximum annual facility gas throughput for storage facilities may be determined according to § 63.1270( a)( 1) and the maximum annual throughput for transmission facilities may be may be determined according to § 63.1270( a)( 2)."

X. B. 4 Comment: Two commenters ( 582, 586) asked that EPA list diesel PM as a HAP. Commenter 582 stated that if EPA fails to act on its own initiative, the commenter will submit a formal listing petition to EPA. Accordingly, the commenter urged EPA to require PM standards for all stationary diesel RICE. Reduction of diesel PM through the use of PM traps on diesel RICE is highly cost effective and will help protect public health from the harmful effects of diesel PM. The commenter provided extensive details on the health effects of diesel PM. Commenter 586 recommended including diesel particulate matter in this MACT and including limits and control measures.

One commenter ( 546) stated that because the rule does not address diesel PM, the rule requirements are not sufficient to meet the risk reduction goals of the Urban Air Toxic Strategy. The commenter stated that the rule is not health protective because it only regulates organic gases and ignores diesel PM. The rule should allow State and local agencies to regulate diesel PM as a more health protective alternative for addressing the risk from diesel exhaust. The commenter stated that the cancer unit risk factor for diesel PM in 50 times greater than that for formaldehyde. Major health agencies agree that adverse human health effects result from environmental exposure to diesel PM exhaust. From a public health perspective, focusing on diesel PM as a surrogate for whole diesel exhaust is a more protective approach compared to focusing only on organics as 114 proposed.

Response: The EPA acknowledges the comments on this issue. However, EPA is not prepared at this time to list diesel PM as a regulated HAP, at least not in the context of the final rule. The EPA proposed the rule for the purposes of promulgating regulations for emissions from stationary RICE that were already listed under section 112 of the CAA. While EPA did mention the diesel exhaust issue, EPA did not include any detailed discussion on the separate issue of whether any additional pollutants should be added to the list of regulated pollutants under CAA section 112. The decision regarding whether to list diesel PM entails several significant issues that have not been discussed in the context of the final rule. This includes the issues of what adverse health effects are related to diesel PM, what components of diesel exhaust should be regulated, whether the regulation of particulate matter as a criteria pollutant is relevant, and other issues. Therefore, it would be inappropriate to take final action on this comment in the context of the final rule. The EPA discussed DPF which can reduce PM in response to comment IV. C. 1. The EPA will be addressing the Urban Air Toxics strategy implications of RICE HAP emissions in a separate rule scheduled to be completed in 2007.

X. B. 5 Comment: One commenter ( 579) urged EPA to go through rule language and streamline the requirements wherever possible to reduce the burden on both the equipment operators and the regulatory personnel including EPA who must process many documents to implement the proposed rule. At the minimum, many of the requirements should be re cast into flow charts so that all the requirements for each type of engine are shown sequentially.

Response: The EPA has tried to streamline the requirements in the final rule as best as possible. However, EPA has not included flow charts in the final rule. The EPA feels that the regulatory text and tables sufficiently indicate the requirements of the final rule. Displaying all the requirements for each type of engine separately is repetitive and not necessary.

X. B. 6 Comment: One commenter ( 564) stated that the Agency should further review the rule to reduce the cost and regulatory burden aspects of the rule that provide no significant environmental benefit. With all the reports that are sent in, a question by the commenter was " are these reports regularly reviewed by regulatory Agencies?" If not, and the commenter's experience suggested they are not, then reporting should be simplified. Some considerations to reduce the ongoing cost of the RICE MACT: Develop a regulatory option to focus on the facilities that pose significant risks and avoid facilities that pose little risk. Eliminate the operation limitations that relate to catalyst pressure drop and temperature differential.

Response: The EPA feels it has done what it can to reduce the cost and regulatory burden aspects of the rule that provide no significant environmental benefit.

X. B. 7 Comment: Two commenters ( 526, 579) expressed concern with the overall extended timeframe of the approval process for performance tests and other procedures petition requests ( 67 FR 77862). The timeframes are compounded by the title V environment of public review and comment and EPA review of significant permit revisions. This in turn is further 115 exacerbated by the pre approval requirement at § 63.6620( f). All these layered requirements should be re reviewed by EPA comprehensively and streamlined to reduce the burden or regulated entities and regulators. The existing title V framework including periodic monitoring should be relied upon to the maximum extent possible to minimize duplicate and redundant requirements under this proposed MACT.

Response: The EPA has performed a thorough review of the requirements and feels it has established a rule that is appropriate and that has adequately considered the impact on regulated entities and regulators.

X. B. 8 Comment: One commenter ( 565) stated that recent court decisions provide EPA with significant flexibility when promulgating MACT standards. During the period of the RICE proposal development, the D. C. Circuit Court of Appeals issued two decisions  National Lime and CKRC  that EPA must consider when establishing NESHAP. These decisions provide significant guidance to the Agency on the scope of its rulemaking and the methodology that EPA must consider before it promulgates a final rule. While placing certain restrictions on EPA's authority and floor determinations, the commenter stated that EPA still retains significant amount of flexibility in setting MACT emission limitations.

Response: The EPA agrees generally with the comment that EPA has significant flexibility in promulgating MACT standards.

X. B. 9 Comment: One commenter ( 536) stated that EPA has entered into a proposed settlement with the Sierra Club regarding those MACT standards for which the Agency did not finalize rules by the statutory MACT hammer deadline. The EPA consequently proposed a twopart extended case by case MACT application process under section 112( j) of the CAA, with part 1 due May 15, 2002 and part 2 due May 15, 2004. Accordingly, the Sierra Club challenged the 2 year window for submission of part 2 case by case MACT applications. The current settlement with Sierra Club provides for a revised part 2 application deadline for RICE MACT of April 28, 2004. The commenter stated that submittal of part 2 case by case MACT applications will be overly burdensome for both affected sources and State regulatory agencies as well as could result in inconsistent MACT determinations to individual applicants. This part 2 deadline would only apply if EPA misses the deadline for final MACT promulgation 60 days before April 28, 2004. Therefore, the commenter urged the EPA to ensure timely finalization on the proposed RICE MACT standards prior to the relevant settlement trigger date.

Response: The EPA also wants to see timely finalization of the rule. The EPA has done everything possible to ensure that the final rule is completed on time, which will result in part 2 applications not being required.

X. B. 10 Comment: One commenter ( 594) stated that the Colorado Air Quality Control Commission, the policy and rulemaking entity in Colorado, looked at engines in 1993 and again in 2002 and has established a comprehensive scheme for threshold reporting of emissions of criteria pollutants and HAP on air pollutant emission notices ( APEN) and threshold levels for permit for 116 criteria pollutants. Colorado's Regulation No. 3 ( 5 CCR 1001 5) Part A. Section II. sets forth the APEN requirements. Air pollutant emission notices reporting requirements for HAP emissions are based on the relative toxicity of the substance and the distance of the emission point to the property line of the facility. Appendix A of Regulation No. 3 sets forth various HAP reporting thresholds which range from 50 250 lb per year for the most toxic category ( Bin A) and 1,000 5,000 lb per year for the least toxic ( Bin C). Formaldehyde is listed in Bin A. In addition, there are categorical exemptions from APEN reporting requirements.

Response: The EPA acknowledges the comments.

X. B. 11 Comment: One commenter ( 579) said that EPA states that if the proposed rule is implemented at all affected RICE facilities, annual cancer incidence is estimated to be reduced on the order of ten cases per year. The commenter suggested that this number be clarified or eliminated, especially since the MACT standards are not risk based and EPA cites many uncertainties in its evaluation.

Response: The EPA is required by Executive Order 12866 to review the benefits of a rule, even if not statutorily required. Moreover, while a review of lives saved may not be required by the statute, it is certainly not forbidden for EPA to review the expected number of lives saved by a rule, just as it is not forbidden to review the expected costs of a rule, which is not a factor under the criteria for determining the MACT floor. In any event, this statement was included in the proposal, but EPA has not included this statement in the final rule.

X. B. 12 Comment: One commenter ( 606) asked how EPA will govern this rule and how EPA will identify existing sites that have rich burn engines over 500 HP that require NSCR equipment. The commenter further asked what the punishment for those who are caught not complying is. The commenter also asked when the final rule will begin.

Response: Existing 4SRB engines will have 3 years from the date of publication of the final rule in the Federal Register to comply with the final rule. The RICE final rule is scheduled to be published in March or April of 2004. That means that existing 4SRB engines will have until approximately March or April of 2007 to comply. After the rule is published in the Federal Register, EPA will undertake an outreach effort to inform the owners and operators of the rule and its requirements. The owners and operators affected by the rule will have to initially notify their enforcing agencies within a certain time period. The EPA will use industry associations, State and local governments, engine manufacturers and control device vendors, and trade magazines to notify owners and operators of the final rule. Any owner or operator who has not notified EPA and is not in compliance with the final rule at the end of the 3 year period will be in non compliance and enforcement action will be taken.

X. B. 13 Comment: One commenter ( 549) stated that EPA should clarify that, pursuant to 42 U. S. C. § 7627, the Department of Interior has jurisdiction over the central and western Gulf of Mexico. 117 Response: The section referred to by the commenter, pertaining to air pollution from outer continental shelf activities, has been the subject of previous EPA rules. The EPA refers the commenter to those rules regarding the application of that provision.