2 115 Fourth, the commenter stated that using add on controls to comply with PBCO will benefit facilities that have process units that emit low levels of HAP. According to the commenter, several companies have already implemented P2 strategies that have been established as BACT in a PSD permit. Because these P2 strategies may fall short of the PBCO limits,

companies implementing these strategies would be unable to achieve compliance with the proposed rule without abandoning the P2 strategy and installing full control.

Fifth, incorporating add on controls in the PBCO provides incentive to find low energy pollution control equipment. The commenter gave an example whereby part of the emission unit exhaust could be used as combustion air for an onsite boiler. The commenter noted that in most cases, the boiler could only handle a portion of the exhaust from multiple dryer stacks. The commenter stated that by combining this type of partial control approach with low temperature drying, a facility may be able to meet the applicable dryer PBCO limit. In this case, allowing for partial control would exclude the need for RTO technology and would provide a net benefit to the environment with a reduction of collateral oxidizer emissions. The commenter gave another example in which a facility with a conveyor dryer could send the exhaust from the first dryer section to a burner and then send the heat back to the dryer; the emissions from the remaining dryer sections would be uncontrolled if the total emissions were below the PBCO limit. In a third example provided by the commenter, a facility would remove enough HAP to comply with the PBCO limit using a scrubber, which would require less energy than incineration. The commenter noted EPA's concern that facilities could operate partial control options at levels lower than than a MACT control level and agreed that " any add on control device used to make up a shortcoming with a PBCO limit would be operated at a level consistent with good air pollution control practices."

Response: Like the proposed rule, the final rule does not allow sources to comply with the PBCO through the use of add on control systems. Our intention for including the PBCO was to provide an alternative to add on controls ( e. g., allow for and encourage the exploration of pollution prevention, which currently has not been demonstrated as achieved by PCWP sources)

and not to create another compliance option for sources equipped with add on control systems that could inadvertently allow add on control equipped systems to no perform to expected control efficiencies. Sources equipped with add on control systems already have six different compliance 2 116 options from which to choose, in addition to the emissions averaging compliance option. We note that the six options for add on control systems are based on emission reductions achievable with MACT control devices and thus are a measure of the performance of MACT control devices.

This might not be true if a source combined PBCO and add on controls, as explained below.

Table 2 3 compares the PBCO limits included in the proposed rule with the emission levels achieved using control devices. As shown in Table 2 3, we did not have total HAP data for all process unit groups equipped with controls. The lack of total HAP data for process units equipped with controls was one of the primary reasons we chose to develop the six add on control systems options in the proposed format ( i. e., can measure THC, methanol, or formaldehyde instead of measuring total HAP). However, we recognized that the format of the add on control system compliance options would preclude P2 techniques, and thus, we needed additional compliance options that could be met without the installation of add on controls in order to accommodate development of P2 techniques. One approach we considered was to review the available total HAP data for facilities equipped with controls and then choose a representative data point for each process unit group; however, we had to discard this approach because controlled total HAP data are not available for half of the process unit groups. We developed a number of other approaches to establishing PBCO limits, and then compared the results of these approaches, where possible, with actual emissions in the outlet of control devices. 9,23 The approach that yielded results closest to actual emissions in the control device outlets was an approach based on a 90 percent reduction from the average emissions within each process unit group. Thus, this approach was the one that resulted in limits that would most closely represent an alternative to the six compliance options for add on control systems.

However, our intention was not to develop an alternative limit to the six limits already established for add on control devices. Our intention was to develop an alternative for P2 techniques. We decided to select an approach that allows sources that develop P2 techniques ( or are otherwise inherently low emitting sources) to comply and that reduces HAP emissions without generating the NOx emissions associated with incineration based controls. As a result, we selected a 90 percent reduction from the highest data point within each process unit group, because the results appeared to be at levels that would not preclude the development of environmentally beneficial P2 options as MACT. 2 117 Table 2 3. Comparison of PBCO with Emissions from Outlet of Control Devices Process unit group Proposed PBCO limita Units Total HAP ( 6 HAP) measurements from outlet of controlled units Ratio of PBCO to Total HAP in outlet of controls Fiber board mat dryers 0.022 lb/ MSF 1/ 2" No data

Green rotary dryers 0.058 lb/ ODTb 0.0086 6.7 Hardboard ovens 0.022 lb/ MSF 1/ 8" 0.0049 4.5 Press predryers 0.037 lb/ MSF 1/ 2" No data

Pressurized refiners 0.039 lb/ ODT No data

Tube dryers 0.26 lb/ ODT No data

Reconstituted wood product board coolers 0.015 lb/ MSF 3/ 4" No data

Reconstituted wood products presses 0.3 lb/ MSF 3/ 4" 0.23; 0.16; 0.079; 0.061; 0.056; 0.022 1.3 to 151 Softwood veneer dryers 0.022 lb/ MSF 3/ 8" 0.015; 0.011; 0.11c 0.2c to 2 Strand dryers 0.18 lb/ ODT 0.081; 0.055; 0.44d 2.2 to 3.3 a PBCO limits are based on a 90 percent reduction applied to the highest available 6 HAP test. b ODT = oven dried ton, MSF = thousand square feet at thickness specified c Data point is for an RCO that achieved < 50 percent control of HAP during testing, although THC control efficiency was 90 percent. d Data for this unit were discarded during MACT floor determinations because unit was operating below its permitted control efficiency.

The text quoted by commenter IV D 27 from the PBCO memo was misinterpreted by the commenter; candidate PBCO limits were only compared to HAP emissions at the outlet of control devices as a way of gauging their appropriateness as applicability cutoffs. 9 As shown in Table 2

3, the resultant PBCO limits are higher than the HAP emission levels measured in the outlet of the MACT control devices, and in some cases, significantly higher. Thus, the PBCO limits are not an appropriate alternative for sources equipped with add on controls. If PBCO were allowed as another option for measuring the performance of add on control devices, operators could run the APCD so that the APCD would not achieve MACT level emissions reductions, but would meet the PBCO. We note that we did not develop the methanol and formaldehyde add on control options ( options 4 and 6 in Table 1B of the proposed rule) based on typical or maximum levels of 2 118 methanol and formaldehyde found in the outlet of the control devices, but instead looked at the performance of the control devices in reducing these HAP, set the levels based on the method detection limits for these compounds, and included a minimum inlet concentration requirement for the use of the outlet concentration options to ensure that MACT level HAP emissions reductions are achieved. Allowing the use of APCD to comply with PBCO could allow cirumvention of such optimization, which could render the MACT control itself to be less effective than MACT. We also note that, in comments elsewhere in this document ( see comment No. <IP_ADDRESS>), the commenters contended that the CAA intended for EPA to focus on emission reductions as opposed to emission levels.

Regarding the other MACT standards referenced by the commenters, we agree that these other rules may allow facilities more flexibility in meeting a production based option ( e. g.,

" lb/ ton" emission limit); however, as stated previously we cannot allow add on controls to be used to meet the PBCO in the PCWP rule because doing so would render these limits not equivalent to the other compliance options ( see also response to comment No. <IP_ADDRESS> and Table 2 3 for a comparison of emissions reductions achieved using different compliance options.) Also,

we note that, although the MACT rules cited by the commenters do not place restrictions on the use of the " lb/ ton" limits, these other rules do not contain the multitude of compliance options found in the PCWP rule and they do not allow multiple compliance options to be used on the same process unit at the same time, which is consistent with the PCWP rule. For example, the Paper and Other Web Coating NESHAP states that: " You may use different compliance options for different web coating/ printing operations or at different times on the same web coating/ printing operation. However, you may not use different compliance options at the same time on the same web coating/ printing operation." As explained previously in the response to comment No. <IP_ADDRESS>, a PCWP facility may use any number of options, as long as these options are not combined for an individual process unit ( i. e., can meet PBCO for one dryer, control emissions from a blender to avoid controlling emissions on the remaining two dryers as part of an emissions average, and use an add on control device for the press.)

Regarding the examples cited by the commenter as candidates for a PBCO if add on controls were allowed, we note that the final rule includes a revised MACT floor for existing conveyor dryers, such that existing conveyor dryers that send the emissions from the first section 2 119 back to the burner should be able to meet the rule requirements without additional controls. We also note that " partial control" ( e. g., routing part of the emission stream from a process unit to an onsite boiler for incineration) is already allowed as part of an emissions averaging plan as long as the actual emission reductions achieved are greater than or equal to the required emission reductions. ( See also response to comment No. <IP_ADDRESS>.) We further note that, when partial control is used as part of an emissions averaging plan, the overall reductions are equivalent to what would be achieved if a source elected to comply using the add on control system compliance options; however, the same would not be true if partial control were used to comply with a PBCO limit. Regarding the use of scrubbers to comply with a PBCO, as stated in our response to comment No. <IP_ADDRESS>, the industry's own data do not support wet scrubbers as a reliable control technology for HAP, and sources equipped with wet control devices will be required to test prior to the wet control device if they elect to comply with a PBCO.

<IP_ADDRESS> Comment: Commenters IV D 19, IV D 27, and IV D 56 agreed that choosing a 90 percent reduction from the highest emission test in each source category is the proper method for developing PBCO limits, but argued that statistical methods should be used to establish a realistic estimate of the highest emission test. Commenters IV D 28 and IV D 43 concurred.

Commenter IV D 27 noted that in section III. F. 1 of the preamble, EPA states that " the available total HAP test data sets are too small to justify use of such statistical methods, and the resulting compliance options, in many cases, seemed unreasonably high compared to the actual emissions from process units with MACT control systems. Therefore, statistical methods were not used."

Commenters IV D 27 and IV D 56 disagreed with EPA's conclusion that statistical methods should not be used and stated that, due to the relatively small data set available for establishing PBCO limits, it is unlikely that the PBCO limits are based on the highest emitting source. The commenters noted that, although the database used to establish the PBCO limits is one of the most comprehensive efforts of this type ever attempted, it is necessarily limited by scope, cost,

and design. The commenters contended that choosing the maximum observed value from this database as the basis for determining the population maximum results in an underestimate of the actual highest value and inappropriately low limits for the PBCO. Commenter IV D 27 added that any source with emissions above the highest level found in the database would have to reduce 2 120 emissions much more than 90 percent to comply with PBCO limits, which is " illogical" and " unfair."

Commenter IV D 27 acknowledged that, for some process groups, there is insufficient information to justify applying statistics, but argued that, for reconstituted wood product presses,

softwood veneer dryers, and tube dryers, there is enough information. The commenter suggested that EPA use regression analyses to determine a minimum data requirement for applying statistical methods. According to the commenter, the first step would be to calculate a more accurate estimate of the true population maximum for each source type using a 95 percent statistical confidence level that 99 percent of the population is enclosed in the estimate. The commenter stated that when this number is multiplied by 0.1, the result will more realistically represent 90 percent control of the true population maximum. ( The commenter referred to an issue paper the commenter had previously submitted to EPA for more details on the methodology [ Docket Item #

II D 521].) In the second step recommended by the commenter, EPA would determine the percentage change in the PBCO from the original limits to the limits determined by statistics and plot the sample size against that percentage change. Using a power curve regression on this plot,

the commenter concluded that a minimum sample size should be eight. According to the commenter, the adjusted PBCO for reconstituted wood product presses would be 0.39 lb/ MSF 3/ 4; for softwood veneer dryers, it would be 0.36 lb/ MSF 3/ 8; and for tube dryers it would be 0.45 lb/ oven dried ton ( ODT). The commenter asserted that the revised PBCO limits are within the realm of values considered by EPA when developing the PBCO; the commenter noted that the memo Development of Production Based Emission Limits for Plywood and Composite Wood Products Process Units ( Docket # II B 32) makes high end estimates of 0.37 lb/ MSF 3/ 4 for reconstituted wood products presses and 0.33 lb/ MSF 3/ 8 for softwood veneer dryers.

For the process unit groups that do not have sufficient data points, the commenter recommended that EPA incorporate the basic findings of the statistical analysis and apply a 30 percent increase to the PBCO limits across the board. The commenter stated that the 30 percent factor is similar to that recommended for the reconstituted wood products presses, the process unit group with the largest data set. Application of the 30 percent increase to the other data sets is based on a assumption that the distribution of emissions data from the largest available data set is similar to the distribution that would be observed in other categories if a sufficient number of 2 121 samples were available. The commenter contended that, at a minimum, a statistical analysis should be applied to the three process groups with at least 8 samples. The commenter stated that revising the PBCO limits would encourage more facilities to pursue pollution prevention options,

enhancing technological progress in that area, and it would lower the cost of MACT implementation while reducing collateral emissions. The commenter asserted that more facilities would be able to ensure compliance 100 percent of the time and would be encouraged to use the PBCO if the limits were less stringent.

Response: We disagree with the commenters' recommended changes to the PBCO.

When we developed the PBCO, we looked at a number of options for establishing the PBCO limits, including several recommendations from the industry, some of which included statistical analyses and some of which did not. We documented the results that would be obtained using each of these potential approaches and compared these results to the total HAP emissions measured at the outlet of control devices. 9 As discussed in the response to the previous comment,

we selected an approach that was close to the emission levels in the outlet of the control because we believed that it would be appropriate to allow this alternative if environmentally beneficial P2 techniques were used to comply. The approach that met this criterion was a 90 percent reduction from the highest total HAP data point. The commenter's assertion that the data set may not include the highest emitting source may be true. However, we note that elsewhere in their comments ( see comment No. <IP_ADDRESS>) the same commenter ( IV D 27) stated that " the data used to establish the floor only included operations at maximum capacity and did not reflect the full operating range of the process," which would imply that testing under more typical conditions would have yielded lower emissions from the process units tested. Regardless, as explained in the response to the previous comment, using the highest emitting source to set the PBCO limits was simply a starting point; the " test" we used to determine if the PBCO limits were appropriate was to compare the resulting PBCO limits to the outlet emissions from control devices. Therefore, the fact that there could be higher emitting sources is immaterial for the purpose of setting the PBCO limits. The same is true regarding the use of statistics; that is, the outcome of the statistical analyses were inconsistent with the outlet emissions from control devices, and therefore, we did not incorporate statistics into the development of the PBCO. We also maintain that, regardless of the outcome, the use of statistics is inappropriate given the limitations of the data set. Regarding 2 122 the comment that high emitting sources would have to reduce emissions by more than 90 percent,

we note that ( 1) the PBCO limits were not developed for high emitting sources or for sources that use add on control devices, but instead were developed to provide a compliance option for inherently low emitting sources; and ( 2) if a high emitting source uses a control device, then that source only has to reduce emissions by 90 percent, not more than 90 percent.

Finally, we note that the emissions from PCWP process units are not insignificant, even when these units operate at the PBCO thresholds. For example, a single wood products press that operates at the applicable PBCO limit ( 0.30 lb/ MSF 3/ 4") still emits 15 tons of HAP per year,

and a single strand dryer operating at the applicable PBCO limit ( 0.18 lb/ ODT) emits 6 tons of HAP per year. Also, raising the PBCO limits to levels recommended by the commenters would be inconsistent with the MACT floor. For example, the commenters recommend that the PBCO limit for softwood veneer dryers be increased from the proposed 0.022 lb/ MSF 3/ 8" to 0.36 lb/ MSF 3/ 8"; however, all of the softwood plywood dryers equipped with MACT controls that were tested by industry have uncontrolled emissions less than 0.36 lb/ MSF 3/ 8". Thus, if we were to raise the limits as suggested, sources already equipped with controls would not be required to keep those controls in place to comply with the PCWP rule, such that, not only would the required MACT emission reductions not be met, but there could also be a net increase in HAP emissions.

2.6.4 Emissions averaging <IP_ADDRESS> Comment: Commenters IV D 12, IV D 19, IV D 21, IV D 27, IV D 28, IV D

43, and IV D 56 expressed support for inclusion of an emissions averaging program in the proposed rule. Commenters IV D 21 and IV D 28 specifically supported the following four elements in the emissions averaging plan: ( 1) allowing sources to control other waste streams in lieu of those specifically subject to MACT; ( 2) not requiring a discount factor for sources using emissions averaging; ( 3) not limiting the number or type of emissions points that can be included in an emissions averaging plan; and ( 4) not requiring a hazard or risk assessment before emissions averaging can be used at a facility.

Commenter IV D 27 stated that, at some PCWP facilities, there may be process units that have the potential to emit quantities of HAP equal to or greater than the most commonly controlled units   dryers and presses   but with a lower volume of exhaust gas to be treated compared to dryers and presses. The commenter noted that the emissions from these other units 2 123 do not require control under the point by point compliance options; however, under emissions averaging, these sources could be controlled to generate credits, and thus, emissions averaging will allow affected sources to achieve the same environmental gains as achieved by point by point compliance, but at reduced cost. The commenter also noted that the emissions averaging program in the HON includes a discount factor, whereas, the proposed PCWP emissions averaging program does not. The commenter stated that the rationale for including a discount factor in the HON does not apply to PCWP sources. According to the commenter, EPA determined in the HON that it was appropriate for the industry to share any cost savings realized from emissions averaging because the costs of controlling different emission points could vary significantly; however, in the PWCP industry, EPA found that the types of process units and the emissions from them are more similar than dissimilar across sources. The commenter further noted that, not only are the emissions from all PWCP process units are similar, but they also require similar controls. For these reasons, the commenter stated that a discount factor is not needed in the PCWP emissions averaging program to maintain an equivalent compliance cost between compliance options. The commenter also agreed with the proposal that the number of sources that can be included in the proposed PCWP emissions averaging program should not be limited. The commenter noted that, under the HON, the number of emission points was limited because of enforcement concerns due to the complexity and large number of emission points in each HON facility. The commenter further noted that, for PCWP facilities, the type and number of emissions points is substantially smaller, minimizing enforcement concerns. Finally the commenter expressed concurrence with the exclusion of a hazard/ risk benefit analysis from the proposed PCWP emissions averaging program. The commenter stated that, unlike the HON facilities ( which must conduct a hazard/ risk benefit analysis due to the many pollutants [ with varying toxicities] emitted from many emission points), PCWP facilities have few pollutants of concern and have similar HAP emissions from the emission points that would be used to generate debits and credits.

Commenter IV D 33 objected to the inclusion of an emissions averaging option in the rule because the proposed option is based on mass of HAP rather than health effects. The commenter asserted that removing a certain mass of HAP regardless of identity is not equivalent to the other compliance options, and when the dose response and exposure data are examined, it is obvious that trading one HAP for another to meet a required mass removal ( RMR) is not an acceptable 2 124 solution. The commenter noted that there are currently no methods for weighting the toxicity of HAP, and that the effects of simultaneous exposure to several HAP also are unknown. The commenter contended that, because EPA's own risk assessment data presented in the preamble shows that 80 percent of the PCWP facilities in the United States pose unacceptable risk to the populations near these facilities ( i. e., cancer risks greater than greater than one in one million),

EPA should require emission reductions at these facilities instead of proposing a " flawed trading scheme" that will potentially increase toxic emissions at certain process units.

Response: We acknowledge the comments in support of the emissions averaging plan ( EAP) and have retained the proposed provisions in the final rule with some minor changes. The final rule changes proposed § 63.2240( c)( 2)( iii) regarding the exclusion of process units controlled to comply with other rules from PCWP emissions averages as follows:

( iii) You may not include in your emissions average process units controlled to comply with a State, Tribal, or Federal rule other than this subpart, except when the control system installation and process unit inclusion in the emissions average both pre date the effective date of the State, Tribal, or Federal rule.

We removed the last phase as shown above to prevent PCWP facilities from taking credit for future emissions reductions that may be required as part of another rule. The emissions averaging provisions must ensure the same degree of reduction that would be achieved through point

bypoint compliance with the PCWP rule and any other rules to which a PCWP is subject. For example, if two process units are part of a PCWP emissions average and the emissions from the first process unit must be further reduced at a later date as part of another rulemaking, the source cannot then recalculate the emissions average to get credit for the increased emission reduction from the first process unit and then reduce the required emission reduction from the second process unit. If the PCWP facility were allowed to take credit for the reduction required as part of the non PCWP rule, then the overall emission reduction would be less than it would have been in the absence of emissions averaging. In this example, the remaining process unit would have to become part of a new emissions average ( that does not include any process units controlled to comply with other rules) or meet one of the other compliance options ( e. g., 90 percent reduction in emissions.) 2 125 We disagree with commenter IV D 33 that the inclusion of the EAP will potentially increase toxic emissions at certain PCWP process units. As stated in the preamble to the proposed rule ( 68 FR 1289 1290, January 9, 2003), we based the emissions averaging provisions ( in part) on the emissions averaging provisions in the HON. However, there are differences in the two rules due to the differences between PCWP facilities and HON facilities. The HON requires a hazard and risk study for emission points included in an emissions average largely because of the many pollutants and many emission points at the source. The PCWP facilities have fewer pollutants of concern and are likely to have similar HAP emissions from the emission points ( process units) that would be used to generate debits and credits. The PCWP facilities emit primarily six HAP ( along with very small amounts of other HAP), whereas HON facilities may emit over 140 different HAP in substantial quantities. The PCWP facilities choosing to comply through emissions averaging must account for the emissions of the six primary HAP ( defined as " total HAP" in the final rule), which represent 96 percent of the HAP emitted from PCWP process units. Because the MACT control technologies are effective in reducing the emissions of all six of these HAP, and the EAP requires the use of add on control technologies for creditgenerating sources in the EAP, we believe that the EAP will achieve a hazard/ risk benefit comparable to what would be achieved through point by point compliance. The same emission reduction would be achieved using emissions averaging as would have been achieved through point by point compliance, and therefore, there would not be an increase in emissions or exposures to these emissions at populations near PCWP facilities. We also note that, although the final rule does not require a hazard/ risk study, States will still have the discretion to require a PCWP facility that requested approval of an EAP to conduct a hazard/ risk study ( or to preclude the facility from using emissions averaging altogether).

<IP_ADDRESS> Comment: Commenters IV D 12, IV D 19, IV D 21, IV D 27, IV D 28, IV D

43, and IV D 56 requested that EPA modify the emissions averaging provisions to allow sources to receive credit for achieving emissions reductions greater than 90 percent. The commenters contended that restricting sources to a maximum control efficiency credit of 90 percent will eliminate an important incentive for sources to take extra steps to maximize the efficiency of addon control devices. The commenters stated that allowing credit for efficiencies above 90 percent would encourage those operators who are able to achieve these levels to run controls in the most efficient manner, as opposed to running at 90 percent, regardless of capability. The commenters 2 126 noted that other control options included in the proposed rule allow credit for achieving greater than 90 percent control. The commenters pointed to the add on control options for methanol and formaldehyde ( i. e., if

10 ppmv in the control device inlet, then meet  1 ppmv in the outlet) as options that require greater than 90 percent control. The commenters also stated that the press provisions for 90 percent capture and control acknowledge that facilities will have to achieve greater than 90 percent reduction from control devices in order to meet the 90 percent reduction limit when capture is less than 90 percent. At a minimum, the commenters requested that the final rule allow credit for control efficiencies greater than 90 percent for those process units with no MACT control requirements. The commenters contended that because these emission units are not required to meet any specified percent reduction, there is no logical reason why they should be limited to receiving credit only for a specified level of removal ( 90 percent).

Response: We disagree with the commenters' request to allow credit for achieving greater than 90 percent control of HAP as part of an EAP. We note that the 90 percent MACT floor level ( upon which the emissions averaging provisions are based) reflects the inherent variability in uncontrolled emissions from PCWP process units and the decline in performance of control devices applied to these process units. The data set used to establish the MACT floor is comprised of point in time test reports, some of which show a greater than 90 percent control efficiency; however we selected 90 percent as the MACT floor level of control to reflect inherent performance variability. Therefore, it would be inappropriate to allow PCWP facilities to receive credit for similar point in time performance tests showing greater than 90 percent control,

considering that the same types of control technologies would be used. We expect that some new installations of add on controls will show greater than 90 percent control efficiency during initial performance tests because these units likely will be designed for greater than 90 percent control efficiency to account for inherent variations in performance over time and to ensure continuous compliance in later years. We also have included routine control device maintenance exemptions to help PCWP facilities to ensure that the add on controls are properly maintained so that the 90 percent compliance can be achieved on a continuous basis.

Regarding the two examples given by the commenters, as explained in our previous response to comment No. <IP_ADDRESS>, the add on control options for methanol and formaldehyde do not require greater than 90 percent control. We also note that the MACT floor level of 90 percent is based solely on the performance of the add on control devices for dryers and other 2 127 process units where emissions capture is not at issue. When setting the MACT floor for presses at proposal, we determined that those presses designed to meet EPA Method 204 design criteria should be able to claim 100 percent capture, such that the combined ( overall) capture and control efficiency also would be 90 percent ( i. e., 0.90 x 1.00 = 0.90). Although we have changed the requirements related to the wood products enclosures in the final rule ( see section 2.3), the MACT floor level of 90 percent has not changed ( i. e., wood products enclosures are still credited with 100 percent capture, and MACT control devices are still capable of reducing emissions by 90 percent). Thus, the overall control requirement for the affected process units remains at 90 percent. Regarding the commenters' assertion that the press provisions for 90 percent capture and control acknowledge that facilities will have to achieve greater than 90 percent reduction from control devices in order to meet the 90 percent reduction limit when capture is less than 90 percent, we note that it will be impossible to achieve 90 percent capture and control if capture is less than 90 percent. Under the EAP, a press may receive credit for achieving greater than 90 percent control via the add on control device; however, the combined capture and control credit for the press cannot exceed 90 percent. Regarding the commenters' request to allow credit for greater than 90 percent control for nonregulated sources, we maintain that this would be inappropriate because the same issues of emissions variability and control device performance reflecting our calculations of what MACT levels are consistently achievable apply to those emission sources, and they likely would share control devices with regulated sources.

<IP_ADDRESS> Comment: Commenter IV D 11 stated that because emissions averaging credits would be based on actual emissions from process units operating " below representative operating conditions," the credits generated would be small and not worth the extra effort to track emissions averaging data to determine compliance. The commenter stated that reductions beyond the required MACT emission level ( 90 percent at proposal) would be the best way to achieve an averaging compliance option. The commenter stated that the reductions should be based on emissions in pounds of total HAP, operating at " representative operating conditions," on a semiannual basis.

Response: We disagree with the commenter that the credits generated through emissions averaging would be " small and not worth the extra effort to track." First, the emissions averaging provisions in the PCWP rule do not require testing of process units while they are operating below representative conditions; the rule requires testing while process units are operating at 2 128 representative conditions, as the commenter suggests. Second, credit generating units must be equipped with add on control systems, and the greater the emission reductions achieved with these control systems, the greater the resulting credited emissions reductions; therefore, it would be very unlikely that a PCWP facility would go to the expense of installing a control device that would only achieve minimal HAP emission reductions. Third, the emissions averaging provisions are offered as an alternative to the add on control system compliance options, and as such, must achieve an emission reduction equivalent to what would be achieved through these other options. The emission averaging provisions were never intended to result in emission reductions greater than those achieved through implementation of the MACT floor.

<IP_ADDRESS> Comment: Commenters IV D 12, IV D 19, IV D 21, IV D 27, IV D 28, IV D

43, and IV D 56 requested that EPA modify the emissions averaging provisions to allow sources to receive credit for production curtailment. The commenters contended that taking production restrictions and eliminating emission points to comply with a standard is not unprecedented,

pointing to synthetic minors that become area sources, the " Oregon PAL program," and State permit limits that include production limits. The commenters stated that, once an initial baseline has been established, any steps taken to reduce emissions by 90 percent should meet the legal requirements of MACT and the proposed requirements of the rule.

Response: As stated in the preamble to the proposed rule ( 68 FR 1285, January 9, 2003),

we do not have facility wide uncontrolled emissions data and facility wide controlled emissions data for each PCWP facility to determine the baseline emissions and percent reduction in HAP achieved by each facility. Therefore, the MACT floor is not based on facility wide emissions and emissions reductions achieved during a particular year. Instead, the MACT floor is based on ( 1)

the presence or absence of certain MACT controls ( in place as of April 2000) on certain types of process units, and ( 2) test data showing that these controls reduce emissions by greater than or equal to 90 percent. We applied the MACT floor methodology at the process unit level because we had the most accurate data at the process unit level, making this approach the most technically and legally sound. The PCWP industry is very dynamic, with frequent shutdowns of equipment for maintenance and occasional longer ( e. g., month long) shutdowns if demand drops. The reported operating hours of various PCWP equipment during 1997 ( base year for the MACT survey) varied widely. 10 The PCWP rule requires emissions from specified process units at impacted PCWP facilities to be reduced by 90 percent, regardless of what the levels of emissions 2 129 are for those facilities in a particular year. Therefore, implementation of the final PCWP rule at individual PCWP facilities will result in greater emission reductions in years of greater production and lesser emission reductions during years of lower production. As mentioned in the response to the previous comment, the emissions averaging provisions must achieve emission reductions that are greater than or equal to those that would be achieved using the add on control systems compliance options which specify which process units must be controlled. If we allowed " credit"

for production curtailments, the overall emission reduction achieved through the emissions averaging provisions would not be equivalent to what would be achieved through the use of the add on control systems compliance options, and therefore, the EAP would not be a MACTequivalent alternative. For example, if we allowed production curtailments to count towards an emissions average, then a facility that shuts down one of two parallel production lines ( each of which includes dryers and a press, plus HAP emitting equipment that does not have associated control requirements) may not be required to control the emissions from any of the dryers or press on the remaining production line. However, if the same facility opted to comply with the add on control systems compliance options, then they would be required to control the press and dryer emissions from the remaining production line by 90 percent regardless of whether or not the other production line was shut down. In order to maintain equivalency between the emissions averaging provisions and the add on control systems compliance options and to preserve the required HAP emission reductions, the final PCWP rule does not allow production curtailment to be counted as part of an EAP.

<IP_ADDRESS> Comment: Commenters IV D 12, IV D 19, IV D 21, IV D 27, IV D 28, IV D

43, and IV D 56 requested that EPA modify the emissions averaging provisions to allow sources to receive credit for pollution prevention projects. According to the commenters, not allowing pollution prevention encourages the use of add on controls, such as incineration, rather than environmentally beneficial options that may not involve add on control technology. The commenters cited three ways in which pollution prevention could be used to generate credits in an emissions averaging plan. First, pollution prevention could be used to reduce emissions at a process unit that is required to be controlled by an amount greater than the MACT level ( i. e.,

greater than 90 percent emission reduction); however, the commenter expects that this would be very difficult to do. Second, pollution prevention could be used to reduce emissions from a process unit that is not required to be controlled, by 90 percent or more. Finally, pollution 2 130 prevention could be used at a regulated emission unit that utilizes an add on control technology but does not achieve the MACT limit ( e. g., a biofilter achieving 80 percent removal). In the latter case, pollution prevention would be used to achieve the additional incremental emissions reductions needed to reach the MACT limit. The commenters asserted that quantifying emissions from pollution prevention projects would not be difficult under the PCWP emissions averaging program. According to the commenters, the facility would calculate the " total allowable emissions" and then apply a 90 percent reduction to determine the equivalent MACT floor level of control, and then compare the total emission level to the controlled emission level. With this approach, an initial test will be used to establish initial compliance and then testing would occur annually to demonstrate continuing compliance.

Response: We disagree with the commenters' suggestion to modify the emissions averaging provisions to allow sources to receive credit for P2 projects because ( 1) compliance options ( i. e., PBCO) already exist for any P2 projects that prove to be feasible and ( 2) inclusion of currently undemonstrated P2 projects within EAPs would unnecessarily complicate these plans and hamper enforcement. We also disagree with the commenters' assertion that quantifying the emissions reductions from P2 projects would not be difficult. Quantifying the emissions reductions associated with P2 projects has historically been a contentious issue, especially when a baseline emission level must be established from which to calculate the emissions reduction. We believe that the same issues apply for PCWP facilities, especially given the fact that P2 techniques have not been widely used or documented in the PCWP industry, and therefore were not the basis for determining the MACT floor. In contrast, emission reductions achieved through the use of add on control systems are easily documented. The PBCO was established to address the future development and implementation of P2 techniques; however, the resultant PBCO limits do not require that emission reductions be determined. Instead, sources simply demonstrate that they are below the PBCO limit and will continue to operate in a manner that ensures they will remain below the PBCO limit. We believe that the lack of a discount factor in the emissions averaging provisions in the final PCWP rule further justifies our decision not to allow credit for P2 techniques as part of an EAP. Under the HON, sources that elect to emissions average must reduce emissions throughout the HON facility by 10 percent more than is required by point

bypoint compliance to share with the environment any cost savings realized from emissions averaging and to account for uncertainties in determining emission reductions under the EAP. 2 131 Unlike the HON, the PCWP rule does not require a 10 percent discount factor in the emissions credit calculations. We believe that the inclusion of the PBCO provides sufficient opportunities and incentives for PCWP facilities to develop and implement P2 techniques. We also note that because the PBCO is based on 90 percent reduction from highest emitting source, there should be plenty of opportunity for the industry to comply using P2, should such techniques actually be developed. Finally, as noted in previous responses, the final rule already allows PCWP facilities to use both P2 and emissions averaging at the same facility; sources are only limited in that they can't apply both options to a single process unit.

<IP_ADDRESS> Comment: Commenters IV D 12, IV D 19, IV D 21, IV D 27, IV D 28, IV D

43, and IV D 56 requested that EPA modify the emissions averaging provisions to allow sources to include the PBCO as part of an EAP. Specifically, the commenters requested that sources be allowed to apply the emissions credit generated from controlling a process unit for which control is not required to another process unit seeking to comply with a PBCO limit. Commenter IV D

27 gave an example where a facility would control emissions from a board cooler and then apply the resultant emission reduction to a press that had emissions above the applicable PBCO limit; by applying the emissions credit to the press, the press emissions would be reduced below the PBCO limit such that no control would be required on the press. The commenters stated that EPA should allow combining of these two compliance options ( emissions averaging and PBCO)

because doing so would make the rule more cost effective, and the result would be equally beneficial to the environment. The commenters stated that combining of compliance options has been allowed in other rules, specifically in the Paper and Other Web Coating NESHAP. The commenters also stated that combining the two compliance options would allow more facilities to use these options and would result in equal emissions reductions. When implementing this approach, the commenters also requested that emissions be calculated in terms of tons per year rather than pounds per year to be more consistent with terminology used in most permits, and for other reporting requirements, such as emission inventories, already in place at wood product facilities.

Response: The commenter is incorrect in stating that combining these two options ( emissions averaging and PBCO) will result in equivalent emissions reductions. As stated in our response to previous comments regarding the PBCO, we developed the PBCO limits to provide an option for sources that develop P2 techniques. The PBCO limits represent applicability cutoffs 2 132 such that sources with emissions below the applicable PBCO limits are not required to further reduce those emissions below MACT levels. By combining PBCO limits with the EAPs as proposed by the commenter, we would be allowing higher emitting sources ( i. e., those that cannot meet a PBCO and which should be controlled) to escape controls by artificially lowering their emissions using the credits from the EAP. This is counter to the intent of the PBCO and would result in lower emission reductions than would be achieved without combining these two compliance options; therefore, this does not represent an option that is equivalent to the MACT floor and is not allowed in the final rule. To demonstrate how the combining of these compliance options results in lower emission reductions, we have taken the example provided by the commenter and presented the emission reductions that would occur using each compliance method separately and together. As shown in Table 2 4, the 90 percent control option and the emissions averaging provisions ( which incorporate the 90 percent control requirements) result in equivalent emission reductions ( i. e., 8.1 tons of HAP reduced per 6 month reporting period).

Compliance with the PBCO would require the facility to develop a P2 technique that would eliminate at least 1.5 tons of uncontrolled HAP from the press per 6 month period. Although this " emission reduction" is lower than what would be achieved through the use of add on controls,

we would allow this because of the benefits of pollution prevention ( i. e., absence of secondary environmental impacts generated through the use of add on control systems on low emitting emission units). As shown in option 4 of Table 2 3, the use of the PBCO limits in EAPs artificially lowers emissions from process units that are not inherently low emitting sources to levels that would qualify as low emitting ( below PBCO limits). This conflicts with the purpose of including the PBCO in the rule and, as stated above, conflicts with the MACT floor; therefore, the final rule does not allow the inclusion of PBCO within an EAP. As for reporting emissions in EAPs in units of tons per year, we disagree that this change would be beneficial and have retained the requirement to report these emissions in units of pounds per year to avoid situations where compliance is achieved through rounding. 2 133 Table 2 4. Effect of Combining Compliance Options on Emission Reductions Achieved Total HAP Emissions Data: Press emissions = 36,000 lb/ yr; ( 0.36 lb/ MSF) Cooler emissions = 10,000 lb/ yr; ( 0.10 lb/ MSF) Production rate = 100 MMSF/ yr; 50 MMSF/ 6 month period PCWP Rule Requirements: Press: ( 1) Reduce emissions by 90%, or ( 2) include in an emissions average, or ( 3) comply with PBCO limit of 0.3 lb/ MSF. Rule does not allow combining of PBCO with other compliance options ( 4).

Cooler: None OPTION STRATEGY EMISSION REDUCTION, lbs per 6 month period ( 1) Comply with 90% reduction Press: Use add on control system to reduce emissions by 90%

Cooler: No action 16,200 ( 2) Comply using emissions averaging Press: Use add on control system to reduce emissions by at least 65% ( 11,700 lbs per 6 month period) ( undercontrolled source in EAP)

Cooler: Use add on control system to reduce emissions by 90% ( 4,500 lbs per 6 month period) 16,200 ( 3) Comply with PBCO Press: use pollution prevention techniques to reduce uncontrolled press emissions from 0.36 lb/ MSF to

0.30 lb/ MSF ( equal to a 17+% " reduction")

Cooler: No action 3,000 ( 4) Comply with EAP that incorporates PBCO ( option suggested by commenter) ( a) Use add on controls to reduce cooler emissions by 90% ( 4,500 lbs per 6 month period), resulting in a credit of 0.09 lb/ MSF ( b) Using cooler credit, artificially reduce uncontrolled press emissions from 0.36 lb/ MSF to 0.27 lb/ MSF ( c) No controls are applied to press because discounted emission rate ( 0.27 lb/ MSF) is less than the PBCO limit of 0.30 lb/ MSF 4,500 <IP_ADDRESS> Comment: Commenters IV D 12, IV D 19, IV D 21, IV D 27, IV D 28, IV D

43, and IV D 56 requested that EPA consider an " enhanced emissions averaging compliance 2 134 option" to address elements in the proposed emissions averaging program that the commenter believes are missing or require modification as discussed above in the preceding comments. The enhanced EAP would allow PCWP facilities to focus on achieving a 90 percent emission reduction of methanol, formaldehyde, or THC instead of the proposed 90 percent reduction of total HAP emissions. The baseline level of methanol, formaldehyde, or THC emissions would be calculated using data from the regulated process units ( e. g., dryers and presses) over the past 10 years ( or some other representative period), but the emissions reductions could be the result of controlling any emissions source. Under this plan, emission reductions could be achieved with add on controls, P2 projects, and operational changes, such as reformulation of the product,

routing process unit exhaust to existing onsite combustion sources, lowering dryer operating temperatures, partial capture and control of process unit emissions, increasing use of hardwood species, production curtailment, production caps, and scheduled process unit downtime.

Commenters IV D 19 and IV D 27 provided examples to show how the emission reductions would be determined under each scenario. The commenters acknowledged that any credit generation would have to be well documented and verified, and that monitoring parameters would be used to determine continuous compliance. Like the proposed EAP, the enhanced EAP would only apply to existing facilities, and new sources would be required to meet the 90 percent reduction level. Under the plan, any changes at a facility that resulted in an increase of methanol,

formaldehyde, or THC emissions would not require the baseline level of emissions to be recalculated as long as the increase was not larger than 10 percent of the original level.

Response: We disagree with the commenters' suggested " enhanced emissions averaging compliance option" and have retained the proposed emissions averaging provisions in the final rule with only minor revisions. Our objections to some of the features of the suggested enhanced emissions averaging compliance option, such as allowing credit for production curtailments and P2 techniques, have been documented in previous responses ( see responses to comment Nos.

<IP_ADDRESS> through <IP_ADDRESS>). Regarding the suggestion to allow compliance to be determined based on methanol, formaldehyde, or THC emissions, we maintain that the EAP needs to be based on total HAP ( i. e., total emissions of the six primary HAP emitted from PCWP process units). We note that the predominant HAP emitted from a given process unit varies, with some process units emitting methanol as the predominant HAP and others emitting formaldehyde or acetaldehyde as the predominant HAP. However, the predominant HAP will always be one of the six we have 2 135 identified in the definition of total HAP in the PCWP rule. If we based the EAP on only one pollutant, process units that emit the target HAP in small quantities will not be correctly accounted for in the EAP, resulting in potentially less stringent control and greater potential risk than would result with other control options. We did not include a hazard/ risk study as part of the proposed EAP because we were requiring that the emission reductions be based on total HAP,

and PCWP process units generally emit the same six primary HAP, although in different quantities and ratios. Basing the EAP on a single pollutant would undermine our basis for not requiring a risk analysis. We also note that, while THC emissions may be an acceptable surrogate for monitoring the performance of an add on control device ( same control device mechanisms that reduce THC emissions reduce HAP emissions), THC emissions are not an accurate surrogate for establishing baseline HAP emissions, and thus, the EAP should not be based solely on THC emissions. Although all PCWP process units emit THC, THC emissions from softwoods are substantially higher than from hardwoods due to non HAP compounds ( e. g., pinenes) present in softwoods. Therefore, allowing sources to focus on THC reductions by increasing hardwood usage might reduce THC emissions but would have a minimal impact on HAP emissions.

Regarding the proposed idea to increase the use of hardwood species, we note that elsewhere in their comments ( see comment No. <IP_ADDRESS>), the same commenter stressed the difficulties associated with maintaining a consistent wood material flow in terms of species,

moisture content, etc., which would suggest that an operating condition based on maintaining a set level of wood species would be unworkable. For veneer dryers, where species identification ( hardwood versus softwood), and thus enforcement, is fairly straightforward from the standpoint of both visual inspection and end product, we have already established separate MACT floors for softwood and hardwood veneer dryers. However, when the end product is particleboard or MDF, and the raw material is in the form of wood chips, planer shavings, or sawdust, determining how much of that material is softwood versus hardwood would be very difficult and unenforceable. Because of the commenters' concerns that an operating condition based on wood species is technically unworkable and the associated enforcement issues, we believe this option is not viable.

Regarding process changes such as reformulation, lowering dryer temperature, and routing process unit exhaust to existing combustion devices, the final rule already includes compliance options that would accommodate all of these strategies. For example, product 2 136 reformulation and lowering dryer temperature are potential P2 options, and the PBCO limits would apply if the P2 efforts sufficiently lower emissions. The PCWP rule distinguishes between green ( high temperature, high moisture) rotary dryers and dry ( low temperature, low moisture)

rotary dryers and requires no further emissions reductions from dry rotary dryers. To then take credit for the difference between the " potential" emissions of the dryer if it were operated at higher temperatures as a " green dryer" relative to operation at lower temperatures that qualify the dryer as a dry dryer ( exempt from regulation) and then apply that credit elsewhere would be double counting. By operating the dryer as a dry dryer, the source is exempt from controls; no additional credits should be assigned to that source. Also, as with many of the proposed process changes/ P2 alternatives, determining a baseline from which to calculate an emission reduction would extremely difficult and contentious, needlessly complicating the EAP and hampering enforcement. Regarding the use of existing combustion units as control devices, we note that the final rule already allows sources to route emissions to onsite combustion units for incineration.

The final rule also allows sources to control a portion of a process unit's emission stream as part of an emissions average. However, we disagree that incineration of emissions in onsite process units is a pollution prevention measure. Therefore, compliance with the PBCO using process incineration is not allowed in the final rule. The add on control system and emissions averaging compliance options are available for process units controlled by routing exhaust to an onsite combustion unit.

<IP_ADDRESS> Comment: Commenters IV D 12, IV D 19, IV D 21, IV D 27, IV D 28, IV D

43, and IV D 56 requested that EPA extend the compliance date for submittal of the EAP. The commenters stated that developing an EAP will be an involved and lengthy process, which will include emission testing to establish credits/ debits, development of emission reduction projects ( e. g., process changes, operating restrictions) and identification and installation of controls. The commenters contended that the EAP development process would be more involved than the other compliance options requiring only controls, and yet, the EAP option has the shortest effective compliance period ( the EAP is required to be submitted one year prior to the compliance date for review). Therefore, the commenters requested that the date of submittal of the EAP be changed to 90 days prior to compliance with an extension, if needed, of up to one year for inclusion of the plan into a federally enforceable mechanism. 2 137 Response: The emissions averaging provisions in the final rule are essentially the same as those provided in the proposed rule, with some minor clarifications. We believe that these provisions are straightforward and uncomplicated, and that developing EAPs would not be " an involved and lengthy process." Therefore, the final rule retains the requirement to submit the EAP for review one year prior to the compliance date. We note that, in most cases, EAPs developed for a PCWP facility will likely include only a small number of process units within the facility. We also note that, had we incorporated some of the suggested changes requested by the commenters ( e. g., incorporating P2 options and PBCO into EAPs) , the emissions averaging provisions would have been much more complicated and more difficult to enforce. Finally, we believe that requiring the EAP to be submitted one year prior to the compliance date gives sources time to adjust their compliance strategies should the EAP prove unworkable ( e. g.,

calculations show that debits exceed credits) or otherwise fail to be approved.

<IP_ADDRESS> Comment: Commenters IV D 12, IV D 19, IV D 21, IV D 27, IV D 28, IV D

43, and IV D 56 stated that the provision in § 63.2240( c)( 2)( vi)( B) ( which prevents emissions during monitoring malfunction and periods of control device maintenance covered in a routine control device maintenance exemption [ RCDME] from being used to generate credits and requires maximum debits) of the proposed rule is overly restrictive and is not representative of the actual emissions from process units. The commenters noted that the referenced provision states that no credits may be assigned to credit generating process units and maximum debits must be assigned to debit generating process units during periods of monitoring malfunctions, associated repairs, and required quality assurance or control activities. The commenters contended that other rules ( e. g., 40 CFR Part 75   Continuous Emissions Monitoring) address missing data in a more structured manner and do not impose worst case debit and credit estimates. Therefore, the commenters recommended that the final rule include a " more realistic approach" for times of monitoring period unavailability.

Response: We have retained the provisions in § 63.2240( c)( 2)( vi)( B) ( which prevents emissions during monitoring malfunction and RCDME from being used to generate credits and requires maximum debits) in the final rule to ensure that emissions averaging credits equal or exceed the required debits. As stated previously, the emissions averaging provisions in the final rule only require that the actual emission reductions be equal to ( or greater than) the required emission reductions. Unlike the HON, we chose not to apply a 10 percent discount factor to the 2 138 actual emission reductions for the PCWP rule, and thus some sources may operate such that the actual HAP reductions are very close to the required HAP reductions. In such cases, we believe it is especially important to ensure that the add on control systems used to generate the necessary credits are properly operating. Because the final PCWP rule does not require continuous monitoring of HAP emissions or periodic stack testing, parameter monitoring will be used to ensure that these add on control devices continuously operate in a compliant manner. As explained in section 2.7, we have reduced the number of parameters to be monitored for add on control devices. For example, PCWP sources that operate RTOs are only required to monitor temperature, which is both a reliable indicator of performance and a parameter that is easily measured and controlled. Therefore, we expect that monitoring malfunctions will be both infrequent and easily corrected.

Regarding the commenter's reference to the provisions for handling " missing data" in 40 CFR Part 75 ( Continuous Emissions Monitoring for NOx, SOx, opacity, etc., for the Acid Rain Program), we note that, in some cases, these provisions would allow sources equipped with CEMS to substitute average data for measurements made before and after the period of missing data, but in other cases, they would have to assign maximum emission rates to these periods. In the case of a PCWP facility, the maximum emission rate would be equivalent to the highest uncontrolled emission rate, which, for a credit generating source, would be the same as not allowing any credits during those periods. For a debit generating source, the maximum rate would also be equal to the highest uncontrolled emission rate, which is also consistent with what the EAP requires. Regarding the use of average values before and after an outage, we do not believe that it is appropriate to allow sources to substitute average data for periods where data are missing and then count those periods towards credit generation. As noted above, unlike CEMS,

temperature monitors are relatively simple pieces of equipment that are generally redundant within a control device such as an RTO, and thus, periods of missing data should be minimal.

We also believe that it is necessary to exclude from EAP calculations those emissions that occur when the add on control device used to generate credits is undergoing maintenance as part of an RCDME. During periods of RCDME, the affected process units are not subject to the compliance options and operating requirements, and thus, a credit generating emission source could operate during these periods without actually achieving any emissions reductions. By maintaining these restrictions in the final rule, we hope to maintain the integrity of the emissions 2 139 averaging provisions and to provide an incentive for PCWP sources to maintain their monitoring equipment and to minimize the hours they will claim under an RCDME.

<IP_ADDRESS> Comment: Commenters IV D 12, IV D 19, IV D 21, IV D 27, IV D 28,

IVD 43, and IV D 56 requested that EPA allow control device downtime to be incorporated into the emissions averaging program. The commenters contended that there are process units in the PWCP industry that require greater periods of control device downtime than are provided for in the proposed downtime provisions ( see also section 2.8 for additional comments and responses regarding routine control device exemptions.) The commenters requested that EPA address this issue by specifically stating that EAPs can be used as an additional mechanism for generating " control device downtime credits." Commenter IV D 27 provided an example to demonstrate how this process would work. In the example case, a mill chooses to reduce emissions from a blender by 90 percent. Because blender emissions are not required to be controlled, the mill would earn credit for the resultant emissions reduction. The mill would then apply the emissions credit to a rotary dryer system which is equipped with a control device that requires periods of control device downtime in excess of that allowed by the rule ( i. e, 3 percent of the dryer operating hours). Thus, the credit generated by controlling the blender would offset emissions from the dryer system when it is operating in " abort mode" during periods of control device downtime. In the commenter's example, the credits created by controlling the blender equated to 9.6 percent of the annual emissions from the dryer, and therefore, 9.6 percent would also be the percentage of the dryer operating hours that could be offset by the blender credits.

Response: We disagree with the commenters' request to allow sources to apply emission reduction credits generated for one process unit to another process unit in order to increase the maximum allowable RCDME hours for the second process unit. The emissions averaging provisions were not created to provide an opportunity for sources to increase the RCDME allowances. Furthermore, as discussed in response to comment No. <IP_ADDRESS>, we disagree that additional downtime is needed beyond the levels already allowed. In addition, PCWP sources are not allowed to receive emissions averaging credit for downtime allowances that are less than the maximum allowed percentages. Combining RCDME allowances within an emissions average would compromise the integrity of the emissions averaging provisions, which are based on the MACT floor of 90 percent control. As explained previously, the data set used to determine the MACT floor included several control devices that achieved greater than 90 percent reduction 2 140 during performance tests; however, the 90 percent control requirement was selected instead of a more stringent percent reduction to account for variability in emissions and control system performance over time. We believe that the variability in control device performance can be related to the need for control device maintenance ( e. g., an RTO with one year old media may perform less effectively than an RTO with new media). Thus, we believe that the MACT floor already accounts for efficiency losses due to varying degrees of maintenance and that combining RCDME allowances within an emissions average would result in a less stringent compliance option. Our intention in including the RCMDE provisions was not to provide an automatic allowance to release uncontrolled emissions up to 3 percent of the time, but instead, to improve the maintenance and uptime of add on control systems at PCWP. We believe that a side benefit to better control device maintenance will be more efficient control devices which will balance out any increases in emissions that may occur during periods of RCDME. Combining the RCDME with emissions averaging would upset this balance in addition to complicating the emissions averaging provisions.

<IP_ADDRESS> Comment: Commenter IV D 27 requested clarification regarding how the required and actual mass removal are to be calculated in the emission averaging program.

Specifically, the commenter asked that EPA make several clarifications to the definitions of several emissions averaging terms, as follows:

a. Definition of UCEPi: " mass of total HAP from an uncontrolled or under controlled process unit ( i) that generates debits, pounds per hour"

Clarification: UCEPi is the uncontrolled mass of total HAP from process unit ( i) ( listed in Tables 1A or 1B) that generates debits.

b. Definition of OCEPi: " mass of total HAP from process unit ( i) that generates credits, pounds per hour"

Clarification: OCEPi is the uncontrolled mass of total HAP from process unit ( i) that generates credits ( which can include those process units listed in Tables 1A or 1B), pounds per hour.

c. Definition of AMR: " actual mass removal of total HAP from all process units generating credits ( i. e., all process units that are controlled as part of the Emissions Averaging Plan), pounds per semiannual period" 2 141 Clarification: " actual mass removal of total HAP from all process units generating credits ( i. e., all process units that are controlled as part of the Emissions Averaging Plan which can include under controlled process units including those listed in Tables 1A or 1B), pounds per semiannual period"

The commenter also requested verification that the following " hypothetical scenario" at " Mill A"

is a valid example of how emissions averaging can be applied:

A rotary green dryer is the only available debit generating source at Mill A. Initial performance testing determines that this dryer has an emission rate of 5.0 pounds of uncontrolled total HAP/ hr. At Mill A, the average operating schedule for this dryer is 4,000 hours over a 6 month period.

From Equation 1: RMR = 0.90 x ( 5.0 lb/ hr x 4,000hr/ 6 mo) = 18,000lb/ 6 mo Mill A decides to control 20 percent of the green dryer emissions and finds a cost effective means to achieve 80 percent control efficiency for the emissions from the blender. Initial performance testing indicates that the blender emits 8 lb/ hr of uncontrolled total HAP. The blender operates 3,800 hours over a 6 month period.

From Equation 2: AMR = ( 0.20 x 5.0 lb/ hr x 4,000hr/ 6 mo) + ( 0.80 x 8.0 lb/ hr x 3,800hr/ 6 mo) = 28,320 lb/ 6 mo Under this scenario, the emissions averaging compliance option would allow Mill A to undercontrol the emissions from both the rotary green dryer and the blender to match the RMR value.

Response: We agree with the changes suggested by the commenter. The suggested changes further clarify that a process unit can sometimes be both a debit generating source and a credit generating source when that source is undercontrolled ( e. g., emissions reduced by less than 90 percent). In the example provided by the commenter, the green dryer is both a debitgenerating unit and a credit generating unit, and thus the uncontrolled emissions from the green dryer are accounted for in the calculations of both the actual mass removal ( AMR) and the RMR.

We agree that the example provided by the commenter is an appropriate use of the emissions averaging compliance option.

2.6.5 Concentration based applicability criteria <IP_ADDRESS> Comment: Commenter IV D 27 requested that, if EPA decides not to adopt the risk based approaches recommended by the commenter ( see also section 2.11 of this document),

then the final rule should include a 50 ppm applicability criteria for the total HAP emitted by the 2 142 regulated sources. The commenter stated that this approach is fully justified under the CAA and applicable case law and " holds great promise in focusing the rule on eliminating meaningful risks without giving rise to offsetting environmental disbenefits." The commenter stated that the 50 ppm applicability criteria could be incorporated into the final rule by adding a definition of process vent that would specifically exclude emission streams with total HAP concentrations below 50 ppm, as follows:

" Process Vent means emission streams that are undiluted and uncontrolled containing less than 50 ppmv total HAP, as determined through process knowledge that no HAP are present in the emission stream or using an engineering assessment as discussed in Sec. 63.___, test data using Methods 18 of 40 CFR part 60, appendix A, or any other test method that has been validated according to the procedures in Method 301 of appendix A of this part, are not considered process vents.

Total HAP means the sum of the concentrations of one or more of the following six compounds: acetaldehyde, acrolein, formaldehyde, methanol, phenol, and propionaldehyde."

The exhaust stream would be excluded from MACT applicability so long as its HAP content remained below the 50 ppm concentration level. The commenter acknowledged that steps would have to be taken to prevent purposeful dilution of exhaust streams if EPA adopted the concentration based applicability criteria; the commenter suggested that requiring permit limits on exhaust stream flow rate may be a possible solution.

The commenter asserted that EPA has implemented similar concentration based applicability criteria on several occasions through the definition and applicability provisions of NESHAP. The commenter pointed to the HON, which requires " Group 2" process vents to be controlled, while defining a separate category, " Group 2" process vents, that do not require control ( 59 FR 19402, 19406 [ April 22, 1994]).

The commenter noted that the HON contains a 50 ppm cutoff in the process vent definition as follows:

A Group 2 process vent is defined as a process vent with a flow rate greater than or equal to 0.005 scmm, an organic HAP concentration greater than or equal to 50 ppmv, and a TRE index value less than or equal to 1.0.

The commenter also noted that, including the HON, there are at least twelve NESHAP promulgated since 1994 that contain applicability provisions that focus the control requirements 2 143 on emissions streams above certain HAP concentrations. The commenter provided a summary of the applicability criteria for these 12 NESHAP; this information is shown in Table 2 5. The commenter claimed that, given the information provided in Table 2 5, EPA's authority to set concentration based applicability criteria " appears to be established beyond question." The commenter asserted that the authority to set concentration based applicability criteria is inherent in EPA's authority to exclude de minimis emission sources from regulatory requirements. The commenter further stated that the D. C. Circuit case law has established that, unless the governing statute is " extraordinarily rigid," EPA has presumptive de minimis authority in implementing its regulatory mandate. According to the commenter, the statutory design and legislative purpose expressed in CAA § 112 demonstrate that the statute is not extraordinarily rigid so that EPA is fully justified in applying its de minimis authority. The commenter also claimed that, even though EPA referred to concentration based applicability critieria as " de minimis cutoffs" in a number of NESHAP, EPA did not consider an explicit explanation of the Agency's de minimis legal authority to be necessary in these rules, and there were no apparent legal challenges.

Table 2 5. NESHAP with Concentration Based Applicability Cutoffs NESHAP ( 40 C. F. R. Part 63) SOURCE OF EMISSIONS CONCENTRATION CUTOFF ADDITIONAL CRITERIA Synthetic Organic Chemical Manufacturing ( Subpart F, § 63.101) Process Vent 0.005 weight percent TOC (

50 ppm) None Synthetic Organic Chemical Manufacturing: Process Vents, Storage Vessels, Transfer Operations and Wastewater ( Subpart G, § 63.111) Process Vent 50 ppmv TOC Waiver of control requirements also applies ( regardless of concentration of vent stream) if flow rate is less than 0.005 m3 per minute or " total resource effectiveness index" is greater than 1.0.

Organic HAP from Equipment Leaks ( Subpart H, § 63.161) Equipment containing or coming into contact with HAP 5 percent TOC by weight (

50,000 ppm) None Group I Polymers and Resins ( Subpart U, § 63.482) Process Vent 50 ppmv TOC Waiver of control requirements also applies ( regardless of concentration of vent stream) if flow rate is less than 0.005 m3 per minute or " total resource effectiveness index" is greater than 1.0. Table 2 5 ( continued)

NESHAP ( 40 C. F. R. Part 63) SOURCE OF EMISSIONS CONCENTRATION CUTOFF ADDITIONAL CRITERIA 2 144 Petroleum Refineries ( Subpart CC, § 63.641) Process Vent 20 ppmv measured as choice of organic HAP or TOCs Also mass based exclusions ( Total THC emissions of no more than 33 kg per day for existing [ 6.8 kg for new] sources prior to reaching any control device and prior to discharge)

Aerospace ( Subpart GG, § 63.742) Primers, Topcoats, Chemical Milling Maskants, Strippers, and Cleaning Solvents HAP and THC content of 0.1 percent for carcinogens and 1.0 percent for noncarcinogens None Equipment Leaks   Control Level 1 ( Subpart TT, § 63.1001) Equipment containing or coming into contact with HAP 5 percent TOC by weight None Pharmaceuticals ( Subpart GGG, § 63.1251) Halogenated vent stream 20 ppmv None Process Vent 50 ppmv Undiluted and uncontrolled Flexible Polyurethane Foam Production ( Subpart III, § 63.1292) HAP based process chemicals in certain applications Prohibited above 5 percent weight control None Pesticide Production ( Subpart MMM, § 63.1361) Process Vent 20 ppmv Also mass based waiver of control requirements ( organic HAP emissions from all process vents less than 0.15 Mg/ yr and the uncontrolled HCl and chlorine emissions from the sum of all process vents less than 6.8 Mg/ yr.)

Manufacture of Amino/ Phenolic Resins ( Subpart OOO, § 63.1402) Process Vent 50 ppmv organic HAP Undiluted and uncontrolled Polyether Polyols Production ( Subpart PPP, § 63.1423) Process Vent ( continuous unit) 0.005 weight percent TOC (

50 ppm) Waiver of control requirements also applies ( regardless of concentration of vent stream) if flow rate is less than 0.005 m3 per minute or " total resource effectiveness index" is greater than 1.0.

The commenter also noted that in a number of NESHAP, EPA has explained the rationale behind concentration based applicability criteria in terms of control efficiency, and included the 2 145 concept of a " total resource effectiveness [ TRE] index" as a supplemental basis for exemption from control requirements. The commenter pointed to the definition of TRE as follows:

Total resource effectiveness index value or TRE index value means a measure of the supplemental total resource requirement per unit reduction of organic HAP associated with a continuous front end process vent stream, based on vent stream flow rate, emission rate of organic HAP, net heating value, and corrosion properties ( whether or not the continuous front end process vent stream contains halogenated compounds) ( reference: 65 Fed. Reg. 38030, 38048 [ June 19, 2000] [ National Emission Standards for Hazardous Air Pollutants: Group I Polymers and Resins]).

According to the commenter, the TRE index is a measure of the efficiency of controlling a particular HAP stream in terms of energy and other resource requirements compared to the amount of HAP reduced. The commenter contended that focusing the applicability of control requirements on the basis of control efficiency is particularly appropriate with respect to low concentration HAP streams from the wood products industry because the energy use of a thermal oxidizer is particularly high as compared to the amount of HAP reduced when applied to a low rather than a high concentration emissions stream.

Other commenters ( IV D 11 and IV D 26) objected to the concept of a concentration based applicability cutoff, stating that such a cutoff is not what Congress intended in the CAAA. Commenter IV D 26 argued that a concentration based applicability cutoff would be unlawful because it would replace the MACT emission limitation with one that places no limit on the mass emission rate. Commenter IV D 26 stated that the concentration of HAP in a source's exhaust steam has no bearing on whether that source is meeting the emissions limitation.

The commenter referred to language in the preamble to the final Brick and Structural Clay Products ( BSCP) NESHAP which states that exhaust gas concentrations have no effect on mass emissions rates, and that mass emission rates are unchanged regardless of how much dilution air is added ( 68 FR 26690 at 26713, May 16, 2003). The commenter also claimed that EPA has already rejected, in prior actions, the idea that de minimis exceptions are available in the way proposed by the PCWP industry.

Response: We disagree with the request from commenter IV D 27 for a concentrationbased applicability cutoff for several reasons. First, as shown in Table 2 6, the process vent characteristics ( e. g., combination of concentration and flow rate) for PCWP facilities are dissimilar to process vents regulated by the NESHAP cited by the commenters as precedents for 2 146 the concentration based applicability exemption, and thus it would not be appropriate to " borrow"

concentration cutoffs from these other rules. Second, and more importantly, when establishing applicability cutoffs for NESHAP, we must evaluate these cutoffs in concert with the MACT floor analysis. To support the inclusion of a 50 ppmv cutoff or an alternative cutoff, we would have to clearly demonstrate that the cut off levels do not exempt emission volumes that are otherwise caught by the MACT floor. The 50 ppmv concentration based applicability cutoff proposed by the commenters does not meet this criterion because it would exempt many process units that otherwise would be subject to MACT floor controls. As shown in Table 2 7, a number of PCWP process units equipped with MACT controls that have been tested by the industry have uncontrolled emission streams with concentrations less than 50 ppmv. Third, a 50 ppmv cutoff would exempt the majority of process units in the PCWP industry from regulation, despite the fact that many of these process units are by themselves " major sources," and therefore by definition are not de minimis. When the 50 ppmv cutoffs were applied in other NESHAP, the affected emission streams had much lower flow rates ( e. g., 100 scfm), and the assumption was that such sources had only minimal emissions that were below levels that would be regulated by the applicable MACT floor. For example, the estimated average HAP emissions from a process vent exempted from the Pharmaceuticals NESHAP is 88 pounds per year. This would not be the case with wood products plants because of the higher flow rates. Table 2 8 shows the effect of higher flow rates on the mass emissions of HAP at the same concentration ( 50 ppmv). As shown in Table 2 8, at a flow rate of 20,000 dscfm, the methanol emissions associated with a 50 ppmv emission stream would be about 21 tons per year, which exceeds the threshold for a major source.

Many PCWP process units have flow rates greater than 20,000 dscfm, and therefore, the mass of HAP associated with a 50 ppmv stream can be even greater. For these reasons, the final PCWP rule does not include a concentration based applicability cut off. Additional details of our analysis of the concentration based applicability exemptions is provided in a separate memorandum. 25 2 147 Table 2 6. Comparison of Emission Sources25 Emission stream characteristic Chemical process plant sources ( e. g., HON, MON, pharmaceuticals) PCWP process sources No. of emission points per plant 25 to > 100 3 to 7 ( e. g., 2 dryers and 1 press)

Typical flowrates, scfm 100 scfm dryers: 30,000 scfm presses: 60,000 scfm Typical HAP concentrations, ppmv >> 1,000 ppmv < 150 ppmv Table 2 7. Summary of NCASI Data25 Process unit No. of units tested by NCASI No. of units tested w/ MACT controls Range in concentration of emissions ( ppmv total for 6 HAP) ( average) a No. of units with uncontrolled concentration < 50 ppmv No. of units with uncontrolled concentration < 20 ppmv All units tested Units with MACT controls All units tested Units with MACT controls Primary tube dryer 4 0 9 to 134 ppmv ( 54 ppmv) 2 ( 50%) NAb 1 ( 25%) NAb Presses 9 7 5 to 153 ppmv ( 49 ppmv) 5 ( 55%) 5 ( 71%) 3 ( 33%) 3 ( 43%)

OSB dryer 3 3 22 to 114 ppmv ( 48 ppmv) 2 ( 67%) 2 ( 67%) 0 ( 0%) 0 ( 0%)

PB dryer ( green) 4 1 6 to 51 ppmv ( 30 ppmv) 3 ( 75%) 1 ( 100%) 1 ( 25%) 1 ( 100%)

Veneer dryer 9 3 4 to 46 ppmv ( 20 ppmv) 9 ( 100%) 3 ( 100%) 6 ( 67%) 1 ( 33%)

TOTAL 29 14 4 to 153 ppmv 21 ( 72%) 11 ( 79%) 11 ( 38%) 5 ( 36%)

a Six HAP are acetaldehyde, acrolein, formaldehyde, methanol, phenol, and propionaldehyde. b NA = Not applicable because no units equipped with MACT controls were tested by NCASI. 2 148 Table 2 8. Flow Rate Versus Mass Emissions for 50 Ppmv Methanol Emission Stream Flowrate, dscfm Mass emissions, ton/ yr 20,000 21 50,000 50 100,000 103 Assumptions: ( 1) 50 ppmv of methanol in emission stream; ( 2) standard conditions; and ( 3) source operates 8,424 hours per year.

We disagree with the commenters who claimed that the requested concentration based applicability exemption can be justified by de minimis principles. Our de minimis authority exists to help avoid excessive regulation of tiny amounts of pollutants, where regulation would yield a result contrary to a primary legislative goal. It is unavailable " where the regulatory function does provide benefits, in the sense of furthering the regulatory objectives, but the agency concludes that the acknowledged benefits are exceeded by the costs." EDF v. EPA, 82 F. 3d 451, 466 ( D. C.

Cir. 1996); Public Citizen v. Young, 831 F. 2d 1108, 1112 13 ( D. C. Cir. 1987); Alabama Power v. EPA, 636 F. 2d 323, 360 61 & n. 89 ( D. C. Cir. 1979). Accordingly, a de minimis exemption to section 112( d)( 3) is unavailable in this PCWP MACT standard, because it would frustrate a primary legislative goal by carving out tons of PCWP sources' HAP emissions from regulation.

Our rejection of the de minimis concept in the MACT context has already been affirmed by the U. S. Court of Appeals for the District of Columbia Circuit, in National Lime Ass'n v. EPA,

233 F. 3d 625, 640 ( D. C. Cir. 2000) (" NLA"), in which the court rejected the industry petitioner's claim that in light of both the high costs and low quantities of HAP at issue in that case, we should read a de minimis exception into the requirement that we regulate all HAP emitted by major sources. In that case, the Court found that " EPA reasonably rejected this argument on the ground that the statute ` does not provide for exceptions from emissions standards based on de minimis principles where a MACT floor exists.'" NLA at 640. We recently re affirmed our position on the unavailability of de minimis exemptions from the MACT floor in its final NESHAP regulating organic liquids distribution. See 63 Fed. Reg. 5048 and 5049 ( February 3, 2004).

Contrary to the commenter's request, we see no reason to revisit this fundamental issue,

and reject the assertion that both EPA and the court decided this issue incorrectly in NLA. 2 149 Section 112 of the CAA is replete with careful definitions of volume or effect based limitation on regulation, indicating that Congress has already defined what amounts of HAP emissions are too small to warrant MACT standards. The requirement to adopt MACT emission limitations, for example, applies without exception to " each category or subcategory of major sources . . . of [ HAP]." CAA section 112( d)( 1). For sources below the major source threshold, however, we have discretion to require " generally available control technologies or management practices."

CAA section 112( d)( 5). Congress has thus itself defined volumetrically which sources' emissions are small enough not to warrant mandatory MACT standards.

Congress likewise defined several MACT exceptions applicable where emissions have de minimis health effects. Section 112( d)( 4) of the CAA allows us to establish standards less stringent than MACT for HAP with an established health threshold, so long as we set a standard below the health threshold with " an ample margin of safety." Section 112( b)( 3)( C) of the CAA directs us to de list HAP   precluding section 112( d) MACT standards   if we determine that " there is adequate data on the health and environmental effects of the substance to determine that emissions, ambient concentrations, bioaccumulation or deposition of the substance may not reasonably be anticipated to cause any adverse effects to the [ sic] human health or adverse environmental effects." Section 112( c)( 9)( B)( i) of the CAA lets us delete source categories from the category list   the consequence again being no MACT control   if we determine that, for emissions of carcinogenic HAP, " no source in the category . . . emits such [ HAP] in quantities which may cause a lifetime risk of cancer greater than one in one million to the individual in the population who is most exposed to emissions of such pollutant from the source." For noncarcinogens, we may delete source categories if we determine that " emissions from no source in the category or subcategory . . . exceed a level which is adequate to protect public health with an ample margin of safety and no adverse environmental effect will result from emissions from any source." CAA section 112( c)( 9)( B)( ii). Moreover, in defining which source modifications trigger additional regulatory standards, CAA section 112( g)( 1)( A) mentions a " greater than de minimis increase in actual emission of a [ HAP]." This shows that Congress knew how to use the de minimis concept when it considered such was appropriate in section 112, and the fact that it did not use it in section 112( d)( 3) supports our   and the D. C. Circuit's   conclusion that it is unavailable to support an exception to a MACT floor. 2 150 We do not find persuasive the proposition by commenter IV D 27 that the overall purpose of section 112 is protecting human health and the environment, and that, therefore, as long as this general purpose is met, we may fashion de minimis exceptions from MACT. First, this position appears to assume that the issue is to be drawn on a clean slate, while the D. C. Circuit has affirmed our view that section 112( d)( 3) provides no discretion to use a de minimis rationale to avoid MACT. Second, the commenter appears to give prominence to an over arching statutory goal over the specific language of the statutory provisions themselves, in assessing whether those provisions are " extraordinarily rigid" regarding our otherwise inherent de minimis authority; the logical extension of such an approach would be to find that no single provision in the CAA could restrict our de minimis authority, in light of the CAA's over arching purpose " to promote the public health and welfare." CAA section 101( b)( 1). Third, the commenter does not present any persuasive statutory arguments to overcome those that we presented to the court   and which the court affirmed   in NLA. Fourth, we are unable to discern the basis for the commenter's suggestion that we have in fact been relying on de minimis authority in the MACT program for several years in establishing applicability thresholds, and are not aware of any instance in which we have explicitly created such an exception from an identified MACT floor. Finally, to the extent the commenters believe such a de minimis exemption is justified by the wish to reduce the costs of the PCWP MACT rule, we are not free to grant a de minimis exemption to account for costs: Congress already took cost into account in section 112( d), relying on prior business judgments by the best performing sources to substitute for the judgment of the rest of the PCWP industry, therefore denying us the leeway to consider costs as a factor to modify the MACT floor.

Only in considering more stringent " beyond floor" standards may we consider costs in the MACT context. Therefore, we do not believe it is appropriate or necessary to revisit the Agency's and the D. C. Circuit's prior conclusions regarding the availability of the de minimis principle in the final PCWP NESHAP. We also note that even if reliance upon a de minimis theory were not precluded under section 112( d), in light of the relatively high flow rates of PCWP process units,

some of which would be major sources on their own while complying with a 50 ppmv cutoff, it would be impossible to find that subjecting these units to the MACT floor would yield a gain of " trivial or no value." 2 151 2.7 TESTING AND MONITORING REQUIREMENTS 2.7.1. Emission measurement test methods <IP_ADDRESS> Comment: Commenters IV D 20 and IV D 27 supported the inclusion of NCASI test methods in the proposed PCWP rule, but recommended that EPA replace NCASI Method IM/ CAN/ WP 99.01 with the revised version of the same method. Commenter IV D 20 provided a revised version of NCASI IM/ CAN/ WP 99.01 ( which was later renumbered as NCASI IM/ CAN/ WP 99.02), noting that the trained NCASI sample team was able to get good consistent results with the original version of the method both in the laboratory and the field, but that sampling contractors had difficulty obtaining valid results. Commenter IV D 20 maintained that the revised version is easier to understand, is more complete in detail, provides a better standard for the impinger/ canister method, and reflects the comments of the contractors that have experience with the original method; the quality assurance requirements were also strengthened to ensure good results.

Another commenter ( IV D 04) stated that their experience with the NCASI Method CI/ WP 98.01 ( proposed for measurement of methanol and formaldehyde) showed that sampling stack emissions with a high moisture content would require a large impinger, isokinetic version of this method to ensure accuracy. Therefore, this commenter requested that EPA add guidance in the final rule to allow the use of the isokinetic version of the NCASI method when needed.

Commenter IV D 27 also noted that NCASI Method DI/ MEOH 94.02 has been revised and is now NCASI Method DI/ MEOH 94.03. The more recent version of this method should be included in the PCWP rule.

Response: The final PCWP rule references the most recent version of NCASI Method IM/ CAN/ WP 99.02, as requested by the commenter. Regarding the revised version of NCASI Method DI/ MEOH 94.02, this method does not apply to this rulemaking, and therefore, we did not update references to this method in the General Provisions ( 40 CFR Part 63.14) as part of this rulemaking. Regarding one commenter's request to allow the use of a " large impinger, isokinetic version" of NCASI Method CI/ WP 98.01 for stack emissions with high moisture content, we note that such a version does not exist. We also note that the majority of the HAP data used in the development of the PCWP rule was collected using NCASI Method CI/ WP 98.01 as is.

Someone would have to develop and validate an alternative large impinger, isokinetic version of 2 152 NCASI Method CI/ WP 98.01 before such a method could be included in the PCWP rule.

Therefore, the final rule does not include an alternative version of NCASI Method CI/ WP 98.01.

<IP_ADDRESS> Comment: Commenter IV D 27 supported the variety of choices given for measurements and methods in Table 4 to proposed subpart DDDD. The commenter stated that having multiple testing options will allow facilities and sampling contractors to choose the method that best fits their needs and application. The commenter contended that EPA should also give PCWP facilities the option to use future methods once they have been reviewed by EPA and have passed Method 301 validation at a PCWP plant. The commenter noted that NCASI is currently developing a method for measuring the six HAP (" total HAP") listed in the PCWP rule. Although this new method probably will be field validated via EPA Method 301 procedures, it will not be eligible for alternate method approval by EPA, since a primary method that has been validated at PCWP sources does not exist. The commenter stated that a change to Table 4 to subpart DDDD could rectify that situation.

Response: As discussed in the preamble to the final PCWP rule, if and when a new method for measuring HAP from PCWP sources is developed and validated via EPA Method 301, we will issue an amendment to the final rule to include the use of that method as an alternative to the methods included in the final rule for measuring total HAP ( i. e., NCASI Method IM/ CAN/ WP/ 99.02 and EPA Method 320 Measurement of Vapor Phase Organic and Inorganic Emission by Extractive FTIR). In the meantime, if the new method is validated using Method 301, then the Method 301 results can be used to request approval to use the new method on a site specific basis.

<IP_ADDRESS> Comment: Commenter IV D 27 supported the use of Method 25A for measuring THC as carbon and Method 18 for measuring methane for the purpose of subtracting methane from THC concentration. Commenter IV D 03 requested that other compounds such as acetone be added to the exempt compound list so that they can be quantified and subtracted from Method 25A results.

Response: We allowed sources to subtract methane from the THC values measured using EPA Method 25A for two reasons. The first reason is that a number of PCWP facilities equipped with MACT level controls installed these controls to reduce VOC emissions, and these facilities are allowed to subtract methane emissions from the THC measurement when reporting VOC emissions because methane is not a VOC according to EPA's definition of VOC. The second 2 153 reason is that we accounted for the effects of methane emissions when setting the outlet THC emission level at 20 ppm and the percent reduction of THC at 90 percent as part of the development of the compliance options for add on control systems. We do not have data on emissions of other compounds excluded from the definition of VOC ( such as acetone) that may be emitted from PCWP process units, and thus, we do not know how subtraction of these compounds would affect our prior determinations. Also, it is important to note that the PCWP rule is not a VOC rule and THC is only used as a surrogate in the final PCWP rule as a means of assessing HAP emissions control device performance. If sources need to calculate total VOC emissions to demonstrate compliance with VOC emission limits, then they can subtract these other compounds for that purpose; however, for the purpose of complying with PCWP MACT,

sources must follow the procedures in the PCWP final rule for determining the THC emission reduction or outlet THC concentration, depending upon which option they choose.

<IP_ADDRESS> Comment: Commenter IV D 19 supported the use of one half detection limits for nondetect HAP to an extent, but not in every case. The commenter noted that, if a test shows a HAP to be below the detection limit but the number of " hits" is statistically significant, then using the one half detection limit is valid, provided the sample is a true representation of the system.

However, in some cases, the one half detection limit is used when only one point in one set of data provides evidence that a HAP exists for that process unit. The commenter contended that EPA should consider alternatives for these types of situations. The commenter also stated that,

" any presumption of one half detection limits based on emission factor data should be a rebuttable presumption which could be remedied by site specific acquisition of a statistically significant number of determinations." Commenter IV D 21 requested that nondetect data not be " arbitrarily" treated as one half detection limit, and stated that " EPA should provide for consistent handling of non detect data throughout the rule."

Response: The final rule requires PCWP facilities to treat all nondetect HAP measurements as being equal to one half the detection limit, with one exception, as explained previously in Section <IP_ADDRESS> of this document. When a PCWP facility measures uncontrolled HAP emissions to demonstrate compliance with the PBCO, the facility may treat the emissions of an individual HAP as being zero if all three test runs yielded a nondetect measurement and the detection limit was set at less than or equal to 1 ppm. 2 154 2.7.2 Capture efficiency test methods <IP_ADDRESS> Comment: Commenter IV D 03 argued that the use of methods other than Method 204 and the tracer gas method should be allowed for determining capture efficiency. The commenter noted that the press emissions from their facility are captured by a canopy hood system designed to meet the American Conference of Governmental Industrial Hygienists ( ACGIH) guidelines and then directed to a venturi scrubber. The commenter requested that the final rule allow their facility to demonstrate a 95 percent or greater capture efficiency by presenting the design information to the regulatory authority for review and approval.

Response: The commenter did not provide any data to confirm that a hood designed by the ACGIH design criteria actually achieves at least 95 percent capture efficiency. However, we would like to note that a facility is allowed to petition the Administrator for permission to use any alternative methods. The commenter should be aware that the Administrator will require evidence that meeting the ACGIH design criteria allows the hood to achieve an acceptable capture efficiency. The facility will have to confirm the hood capture efficiency with a test like the tracer gas method in Appendix A of the final PCWP rule. Alternatively, appendix A to subpart KK to part 63, Data Quality Objective and Lower Confidence Limit Approaches for Alternative Capture Efficiency Protocols and Test Methods, establishes the criteria for using alternative methods to demonstrate capture efficiency. Unless the facility confirms the hood capture efficiency, the facility is not likely to receive permission to use the ACGIH guidelines as an alternative method to determining capture efficiency.

<IP_ADDRESS> Comment: Commenter IV D 27 requested that the sampling period for press vent enclosure certification via method 204D be reduced from three hours to no more than one hour.

The commenter stated that this press test method was developed for surface coating and printing operations, which have much longer production cycles than the hot presses used in wood panels manufacturing. The commenter noted that a batch cycle for a batch wood panel press lasts only minutes rather than hours, and continuous presses will probably replace batch presses over time.

Therefore, the commenter recommended that the duration of each test run should be based on the cycle time of the individual press operation.

Response: We decided not to change the sampling period requirements in EPA Method 204D. We do not have data to ensure that Method 204D sampling periods lasting only minutes would yield optimal results, especially given the commenter's assertions elsewhere that press 2 155 emissions within enclosures may not flow freely to the exhaust point in the top of the enclosure ( See related comments in Section <IP_ADDRESS> and <IP_ADDRESS>). We note that section 1.3 of Method 204D states that the capture efficiency test must include three sampling runs, and that " each run shall cover at least one complete production cycle, but shall be least 3 hours long." The method also states that, " Alternative sampling times may be used with the approval of the Administrator."

Therefore, PCWP facilities using Method 204D still have the option of requesting alternative sampling times on a site specific basis.

In addition, we are not compelled to change the sampling time in EPA Method 204D because PCWP facilities are not required to use Method 204D. Facilities may use the alternative tracer gas method in appendix A of the final PCWP rule, which requires only 20 minute test runs.

Also, appendix A to subpart KK to part 63 ( Data Quality Objective and Lower Confidence Limit Approaches for Alternative Capture Efficiency Protocols and Test Methods) establishes the criteria for using alternative methods to demonstrate capture efficiency, and this appendix states a minimum sampling time of 20 minutes per run.

<IP_ADDRESS> Comment: Commenter IV D 27 supported EPA's recognition of the need for flexibility in determining capture efficiency for PCWP press enclosures and inclusion of the tracer gas method as an alternative to Method 204 in the PCWP rule. The commenter noted that the tracer gas method is a " work in progress" and included with their comments a copy of field validation tests conducted at a Georgia Pacific Corporation OSB facility. Commenter IV D 19 also submitted test results for the tracer gas method as part of their comments on the proposed rule. Commenter IV D 27 stated that two more tests are scheduled for the second quarter of 2003, one to verify the Georgia Pacific results and the other to determine the capture efficiency of a PTE at a second OSB facility. Commenter IV D 27 stated that the results of these tests should help EPA improve the use and application of the proposed tracer gas test.

Response: We have reviewed the results of the first field validation test of the tracer gas method, and we note that the commenters did not provide any specific recommendations for modifying the tracer gas method as it was proposed. Therefore, other than a few minor wording changes, we did not make any substantive changes to the tracer gas method in the final rule. If the results of subsequent field tests demonstrate a need to ( further) modify the tracer gas method,

we will issue an amendment to the final rule to incorporate the necessary changes. Furthermore,

appendix A to subpart KK to part 63, Data Quality Objective and Lower Confidence Limit 2 156 Approaches for Alternative Capture Efficiency Protocols and Test Methods, establishes the criteria for using alternative methods to demonstrate capture efficiency, and this appendix would allow the industry to submit a modified tracer protocol for approval, as long as it met the acceptance criteria for an alternative procedure.

<IP_ADDRESS> Comment: Commenters IV D 19, IV D 21, and IV D 27 recommended that the final rule include work practice requirements in lieu of requiring EPA Method 204 certification for press enclosures, based on their assertion that press enclosures certified to meet EPA Method 204 do not constitute the MACT floor for presses ( see previous discussion in Section 2.3   Existing Source MACT Floor). The commenters noted that the proposed PCWP rule does not require an initial performance test for work practice requirements, so verification of the capture efficiency for PTEs should be a one time determination based on satisfying the press enclosure work practice requirements. The commenters stated that, for any enclosure that is not a PTE, a facility should have to determine the capture efficiency using the tracer gas method, Methods 204A through 204F, or alternate methods approved by the Administrator. The commenters recommended the following additions to Table 6 to subpart DDDD ( Initial compliance demonstrations for work practice requirements):

For each . . . For the following work practice requirements . . . You have demonstrated initial compliance if . . .

( 5) Hot Presses Minimize fugitive emissions from the capture device through appropriate operation and maintenance procedures applied to PTE system. You meet the work practice requirements AND you submit with the Notification of Compliance Status a copy of your plan for minimizing fugitive emissions from the capture device ( as required in § 63.2267) 2 157 Also, commenter IV D 27 suggested the following additions to Table 3 to subpart DDDD to include the new work practice requirements for presses:

For the following process units at existing or new affected sources . . . You must . . .

( 5) Hot Presses Install and operate a capture device according to the following: For PTEs: Permanent Total Enclosure ( PTE) means a permanently installed containment that was designed to meet the following physical design criteria: 1. Any NDO shall be at least four equivalent opening diameters from each THC emitting point unless otherwise specified by the Administrator. The MACT floor configuration of the PTE includes capturing emissions from the press unloader. For purposes of determining compliance with criteria 1, the distance from the THCemitting point will be considered to the press. 2. The total area of all NDOs shall not exceed 5 percent of the surface area of the enclosure's four walls, floor, and ceiling. 3. The average facial velocity ( FV) of air through all NDOs shall be at least 3,600 m/ hr ( 200 ft/ min). The direction of airflow through all NDOs shall be into the enclosure. 4. All access doors and windows whose areas are not included in 2 and are not included in the calculation of FV in 3 shall be closed during routine operation of the process. 5. Fugitive emissions shall be minimized through appropriate operation and maintenance procedures applied to the PTE system. If a PTE meets the above criteria, it will meet the emissions capture requirements of the floor technology. The destruction efficiency for the captured emissions would be 90 percent. For Non PTEs: Existing and future enclosures that are not PTE, should be required to demonstrate 90 percent capture and control efficiency using the tracer gas method or some other method subject to the approval of the Administrator, and the appropriate test method for the compliance pollutant. Any shortfall in capture could be remedied via an emission averaging approach or through acceptance of a higher offsetting destruction efficiency requirement. 2 158 Commenter IV D 21 recommended a similar addition, but with some slight changes to item 1 as follows:

1. Any natural draft opening ( NDO) shall be at least four equivalent opening diameters from each VOC emitting point, except for where mat enters the enclosure and the board from the unloader exits the enclosure, unless otherwise specified by the Administrator.

Finally, commenter IV D 27 recommended the following changes to Table 4 to subpart DDDD to reflect changes to performance test requirements:

For . . . You must . . . Using . . .

( 9) Each reconstituted wood products press at a new or existing affected source or reconstituted wood product board cooler at a new affected source subject to a compliance option in Table 1B or used in calculation of an emissions average under § 63.2240( c). For Non PTEs  Determine the percent capture efficiency of the enclosure directing emissions to an add on control device.

For PTEs  Determine the reduction in emissions or percent destruction efficiency of the control device. Methods 204 and 204A through 204F ( as appropriate) of 40 C. F. R. part 51, appendix M. As an alternative to Methods 204 and 204A through 204F, you may use the tracer gas method contained in appendix A to this subpart.

Refer to ( 1) through ( 8) of this Table for the appropriate test method.

Response: As discussed in response to comment <IP_ADDRESS>, the final PCWP rule sets forth design criteria for wood products enclosures. These criteria are slightly different from the EPA Method 204 design criteria for PTEs. The final PCWP rule contains a definition of " wood products enclosure" which states the design criteria, and a definition of " partial wood products enclosure" which includes any enclosure other than a " wood products enclosure." Capture devices meeting the definition of " wood products enclosure" are assumed, for all practical purposes, to achieve 100 percent capture of emissions. Because the capture efficiency of " partial wood products enclosures" is unknown, the final rule requires facilities to test the capture efficiency of partial wood products enclosures using EPA Methods 204 and 204A F ( as appropriate), or the alternative tracer gas procedure included in appendix A to subpart DDDD.

The final rule requires facilities using partial wood products enclosures to demonstrate a combined 90 percent capture and control efficiency for those facilities showing compliance with the percent reduction requirements for APCDs. If the partial wood products enclosure does not 2 159 achieve high capture efficiency, then facilities must offset the needed capture efficiency by achieving a higher destruction efficiency or by using emissions averaging ( with the press being an undercontrolled process unit).

The final rule requires a one time verification of the capture efficiency for wood products enclosures and partial wood products enclosures. To assume 100 percent capture efficiency using a wood products enclosure, facilities must submit with the Notification of Compliance Status documentation that the wood products enclosure meets the design criteria defined in the rule. For partial wood products enclosures, facilities must submit with the Notification of Compliance Status the results of capture efficiency verification using EPA Methods 204 and 204A F ( as appropriate), or the alternative tracer gas procedure included in appendix A to subpart DDDD.

Wording changes were made in various places in the proposed rule to incorporate the revised requirements for wood products enclosures and partial wood products enclosures. These wording changes are different from the wording suggested by the commenters but accomplish the same purpose ( i. e., the design criteria are included in the definitions but not included as work practices).

2.7.3 General monitoring <IP_ADDRESS> Comment: Commenter IV D 27 noted that the third column of Line 1 in Table 7 to subpart DDDD currently states that compliance is demonstrated by " maintaining the average operating parameter at or above the maximum, at or below the minimum." However, based on the definitions of maximum and minimum, this phrase should be " at or below the maximum, at or above the minimum."

Response: We agree with the suggested change and have modified Table 7 to subpart DDDD in the final rule as suggested.

2.7.4 Block averaging period for operating requirements <IP_ADDRESS> Comment: Commenters IV D 19, IV D 21, and IV D 27 requested that the proposed 3 hour block averaging period specified by the proposed operating requirements be extended for most of the monitoring parameters. The commenters specifically recommended that the 3 hour block averaging period be extended to a 12 hour block, except as noted elsewhere.

The commenters noted that the 3 hour averaging time was selected by EPA because the initial performance test requires three 1 hour test runs, but contended that this time period is impractical for continuous monitoring of control device performance. The commenters stated that a 3 hour 2 160 block average monitoring requirement would increase monitoring and recordkeeping requirements without guaranteeing compliance and would increase the number of insignificant deviations reported. The commenters argued that 3 hours would not be enough time in all cases for operators and equipment to respond and adjust to changes along the process line, such as a change in the wood species. As an example, the commenters pointed to variation in measurements and instrumentation as another justification for extending the block average.

According to the commenters, there can be a large variation between instruments measuring a specific parameter at different locations on a process unit or control device. As an example, the commenters pointed to the variation between thermocouples used to measure the temperature of the RTO combustion chamber and control the burners. The commenters stated that the temperature reading will vary from thermocouple to thermocouple, and the variation could be as high as 50 º F. The commenter noted that, depending on the operating conditions, this variation could be much lower, and a longer block averaging time would enable plant operators to get a better sense of whether or not a device is actually within the operating limits. The commenters also noted that some of these problems could be alleviated by allowing the source to establish an operating window during compliance testing instead of being required to operate at typical conditions during the compliance test ( see related comment in Section 2.7.5). The commenters specifically recommended recording data readings for RTOs and RCOs every 15 minutes and then including all the data in a 12 hour block average.

The commenters further justified the 12 hour block average as being consistent with industry practice. According to the commenters, several of the consent decrees negotiated between EPA and industry that were included in the MACT floor determination contain 12 hour block average parameter monitoring requirements. The commenters contended that the 12 hour time period in these consent decrees reflects the agreement between EPA and industry that this longer time period is adequate for monitoring control device performance.

Response: We have decided to reduce the number of control device operating parameters that must be measured to ensure compliance with the final rule ( see responses to comments in Sections 2.7.10 through 2.7.14). In the final PCWP rule, temperature is the only parameter that is required to be continuously monitored to meet the operating requirements for the listed add on control devices. Because we have reduced the stringency of the operating requirements for addon controls and because temperature is both a controllable parameter and a reliable indicator of 2 161 control device performance, we have decided to retain a block averaging period of 3 hours.

Regarding the comments related to variation among thermocouple readings, we agree that individual thermocouple readings within an RTO may vary by as much as 50  F. In a typical RTO,

there are multiple combustion chambers, each with one or more thermocouples. The final rule clarifies the temperature monitoring requirements for RTOs to make it clear that the operating limit applies to the combined average temperature of the thermocouples in each combustion chamber rather than to the temperature measurement for one individual thermocouple. If there are multiple thermocouples within each combustion chamber, we expect that facilities would average the measurements from each thermocouple to provide a representative temperature for the combustion chamber. Regarding consent decrees between EPA and wood products companies, we note that, although some of the companies are allowed to use a 12 hour block average, these companies also are required to monitor multiple operating parameters ( e. g.,

temperature, air flow, pressure drop).

2.7.5 Testing at boundary conditions <IP_ADDRESS> Comment: Commenters IV D 21 and IV D 27 argued that because the initial compliance tests determine the outer limits of compliance, those tests should be performed at the boundaries of expected performance for the process and control units. The commenters noted that the PCWP rule currently requires testing at " representative" conditions, but only using " representative" conditions would not accurately simulate true operating conditions, and thus, the operating parameter limits would be too narrow. Therefore, the commenters contended that the rule should specify that initial compliance tests should be conducted at the extremes of the expected operating range for the parameter and control device function. The commenters stated that removing the requirement to test under representative conditions would eliminate the need for facilities to explain why the initial compliance testing conditions are " representative," and instead, facilities should be required to explain why the boundary conditions chosen for testing are valid. In addition, commenter IV D 21 noted that this approach should also address potential conflicts with traditional State requirements to test at maximum or design conditions.

Response: Our definition of " representative operating conditions" refers to the full range of conditions at which the process unit will be operating in the future. We expect that facilities will test a variety of conditions, including upper and/ or lower bounds, to broaden their operating limit ranges. There are advantages to requiring performance testing at representative operating 2 162 conditions for the PCWP rule. Facilities do not routinely operate at maximum conditions; two commenters pointed out ( see comment No. <IP_ADDRESS>) that maximum operating conditions occur less that 5 percent of the time. Compliance with the PCWP rule can be achieved using a variety of APCD ( e. g., RTO, RCO, biofilter) or through use of emissions averaging or PBCOs. One reason we chose to require representative conditions rather than maximum conditions was to ensure consistency in determining emissions averaging credits and debits. In addition, operating parameters required to be monitored to show compliance do not always correlate with maximum conditions. For example, commenters noted in comment <IP_ADDRESS> that when the RCO inlet THC concentration is high ( as would be the case for testing under maximum operating conditions), the RCO would operate at temperatures higher than the set point during the performance test and the RCO minimum temperature limit would be set too high for production rates less than full capacity. Requiring testing at representative operating conditions resolves this problem.

Furthermore, as discussed in response to comment No. <IP_ADDRESS>, for process units without control devices, the final PCWP rule requires facilities to select the process unit controlling operating parameter( s) based on representative operating conditions; to establish the operating limit for each controlling parameter as the minimum, maximum, range, or average ( as appropriate depending on the parameter) recorded during the performance test( s); and maintain these parameters within the ranges established during the performance test( s). Facilities operating biofilters must maintain their biofilter bed temperature within the range established during the initial performance test and,

if available, previous performance tests. If the final PCWP rule required testing at maximum operating conditions, then there would be no way for facilities to identify their operating parameter ranges. For these reasons, we maintain that the requirement to test at representative operating conditions is appropriate for the PCWP rule.

2.7.6 Compliance exemption during performance testing <IP_ADDRESS> Comment: Commenters IV D 21 and IV D 27 requested that EPA make an addition to sections 63.2262( k)( 4) ( Establishing thermal oxidizer operating requirements) and 63.2262( l)( 4) ( Establishing catalytic oxidizer operating requirements) so that facilities can avoid being in violation of compliance when they are testing new operating ranges. Commenter IV D

27 provided the following sentence to be added to the end of the paragraph at ( 4): " If, in attempting to expand the operating range the required removals are not attained, it does not constitute a violation during the period of the testing." Commenter IV D 21 provided similar 2 163 language: " If, in attempting to expand the operating range the required removals are not attained,

said failure to achieve the required removals shall not constitute a violation during the period of the testing."

Response: The final rule does not include the sentence requested by the commenter. We believe that decisions regarding whether or not a violation has taken place during the period of testing should be made if and when such a situation arises on a case by case basis. We note that,

in the final PCWP rule, temperature is the only parameter that is required to be continuously monitored to meet the operating requirements for thermal oxidizers and catalytic oxidizers. When conducting tests to expand the temperature range ( e. g., lower the minimum temperature for an RTO), we expect that most PCWP sources will exercise some caution ( e. g., reduce the temperature in a stepwise fashion rather than making a significant drop) and will choose a temperature level that gives them an acceptable " margin of safety" to avoid the situation cited by the commenter.

2.7.7 Post deviation performance testing <IP_ADDRESS> Comment: Commenters IV D 21 and IV D 27 argued that a deviation from the parameter limits set when a Continuous Parameter Monitoring System ( CPMS) is used may not indicate violation of compliance. The commenters noted that a deviation indicates that a plant is outside the lines of assured compliance, but the normal operation of a process unit may change slightly after maintenance. For example, when the ceramic media in an RTO is replaced, there can be a noticeable increase in the air flow through the RTO, which could deviate from the established parametric range. The commenters argued that the rule should include an exemption from noncompliant status if follow up performance testing shows that the compliance options were being met during an " operating requirement" deviation. The commenters further stated that the Pulp and Paper NESHAP ( 40 CFR § 63.453( p)) includes a similar exemption, so the ideas and wording from that rule could be incorporated into the PCWP NESHAP. Specifically, the commenters requested that the following paragraph be added to section 63.2240 ( What are the compliance options and operating requirements and how must I meet them?):