125 enclosure and incineration based control or biofilter,

regardless of whether or not batch and continuous presses are treated as separate equipment groups. In addition,

there is a Method 204 certified PTE around a 181 ft continuous press at a newer PCWP facility ( which was not included in original data collection efforts and the preproposal MACT floor determination); however, this press has had some operational problems associated with its PTE. It is not clear if the operational problems experienced by this 181 ft long press are the result of poor PTE design or inherent technical difficulties associated with enclosing long continuous PCWP presses.

Long continuous presses are generally being installed at new PCWP facilities, as opposed to being retrofit at existing facilities. Given that there is at least one long continuous press ( 110 ft) with a Method 204 certified PTE that has not experienced operational problems with its press enclosure, we feel that wood products enclosures ( as defined in today's final rule) can be designed around long continuous presses. We recognize that higher cost may be associated with wood products enclosures around long continuous presses than for batch presses, but the CAA does not allow us to consider cost at the MACT floor control level.

We note that enclosures greater then 200 ft in length 126 are common in the printing/ publishing industry. However, we do recognize there are differences in the enclosures used in the printing/ publishing industry and those in the PCWP industry. Although not cyclical in operation like batch presses, continuous presses are heated operations and may also have internal pressurization issues similar to those raised by the commenters for batch presses. Therefore, we feel it is appropriate for the same definition of wood products enclosure promulgated for batch presses to apply to long continuous presses as well ( as opposed to Method 204 certification).

3. MACT Floor Determinations of No Emissions Reductions Comment: Industry commenters stated that thesupported our proposed MACT floor determinations of no emissions reductions for some process units are correct and accurately reflect current PCWP facility practices. The commenters stated that the method used to determine the MACT floors was proper under the CAA and, arguing our approach was fully consistent with recent decisions made byapplicable case law in the U. S. Court of Appeals for the D. C. Circuit ( i. e.,

Cement Kiln Recycling Coalition v. EPA, 255 F. 3d 855 ( D. C.

Circuit 2001) and National Lime Association v. EPA, 233 F. 3d 625 ( D. C. Cir. 2000)). According to the industry commenters, in Cement Kiln, EPA identified the median of the best performing 12 percent of sources and set the MACT floor 127 at the worst emission level achieved by any source using the same emission control technology that was used by most of the top 12 percent. The industry commenters noted that the D. C. Circuit ruled that this MACT floor was not a valid estimate of the performance of the best performing sources in practice and that EPA assumed that control technology was the only way to reduce HAP emissions, but other factors were influencing the reduction. The industry commenters noted that some of those factors could have been inadequate maintenance or inferior operating practices, in which case the worst performing sources would certainly not be an estimate of the best performing sources under the most adverse conditions. According to the industry commenters,

the court noted that if EPA could demonstrate that MACT technology significantly controlled emissions, or that factors other than the control had a negligible effect, the MACT approach could be a reasonable means of satisfying the statute's requirements. The industry commenters noted that,

in developing the PCWP rule, EPA again followed the MACT approach, determining. EPA properly determined that the average of the best performing 12 percent of certain existing PCWP process units did not reflect the use of any control technology. The industry commenters further noted that, in the proposed PCWP rule, EPA determinedand that no other universally applicable variables would affect HAP 128 emissions, a determination it did not make in Cement Kiln.

According to the industry commenters, for the PCWP process units for which the MACT floor is 90 percent, EPA again determined that there are no other factors that significantly impact the removal efficiencies of the add on controls. For these reasons, the industry commenters contended that EPA corrected the mistakes made in the Cement Kiln situation when developing the PCWP MACT.

The industry commenters noted that in National Lime, EPA followed a similar MACT approach to Cement Kiln, but it had insufficient data for some HAP. According to the commenters, if EPA found an insufficient number of plants in its database controlling a particular HAP with pollution control technology, it determined that the emission floor was no control. The industry commenters noted that the D. C.

Circuit stated that if EPA did not consider alternative pollution reducing measures, it could not decline to set emissions standards on the grounds that the best performing sources did not use control technology. The industry commenters stated that the D. C. Circuit ruling in National Lime does not prevent EPA from setting a MACT floor of no emissions reductions; however, it does require EPA to examine all methods of removing HAP before setting a floor.

According to the industry commenters, in developing the PCWP rule, EPA did look. The commenters also claimed that EPA 129 looked at pollution prevention ( P2) measures and other approaches to determining the MACT floor but, found none that are universally applicable to reduce HAP emissions.

Therefore, the industry commenters contended that EPA is permitted by statute to set the MACT floor for existing sources at any level not less stringent than the average limitation achieved by the best performing 12 percent, even if that floor level reflects no reduction in emissions.

One commenter disagreed with the industry commenters and stated that not establishing emission reduction limits for operations like miscellaneous coating and wastewater is unlawful. The commenter argued that EPA should not make its MACT floor decisions based on insufficient information and the fact that there is no current control in place. The commenter stated that, according to National Lime Ass'n v.

EPA, 233 F. 3d 625, 633 634 ( D. C. Cir. 2000), EPA cannot set a MACT floor of, and therefore was permitted to base a no emissions reductions because it feels that a pollutant is not controlled by any particular technology. The commenter also stated that EPA failed to explain why insufficient data are available and what additional steps could be taken to obtain the necessary data. For these reasons, the commenter stated that EPA's proposed MACT floor levels of no emissions reductions are unlawfulreduction floor on the PCWP record.

Response: As explained in the proposal preamble and 130 supporting documentation, for those process units not required to meet the control requirements in the PCWP rule as proposed, we determined that: ( 1) the MACT floor level of control is no emissions reductions, and beyond the floor control options are too costly to be feasible; or ( 2)

insufficient information is available to conclude that the MACT floor level of control is represented by any emissions reductions. We based our MACT floor determinations for PCWP emission sources on the presence or absence of an add on air pollution control device because we are not aware of any demonstrated P2 techniques that can be universally applied across the industry, and we have no information on the degree of emissions reduction that can be achieved through P2 measures. Therefore, to our knowledge the use of add on controls is the only way in which PCWP sources can currently limit HAP emissions, and the only way to identify the MACT floor for these sources is to identify a level that corresponds to that achieved by the use of add on controls.

When determining the MACT floor, we ranked the process units by control device rather than by actual unit specific emissions reductions because we have limited inlet/ outlet emissions data. Based on the available information, we are not aware of any significant design or operational differences among each type of control system evaluated that would affect the ranking of process units. Furthermore, we 131 are not aware of factors other than the type of control system used that would significantly affect the ranking of process units. An analysis of the available emissions data does not reveal any process variables that can be manipulated ( without altering the product) to achieve a quantifiable reduction in emissions. Ranking process units according to control device, we determined that the MACT floor is no emissions reductions for several process unit groups including press predryers, fiberboard mat dryers, and board coolers at existing affected sources; and dry rotary dryers, veneer redryers, softwood plywood presses, hardwood plywood presses, engineered wood products presses, hardwood veneer dryers, humidifiers, atmospheric refiners, formers,

blenders, rotary agricultural fiber dryers, agricultural fiber board presses, sanders, saws, fiber washers, chippers,

log vats, lumber kilns, storage tanks, wastewater operations, miscellaneous coating operations, and stand alone digesters at new and existing affected sources.

As explained in the promulgation BID and supporting documentation, we also determined that beyond the floor control options are too costly for these process unit groups.

At proposal, we requested comment on whether no emissions reductions for miscellaneous coating operations and for wastewater operations is appropriate ( 68 FR 1276, 132 January 9, 2003). We also requested that commenters on this issue submit any information they might have on HAP or VOC emissions from miscellaneous coating operations and wastewater operations. However, no additional information on these operations was received from any of the commenters on the proposed rule. Following proposal, we reviewed our MACT analyses for miscellaneous coating and wastewater operations, as described in the following paragraphs and in the promulgation BID and supporting documentation. For miscellaneous coating operations, we gathered some additional information and were able to revise our conclusions regarding MACT in the absence of specific information on the emissions reduction achieved. However,

we have no more reason to feel now than we did at proposal that PCWP wastewater operations are in fact subject to any emission control measures.

Based on the available information, we have no basis to conclude that the MACT floor for new or existing sources is represented by any emission reductions for several of miscellaneous coating processes ( i. e., anti skid coatings,

primers, wood patches applied to plywood, concrete forming oil, veneer composing, and fire retardants applied during forming), and we determined that there are no cost effective beyond the floor measures to reduce HAP from these coating processes. However, some facilities reported use of 133 water based ( non HAP) coatings in their MACT survey responses for other types of coatings ( including edge seals,

nail lines, logo paint, shelving edge fillers, and trademark/ gradestamp inks). Other facilities reported use of solvent based coatings for these processes. In some instances, a few respondents provided information on the percent HAP content of a solvent based coating.

Solvent based coatings do not always contain HAP ( e. g., the solvent may be mineral oil which does not contain HAP), and water based coatings typically do not contain HAP. Thus,

many of the coatings reported in the MACT survey responses are non HAP coatings. While the emission reduction achieved as a result of coating substitutions cannot be determined,

it is clear that use of non HAP coatings represents the MACT floor because of the large number of facilities reporting use of non HAP coatings. Beyond the floor options were not considered for edge seals, nail lines, logo paint, shelving edge fillers, and trademark/ gradestamp inks because no further emissions reductions can be achieved than through use of non HAP coatings. Based upon our revised MACT analysis, the final PCWP rule requires use of non HAP coating for processes identified as group 1 miscellaneous coating processes.

The definition of non HAP coating included in the final rule was based on the description of non HAP coatings in the 134 final WBP NESHAP ( subpart QQQQ to 40 CFR part 63). This definition allows for unavoidable trace amounts of HAP that may be contained in the raw materials used to produce certain coatings. Through the definition of group 1 miscellaneous coatings in the final rule, kiln dried lumber is excluded from the requirement to use non HAP coatings because application of coatings used at kiln dried lumber manufacturing facilities is not part of the PCWP source category. Although trademarks/ gradestamps are applied to kiln dried lumber, lumber kilns are the only processes at kiln dried lumber manufacturing facilities covered under the PCWP source category.

For wastewater operations, we concluded that we had insufficient information to conclude that the MACT floor level of control is represented by any emissions reductions.

The available information on wastewater operations collected as part of the MACT survey of the PCWP industry and information contained in State permits indicated that these sources of emissions were not the subject of control requirements and were not expected to be significant sources of HAP or VOC emissions. As stated above, we received no comments containing additional information on emissions reduction measures or HAP/ VOC emissions from wastewater operations. Thus, we have no more reason to feel now than we did at proposal that PCWP wastewater operations are in 135 fact subject to any control measures. As a result, since no information shows that these PCWP operations use add on controls, there is no identifiable numerical emissions level that would correspond to a MACT floor level reflecting the use of controls, and the only floor level demonstrable based on current data is no emissions reduction. Furthermore,

given that our best data show that the emissions from wastewater operations are less than 1 ton/ yr, we concluded that application of the control measures mentioned above would not be cost effective beyond the floor options. In response to the commenter's objection to the incompleteness of the data set for these PCWP operations, we note that the D. C. Circuit does not require EPA to obtain complete data as long as we are able to otherwise estimate the MACT floor ( Sierra Club V. EPA, 167 F. 3d 658,662 ( D. C. Cir. 1999)).

Unlike dryers and presses at PCWP plants, wastewater operations have not been subjected by permitting authorities to controls for HAP emissions. We expended much effort in the early stages of the project gathering complete and accurate information on the PCWP processes with the most potential for HAP emissions and the greatest potential for emission control ( i. e., the processes that have been the focus of permit requirements limiting HAP/ VOC emissions) and the final PCWP rule addresses emissions from these process units. 136 Had we been given reason to feel that there were emissions control measures associated with wastewater operations, we would have gathered more information for these processes earlier in the project. Even though we have determined that the current MACT floor for these PCWP operations is no emission reduction, since available information indicates they are not controlled, the HAP emissions from wastewater operations ( and other PCWP sources with MACT determinations reflecting no emissions reductions)

will be considered further when we review residual risk as required under section 112( f).

E. New Source MACT Comment: One commenter objected to our determination that MACT is the same degree of control for new and existing sources for many process units based on the fact that the best technology is the same for new and existing sources ( i. e., incineration based controls or biofilters). The commenter pointed out that, according to the proposal BID,

the maximum percent control efficiency is in the upper 90s for THC, formaldehyde, and methanol. The commenter noted that the CAA requires the MACT floor to be based on the degree of emissions reduction achieved in practice by the best controlled similar source. Thus, the commenter requested that we revise the new source MACT requirements for process units based upon the greatest reductions 137 recorded.

Response: As explained in the preamble to the proposed rule and supporting documentation, the MACT floor for both new and existing sources is based on the estimate of the performance achieved through application of RTO, RCO, or biofilters. We acknowledge that some incineration based controls and biofilters can achieve greater than 90 percent reduction in HAP or THC during a single performance test or a test run within a performance test. However, we also recognize that the percent reduction achieved can vary according to pollutant inlet concentration, a factor that is not directly controllable from a process or control device standpoint. Other unknown factors may also cause variability in control system performance. For example, we have THC percent reduction data for an RTO used to control emissions from three tube dryers and a press at an MDF plant for two emission tests conducted at different times. In 1996, the RTO achieved 92.7 percent reduction of THC, and in 1998 the same RTO achieved 98.9 percent reduction of THC.

In addition, we have emissions test data for the same process unit and control system for multiple years, and these data show different emission factors, indicating that variability is inherent within each process unit and control system combination. Thus, we estimate that the best MACT technology achieves 90 percent HAP reductions when 138 variations in operations and measurements are considered.

F. Definition of Control Device Comment: Several commenters requested that we add scrubbers and adsorbers to the proposed definition of " control device" and that condensers be omitted from the definition. One of the commenters operates a particleboard press that is equipped with a condenser that condenses steam from the press exhaust and then routes the condensate to an onsite wastewater treatment system. The remaining noncondensed gases are combusted in an onsite boiler as supplemental fuel. This commenter would like to be able to comply with the PBCO for reconstituted wood products presses rather than demonstrate compliance with one of the add on control system compliance options ( e. g., 90 percent emissions reduction) or emissions averaging provisions;

however, the commenter noted that PBCO only apply to uncontrolled emission sources. Therefore, the commenter requested that the definition of control device be limited only to those add on control systems that were designed with HAP removal as the primary goal.

Response: We disagree with the commenters that the proposed definition of control device should be changed.

The definition in the final rule does not include scrubbers or absorbers but does include condensers and combustion units that incinerate process unit exhausts. For purposes 139 of MACT standards development, the reason a control device is installed is immaterial. All control devices or techniques that reduce HAP emissions are considered when setting MACT standards. We note that the PBCO were developed and included in the PCWP rule for inherently lowemitting process units or process units with P2 techniques and not for process units with add on control systems.

Therefore, the particleboard press equipped with the condenser and combustion unit described by the commenter cannot comply using the PBCO.

In the proposed PCWP rule, we intentionally omitted absorbers ( e. g., wet scrubbers) from the list of potential control devices because these technologies generally are not reliable for reducing HAP emissions. These wet systems may achieve short term reductions in THC or gaseous HAP emissions; however, the HAP and THC control efficiency data,

which range from slightly positive to negative values,

indicate that the ability of these wet systems to absorb water soluble compounds ( such as formaldehyde) diminishes as the recirculating scrubbing liquid becomes saturated with these compounds. We wished to limit the examples included in the definition of control device to those devices for which we have data to demonstrate that they are effective in reducing HAP emissions from PCWP facilities. However, we note that the definition includes the phrase " but not 140 limited to" and does not exclude other types of controls.

We are aware that new technologies ( some of which may be adsorption based or absorption based) may be developed that effectively reduce HAP emissions from PCWP sources. The definition of control device does not prevent their development or use.

Facilities using wet scrubbers or WESP to meet the addon APCD or emissions averaging compliance options can petition the Administrator for approval of site specific operating requirements to be used in demonstrating continuous compliance. Alternatively, facilities using a wet scrubber or WESP may use a THC CEMS to show that the THC concentration in the APCD exhaust remains below the minimum concentration established during the performance test. In addition, facilities using wet control devices ( e. g., wet scrubber or WESP) as the sole means of reducing HAP emissions must submit with their Notification of Compliance Status a plan for review and approval to address how organic HAP captured in the wastewater from the wet control device are contained or destroyed to minimize re release to the atmosphere such that the desired emission reduction is obtained. Because wet scrubbers or WESP are add on APCD and have variable effects on HAP emissions, today's final rule specifies that sources cannot use add on control systems or wet control devices to meet PBCO. As part of this change, 141 we added a definition of " wet control device" to today's final rule. We note that PCWP facilities demonstrating compliance with the PBCO for process units equipped with any wet control device that effects HAP emissions must test prior to the wet control device.

G. Compliance Options 1. Add on Control System Compliance Options Comment: We received a number of comments related to the six add on control systems compliance options and how these options might be implemented at an actual PCWP facility. One commenter argued that the use of multiple compliance options for add on control systems will make it difficult for State agencies to determine if a facility is actually in compliance. The commenter pointed out that, if a facility tested for two options but passed only one, it would still be in compliance. However, the commenter stated that the rule as proposed was unclear whether a facility would be in violation if the facility chose to test for one option, failed that test, and then conducted another test to determine compliance with a different option. The commenter contended that this would constitute a violation of the standard, and any retesting to determine compliance with a different option would not reverse the initial violation.

Therefore, the commenter requested that we clarify that the option to use the most beneficial results of two or more 142 test methods applies only when these tests are conducted during a single performance test. According to the commenter, any facility that chose to use only one test method during the compliance test would have to accept the results of that test.

Other commenters argued that a facility should be able to switch among the six add on control options as needed to maintain compliance. To illustrate the necessity of the ability to switch from one add on control option to another,

the commenters provided an example whereby the operator of a veneer dryer might want to demonstrate compliance with the 90 percent THC reduction option ( option 1 in Table 1B to the final rule) under certain operating conditions and with the 20 parts per million by volume ( ppmv) THC option ( option 2 in Table 1B to the final rule) under other operating conditions. One of the commenters also noted that production starts and stops and minor malfunctions are common at PCWP facilities, and most of them do not affect the performance of the air pollution control device.

However, frequent SSM events resulting in a low concentration to the inlet of the control device could affect a facility's ability to comply with the percent reduction option. In this case, the commenter stated that the freedom to switch compliance options would be valuable.

For these reasons, the commenters requested that we 143 explicitly state in the final PCWP rule that " a facility only need comply with any one of the six options at any one time, and that it can change between them as needed to fit process operating conditions."

Response: We understand the commenters' concerns on this issue and have written the final rule to clarify our intentions regarding how the add on control system compliance options should be implemented at PCWP facilities.

The proposed rule states at 40 CFR 63.2240 that " You cannot use multiple compliance options for a single process unit."

We included this provision to prevent PCWP sources from partitioning emissions from a single process unit and then applying different control options to each portion of the emissions stream. The MACT floor determinations and compliance options were all based on the full flow of emissions from process units, and therefore, compliance options should be applied to the same mass of emissions to ensure that the required MACT floor emissions reductions are achieved. When including this restriction, we did not intend necessarily to limit PCWP facilities to only one of the six options for add on control systems. We did assume that each source would likely select only one option, and that at any point in time for purposes of assessing compliance, the given compliance option would have been preselected and reflected as applicable in the source's permit. 144 In fact, in discussions with industry representatives prior to proposal, they expressed concern that the final rule be written to make it clear that a source would only have to comply with one option and not all six.

Based on available data, we expect that most facilities will be able to demonstrate compliance with more than one of the compliance options for add on control systems. When developing the six compliance options for add on control systems, we felt that PCWP facilities would conduct emissions testing ( e. g., inlet and outlet testing for THC,

methanol, and formaldehyde over a range of APCD operating temperatures) and then, based on the results of testing,

select the option that provides them with the most operating flexibility as well as an acceptable compliance margin ( i. e., select the option that they feel will be easiest for them to meet on a continuous basis under varying conditions). The operating parameter limit to be reflected in the source's permit ( e. g., minimum temperature) would be based on the measurements made during the compliant test runs. For example, if test results show that a facility can achieve 90 percent reduction for formaldehyde, 92 percent reduction for methanol, and 94 percent reduction for THC,

then the facility may decide to reduce THC emissions by 90 percent, since this option appears to provide the greatest compliance margin. The corresponding operating 145 parameter level measured during the testing ( e. g., minimum 15 minute RTO temperature during a three run test) would then be set as the operating limit in the permit for that source. In this example, if the RTO operating temperature drops below the operating limit, that would be a deviation,

and any subsequent retesting done by the facility would presumably be done based on the chosen compliance option ( e. g., reduce THC emissions by 90 percent). Determining compliance in this case is relatively straightforward.

However, we are aware that State agencies may simply refer to a NESHAP as part of a permit and not stipulate which compliance option the facility must meet. In these cases,

we agree with the commenter who was concerned that compliance can be complicated when the referenced NESHAP contains multiple options, and that such a broad reference would not be adequate to identify the particular option ( and parameter operating limits) applicable to the source. We also agree that, if a facility selects multiple options under the compliance options for add on control systems, it should be required to conduct all necessary testing associated with compliance with the selected options concurrently. In addition the facility should obtain permit terms reflecting these options as alternate operating scenarios that clearly identify at what points and under what conditions the different options apply, such that 146 compliance can be determined during a single time frame.

For example, if the source wishes to include options 1, 3,

and 5 in their permit, then it must perform inlet and outlet testing for THC, methanol, and formaldehyde any time the State agency has reason to require a repeat performance test ( if all three options are simultaneously applicable) or test for the single applicable option that corresponds to the given time and condition ( if the options apply as alternate operating scenarios under different conditions). With this approach, we would avoid situations where a facility retests to determine compliance with a compliance option, fails to demonstrate compliance with that option, and then conducts additional testing to determine compliance with other options that are not pre established as applicable at a later date.

The final rule clarifies our intentions regarding the use of multiple control options with respect to add on control systems versus the combining of control options for a single process unit. The language in 40 CFR 63.2240 of the final rule has been modified to remove the proposed text stating that a source " cannot use multiple compliance options for a single process unit" and replace it with a statement that a source " cannot combine compliance options in paragraphs ( a)[ PBCO], ( b)[ add on control systems compliance options] or ( c)[ emissions averaging provisions] 147 for a single process unit." We feel that this wording change clarifies our intention to prevent sources from applying different control options to different portions of the emissions from a single process unit, while leaving open the potential for PCWP facilities to be able to include multiple compliance options for add on control systems ( i. e., one option per defined operating condition) in a State permit. Although add on controls are used in emissions averaging plans to achieve full or partial control of emissions from a given process unit, the emissions from a single process unit cannot be parceled such that a portion of the emissions meets one of the add on control system compliance options and another portion is used as part of an EAP. The final rule continues to state that sources must meet at least one of the six options for add on control systems.

2. PBCO Limits Comment: Several commenters requested that PCWP facilities be allowed to use add on control methods to achieve the PBCO limits. The commenters argued that allowing compliance with the PBCO using APCD is consistent with other MACT rules and P2 approaches. According to the commenters, numerous NESHAP allow emissions limits to be reached using add on controls, P2 techniques, or a combination of both. The commenters stated that there was 148 no legal or policy basis for imposing restrictions on the use of PBCO in the PCWP MACT. The commenters also 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, some companies have already implemented P2 strategies that have been established as BACT in a prevention of significant deterioration ( PSD)

permit. Because these P2 strategies may fall short of the PBCO, companies implementing these strategies would be unable to achieve compliance with the proposed rule without abandoning the P2 strategy and installing full control. The commenters also stated that incorporating add on controls in the PBCO would provide incentives to find low energy pollution control equipment. The commenters gave an example whereby part of the emission unit exhaust could be used as combustion air for an onsite boiler. The commenters noted that in most cases, the boiler could only handle a portion of the exhaust from multiple dryer stacks. The commenters 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. According to the commenters, 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 commenters gave another example in 149 which a facility with a conveyor strand 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 commenters, a facility would remove enough HAP to comply with the PBCO limit using a scrubber, which would require less energy than incineration.

Response: As in 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 P2, 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 not perform to expected control efficiencies. Sources equipped with add on control systems already have six different compliance 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 emissions 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 150 controls, as explained below.

At proposal, we established PBCO limits for 10 process unit groups. Initially, we felt that we needed total HAP data for at least one process unit in each process unit group that was equipped with a control system in order to establish the PBCO limits. However, we had to discard this approach because controlled total HAP data are not available for half ( 5 of 10) of the process unit groups. We developed a number of other approaches to establishing PBCO, and then compared the results of these approaches, where possible,

with actual emissions in the outlet of MACT control devices.

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 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 151 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.

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 to the final rule) based on typical or maximum levels of methanol and formaldehyde found in the outlet of the control devices, but instead looked at the performance of the MACT 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 HAP emissions reductions are achieved. Allowing the use of APCD to comply with PBCO could allow circumvention of such optimization,

which could render the MACT control itself to be less effective than MACT.

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 152 option ( e. g., " lb/ ton" emission limit); however, we cannot allow add on controls to be used to meet the PBCO in the final PCWP rule because doing so would render these limits not equivalent to the other compliance options. For example, consider a typical wood products press with an annual production rate of 100 million square feet of board per year and a total HAP emission rate of 1.0 pound per thousand square feet of board on a ¾  inch basis ( lb/ MSF ¾ " ).

On an annual basis, the example press emits 50 tons of HAP per year. If the example press complies with the 90 percent HAP reduction requirement, then the HAP emissions reductions achieved will be at least 45 tons/ yr. However, if this same press were allowed to comply with the applicable PBCO limit ( 0.30 lb/ MSF ¾ " ) using an APCD ( e. g., RTO), then the emissions reductions achieved could be as little as 35 tons/ yr if the APCD is only applied to a portion of the press' emissions or if the APCD is not operated at MACTlevel efficiency. Not only would a significantly lower HAP emission reduction be achieved in this situation, but there also would not be any net benefit to the environment to justify the lower HAP reduction ( i. e., NOX emissions would still be created). Also, we wish to point out that the emissions from PCWP process units are not insignificant,

even when these units operate at the PBCO thresholds. For example, a typical wood products press that operates at the 153 applicable PBCO ( 0.30 lb/ MSF ¾ " ) still emits 15 tons of HAP per year, and a typical rotary strand dryer operating at the applicable PBCO ( 0.18 lb/ ODT) emits 6 tons of HAP per year.

Therefore, we feel it is appropriate and in keeping with the MACT floor to require PCWP process units with uncontrolled HAP emissions above the PBCO thresholds to achieve the full 90 percent reduction in emissions. We also wish to clarify that a PCWP facility may use any number of compliance options, as long as these options are not combined for an individual process unit. For example, a facility may choose to meet the applicable PBCO limit for one dryer, control emissions from a blender to avoid controlling emissions on the remaining two dryers as part of an emissions average,

and comply with one of the add on control systems compliance options 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 strand dryers, such that existing conveyor strand dryers that send the emissions from the first dryer section back to the combustion unit that heats the dryer should be able to meet the rule requirements without additional controls. In addition, partial control ( e. g.,

routing part of the emission stream from a process unit to an onsite combustion unit for incineration) is allowed as 154 part of an EAP as long as the actual emissions reductions achieved are greater than or equal to the required emissions reductions. When partial control is used as part of an EAP,

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. Therefore partial incineration control is not allowed in the PBCO.

Regarding the use of scrubbers to comply with a PBCO, as stated earlier in this preamble, the PCWP 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.

Comment: Several commenters stated that PCWP facilities should be allowed to neglect nondetect HAP measurements for PBCO calculations. The commenters argued that if a facility is forced to use values of one half the detection limit for nondetect HAP, that facility may be unable to use PBCO because the mass of emissions attributed to undetected compounds may consume 50 percent or more of the PBCO limit.

The commenters also noted that the detection levels measured in the field by the NCASI test method, NCASI IM/ CAN/ WP

99.01, generally range between 0.35 and 1 ppm, and the 155 detection levels of the FTIR method averages about 1 ppm.

According to the commenters, even at these low concentrations, using one half the detection limit for nondetect compounds can put the PBCO out of reach for a high flow rate PCWP stream. The commenters also provided a sample calculation to demonstrate the effect that the detection level has on the compliance calculation.

Response: In responding to this request, we reviewed the information supplied by the commenters and analyzed the potential effects of making the requested change using available emissions data. After reviewing the total HAP data used to establish the PBCO limits, we decided that sources should be able to treat nondetect measurements for an individual HAP as zero for the sole purpose of determining compliance with the PBCO, if, and only if, the following two conditions are met: ( 1) the detection limit for that pollutant is set at a value that is less than or equal to 1 ppmvd, and ( 2) emissions of that pollutant are nondetect for all three test runs. We included the first condition to prevent test contractors from setting the detection limits too high, and thus generating false zeroes.

We selected 1 ppmvd as the maximum detection limit value because it matches the detection limits achievable with the test methods included in the final PCWP rule. We included the second condition to ensure that the source is truly low 156 emitting, as evidenced by three nondetect test runs. If emissions of the HAP are detected during any one test run,

then any nondetect runs must be treated as being equal to one half the detection limit. The option to treat nondetect measurements as zero does not apply to the compliance options for add on control systems because treating the outlet emissions from a control device as zero would artificially increase the calculated control efficiency for that pollutant to 100 percent.

To ensure that the PBCO limits were developed in a manner consistent with how they would be applied, the PBCO limits were recalculated using zero for nondetect measurements when all test runs were nondetect. As a result, the PBCO limit for reconstituted wood product board coolers changed from 0.015 to 0.014 lb/ MSF ¾ " . No other PBCO limits changed as a result of using zero for nondetects when calculating the PBCO limits.

We added a new PBCO limit to the final rule for secondary tube dryers. This new limit corresponds to our decision to treat primary and secondary tube dryers as separate process units, as discussed previously in this preamble. The final rule also differentiates between rotary strand dryers and conveyor strand dryers, as discussed previously in this preamble; however, no new PBCO limits have been added for these two process units groups. The 157 final PBCO limit for rotary strand dryers is the same as the proposed limit for strand dryers because the data used to establish the proposed PBCO limit was based on data from rotary strand dryers exclusively. We do not have the necessary data to establish a PBCO for conveyor strand dryers, and thus the final rule does not include a PBCO limit for that process unit group.

3. Emissions Averaging Provisions Comment: Industry commenters generally expressed support for the inclusion of an emissions averaging program in the PCWP rule as proposed, but requested that the proposed provisions be modified to allow for broader use of emissions averaging at PCWP facilities. Requested modifications include allowing sources to receive credit for achieving emissions reductions greater than 90 percent;

basing compliance on a single pollutant; allowing sources to combine emissions averaging with PBCO; and allowing sources to receive credit for P2 alternatives as part of an EAP.

Several of the industry 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 add on 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 158 controls in the most efficient manner, as opposed to running at 90 percent, regardless of capability. 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 for only up to a 90 percent reduction.

Several commenters suggested that we allow compliance with the emission averaging provisions to be based on a single pollutant, specifically, THC, methanol, or formaldehyde. With this modification, sources would only be required to test for one pollutant instead testing for all six HAP that comprise total HAP.

Several commenters requested that we allow sources to combine emissions averaging with the PBCO. 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. The commenters provided an example where a facility would control emissions from a board cooler and then apply the resultant emissions reductions to a press that had emissions above the applicable PBCO limit; by applying the emissions credit to 159 the press, the press emissions would be reduced below the PBCO such that no control would be required on the press emissions. 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.

Industry commenters also requested that we modify the emission averaging provisions to allow facilities to receive emission credits for P2 activities, such as product reformulation, 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, and scheduled process unit downtime. According to the commenters, not allowing P2 encourages the use of add on controls like incineration, rather than environmentally beneficial options that may not involve addon control technology. The commenters asserted that quantifying emissions from P2 projects would not be difficult under the PCWP emission 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 160 controlled emission level.

Response: We included an emission averaging compliance option in the proposed rule as an equivalent, more flexible,

and less costly alternative to the compliance options for add on control systems. As explained in the preamble to the proposed rule, we based theUnlike previous MACT standards with emissions averaging provisions, in part, on the emissions averaging provisions in the Hazardous Organic NESHAP ( HON), with some differences. Unlike the HON, the proposed ( and final) emissions averaging provisions in the PCWP rule do not include ( 1) limits on the number of sources that can be included in an emissions average, ( 2)

requirements for a hazard or risk analysis, or ( 3)

application of a 10 percent discount factor to emissions credit calculations. In addition, the emissions averaging provisions in the final PCWP rule require that credits for emissions reductions be achieved using APCD, and that the EAP be based on emissions of the six predominant HAP emitted from PCWP process units, referred to as total HAP. Also,

the emissions averaging provisions do not allow credit for reductions beyond 90 percent.

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) 161 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 composed of pointin 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.

Regarding the commenters' request to allow credit for greater than 90 percent control for those sources with no MACT control requirements, we maintain that this would be inappropriate because the same issues of emissions variability and control device performance apply to those emission sources, and they likely would share control devices with PCWP process units that do have MACT control requirements.

We have rejected the commenters' suggestion to base the emissions averaging provisions on a single pollutant ( e. g.,

THC, methanol or formaldehyde), and retained the requirement in the final rule that the EAP must be based on total HAP.

The predominant HAP emitted from a given process unit 162 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 identified in the definition of total HAP in the final 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. As noted above, we did not include a hazard/ risk study as part of the proposed EAP because we were requiring that the emissions 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 eliminate our rationale for not requiring a risk analysis. We also note that, while THC emissions are 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 for uncontrolled process units, and thus the EAP should not be based solely on THC emissions. Although all PCWP process units emit THC, uncontrolled THC emissions from softwoods are substantially higher than from hardwoods due 163 to non HAP compounds ( e. g., pinenes) present in softwoods.

Therefore, allowing sources without add on controls to focus on THC reductions achieved by increasing hardwood usage might reduce THC emissions but would have a minimal impact on HAP emissions. For these reasons, we feel that, for the purpose of the final rulemaking, THC should only be used as a surrogate for HAP when assessing the performance of an add on control device, and should not be used as a surrogate for establishing the required and actual mass removal of HAP as part of an EAP.

We disagree with the commenters that combining the emissions averaging option and PBCO will result in equivalent emissions reductions. As we stated in our response to previous comments in this section regarding PBCO, we developed the PBCO limits to provide an option for sources that develop P2 techniques. The PBCO limits represent applicability cutoffs such that sources with emissions below the applicable PBCO thresholds are not required to further reduce those emissions below MACT levels. By combining PBCO limits with the EAP, 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) to levels that would qualify as low emitting ( below PBCO 164 limits). This is counter to the intent of the PBCO and would result in lower emissions 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.

We also 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 feasible, and ( 2) inclusion of currently undemonstrated P2 projects within EAP would unnecessarily complicate these plans and hamper enforcement. As we noted previously in this preamble, the final rule allows PCWP facilities to use both P2 ( i. e., the PBCO) and emissions averaging at the same facility; sources are only limited in that they cannot apply both options to the same process unit. 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 feel that the same issues apply for PCWP facilities, especially given the fact that P2 techniques 165 have not been widely used or documented in the PCWP industry. In contrast, emissions reductions achieved through the use of add on control systems are easily documented. The PBCO were established to address the future development and implementation of P2 techniques; however,

the resultant PBCO limits do not require that emissions 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.

Regarding the suggested P2 option of increasing a facility's use of hardwood species, in addressing other issues, commenters 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. Furthermore, for veneer dryers, where species identification ( hardwood vs.

softwood), and thus enforcement, is fairly straightforward from the standpoint of both visual inspection and endproduct we have already established separate MACT floors for softwood and hardwood veneer dryers ( and require no further emissions reductions from hardwood veneer dryers).

When the end product is particleboard or MDF, and the raw material is in the form of wood chips, planer shavings, or 166 sawdust, determining how much of that material is softwood versus hardwood would be very difficult, and likely unenforceable. Because of commenters' concerns that an operating condition based on wood species is technically unworkable and the associated enforcement issues, we feel 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 reformulation and lowering dryer temperature are potential P2 options, and the PBCO limits would apply if the P2 efforts sufficiently lower emissions. The final 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.

Regarding the use of existing combustion units as control devices, the final rule 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 P2 measure. Therefore, compliance with the PBCO using process incineration is not allowed in the final rule. 167 The add on control system and emissions averaging compliance options are available for process units controlled by routing exhaust to an onsite combustion unit.

The final PCWP rule does not allow production curtailment to be counted as part of an EAP. As stated in the preamble to the proposed rule ( 68 FR 1276, 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 year " x."

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 occasionally longer shutdowns ( e. g.,

monthlong if demand drops. The final PCWP rule requires emissions from specified process units at impacted PCWP facilities to be reduced by 90 percent, regardless of what 168 the levels of emissions are for those facilities in a particular year. Therefore, implementation of the final PCWP rule at individual PCWP facilities will result in greater emissions reductions in years of greater production and lesser emissions reductions during years of lower production. As mentioned in the response to the previous comment, the emissions averaging provisions must achieve emissions reductions that are greater than or equal to those that would be achieved using the add on control system compliance options, which specify which process units must be controlled. If we allowed credit for production curtailments, the overall emissions reductions achieved through the emissions averaging provisions would not be equivalent to what would be achieved through the use of the add on control system compliance options, and therefore, the EAP would not be a MACT equivalent alternative. For example, if we allowed production curtailments to count toward 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 system compliance options, then it would be required to control the 169 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 system compliance options and to preserve the required HAP emissions reductions, the final PCWP rule does not allow production curtailment to be counted as part of an EAP.

Comment: One commenter objected to the inclusion of the emissions averaging option in the rule primarily because of the lack of a requirement to conduct a hazard or risk study.

This 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 should be obvious that trading one HAP for another to meet a RMR is not an acceptable option. 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 80 percent of the PCWP facilities in the U. S. pose cancer risks greater than 1 in 1 million, emissions reductions should be required at these facilities rather than allowing potential increases in toxic emissions from certain process units.

Response: We disagree with commenter's assertion that 170 inclusion of the emissions averaging provisions will potentially increase toxic emissions at certain PCWP process units. As stated in the preamble to the proposed rule ( 68 FR 1289, January 9, 2003), PCWP facilities have fewer pollutants of concern ( as compared to HON facilities) 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 six primary HAP,

whereas HON facilities may emit over 140 different HAP. The PCWP facilities choosing to comply through emission averaging must account for the emissions of the six primary HAP ( total HAP), which represent greater than 96 percent of the mass of 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 emissions averaging provisions require the use of add on control technologies for credit generating sources in an EAP, we feel that the emissions averaging provisions will achieve a hazard/ risk benefit comparable to what would be achieved through point by point compliance. 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 could preclude the facility from using emissions averaging altogether). 171 Comment: Several commenters requested that we write the definitions of some of the variables used in the emissions averaging equations in the final rule to clarify that sources can take credit for emission reductions achieved through partial control of debit generating process units.

Response: We agree with the commenters' request and have written the definitions of some of the variables used in the emissions averaging equations in today's final rule to clarify that partial credits generated from debitgenerating process units that are undercontrolled can be included in the calculation of the AMR. For example, a PCWP facility may decide to control 30 percent of the emissions from a green rotary dryer and 80 percent of the emissions from a blender as part of an EAP in order to achieve a HAP reduction that is the same as or greater than what the facility would have achieved by controlling the green dryer emissions alone by 90 percent. In this example, the green rotary dryer is a debit generating unit because it has MACT control requirements; however, the green dryer can receive credit in the AMR calculation for any partial emissions reductions that are achieved.

H. Testing and Monitoring Requirements 1. Test Methods Comment: Several commenters noted that one of the NCASI test methods, NCASI IM/ CAN/ WP 99.01, has been updated, and 172 requested that the final rule refer to the revised version.

One of the commenters provided a revised version of the method, identified as NCASI IM/ CAN/ WP 99.02. This commenter noted that the trained NCASI sampling team was able to get good consistent results with the original version of the method both in the laboratory and in the field, but that sampling contractors had difficulty obtaining valid results.

The commenter maintained that the revised version is easier to understand, includes more details, and reflects the comments of the contractors that have experience with the original method. The commenter also stated that the quality assurance requirements were strengthened in the revised version to ensure good results. Several commenters also noted that NCASI is currently developing a new method for measuring the six HAP ( total HAP) listed in the PCWP rule as proposed. Therefore, the commenters requested that we include language in the final rule that would allow PCWP facilities to use future methods once they have been reviewed by EPA and have passed Method 301 validation at a PCWP plant.

Response: We reviewed the revised NCASI method IM/ CAN/ WP 99.02 supplied by the commenter and agree that the revised method is appropriate for measurement of the six HAP that comprise " total HAP;" therefore, we have included NCASI IM/ CAN/ WP 99.02 in the today's final rule. Regarding the 173 development of future test methods, 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.

Comment: Several commenters noted that the tracer gas method for determining capture efficiency, developed by a PCWP company and included in the proposed rule ( 68 FR 1276,

appendix A to 40 CFR part 63), is a work in progress. These commenters included with their comments a copy of field validation tests conducted at a PCWP facility. The commenters noted that future tests are planned using the tracer gas method and 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 note that the commenters did not provide any specific recommendations for modifying the tracer gas method as it was proposed. 174 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.

2. Sampling locations Comment: Several commenters recommended that the final rule be reworded to clearly state that inlet sampling should take place at the functional inlet of a control device sequence or at the primary HAP control device inlet. For example, the commenters noted that the final rule needs to clarify that sampling should take place at the inlet of a WESP that precedes an RTO instead of between the two devices. The commenters noted that many WESP RTO control systems are too closely coupled to allow for a sampling location in between that meets the requirements of Method 1 or 1A, 40 CFR 60, appendix A.

Response: We agree with the commenters and have written the final PCWP rule to indicate that, for HAP altering controls in sequence, such as a wet control device followed by a thermal oxidizer, sampling sites must be located at the functional inlet of the control sequence ( e. g., prior to the wet control device) and at the outlet of the control sequence ( e. g., thermal oxidizer outlet) and prior to any 175 releases to the atmosphere. In addition, as discussed previously in this preamble, the final rule also clarifies that facilities demonstrating compliance with a PBCO limit for a process unit equipped with a wet control device must locate the sampling site prior to the wet control device.

3. Testing Under Representative Operating Conditions Comment: Several commenters objected to the proposed requirement to test process units under representative operating conditions. The commenters argued that, because the initial compliance tests determine the outer limits of compliance, those tests should be conducted at the boundaries of expected performance for the process and control units. These commenters noted that testing at 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 final 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. In addition, one of the commenters noted that the testing provisions should also address potential conflicts with traditional State requirements to test at maximum or design conditions.

Response: The proposed rule defined representative operating conditions as those conditions under which " the 176 process unit will typically be operating in the future,

including use of a representative range of materials[...]

and representative temperature ranges." We disagree that the proposed requirement to test under representative operating conditions will conflict with State requirements and result in operating parameter limits/ ranges that are too narrow. We wish to clarify that the 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 under a variety of conditions, including upper and/ or lower bounds,

to better define the minimum or maximum operating parameter limit or broaden their operating limit ranges ( where applicable). For example, if a facility generally operates a process unit ( equipped with an RTO) under conditions that require the RTO to be operated at a minimum temperature of 1450

F to ensure compliance with the standards, but at other times operates that process unit under conditions such that the minimum RTO operating temperature must be 1525

F to ensure compliance, then the facility has two options. One option is for the facility to incorporate both of these operating conditions into their permit such that they are subject to two different operating parameter limits ( minimum temperatures), one for each ( defined) operating condition.

As an alternative, the facility could decide to comply with 177 the parameter limit associated with the worst case operating conditions ( most challenging conditions for the RTO), which in this example would correspond to maintaining a minimum RTO operating temperature of 1525

F, and thus, they could demonstrate continuous compliance regardless of the operating condition as long as they maintained the RTO temperature at or above 1525

F. We have revised the monitoring requirements for process units without control devices to allow these sources to establish a range of compliant parameter values. In addition, those PCWP 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, 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.

4. Process Incineration Monitoring Requirements Comment: Several commenters expressed approval for the proposed exemption from testing and monitoring requirements for those process units with emissions introduced into the flame zone of an onsite combustion unit with a capacity greater than or equal to 44 megawatts ( MW) ( 150 million 178 Btu/ hr). In addition, several of these commenters requested that we expand upon this exemption in the final rule.

First, the commenters requested that we extend the exemption to include situations where the process unit exhaust is introduced into the combustion unit with the combustion air.

The commenters noted that we had included such exemptions in the HON ( 40 CFR part 63, subpart G) and in the Pulp and Paper Cluster Rule ( 40 CFR part 63, subpart S) in recognition of the fact that boilers greater than 44 MW typically had greater than ¾  second residence time, ran hotter than 1,500

F, and usually had destruction efficiencies greater than 98 percent ( see 65 FR 3909,

January 25, 2000, and 65 FR 80762, December 22, 2000, at § 63.443( d)( 4)( ii)). The commenters stated that the design and construction of PCWP boilers follow the same principles that would allow for these operating conditions. Second,

the commenters requested that we also exempt smaller combustion units ( less than 44 MW, or 150 million Btu/ hr)

from the testing and monitoring requirements if the process unit exhaust is introduced into the flame zone of the combustion unit. The commenters noted that most of the combustion units associated at PCWP facilities are smaller units and that testing of these units can be complicated by their configuration and integration with other process units. 179 Response: After reviewing available information on process incineration at PCWP facilities, we decided to include smaller combustion units in the exemption from testing and monitoring requirements if the process exhaust enters into the flame zone. As part of this change, we have included definitions of " flame zone" and " combustion unit"

in the final rule. However, we decided not to include an exemption for PCWP combustion units that introduce the process exhaust with the combustion air. As noted by the commenters, the HON and the final pulp and paper MACT I rule exempt from testing and monitoring requirements combustion devices with heat input capacity greater than or equal to 44 MW. The HON also exempts from testing and monitoring combustion devices with capacity less than 44 MW if the exhaust gas to be controlled enters with the primary fuel.

If the exhaust gas to be controlled does not enter with the primary fuel, then testing and continuous monitoring of firebox temperature is required by the HON. Similarly, the final pulp and paper MACT I rule exempts from testing and monitoring requirements combustion devices ( including recovery furnaces, lime kilns, boilers, or process heaters)

with capacity less than 44 MW if the exhaust stream to be controlled enters into the flame zone or with the primary fuel. Similar to the HON and pulp and paper MACT I rules,

the final PCWP rule extends the exemption from testing and 180 monitoring requirements to combustion units with heat input capacity less than 44 MW, provided that the exhaust gas to be treated enters into the combustion unit flame zone. If the exhaust gas enters into the combustion unit flame zone,

the required 90 percent control efficiency may be assumed.

If the exhaust gas does not enter into the flame zone, then the testing and monitoring requirements for thermal oxidizers will apply.

As noted by the commenter, the HON and the final pulp and paper MACT I rule exempted boilers ( and recovery furnaces at pulp and paper mills) with heat input capacity greater than 44 MW from testing and monitoring requirements because performance data showed that these large boilers achieve at least 98 percent combustion of HAP when the emission streams are introduced with the primary fuel, into the flame zone, or with the combustion air. Lime kilns at pulp and paper mills were excluded from this provision because we did not have any data to show that lime kilns can achieve the required destruction efficiency when the HAP emission stream is introduced with the combustion air.

Therefore, lime kilns at pulp and paper mills that accept HAP emission streams must introduce the stream into the flame zone or with the primary fuel. We do not have the data to show that the design and construction of large ( greater than 44 MW) combustion units at PCWP plants would 181 be similar to boilers found at pulp and paper mills.

Furthermore, combustion units at PCWP plants with heat input capacity of greater than 44 MW are less prevalent than smaller ( i. e., less than 44 MW) PCWP combustion units, and many of these smaller combustion units are not boilers. As stated above, the final rule exempts these smaller combustion units from the testing and monitoring requirements provided that the HAP emission stream is introduced into the flame zone. For these reasons, the final PCWP rule does not extend the exemption from testing and monitoring to those boilers greater than 44 MW that introduce the HAP emission stream with the combustion air.

5. Selection of Operating Parameter Limits for Add on Control Systems Comment: Several commenters stated that the inlet static pressure to a thermal or catalytic oxidizer is not a reliable indicator of the flow through the oxidizer, the destruction efficiency, or the capture efficiency. The commenters also noted that the preamble to the PCWP rule stated that monitoring the static pressure can indicate to the operator when there is a problem such as plugging.

However, the commenters stated that static pressure is usually the last indicator of these types of control device problems. As discussed in the promulgation BID, the commenters agreed that measuring those parameters helps to 182 assess the overall condition of the oxidizer but provided reasons why setting limits on these parameters is inappropriate. The commenters further noted that monitoring the static pressure helps to control the speed of the fan or the oxidizer dampers so that all the air flows are balanced.

According to the commenters, static pressure is adjusted to avoid vacuum conditions in the ductwork of multiple dryer systems treated by one control device when one dryer is shut down, to improve emission collection efficiency and prevent fugitive emissions, and to adjust the pressure drop across a bag filter as it fills with particulates, among other reasons. However, the commenters stated that, if operators are required to keep the static pressure within an operating range, it will limit their ability to maintain capture efficiency. The commenters expressed similar concerns regarding air flow rate monitoring and noted that numerous factors affect the air flow through the control device,

including the rate of water removal in dryers, leakage of tramp air into the process, the number of processes operating for control units that receive emissions from multiple production units, and the overall production speed due to process adjustments. The commenters noted that, in those cases where air flow to the oxidizer is not constant,

monitoring the air flow through the oxidizer will not be an accurate measure of capture efficiency. 183 Response: After reviewing the information provided by the commenters, we agree that, while monitoring the static pressure or air flow rate helps to assess the overall condition of the oxidizer and provides an indication that emissions are being captured, setting operating limits on these parameters is not appropriate for the reasons given by the commenters. Therefore, today's final rule does not include the proposed requirement to monitor the static pressure or air flow rate for thermal and catalytic oxidizers.

Comment: Several commenters requested that we modify the procedures for determining the minimum operating temperature ( operating limit) for thermal and catalytic oxidizers. The commenters stated that, due to the normal variation in combustion temperatures, a facility will have to perform the initial compliance test at lower than normal temperature conditions to ensure that the minimum combustion temperature will be set at a level that they can continuously meet. The commenters requested that we allow facilities to operate the thermal oxidizers up to 50 ° F lower than the average obtained by the performance test and allow facilities to operate RCO at a level that is 100 ° F above the minimum operating temperature of the catalyst. The commenters also noted that, when the THC concentration in the inlet is high, the RCO will not need any additional heat 184 and it can operate at temperatures higher than the set point. Therefore, if the initial compliance tests are conducted under these conditions, the operating temperature limit will be too high for production rates at less than full capacity.

Commenters also stated that, for RCO, the thermocouple should be placed in a location to measure the temperature of the gas in the combustion chamber between the catalyst beds instead of in a location to measure the gas stream before it reaches the catalyst bed. The commenters noted that,

because the gas flow reverses direction in RCO, the inlet temperature monitor will not consistently measure the gas at the same point in the process such that sometimes the gas temperature will be recorded after the catalyst beds instead of before. The commenters further noted that placement of the monitor inside the combustion chamber would eliminate the need for multiple monitors and avoid problems such as overheating and burnout of the catalyst media caused by the temperature delay between the burner and the RCO inlet.

Response: We disagree with the commenters' request to include a 50

F margin around the minimum operating temperature established during the thermal oxidizer compliance test. In general, selection of the representative operating conditions for both the process and the control device for conducting the performance test is an 185 important, and sometimes complex, task. We maintain that establishing the add on control device operating limit at the level demonstrated during the performance test is appropriate. We note that the PCWP rule as proposed allows a facility to select the temperature operating limits based on site specific operating conditions, and the facility is able to consider the need for temperature fluctuations in this selection. The PCWP rule as proposed requires that the operating limit be based on the average of the three minimum temperatures measured during a 3 hour performance test ( rather than on the average temperature over the 3 hour period, for example) to accommodate normal variation during operation and ensure that the minimum temperature established represents the lowest of the temperatures measured during the compliant test. For example, during a 3 hour, three run performance test, the operating limit would be determined by averaging together the lowest 15

minute average temperature measured during each of the three runs. However, continuous compliance with the operating limit is based on a 3 hour block average. For a typical 3

hour set of data, this means that the 3 hour block average will be higher than the average of the three lowest 15

minute averages, so the temperature monitoring provisions already have a built in compliance margin. In addition, the final rule allows PCWP facilities to conduct multiple 186 performance tests to set the minimum operating temperature for RCO and RTO, so PCWP sources would have the option to conduct their own studies ( under a variety of representative operating conditions) in order to establish the minimum operating temperature at a level that they could maintain and that would provide them with an acceptable compliance margin. We feel these provisions allow sufficient flexibility, and an additional tolerance for a 50oF temperature variation is not necessary. Therefore, the final rule does not allow facilities to operate thermal oxidizers 50 ° F lower than the average temperature during testing.

With regard to RCO, we agree with the commenters that when the THC concentration in the inlet is high, the RCO will not need any additional heat and it can operate at temperatures higher than the set point. Therefore, if the initial compliance tests are conducted under these conditions, the operating temperature limit will be too high for production rates at less than full capacity. However,

the final rule requires emissions testing under representative operating conditions and not maximum operating conditions. In addition, we do not agree with the commenter's solution to set the operating limit at 100 ° F above the minimum operating ( design) temperature of the catalyst. As with RTO, we feel it is incumbent upon the 187 facility to demonstrate performance and establish the operating limits during the compliance demonstration test.

Therefore, the final rule requires the facility to establish the minimum catalytic oxidizer operating temperature during the compliance test. However, as noted below, we have provided more flexibility to the facility regarding temperature monitoring for RTO and RCO.

We recognize that in a typical RTO and RCO the combustion chamber contains multiple burners, and that each of these burners may have multiple thermocouples for measuring the temperature associated with that burner. The final rule requires establishing and monitoring a minimum firebox temperature for RTO. In an RTO, the minimum firebox temperature is actually represented by multiple temperature measurements for multiple burners within the combustion chamber. Thus, the final rule clarifies that facilities operating RTO may monitor the temperature in multiple locations within the combustion chamber and calculate the average of the temperature measurements to use in establishing the minimum firebox temperature operating limit.

Regarding RCO, we agree with the commenters that,

because the gas flow reverses direction in RCO, the inlet temperature monitor will not consistently measure the gas at the same point in the process, such that sometimes the gas 188 temperature will be recorded after the catalyst beds instead of at the inlet to the beds. We did not intend to require the separate measurement of each inlet temperature by switching the data recording back and forth to coincide with the flow direction into the bed. The intention is to monitor the minimum temperature of the gas entering the catalyst to ensure that the minimum temperature is maintained at the operating level during which compliance was demonstrated. This can be accomplished by measuring the temperature in the regenerative canisters at one or more locations. Measuring the inlet temperatures of each catalyst bed and then determining the average temperature for all catalyst beds is one approach. Even though some of the beds are cooling and others are heating, the average across all of the catalyst beds should not vary significantly. Another acceptable alternative is monitoring the combustion chamber temperature, as suggested by the commenters. The monitoring location( s) selected by the facility may depend on the operating conditions ( i. e., THC loading to the unit) during the performance test and how the unit is expected to be operated in the future. The objective is to establish monitoring and operating limits that are representative of the conditions during the compliance demonstration test( s) and representative of the temperature to which the catalyst is exposed. We recognize 189 the need for flexibility in selecting the temperature( s) to be monitored as operating limits for RCO. Therefore, the final rule provides flexibility by allowing facilities with RCO to choose between basing their minimum RCO temperature limit on the average of the inlet temperatures for all catalyst beds or the average temperature within the combustion chamber. If there are multiple thermocouples at the inlet to each catalyst bed, then we would expect facilities to average the measurements from each thermocouple to provide a representative catalyst bed inlet temperature for each individual catalyst bed.

Finally, the final rule also includes an option ( in lieu of monitoring oxidizer temperature) for monitoring and maintaining the oxidizer outlet THC concentration at or below the operating limit established during the performance test. Use of the THC monitoring option would eliminate the concerns regarding establishing and monitoring oxidizer operating temperatures ( in effect, it provides facilities complete flexibility in operation of the control device, as long as the THC outlet concentration remains below the operating limit).

Comment: One commenter recommended that we require sampling and testing of the catalyst activity level for RCO.

The commenter stated that the proposed requirement to monitor inlet pressure may not be sufficient to detect 190 catalyst problems such as poisoning, blinding, or degradation.

Response: We agree with the commenter that a catalyst activity level check is needed because catalyst beds can become poisoned and rendered ineffective. An activity level check can consist of passing an organic compound of known concentration through a sample of the catalyst, measuring the percentage reduction of the compound across the catalyst sample, and comparing that percentage reduction to the percentage reduction for a fresh sample of the same type of catalyst. Generally, the PCWP facility would remove a representative sample of the catalyst from the catalytic oxidizer bed and then ship the sample to a testing company for analysis of its ability to oxidize organic compounds ( e. g., by a flame ionization detector).

In response to this comment, we added to the final rule a requirement for facilities with catalytic oxidizers to perform an annual catalyst activity check on a representative sample of the catalyst and to take any necessary corrective action to ensure that the catalyst is performing within its design range. Corrective actions may include washing or baking out the catalytic media,

conducting an emissions test to ensure the catalytic media is resulting in the desired emissions reductions, or partial or full media replacement. Catalysts are designed to have 191 an activity range over which they will reduce emissions to the desired levels. Therefore, the final rule specifies that corrective action is needed only when the catalyst activity is outside of this range. It is not our intention for facilities to replace catalyst if the catalytic media is not performing at the maximum level it achieved when the catalyst was new. Also, the final rule specifies that the catalyst activity check must be done on a representative sample of the catalyst to ensure that facilities that may have recently conducted a partial media replacement do not sample only the fresh catalytic media for the catalyst activity check.

Comment: Several commenters stated that the proposed operating requirements for pressure drop across the biofilter bed should be removed from the final PCWP rule.

The commenters contended that pressure drop is a good parameter to monitor voluntarily because it indicates the permeability and age of the biofilter bed, helping to determine maintenance and replacement needs; however, it is not an indicator of destruction efficiency. The commenters noted that, because of normal wear and tear, the pressure drop gradually increases over the 2 to 5 year life span of the biofilter, so it would not be possible to maintain a constant operating pressure. The commenters further noted that the supporting materials in the project docket did not 192 provide any information or data that would support the idea that pressure drop is an indication of HAP destruction efficiency, but only indicated that pressure drop was an indication of the age of the biofilter. For these reasons,

the commenters argued that setting an absolute limit on pressure drop was inappropriate.

The commenters also requested that the proposed requirements to monitor the pH of the biofilter bed effluent be removed from the final PCWP rule. The commenters noted that pH is a good parameter to monitor voluntarily because it indicates the environmental conditions inside the biofilter bed and can indicate the presence of organic acids and THC decomposition products, but it is not a reliable indicator of destruction efficiency. According to the commenters, small fluctuations of pH are expected and have little effect on the biofilter performance; therefore, the narrow range of pH values that would be established as an operating range by the initial compliance tests should not be used alone to determine biofilter performance. The commenters also noted some problems associated with continuous measurement of pH. According to the commenters,

some biofilter units operate with periodic irrigation of the bed, such that the effluent flow is not constant and continuous monitoring is not possible. The commenters also pointed to an NCASI survey that confirmed that continuous pH 193 monitoring would be impractical for the facilities surveyed.

The commenters stated that, because none of the PCWP facilities surveyed could find a link between pH alone and biofilter performance, none of those facilities currently have continuous pH monitors on their biofilters.

In addition, several commenters requested changes to the proposed requirement to monitor the inlet temperature of the biofilter. These commenters agreed that temperature is a parameter that should be monitored for biofilters, but argued that the location of the temperature monitor should be changed from the biofilter inlet to the biofilter bed or biofilter outlet. The commenters noted that the biofilter bed temperature has the greatest impact on biological activity. According to the commenters, the biofilter inlet temperature is not a good indicator of bed temperature and can change very rapidly depending upon the operating rate of the press, the humidity, and the ambient temperature.

Response: We agree with the commenters that increases in pressure drop will occur over time and will not necessarily equate to a reduction in control efficiency,

making an absolute limit on pressure drop ineffective in demonstrating continuous compliance. Therefore, we have not included the requirement to monitor pressure drop in the operating requirements for biofilters in the final PCWP rule. We have also removed the requirement to monitor pH 194 from the final rule. Although pH is an indicator of the health of the microbial population inside the biofilter, we agree with the commenters that including continuous pH monitoring as an operating requirement for biofilters may not be appropriate.

We also agree with the commenters that the biofilter bed temperature has the greatest impact on biological activity and that the location for monitoring the biofilter temperature should be changed. We did not propose monitoring of biofilter bed temperature because we thought that monitoring of biofilter inlet temperature would be simpler because only one thermocouple would be required.

The temperature inside the biofilter bed can change in different areas of the bed, and therefore, depending on the biofilter, multiple thermocouples may be necessary to get an accurate picture of the temperature conditions inside the biofilter bed. Prior to proposal we rejected the idea of monitoring the biofilter exhaust temperature because temperature measured at this location can be affected by ambient temperature ( especially for biofilters with short stacks) more than the temperature inside the biofilter bed.

We now conclude that there is no better, more representative way to monitor the temperature to which the biofilter microbial population is exposed than to directly monitor the temperature of the biofilter bed. According to our MACT 195 survey data, most facilities with biofilters are already monitoring biofilter bed temperature. Therefore, the final rule requires continuous monitoring of the temperature inside the biofilter bed.

The proposed rule would have allowed facilities to specify their own monitoring methods, monitoring frequencies, and averaging times for the proposed biofilter operating parameters ( i. e., inlet temperature, effluent pH,

and pressure drop). However, monitoring of temperature is not as subjective as monitoring biofilter effluent pH and pressure drop; therefore, as an outgrowth of our decision to not require monitoring of biofilter effluent pH and pressure drop, the final rule specifies the monitoring method,

frequency, and averaging time for biofilter bed temperature monitoring. The final rule requires that each thermocouple be placed in a representative location and clarifies that multiple thermocouples may be used in different locations within the biofilter bed. The temperature data ( i. e.,

average temperature across all the thermocouples located in the biofilter bed if multiple thermocouples are used) must be monitored continuously and reduced to a 24 hour block average. A 24 hour block average was selected for biofilter temperature monitoring because we recognize that there may be some diurnal variation in temperature. Facilities wishing to reflect a diurnal temperature variation when 196 establishing their biofilter temperature may wish to perform some test runs during peak daily temperatures and other test runs early in the morning, when temperatures are at their lowest.

Facilities may choose to observe parameters other than biofilter bed temperature, but will not be required to record or control them for the final PCWP rule. We feel that many factors can affect biofilter performance, either alone ( e. g., a media change) or in concert with one another ( e. g., a loss of water flow results in a sharp change in temperature and pH). The factors that have the greatest effect on biofilter performance are likely to be sitespecific However, based on the comments we have received,

we conclude that extensive biofilter parameter monitoring is not the best method for ensuring continuous compliance. To promote enforceability of the final PCWP rule, we have added a requirement to perform periodic testing of biofilters.

The final rule requires facilities to conduct a repeat test at least every 2 years and within 180 days after a portion of the biofilter bed is replaced with a new type of media or more than 50 percent ( by volume) of the biofilter media is replaced with the same type of media. Each repeat test must be conducted within 2 years of the previous test ( e. g., 2 years after the initial compliance test, or 2 years after the test following a media change). We are requiring repeat 197 testing after a partial or wholesale change to another media type ( considered a modification of the biofilter) because such a modification can impact the performance of the biofilter. Facilities that replace biofilter media with a new type of media ( e. g, bark versus synthetic media) must also re establish the limits of the biofilter bed temperature range. We feel that substantial replacement of the biofilter media ( e. g., replacement of more than 50 percent of the media) with the same type of media may affect short term performance of the biofilter while the replacement media becomes acclimated, and therefore, the final rule requires a repeat performance test following this type of media replacement. However, PCWP facilities that replace biofilter media with the same type of media are not required to re establish the biofilter bed temperature range. In the case of same media replacements, we feel it is appropriate for PCWP facilities to be able to use data from previous performance tests to establish the limits of the temperature range. During repeat testing following replacement with the same type of media, facilities can verify that the biofilter remains within the temperature range established previously or establish a new compliant temperature range. Facilities using a THC CEMS that choose to comply with the THC compliance options ( i. e., 90 percent reduction in THC or outlet THC concentration less than or 198 equal to 20 ppmvd) may use the data from their CEMS in lieu of conducting repeat performance testing.

Comment: Several commenters requested that the final rule allow new biofilters a longer period than 180 days to establish operating parameter levels. These commenters suggested a 1 year period, because that would be long enough to observe the full seasonal variation in parameters and find the true operating maxima and minima.

Response: We disagree that more than 180 days is necessary to establish operating parameter limits for biofilters. As mentioned previously, we have eliminated the proposed requirement to establish operating limits for pH and pressure drop. Today's final rule contains two options for biofilter operating parameter limits: biofilter bed temperature range and outlet THC concentration. While allowing 1 year to establish the biofilter bed temperature operating range is reasonable due to seasonal temperature variations, 1 year is not necessary for establishing an outlet THC concentration limit. Furthermore, the final rule already allows facilities to expand their operating ranges ( see § 63.2262( m)( 3)) through additional emissions testing.

The compliance date for existing facilities is 3 years after promulgation of the final PCWP rule, and existing facilities are allowed 180 days following the compliance date to conduct performance testing and establish the 199 operating parameter limits. If there is concern that 180 days is not long enough for a new biofilter installation to operate under the full range of biofilter bed temperatures,

then existing facilities should begin operation of their biofilter well before the compliance date ( e. g., 180 days prior to the compliance date if 1 year is needed).

Facilities also have the option of testing their biofilter prior to the compliance date to establish one extreme of their biofilter bed temperature range. The compliance date for new PCWP facilities is the effective date of the rule ( if startup is before the effective date) or upon initial startup ( if the initial startup is after the effective date of the rule), and biofilters installed at new PCWP facilities would have up to 180 days following the compliance date to establish the operating parameter limits.

To address situations where a new biofilter is installed at an existing facility more than 180 days after the compliance date ( e. g., to replace an existing RTO), we have included section § 63.2262( m)( 2) to the final PCWP rule, which allows existing sources that install new biofilters up to 180 days following the initial startup date of the biofilter to establish the operating parameter limits. Thus, new biofilter installations are given time for establishment of operating parameter limits regardless of where they are installed at new or existing sources. 200 Comment: Multiple commenters supported the option to continuously monitor THC at control device outlets to demonstrate compliance, but suggested that either the procedure for determining the operating limits or the length of the averaging periods be altered. The commenters stated that THC concentration at a control device outlet is not a parameter that can be easily adjusted by operators over short periods of time. The commenters stated that 3 hours is not a long enough block to avoid deviations from compliance given the variability of the process. The commenters provided an analysis of THC data from a biofilter outlet that showed multiple deviations occurring over a two month period when a 3 hour block average was used and few to zero deviations when a 24 hour or 7 day block average was used for the operating limits. The commenters stated that because HAP destruction efficiency of biofilters does not vary much with time, the longer block average would not be environmentally harmful.

Response: While THC emissions at the outlet of a biofilter may vary, the THC emissions at the outlet of a thermal or catalytic oxidizer should not vary greatly.

Although, as stated by the commenters, the HAP destruction efficiency of biofilters is not subject to large short term variations, the same is not true for thermal and catalytic oxidizers ( e. g., a sudden significant decrease in 201 temperature could result in a sudden decrease in HAP reduction). Therefore, we feel it is appropriate to maintain the 3 hour block averaging requirement for THC monitoring for thermal and catalytic oxidizers. However, we have expanded the THC averaging requirement for biofilters to a 24 hour block average to provide more flexibility. The THC operating limit for biofilters would be established as the maximum of three 15 minute recorded readings during emissions testing. We also note the continuous monitoring of THC is not required for all APCD, but is an alternative to continuous monitoring of temperature. Furthermore,

facilities can conduct multiple performance tests at different operating conditions to increase their maximum THC concentration operating limit.

6. Selection of Monitoring Requirements for Uncontrolled Process Units Comment: Several commenters recommended that we change the title of proposed § 63.2262 ( n) ( How do I conduct performance tests and establish operating requirements?

Establishing uncontrolled process unit operating requirements) to " Establishing operating requirements for production based compliance option process units" for the final rule. The commenters stated that the proposed title implied that no controls of any kind are being applied to these process units, when in fact facilities may be using P2 202 techniques to reduce emissions. The commenters also objected to wording within the proposed section that suggests that temperature is the only parameter affecting HAP emissions from the process units. The commenters suggested that the requirements be revised in the final rule to give sources more flexibility in identifying and documenting those process unit operating parameters that are critical to maintaining compliance with the PBCO limits.

Response: At proposal, our intention was to establish operating requirements for those process units complying with rule requirements without the use of an APCD. There are two situations in the PCWP rule as proposed where process units may not have an add on control device: ( 1)

when process units meet the PBCO, or ( 2) when process units used to generate emissions averaging debits do not have an add on APCD that partially controls emissions. To clarify this for the final rule and to address the commenters'

concern regarding applicability of § 63.2262( n), we changed the title of the section to " Establishing operating requirements for process units meeting compliance options without a control device."

We agree with the commenters that temperature alone is not necessarily the sole factor affecting HAP emissions from some process units. A variety of factors can affect HAP emissions, and the controlling parameter for one process 203 unit may be different than the controlling parameter for another process unit. Therefore, the final rule gives sources more flexibility in selecting and establishing operating limits for process units without add on controls.

The final rule requires facilities to identify and document the operating parameter( s) that affect HAP emissions from the process unit and to establish appropriate monitoring methods and monitoring frequencies. We recognize that it is not practical to continuously monitor every process

unitspecific factor that could affect uncontrolled emissions ( e. g., there is no way to monitor and determine a 3 hour block average of wood species mix for a particleboard plant). However, some parameters are suitable for continuous monitoring ( e. g., process operating temperature,

furnish moisture content) and are already monitored as part of normal operation but not for compliance purposes. We feel that daily records of most parameters would be sufficient to ensure ongoing compliance ( e. g., daily average process operating temperature, furnish moisture, resin type,

wood species mix) if the parameters do not deviate from the ranges for these parameters during the initial compliance test. Therefore, in the final PCWP rule, we have replaced the proposed 3 hour block average temperature monitoring requirements for process units without control devices with a requirement to maintain, on a daily basis, the process 204 unit operating parameter( s) within the ranges established during the performance test. This gives facilities the flexibility to decide which parameters they will monitor and control, while providing enforcement personnel with records that can be used to assess and compare the day to day operation of the process unit to the controlling operating parameters. Facilities are also allowed to decide for each parameter the appropriate monitoring methods, monitoring frequencies, and averaging times ( not to exceed 24 hours for continuously monitored parameters such as temperature and wood furnish moisture). Also, to ensure that the HAP emissions measured during the compliance tests are representative of actual emissions, the final rule requires testing at representative operating conditions, as defined in the rule.

7. Data Collection and Handling Comment: Several commenters requested clarifications and changes to the proposed requirements related to data collection and handling for CPMS. The commenters stated that the requirement that a valid hour of data must include at least three equally spaced data values for that hour is ambiguous and should be revised. The commenters recommended that the final rule require facilities to average at least three data points taken at constant intervals, provided the interval is less than or equal to 15 minutes. The 205 commenters further noted that a better approach would be to drop the concept of an hourly average altogether and simply calculate the block average as the average of all evenly spaced measurements in the block period with a maximum measurement interval of 15 minutes. The commenters also noted that the proposed rule did not specify how to calculate the 3 hour block average when one or more of the individual hours does not contain at least three valid data values.

Commenters also requested that the final rule consolidate and clarify the requirements in proposed § § 63.2268 and 63.2270 regarding data that should be excluded from block averages. The commenters recommended that the final rule explicitly state that any monitoring data taken during periods when emission control equipment are not accepting emissions from the production processes should be excluded from hourly or block averages. The commenters also noted inconsistencies in the proposed rule language that seemed to imply that data collected during production downtime and SSM events would be included in the hourly averages but not in the block averages. The commenters stated that, because SSM events occur when the process is not in operation, there is no need to collect data from these periods.

Response: We agree with the commenters that the 206 proposed rule language regarding acceptable data and data averaging was somewhat ambiguous and have revised the language accordingly. Following the commenters'

recommendation, we removed the concept of an hourly average from the final rule to allow block averages to be calculated as the average of all evenly spaced measurements in the 3

hour or 24 hour block period with a maximum measurement interval of 15 minutes. In place of the requirement for a valid hourly average to contain at least three equally spaced data values for that hour, we added a minimum data availability requirement. The minimum data availability requirement specifies that to calculate data averages for each 3 hour or 24 hour averaging period, you must have at least 75 percent of the required recorded readings for that period using only recorded readings that are based on valid data. The minimum data availability requirement appears in § 63.2270( f) of today's final rule. To clarify what constitutes valid data and how to calculate block averages,

we rearranged proposed § § 63.2268 and 63.2270. We moved proposed § 63.2268( a)( 3) and ( 4) to final § 63.2270 ( now § 63.2270( d) and ( e)) of today's final rule. Rather than repeating which data should be excluded from data averages in § 63.2270( d) and ( e), these new sections now refer to § 63.2270( b) and ( c) when discussing data that should not be included in data averages. We also added data recorded 207 during periods of SSM to the list of data that should be excluded from data averages in § 63.2270. We feel these changes to the structure and wording of the rule should fully address the commenters' concerns.

Comment: Several commenters noted that the proposed PCWP rule does not provide any alternatives to the definition of a 1 hour period found in the MACT general provisions ( 40 CFR 63.2), which states that a 1 hour period is any 60 minute period commencing on the hour. These commenters requested that facilities be given the option of beginning a 1 hour period at a time that is convenient depending on shift changes, employee duties at the end of a shift, and settings on the systems that record data.

Response: We agree with the commenters and have included a definition of 1 hour period in today's final rule that omits the phrase " commencing on the hour."

8. Performance Specifications for CPMS Comment: Several commenters requested that we write sections of the final rule language that address temperature measurement. The commenters stated that the phrase " minimum tolerance of 0.75 percent," found in proposed sections 63.2268( b)( 2), 63.2268( c)( 3), and 63.2268( e)( 2), should be revised to read " accurate within 0.75 percent of sensor range." The commenters argued that, because tolerances usually refer to physical dimensions, this revision more 208 accurately reflects the intent of the final PCWP rule.

Commenters also recommended that the sensitivity for chart recorders be changed from a sensitivity in the minor division of at least 20 ° F to minor divisions of not more than 20 ° F. The commenters noted that the wording in the proposed rule means that minor divisions could be 30 ° F or 50 ° F, but assumed that we probably meant that 20 ° F is the largest minor division that a facility can use, and therefore, stated that the suggested revision is more accurate.

Response: We agree that the proposed temperature measurement requirements should be clarified. In today's final rule, we wrote the requirement in § 63.2269( b)( 2)

( formerly proposed § 63.2268( b)( 2)) to read " minimum accuracy of 0.75 percent the temperature value." We eliminated proposed sections § § 63.2268( c) and 63.2268( e) from the final rule because we removed the requirements for monitoring of pressure or flow. We also wrote proposed § 63.2268( b)( 3) to state that " If a chart recorder is used, it must have a sensitivity with minor divisions of not more than 20oF."

Comment: Several commenters requested changes to the proposed work practice requirements for dry rotary dryers and veneer redryers related to moisture monitoring. The commenters noted that the proposed requirement to use a moisture monitor with a minimum accuracy of 1 percent was 209 appropriate for rotary dry dryers in the 25 to 35 percent moisture content range. However, the commenters stated that less stringent accuracy requirements should be included for veneer redryers to better correspond with current practices at softwood plywood and veneer facilities. Specifically,

the commenters requested that the final rule revise the proposed performance specifications for moisture monitors for veneer redryers to allow the use of monitors with an accuracy of ± 3 percent in the 15 to 25 percent moisture range. Several commenters also requested that the proposed calibration procedures for moisture monitors be revised in the final rule to eliminate grab sampling and to allow facilities to follow the calibration procedures recommended by the manufacturer. The commenters argued that the proposed grab sampling procedure is impractical and that obtaining a representative grab sample would be difficult.

Response: We agree with the commenters that the proposed moisture monitoring requirements should be adjusted in the final rule and have made the requested changes to the accuracy requirements for moisture monitors used with rotary dry dryers and veneer redryers. We have also adjusted the calibration procedures in the final rule to eliminate grab sampling and to allow facilities to follow the manufacturer's recommended calibration procedures for moisture monitors. 210 I. Routine Control Device Maintenance Exemption ( RCDME)

Comment: Several commenters requested that the proposed requirements for the RCDME be modified in the final rule to give PCWP facilities more flexibility. First, the commenters requested that the proposed RCDME allowances ( expressed as a percentage of the process unit operating hours) be increased. The commenters argued that the proposed downtime allowance periods are too short to allow for proper maintenance. The commenters noted that the NCASI survey that was used to set the downtime allowance only included data from 1999, and many facilities may have conducted nonannual maintenance and repairs in the years preceding or following that year. According to the commenters, the 1999 survey was also limited in that the majority of the RTO included in the survey were less than 5 years old, and as the equipment ages over a lifetime of 5 to 15 years, performance will degrade below the levels seen in the 1999 survey. Therefore, the commenters suggested that we reexamine the NCASI downtime data and use the 79th percentile instead of the 50th percentile to select downtime allowances that represent the time needed for nonannual events.

Response: After reviewing our previous analysis of the downtime data, we maintain that the percentage downtime we proposed ( 3 percent for some process units and 0.5 percent 211 for others) calculated on an annual basis is appropriate for the final PCWP rule. The downtime allowance allowed under the RCDME is intended to allow facilities limited time to perform routine maintenance on their APCD without shutting down the process units being controlled by the APCD. We included the downtime allowance in the proposed rule because we recognize that frequent maintenance must be performed to combat particulate and salt buildup in some RTO and RCO for PCWP drying processes. The downtime allowance is not intended to cover every APCD maintenance activity, only those maintenance activities that are routine ( e. g.,

bakeouts, washouts, partial or full media replacements) and do not coincide with process unit shutdowns. Most APCD maintenance should occur during process unit shutdowns; the RCDME is a downtime allowance in addition to the APCD maintenance downtime that occurs during process unit shutdowns. We note that most PCWP plants do not operate 8,760 hours per year without shutdowns. For example, the MACT survey responses indicate that softwood plywood plants operate for an average 7,540 hours per year, which would allow 1,220 hours for control device maintenance without the RCDME. Furthermore, the RCDME is allowed in addition to APCD downtime associated with SSM events covered by the SSM plan ( e. g., electrical problems, mechanical problems,

utility supply problems, and pre filter upsets). For these 212 reasons, the final rule retains the RCDME allowances included in the proposed rule.

Comment: Several commenters objected to the proposed requirement that the maintenance be scheduled at the beginning of the semiannual period. The commenters argued that scheduling maintenance activities at the beginning of each semiannual period is neither consistent with industry practice nor practical. The commenters noted that downtime for maintenance is scheduled as the need arises, and downtime schedules change with need and production requirements. The commenters stated that most facilities have a general idea of when they intend to conduct routine maintenance activities and will schedule those activities whenever possible to coincide with process downtime as it approaches. The commenters further noted that the proposed PCWP rule does not clarify what would happen if maintenance were necessary before the scheduled date. Therefore, the commenters concluded that deleting the requirement to set the maintenance schedule at the beginning of each semiannual period would eliminate confusion and better represent industry practice.

Response: We agree with the commenters and have removed the requirement to record the control device maintenance schedule for the semiannual period from the final rule. We agree that the proposed requirement would be impractical 213 because process unit shutdowns are not scheduled semiannually. Also, the SSM provisions do not require scheduling of maintenance, and therefore, requiring scheduling of routine maintenance covered under the RCDME would be more restrictive than the requirements for SSM. To the extent possible, APCD maintenance should be scheduled at the same time as process unit shutdowns. Thus, today's final rule retains the requirement that startup and shutdown of emission control systems must be scheduled during times when process equipment is also shut down.

Comment: Commenters also requested that the proposed RCDME requirement that facilities must minimize emissions to the greatest extent possible during maintenance periods be revised to require that facilities make reasonable efforts to minimize emissions during maintenance. The commenters stated that this revision is necessary because the proposed wording could be interpreted to mean that sources should limit production or shut down entirely during maintenance periods, which is contrary to the intent of the RCDME.

Response: We agree with the commenters and have modified the referenced requirement as suggested by the commenters.

J. Startup, Shutdown, and Malfunction ( SSM)

Comment: Several commenters noted inconsistencies between the proposed rule and the NESHAP General Provisions 214 ( 40 CFR part 63, subpart A) and requested that these inconsistencies be resolved by making the final PCWP rule consistent with the latest version of the General Provisions.

Response: Approximately 1 month prior to publication of the proposed PCWP rule, we published proposed amendments to the NESHAP General Provisions concerning SSM procedures ( 67 FR 72875, December 9, 2002) and promulgated them in May 2003 ( 68 FR 32585, May 30, 2003). Due to the timing of the these rulemakings, the proposed PCWP rule language did not reflect our most recent decisions regarding SSM. To avoid confusion and promote consistency, we have written the final rule to reference the NESHAP General Provisions directly, where applicable, and to be more consistent with other recently promulgated MACT standards. Although the amendments to the NESHAP General Provisions regarding SSM plans are currently involved in litigation, the rule requirements promulgated on May 30, 2003, apply to the final PCWP NESHAP unless and until we promulgate another revision. In response to suggestions made by commenters, we also consolidated several sections to clarify the requirements related to SSM and to eliminate redundancies in the final rule. Specifically, we combined proposed § 63.2250( d) with proposed § 63.2250( a) and revised the resulting § 63.2250( a) to clarify that the SSM periods mentioned in proposed § 63.2250( a) apply to both process units and control devices and to clarify when the compliance options, operating requirements, and work practice requirements do and do not apply. We also removed proposed § 63.2250( e) from the final rule because it was a duplication of proposed § 63.2251( e) regarding control device maintenance schedules. In addition, we removed proposed § 63.2250( f) related to RCO catalyst maintenance because this section was misplaced and is not consistent with the RCO monitoring requirements in today's final rule.

K. Risk Based Approaches 1. General comments Risk based approaches Comment: Numerous commenters encouraged EPA to exercise all of the flexibility within its authority and offer the widest possible array of options so that facilities that pose little risk to public health or the environment would not be forced to add expensive and unproductive control equipment which would weaken them financially or cause them to close. Commenters specifically recommended that EPA incorporate risk based options similar to all three industry white papers, which would exclude facilities that pose no significant risk to public health or the environment. ( As an alternative, one commenter recommended that EPA at least incorporate the concentration based de minimis applicability exemption.)

Commenters stated that inclusion of risk provisions has 216 the potential to achieve overall environmentally superior results in a cost effective manner, particularly in cases where criteria pollutants from control devices ( i. e.,