>> Questions or Comments: airperm@tceq.texas.gov
You are here:

Title 30 TAC Chapter 117 Rule Change, November 21, 1999

Outdated 30 TAC 117 and 31 TAC 117 rules, 31 TAC 117 date from 1972 and the rule changed to 30 TAC 117 in September 1993

Permanent Rule Adoption

Preface to Chapter 117 (Regulation VII)
Subchapters A, B and D

1. Purpose. This change transmittal provides the page(s) that reflect changes and additions to the Texas Natural Resource Conservation Commission (commission) Volume of Permanent Rules.

2. Explanation of Change. On October 27, 1999, the commission adopted amendments to § 117.10, concerning Definitions; §§ 117.205, 117.207, 117.208, 117.209, 117.211, 117.213, 117.219, and 117.223, concerning Commercial, Institutional and Industrial Sources; and § 117.520 and § 117.570, concerning Administrative Provisions. The commission adopts these amendments to Chapter 117, concerning Control of Air Pollution from Nitrogen Compounds, and revisions to the State Implementation Plan (SIP) in order to conform with the U.S. Environmental Protection Agency's (EPA) revised ozone transport policy and allow the Beaumont/Port Arthur (BPA) ozone nonattainment area's attainment date to be extended. The changes require certain lean-burn stationary engines in BPA to meet new emission specifications and other requirements in order to reduce nitrogen oxides (NOx) emissions and ozone air pollution. Secondarily, in an effort to improve implementation of Chapter 117, applicable to existing major stationary sources of NOx in the BPA, Dallas/Fort Worth (DFW), and Houston/ Galveston (HGA) ozone nonattainment areas, the commission adopts changes to Chapter 117 which: eliminate the requirement to operate wood-fired boilers with flue gas sensor-based trim, add an option to monitor exhaust flow instead of fuel flow, and clarify several other requirements and rule references.

Sections 117.205, 117.211, 117.213, 117.223, and 117.570 are adopted with changes to the proposed text as published in the July 16, 1999 issue of the Texas Register (24 TexReg 5436). Sections 117.10, 117.207, 117.208, 117.209, 117.219, and 117.520 are adopted without changes and will not be republished.

3. Effect of Change. The adopted change to § 117.10, concerning Definitions, adds a definition of "thirty- day rolling average" to the rule, in response to a request for clarification from a monitoring system vendor. The definition is taken from Title 40 Code of Federal Regulations (CFR) Part 60, Subpart Db, the definition of steam generating unit operating day in 䅸.41b, and the NOx compliance procedure in 䅸.46b(e)(3). This clarification is consistent with the preamble discussion in the original NOx RACT rule (18 TexReg 3427, May 28, 1993).

The adopted change to § 117.205(b), concerning Emission Specifications, relocates the averaging time requirements from the beginning of the subsection to new paragraphs (7) and (8) and uses a listing format to make the text less dense and more readable. The adopted changes to § 117.205(b)(5) and § 117.207(d) and (e), concerning Alternative Plant-wide Emission Specifications, make rule terminology more consistent by substituting the term "sum" for "average" in reference to heat input weighting.

The adopted new § 117.205(e) and revised § 117.205(g)(6), now renumbered (h)(6), add an emission specification for lean-burn gas-fired engines in BPA. The adopted limit of 3.0 grams NOx per horsepower-hour (g/hp-hr) is consistent with previously established NOx RACT rules in a number of other states. A block one-hour average compliance period for the emission limits was proposed and adopted. In addition, in order to allow the pipeline compressor engines to continue to operate efficiently, higher short term emissions are allowed under an optional, 30-day rolling average compliance period. This option requires use of one of several monitoring options to demonstrate emissions compliance. The adopted limit of 3.0 g carbon monoxide (CO)/hp-hr is consistent with the existing emission specification for rich-burn engines. The purpose of this requirement is to ensure that the NOx control technique selected does not unnecessarily increase CO emissions.

The adopted changes to § 117.205(g)(3), now relettered (h)(3), § 117.207(f)(4), § 117.209(b)(2), concerning Initial Control Plan Procedures, and § 117.213(a)(1)(C), now relettered (a)(1)(A)(iii), concerning Continuous Demonstration of Compliance, clarify the exemption from NOx emission specifications for boilers and industrial furnaces (BIFs) regulated by EPA at 40 CFR 266, Subpart H. The exemption became effective on June 9, 1993 with the original NOx RACT rules and has not been modified since. However, on June 19, 1998, EPA excluded from regulation under Subpart H some hazardous waste-derived fuels which are comparable to certain commercial liquid fuels ("comparable fuels"). The adopted revision clarifies that the exemption applies to BIFs regulated by the version of the EPA rules which were in effect on June 9, 1993. Although it may be appropriate to eventually bring some or all of the original BIFs into the Chapter 117 emission specifications, it would only be appropriate to do so through the rulemaking process, which allows for public notice and comment. The commission will evaluate the feasibility of NOx controls from BIFs in BPA during the development of Phase II rules.

The adopted change to § 117.207(f) updates a cross-reference. The adopted change to § 117.208(d)(1), concerning Operating Requirements, exempts wood-fired boilers from the requirement to operate with oxygen (O2) or CO trim. Boiler trim uses feedback from exhaust gas O2 or CO sensors to minimize the amount of combustion air fed to a boiler. With trim, gas-fired boilers are typically capable of operating around 2% exhaust O2; in this range, a reduction of O2 reduces NOx formation. In contrast, wood-fired boilers typically need to operate in the range of 7% to 8% exhaust O2 in order to burn the fuel completely and minimize CO. In this O2 range, the NOx production rate (pound per million British thermal units of heat input) increases with tighter O2 control. Therefore, NOx reductions caused by fuel efficiency improvement (reducing the total amount of fuel fired reduces emissions) due to combustion trim are likely to be negated by the increased NOx production rate. Furthermore, the moisture content of wood fuel varies greatly. The moisture variability may make the operation of trim control unworkable on wood-fired boilers. Because it is ineffective for NOx control and the operation is challenging, the commission has eliminated the boiler trim requirement for wood-fired boilers.

The adopted change to § 117.211(d), concerning Initial Demonstration of Compliance, clarifies the rule language by substituting "November 21, 1999" for "the effective date of this rule as revised." The specific effective date was not inserted here in the previous revision because the effective date is not known with certainty until after rule language is adopted. The adopted change to § 117.211(g)(8) corrects the cross reference to the CEMS requirements, changing § 117.211(d) to § 117.211(e).

In response to a suggestion from a representative of an affected source with six fuels fed to one unit, the adopted new § 117.213(a)(2) adds the option of using a calibrated exhaust flow monitor instead of fuel flow meters for units which are monitored with a NOx continuous emission monitoring system (CEMS). Installation of one exhaust flow monitor may be less expensive than installing multiple fuel flow meters. Procedures for calibration of exhaust flow monitors are available in existing federal regulations in 40 CFR Part 75, Appendix A, and are referenced to assure the accuracy of the monitoring. Properly calibrated and quality assured exhaust flow monitors should be at least as accurate in determining the NOx mass emission rate as fuel flow meters.

The adopted new § 117.213(b)(2) lists units not required to monitor exhaust O2 under § 117.213(b). First, the list excludes units currently exempt from the Chapter 117 NOx emission specifications. It would not be logical for the monitoring to apply to a unit that is not currently subject to an emission specification. It would be more appropriate to establish the monitoring requirements for these exempt units concurrently with any new emission specifications necessary for future attainment demonstration rules. Second, the adopted § 117.213(b)(2)(B) excludes process heaters which operate with CO2 CEMS from the § 117.213(b) exhaust O2 monitoring requirement in order to correct a drafting error in the previous rulemaking which eliminated this alternative. Excess air may be measured by either O2 or CO2, and process heaters are not required to measure O2 for trim purposes, as is required for boilers under § 117.208(d)(1). Therefore, monitoring excess air with CO2 CEMS is an acceptable alternative to O2 monitors for process heaters. Last, the adopted § 117.213(b)(2)(C) excludes wood-fired boilers from the § 117.213(b) exhaust O2 monitoring, to be consistent with the elimination of the requirement to operate these boilers with O2 trim.

The adopted new § 117.213(b)(3) clarifies that the O2 monitors required by subsection (b) are not subject to the location and calibration requirements of the O2 monitors required by subsection (e). The O2 monitors required by subsection (b) are for uses such as inputs for predictive monitoring, boiler trim control, and process control. Most units already operate with O2 monitors for combustion process control. Therefore, because of the potential costs of imposing retroactive requirements on existing monitors, the O2 monitors should only be required to meet the location specifications and quality assurance requirements referenced in subsection (e) if the monitors are used to monitor diluent under subsection (e). However, if new O2 monitors are necessitated as a result of subsection (b), subsection (e) requirements should be considered the appropriate guidance for the location and calibration of the monitors. Flexibility in applying the O2 monitoring requirement is consistent with the preamble discussion in the original NOx RACT rule (18 TexReg 3436, May 28, 1993). Because subsection (b) currently does not specify compliance with the location and calibration requirements of subsection (e), the adopted changes clarify, but do not lessen, existing requirements.

Other adopted changes update a cross-reference in § 117.213(c)(2)(A) and reduce the number of words used in § 117.213(c)(2)(B) without changing the intended meaning. In response to a request for clarification from the regulated community, § 117.213(f)(5)(C)(ii) is revised by substituting the words "Performance Specifications" for "appropriate procedures." This wording change clarifies that the reference to § 117.213(f)(5)(A)(i)(I)-(III) does not include the three load testing specified in § 117.213(f)(5)(A)(i). The adopted changes to § 117.213(i) and (m) correct rule cross-references.

The adopted changes to § 117.219(e)(2), concerning Notification, Recordkeeping, and Reporting Requirements, revise the criteria for reporting excess emissions caused by catalytic converter or air- fuel ratio controller malfunction, to more generally include excess emissions caused by emission control system failures. This change is adopted to expand the reporting to include the newly regulated category of lean-burn engine emissions. The adopted change to § 117.219(f)(1) adds a recordkeeping requirement for exhaust flow monitoring, in case that option (as newly adopted) is used. The adopted revision to § 117.219(f)(2) requires recordkeeping of maintenance of the engine emissions control system for components other than catalytic converters or air-fuel ratio controllers. This change ensures that records of maintenance of lean-burn engine emissions control systems are kept and made available upon request. The adopted revision to § 117.219(f)(5) updates a rule cross-reference.

The adopted changes to § 117.223, concerning Source Cap, establish new baseline dates for owners or operators who wish to use the source cap compliance option for compliance with the new lean-burn engine NOx emission specification in BPA. New § 117.223(g)(6) and (k)(3) modify § 117.223(g)(3), moving the starting period from November 15, 1990, to September 10, 1993, for creditable shutdowns which occurred before the new lean-burn engine rule effective date. The attainment demonstration is based on the modeling inventory for September 10, 1993, the controlling date of the modeled ozone episode. This change ensures that sources that shut down before 1993 and were not included in the attainment demonstration modeling inventory are not eligible for generating reduction credits for compliance with the lean-burn engine NOx specification. Reductions from such shutdowns have been relied upon in the current BPA ozone attainment demonstration and are not surplus. The end date for creditable shutdowns is moved from the original NOx RACT rule effective date of June 9, 1993, to December 31, 1999, approximately the new lean-burn engine rule effective date. In addition, § 117.223(k)(3) modifies § 117.223(g)(3) to require the heat input used to calculate emission credit be consistent with the heat input used to represent the source's emissions in the attainment demonstration modeling inventory. This change ensures that creditable reductions are surplus. Also, the heat input baseline is updated to a three-year period between January 1, 1997 and December 31, 1999 to make the rule easier to use. As time passes, heat input records become increasingly hard to obtain on a unit- by-unit basis for the period specified in the original NOx RACT rule.

The adopted changes to § 117.520, concerning Compliance Schedule for Commercial, Institutional, and Industrial Combustion Sources, subdivide the sections into a BPA and HGA subsection to allow for separate compliance schedules for sources located in BPA and HGA and to correct a cross-reference error. The commission adopts a compliance date for BPA lean-burn engine NOx RACT of November 15, 2001. This time frame allows a two-year implementation of the necessary control measures and is consistent with the time period for compliance with the other NOx RACT emission specifications in Chapter 117.

Adopted changes to § 117.570(b)(2), concerning Trading, correct drafting errors in three defined terms used in the equations for calculating reduction credits. The adopted change to the heat input term "Hj" in § 117.570(b)(2) adds "except that the term may not include one standard deviation of the average daily heat input for the period in either calculation" at the end of the definition. The definition of "Hj" cross-references the calculation procedure in § 117.223 of this title. However, the cross-reference was not meant to include one standard deviation to be added to the actual historical average daily heat input, as is allowed for operational flexibility under the source cap. Adding one standard deviation to an emission credit would be inconsistent with the policy goal that traded credits be real. An adopted change to the emission limit term "RAj," adds "Hj" and deletes "period in § 117.223(g)(3) of this title" at the end of the definition. The change simplifies the definition without changing its meaning. An additional adopted change to "RAj" modifies the definition as it applies to discrete emission reduction credits (DERCs). The term "RAj" is the lower of any enforceable emission limitation applicable during the generation period or of the baseline emission rate. This revision clarifies that the baseline for calculating DERCs is based on the lower of applicable limits or actual rates, and not the NOx RACT limits, until after the NOx RACT compliance date. An adopted change to the enforceable emission rate term "RBj," distinguishes a separate meaning for the term "RBj" for DERCs. Since DERCs may be generated before the rule compliance date and the emission rate in the rule is not enforceable during this period, the average actual emission rate is applicable rather than the enforceable emission rate.

An adopted change in § 117.570(b)(4) clarifies that the paragraph is applicable to emission reduction credits (ERCs), rather than both ERCs and DERCs. One purpose of DERCs is to generate credit for early reductions, and requiring the source cap allowable to be reduced after the compliance date by the amount of the DERC credit removes the incentive to create early reductions.

In addition, the equations in § 117.570(c)(1), (c)(2), and (d) are readopted to correct printing errors in the version of the rule filed with the Secretary of State on December 3, 1997. This previous version of the adopted rule inadvertently contains the bold and bracket markings of the proposal, indicating text to be added and removed.

Other adopted changes to § 117.570 establish new baseline dates for owners or operators who wish to use the trading compliance option for compliance with the adopted new lean-burn engine NOx emission specification in BPA. New § 117.570(f) specifies that emission reductions which were relied upon in the attainment demonstration modeling inventory may not be used for generating emission reduction credits to comply with the lean-burn engine NOx specification of § 117.205(e) of this title. In addition, § 117.570(f) modifies § 117.570(b)(1)(A), moving the starting period for creditable reductions from 1990 to 1993. These changes ensure that creditable reductions have not been relied upon in the attainment demonstration and are therefore surplus. New § 117.570(f)(2)-(4) update the rule effective date to December 31, 1999, approximately the new lean-burn engine rule effective date, and cross reference the date adjustments in § 117.223(k) to ensure consistency between § 117.223 and § 117.570.

Questions? We Can Help

If you have questions contact us.