Section NR 428.21 - Emissions unit exceptions The emissions units described in this section are exempt from the emission limitation requirements of s. NR 428.22, but shall comply with applicable record keeping requirements under s. NR 428.24. Once an emissions unit no longer qualifies for an exemption, the owner or operator of the emissions unit shall comply with the requirements of s. NR 428.22 by December 31 of the following calendar year, unless an alternate date is approved in writing by the department and the administrator.
(1) GENERAL EXEMPTIONS. The following emissions units and processes are exempt from the emission limitations in s. NR 428.22:(a) Any emissions unit operated only to restart electric generation in the event of a complete loss of facility power.(b) Any emissions unit which is operated no more than 500 hours per year and no more than 200 hours during the ozone season and whose only purpose is to provide electricity to a facility if normal electricity service is interrupted or to replace normal critical operations at a facility.(c) Any emissions unit whose only function is to pump water in the case of a fire emergency.(d) Any emissions unit whose utilization is less than 10% of its capacity factor on an annual average basis over a 3-year rolling period and less than 20% of its capacity factor in any year of the 3-year rolling period and which is owned or operated by an electric generation utility or gas transmission utility.(e) A research or development unit.(f) An engine testing operation or process line.(g) Any gaseous fuel fired unit used to control VOC emissions from a commercial or industrial process.(2) LOW OPERATING UNIT. An emissions unit described in s. NR 428.20 is exempt from the emission limitations of s. NR 428.22 if, during each ozone season, the emissions unit's utilization based on actual measured heat input or output is less than the utilization threshold for the source category according to the following equation: UU i<(Category capacity) x (3,672 hours / Ozone Seaso) x Capacity Factor Equation 1
where:
UU i is the unit's actual fuel consumption or output in measurement units consistent with the calculated utilization threshold for the source category in s. NR 428.22
Category capacity is the lower value in the range of unit capacity or design output used to describe the unit's source category i in s. NR 428.22
Capacity factor is 0.20 for all source categories in s. NR 428.22
(2m) RECIPROCATING ENGINES. Any reciprocating engine that is certified to meet the applicable federal non-road engine emission standards specified in this subsection is exempt from the emission limitations of s. NR 428.22 (1) (i): (a) A reciprocating compression ignition engine that is certified as meeting Tier 1 requirements as specified in 40 CFR part 89, if one of the following applies: 1. The engine has a maximum design power output of less than 2,000 horsepower.2. The engine has a maximum design power output equal to or greater than 2,000 horsepower and has a total utilization during each ozone season of less than 1.5 million horsepower-hours, based on actual measured output.(b) A reciprocating compression ignition engine that is certified as meeting the Tier 2 standard, as specified in 40 CFR part 89, or a reciprocating compression ignition engine that is certified as meeting the requirements of a more stringent Tier standard, as specified in 40 CFR part 89 or 1039.(c) A reciprocating spark ignition engine that is certified as meeting the Tier 1 standard or a reciprocating spark ignition engine that is certified as meeting a more stringent Tier standard, as specified in 40 CFR part 1048.(3) OTHER REGULATED UNIT. An emissions unit is exempt from the emission limitations under s. NR 428.22 if it meets all of the following conditions: (a) The emissions unit does not emit more than 75 tons of NOx per year due to a physical operating constraint or a federally enforceable condition in an air permit.(b) The emissions unit is located in a facility subject to the applicability thresholds specified under s. NR 428.20 (1) (a) 1., 2. a., or 3. a.(c) The emissions unit is subject to and meeting an emission limitation under s. NR 428.04 (2) or 428.05 (3).(d) The emissions unit was constructed prior to August 1, 2007.Wis. Admin. Code Department of Natural Resources NR 428.21
CR 07-016: cr. Register July 2007 No. 619, eff. 8-1-07.Amended by, CR 21-022: am. (3) (intro.), (a), (b), cr. (3) (c) Register February 2022 No. 794, eff. 3-1-22; correction in (3) (intro.) made under s. 35.17, Stats., Register February 2022 No. 794, eff. 3/1/2022Amended by, CR 23-017: cr. (3) (d) Register February 2024 No. 819, eff. 4/1/2024