The Indiana Environmental Rules Board voted at its February 13 meeting to preliminarily adopt IDEM’s proposed air permitting exemption for short term backup units (LSA #16-309), moving the new exemption one step closer to becoming final.

IDEM’s air permitting rules at 326 IAC 2-1.1-3 list out several types of activities or emission units which are exempt from construction or modification permitting requirements.  While this list includes an exemption for temporary operations, that particular exemption includes some restrictions which make it typically unavailable in situations where an emission unit has failed or otherwise needs to be taken offline for critical maintenance or repair, and a temporary unit needs to be brought in until repairs or maintenance is complete.  The lack of a suitable exemption allowing temporary operation of a backup, rental, or other replacement unit has put sources in the position of having to submit a permit application to authorize construction and operation of the backup unit, at additional cost and downtime, or forgo use of any backup at all.  Sources whose repairs unexpectedly went beyond the 30-operating day limit of the current temporary operations exemption were subject to enforcement exposure relating to those delays.  Also, IDEM’s permitting resources are strained by having to process permits for backup units which are only expected to operate for weeks to a few months. 

While this exemption will potentially allow many types of maintenance or repair projects to move forward without the need for permitting the backup unit, the draft rule sets out some restrictions as to the specifications of the short term replacement unit.  These include a requirement that any control device associated with the backup must be the same type as on the permitted unit, with a control efficiency as good as or better than the device on the permitted emission unit.  The draft rule also states that the throughput rate of the backup unit must not exceed the rate of the permitted unit.  These restrictions may make it difficult for facilities to find suitable backup units in the rental market, where ability to dictate these specifications could be limited.  It may also make it difficult to find allowable backups for “stick-built” equipment; for example, a source would need to evaluate whether a rental package boiler would be able to be used as a backup for a custom boiler of a similar size.

Under the draft rule, the short term unit is generally allowed to be on the property for up to 180 days from the date it is placed onsite.  This timeframe may constrict some larger projects, but will still be able to accommodate many more types of repair/maintenance projects than the current temporary operation exemption.  Once the repair/maintenance project is complete, the backup unit must be removed from the permitted source property within fourteen days.  IDEM had originally proposed a five-day timeframe, but expanded this to fourteen in response to a comment noting that five days is too short a time to allow a source to confirm that the permitted emission unit is operating properly after repair or maintenance. 

Sources hoping to take advantage of this exemption will need to be mindful of its notification requirements.  The proposed rule requires the source to submit a notification not later than seven days prior to planned maintenance, or not later than three days after the placement of the backup unit in the case of malfunction, emergency, or operational failure.  Among other things, the notification must include description of the planned maintenance or description of the unplanned failure as applicable, specifications on the backup unit, and a preventive maintenance plan for the backup.  A notification is also required after completion of the repair or maintenance, and must include a statement “certifying” that the permitted emission unit and the short term backup unit were never operated at the same time, the backup unit was never operated at a throughput rate that exceeded the throughput rate of the permitted emission unit, and the backup unit has been removed from the property of the permitted source (or transferred to a different emission unit on the same property, as allowed in the rule). 

As well as adding this new exemption to the rule, IDEM also took the chance to revise language for several existing exemptions.  These other changes mostly have the effect of clarifying rule language.  IDEM anticipates final adoption of this rule will occur at the ERB meeting scheduled for May 8, 2019.  The current draft is available at