MEMORANDUM
SUBJECT:	Temporary Boilers in the CAA 112(c)(6) Listing Notice and Emissions Inventory and 112(c)(3) Inventory
DATE:	December 14, 2012
FROM:	Nathan E. Topham, Environmental Engineer
		Metals and Inorganic Chemicals Group, EPA/OAQPS/SPPD 
TO:		Docket ID: EPA - HQ - OAR - 2006 - 0790
______________________________________________________________________________

	Temporary boilers are not a listed source category in the 112(c)(6) inventory. They are not listed in Table 1, Table 2, or Table 3 in the 1998 112(c)(6) listing notice. Temporary boilers are not discussed in that notice as a source category already subject to regulation or being considered for regulation. See 63 FR 17838. The source categories of industrial boilers and commercial/institutional boilers in the 112(c)(6) listing are consistent with the source categories regulated through the Subpart DDDDD and JJJJJJ NESHAPs.
	We do not have data for emissions of 112(c)(6) pollutants from temporary boilers in 1990, the year on which the 112(c)(6) inventory is based. Estimating emissions from temporary boilers would have been impractical when the inventory was developed for the 1998 listing notice and is impossible to do at this stage. Despite the practical obstacles in estimating their emissions, these boilers are only used for short periods in limited circumstances. Therefore, we expect the emissions from such boilers would be negligible when compared to the emissions of industrial, commercial, and institutional boilers that are part of the listed source category and 112(c)(6) inventory. 
	The same circumstances apply to the inventory developed to fulfill the requirements of CAA 112(c)(3) and 112(k)(3)(B). The list of area source categories used for 112(c)(3) does not include temporary boilers as a category listed for regulation or contemplated for future regulation. See 64 FR 38706, 66 FR 8220, 67 FR 43112, and 67 FR 70427. The same problems associated with estimating emissions from these sources for 112(c)(6) exists for the purposes of 112(c)(3). In fact, the problem is compounded as there are 30 pollutants regulated under 112(c)(3), compared with seven pollutants for 112(c)(6). Emissions of the 30 112(c)(3) HAP, if present, would be inconsequential when compared to the emissions from industrial, commercial, and institutional boilers that are a part of the listed source category and 112(c)(3) inventory.
