Portable & Temporary Source Applicability Notes

This issue has come up many times. One example was Title V major source applicability and inclusion, or not, of generators for lights at a mine. Another example was the need to permit a power generator for construction at a power plant. There are a variety of considerations and applications. Thompson River Power was forced to add to their permit combustion emissions related to curing their refractory brick. During the power shortages of the early 2000's, MDEQ forced the permitting of diesel locomotives that were going to be used as temporary generators, even though it could be argued that they were temporary and mobile sources (and MAR 17.8.744 specifically excludes from permitting requirements "mobile emitting units, including motor vehicles, trains, aircraft, and other such self-propelled vehicles.")

Federal rules key on the definition of "stationary source." (Surprisingly, the Montana minor source rules don't use that term.) Mobile sources are obviously not stationary. Non-road engines too are seemingly not meant to be included in the CAA rules that govern stationary sources. First, they have their own (extensive) set of rules. Second, the three alternative defining characteristics speak to mobility: "self propelled", "propelled", and "portable or transportable."

It's the last nonroad engine characteristic, though, that muddies the waters a bit. First, there is a caveat that the otherwise-nonroad engine must not stay in one location for more than 12 months - or less for a seasonal source. Note, too, that a "location" is any "single site at a building, structure, facility or installation." (See links below to my notes and Iowa guidance.) The implication is that a nonroad engine that stays in one place for too long becomes a stationary source.

Then there's potentially some confusion about permitting requirements for a "portable" source. On one hand, nonroad engines that are classified as such due to their portability, would seem to be exempt from stationary source permitting. On the other hand, federal and state regs require permitting of portable sources. The federal rules refer to a "portable stationary source" and provide for moving it without going through the permitting process; but the provision assumes the source was permitted in the first place. Montana regs don't use the "portable stationary source" terminology, but provide for transferring a permit from one location to another (ARM 17.8.765). By that, they clearly mean moving an already-permitted piece of equipment.

So here's one interpretive summary:
-- Emissions from self-propelled sources do not need to be permitted and should not be included in a facility's PTE. (An exception to this, at least in practice, is fugitive road dust that results from the operation of self-propelled sources. These emissions typically are included in a source's PTE. I suppose the distinction is that road dust is an indirect, not a direct, mobile source emission.)
-- Nonroad engines that are portable but not self- or otherwise propelled do not need to be permitted and should not be included in a facility's PTE, EXCEPT...
-- Nonroad engines that will stay in one location for more than a year (or more than 3 months each year for a seasonal source) should be considered a stationary source. But, the engine can move even within the facility to be considered as having not stayed at one location.
-- Other, non-engine portable sources should be considered to be stationary sources and require permitting.
-- It appears that, from the regulatory definitions, construction-related emissions should be considered to be secondary and to not contribute to the potential emissions of the source being constructed.
-- I suppose, though, that the construction emissions could constitute a permittable source in and of themselves. This gets into the concept of "temporary" sources which is even less clear than mobile and portable. At least one bit of EPA policy indicates that temporary sources should not be permitted under federal rules. But I've seen no definition of "temporary", and EPA may no longer fully agree with that policy. Further, I'm not aware of any guidance at all on the state level regarding temporary sources. One thing to consider would be whether a source is temporary only in the sense that it will operate at a single location for a limited time, in which case it may be more appropriately deemed a portable source.

Advanced NSR Guidance notes and Regulatory definition

EPA letter addressing "portable stationary" sources

ICE NSPS and NESHAP Applicability FAQs, Iowa DNR, 11/2209


More stuff specific to off-road engines (8/6/2010):

Cloud Peak Energy prepared the following letter to MDEQ analyzing NSPS, PSD and Title V exclusions for off-road engines.

Off-road Engine Emissions for Major Source Determinations

Here's a more complete citation of the NSPS exclusion:

40 CFR Part 60‚ Section 4219‚ Paragraph (Stationary_internal_co) [NSPS Subpart IIII]

Stationary internal combustion engine means any internal combustion engine, except combustion turbines, that converts heat energy into mechanical work and is not mobile. Stationary ICE differ from mobile ICE in that a stationary internal combustion engine is not a nonroad engine as defined at 40 CFR 1068.30 (excluding paragraph (2)(ii) of that definition), and is not used to propel a motor vehicle or a vehicle used solely for competition. Stationary ICE include reciprocating ICE, rotary ICE, and other ICE, except combustion turbines.

40 CFR Part 1068‚ Section 30‚ Paragraph (Nonroad_engine)

Nonroad engine means:

(1) Except as discussed in paragraph (2) of this definition, a nonroad engine is an internal combustion engine that meets any of the following criteria:
(i) It is (or will be) used in or on a piece of equipment that is self-propelled or serves a dual purpose by both propelling itself and performing another function (such as garden tractors, off-highway mobile cranes and bulldozers).
(ii) It is (or will be) used in or on a piece of equipment that is intended to be propelled while performing its function (such as lawnmowers and string trimmers).
(iii) By itself or in or on a piece of equipment, it is portable or transportable, meaning designed to be and capable of being carried or moved from one location to another. Indicia of transportability include, but are not limited to, wheels, skids, carrying handles, dolly, trailer, or platform.

(2) An internal combustion engine is not a nonroad engine if it meets any of the following criteria:

(i) The engine is used to propel a motor vehicle, an aircraft, or equipment used solely for competition.

(ii) The engine is regulated under 40 CFR part 60, (or otherwise regulated by a federal New Source Performance Standard promulgated under section 111 of the Clean Air Act (42 U.S.C. 7411)).

(iii) The engine otherwise included in paragraph (1)(iii) of this definition remains or will remain at a location for more than 12 consecutive months or a shorter period of time for an engine located at a seasonal source. A location is any single site at a building, structure, facility, or installation. Any engine (or engines) that replaces an engine at a location and that is intended to perform the same or similar function as the engine replaced will be included in calculating the consecutive time period. An engine located at a seasonal source is an engine that remains at a seasonal source during the full annual operating period of the seasonal source. A seasonal source is a stationary source that remains in a single location on a permanent basis (i.e., at least two years) and that operates at that single location approximately three months (or more) each year. See §1068.31 for provisions that apply if the engine is removed from the location.