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OAR Box 1787 

Prepped by Ollie Stewart 

Document Number: 

92) ll-C-50 

Docket Number: 

A-90-37 

Printed 11/4/200810:22:20 AM Sheet 92 of 147 
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UNITED STATES ENVIRONMENTAL PROTECTION AGENCY 

WASHINGTON, D.C. 20460 

MAR 3 0 1993 

OFFICE OF 

AIR AND RADIATION 

James M. Lents, Ph.D. 

Executive Office 

South Coast Air Quality 

Management District 

21865 E. Copley Drive 

Diamond Bar, CA 91765-4182 

Dear Dr. Lents: 

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In your letter of August 19, 1992, the South Coast Air 

Quality District requests EPA to issue an interpretation of the 

term "stationary internal combustion engines" to include portable 

internal combustion engines and to exclude these from the 

definition of nonroad engines or vehicles set forth in section 209 

of the Clean Air Act. We regret the delay in responding, but we 

wanted to respond as adequately as possible which requires 

coordination between several offices. The internal combustion 

engines at issue include portable electric generators, compressors 

and other sources which are operated in a stationary manner. You 

note that while these types of sources are mounted on wheels or 

skids merely to facilitate transport from one location to another, 

they are intended to be, and in fact are, operated in a fixed 

position. The District is concerned about its ability to continue 

to regulate stationary internal combustion engines that are 50 

horsepower and above. 

Although we cannot issue at this time an interpretation of 

the term "stationary internal combustion engines" as requested, 

the District is not preempted by section 209(e) from regulating 

such sources. EPA is considering proposing regulations to define 

nonroad engines to include all engines with power output below 175 

horsepower. A draft of the rulemaking proposal is currently being 

reviewed by the Office of Managment and Budget. Any final 

definition of "nonroad engines" promulgated will consider all 

public comments received on the proposal. However, States and 

local jurisdictions may continue to impose restrictions on such 

sources as stationary sources until the effective date of the 

regulations. EPA believes that the preemption, if any, will then 

apply only to those internal combustion engines that are 

manufactured after the effective date of the regulations. 

As you are aware, the Clean Air Act Amendments of 1990 have 

given EPA explicit authority to set emissions standards for 

"nonroad" engines as part of the Agency's Title II mobile source 

program. See Clean Air Act, section 213. Unlike the South Coast, 

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which has adopted permitting provisions covering some of its 

nonroad sources, most jurisdictions do not regulate nonroad 

engines. Although these sources account for substantial 

emissions, they escape control under either Title I or Title II 

programs. To address this omission, EPA is in the process of 

developing nation-wide, tail-pipe emissions standards for many 

different types of internal combustion engines utilizing its new 

authority under section 213. For instance, early this year, EPA 

intends to propose emissions standards for diesel nonroad engines 

of 50 horsepower and above. This new standard and others to 

follow will ensure that emissions from internal combustion engines 

in temporary generators, moveable cranes, and other nonroad engine 

applications are substantially reduced at the cheapest and most 

effective point --at the time of manufacturing. Moreover, the 

Title II standards reduce emissions from all nonroad engines 

nationwide, whether subject to a local permitting program or not. 

In the 1990 Amendments, Congress also changed the definition 

of stationary source applicable to the various permitting 

provisions in Title I. Specifically, in section 302 (z), Congress 

excluded from the definition of stationary source "those emissions 

resulting from a nonroad engine or nonroad vehicle as described in 

section 216." At this point in time, EPA has not fully determined 

the extent to which this language precludes regulation of nonroad 

engines under Title I programs. 

EPA may be proposing under its Title II regulations to 

include all internal combustion engines under 175 horsepower as 

nonroad engines. Further, EPA may be soliciting comments, as part 

of the proposal, on whether to limit any preemption to engines 

that are subject to a manufacturer's emission limitation 

established under section 213. Under this interpretation, engines 

manufactured after the promulgation of these regulations would not 

be considered excluded as a stationary source until they are in 

fact subject to an emission limitation established under section 

213. This interpretation would avoid a regulatory gap which would 

otherwise exist between the period these regulations are 

promulgated and when all nonroad engines are covered by emission 

standards established under Title II. 

In any case, the District retains the authority to impose inuse restrictions such as limits on hours of use on these and other 

nonroad engines. Furthermore, these engines may be subject to 

State regulation under section 209(e)(2). The draft proposal also 

suggests that even where an engine is found to be a nonroad engine 

for Title II purposes in the manufacturing stage, States may in 

certain circumstances retain authority to regulate these engines 

as stationary sources in-use where such engines are in fact used 

primarily as stationary internal combustion engines (see 

section 111(a)(3)). The District may consider commenting on this 

proposal when it is published. 
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Therefore, at this time, we cannot issue an interpretation, 

as you request, that the term "stationary internal combustion 

engines" includes portable engines and that these engines are not 

nonroad engines or vehicles within the meaning of section 209. We 

believe, however, that at a minimum the District may continue to 

regulate all engines manufactured before the final promulgation of 

regulations under Title II defining "nonroad engine." Further, 

the District may retain authority to impose in-use regulations on 

nonroad engines. The proposal addressing nonroad engines may 

address these issues more clearly and you may consider commenting 

on the proposal when it is published. 

If you or your staff have any questions regarding this 

letter, please contact me or Clara Poffenberger of the Stationary 

Source Compliance Division at (703) 308-8709. 

Sincerely, 

Seitz 

Director 

Office of Air Quality Planning 

and Standards 

cc: William Tyndall, OGC 

Michael Horowitz, OGC 

David Solomon, AQMD, OAQPS 

Kelly Fortin, Region IX 

Debra Woods, OMS