  SEQ CHAPTER \h \r 1    

MEMORANDUM

DATE:		August 10, 2010

SUBJECT:	MACT Floor and MACT Determination for Existing Stationary
Non-Emergency SI RICE <100 HP and Existing Stationary Emergency SI RICE
Located at Major Sources and GACT for Existing Stationary SI RICE
Located at Area Sources

FROM:	Tanya Parise, EC/R, Inc.

		

TO:		Melanie King, EPA OAQPS/SPPD/ESG

1.0	PURPOSE

The purpose of this memorandum is to document the analysis of the
maximum achievable control technology (MACT) floor and MACT for existing
stationary non-emergency spark ignition (SI) reciprocating internal
combustion engines (RICE) less than 100 horsepower (HP) and existing
stationary emergency and black start SI engines located at major
sources.  The generally achievable control technology (GACT)
determination for existing stationary SI RICE located at area sources of
hazardous air pollutants (HAP) emissions that are subject to National
Emission Standards for Hazardous Air Pollutants (NESHAP) is also
presented in this memorandum.  

≤500 HP Located at Major Sources,” which is available in the
rulemaking docket (EPA-HQ-OAR-2008-0708).  

2.0	INTRODUCTION

EPA proposed NESHAP for existing stationary SI engines at area sources
and existing stationary SI engines that are less than or equal to 500 HP
at major sources on March 5, 2009 (71 FR 9698).  The EPA previously
promulgated NESHAP for existing stationary SI engines greater than 500
HP that are located at major sources, which were published on June 14,
2004 (69 FR 33474).  The final NESHAP for existing stationary SI engines
at area sources and existing stationary SI engines that are less than or
equal to 500 HP at major sources will add requirements to 40 CFR part
63, subpart ZZZZ, for these engines.  

The regulation was developed following criteria set forth under section
112 of the Clean Air Act (CAA).  Section 112(d) of the CAA stipulates
that EPA must promulgate emission standards that require the maximum
degree of HAP reduction.  According to 112(d)(3)(A) of the CAA, the
emission standards for existing major sources must be no less stringent
than the average emission limitation achieved by the best performing 12
percent of existing sources for which the Administrator has emissions
information.  For existing area sources, EPA has the option under
112(d)(5) of the CAA to promulgate emission standards or requirements,
which provide for the use of generally available control technologies
(GACT) or management practices in order to reduce HAP emissions.  

Section 112 of the CAA outlines the statutory requirements for the
EPA’s stationary source air toxics program.  Section 112(k) of the CAA
requires the development of standards for area sources which account for
90 percent of the emissions in urban areas of the 33 urban HAP listed in
the Integrated Urban Air Toxics Strategy (UATS).  These area source
standards can require control levels which are equivalent to either MACT
or GACT, as defined in the CAA under section 112(d)(2) and (3) and
section 112(d)(5), respectively.  Section 112 of the CAA allows the EPA
to establish subcategories among a group of sources.  EPA has determined
that the following subcategories are necessary to distinguish between
existing stationary RICE located at area sources:

Non-emergency 2-stroke lean burn (2SLB) stationary SI RICE; 

Non-emergency 4-stroke lean burn (4SLB) stationary SI RICE; 

≤500 HP

>500 HP

Non-emergency 4-stroke rich burn (4SRB) stationary SI RICE;

≤500 HP

>500 HP

Non-emergency landfill and digester gas stationary SI RICE; and

Emergency stationary SI RICE.

EPA has discussed the appropriateness of distinguishing stationary
engines by fuel, mode of operation (emergency versus non-emergency),
burn type (lean burn versus rich burn), and number of strokes (2-stroke
versus 4-stroke) in a previous memorandum.  The rationale provided in
that memorandum supports establishing the subcategories listed above.  

In addition to the above subcategories established for existing
stationary RICE located at area sources, this memorandum will also
discuss the MACT floor and MACT for existing non-emergency stationary SI
RICE less than 100 HP that are located at major sources and existing
emergency and black start stationary SI RICE that are located at major
sources. 

	EPA believes that previous determinations regarding the appropriateness
of using formaldehyde levels in concentration (parts per million (ppm))
as surrogates for HAP for 4SRB stationary SI RICE, and carbon monoxide
(CO) levels in concentration for all other stationary SI RICE, are still
valid.  Consequently, EPA is finalizing formaldehyde standards for 4SRB
RICE and CO standards for other SI RICE to regulate HAP emissions.

 3.0	MACT FLOOR AND MACT DETERMINATION

Non-Emergency SI Engines <100 HP

	For stationary SI engines less than 100 HP, EPA determined that it is
not feasible to prescribe or enforce an emission standard because the
application of measuring methodologies to this subcategory of engines is
not practicable due to technological and economic limitations.  In order
to measure the formaldehyde or CO emissions from these engines in terms
of volumetric concentration on a dry basis and corrected to 15 percent
oxygen (O2), the following test methods are required:

EPA Method 1 or 1A for selection of sampling ports;

EPA Method 3, 3A, or 3B or ASTM Method D6522-00 (2005) for determining
the O2 concentration;

EPA Method 4 for measuring the moisture content;

EPA Method 10 or ASTM Method D6522-00 (2005) for measuring the carbon
monoxide (CO) concentration; and

EPA Method 320 or 323 or ASTM Method D6348-03 for measuring the
formaldehyde concentration.

The test methods require the sample point to be a certain distance
between the engine and the exhaust.  Because engines below 100 HP often
have exhaust pipes with very small diameters and lengths, stack testing
using these methods could require a modification or extension of the
exhaust pipe to accomplish the test.  Furthermore, the cost of
performing a stack test ranges from approximately $1,000-$2,000
depending on the method used.  The cumulative cost of testing existing
stationary non-emergency engines below 100 HP at major sources would be
high.  EPA estimates that there are more than 67,000 of these engines
and to test them engines could cost as much as $135 million.  Given the
cost of the testing itself, the physical adjustments necessary to
accomplish the test, and the particular circumstances pertaining to
engines below 100 HP, EPA believes that the application of measurement
methodology to this class of engines is not practicable due to
technological and economic limitations.  Therefore, work practices are
the MACT floor for existing stationary non-emergency SI engines less
than 100 HP.  This is consistent with decisions made for existing
stationary non-emergency compression ignition (CI) engines less than 100
HP, which EPA finalized requirements for on March 3, 2010 (75 FR 9674). 


To determine the work practices, EPA reviewed information obtained from
different manufacturers and operators of SI engines.  The EPA has
determined that the maximum achievable control, based on the work
practices of the best controlled engines, is to maintain and replace the
following stationary engine components:  oil and oil filter, spark
plugs, hoses, and belts.  According to information received from
manufacturers and operators of stationary engines, these parameters are
the most appropriate to ensure proper operation for minimizing HAP
emissions.  Each of these work practices limit HAP emissions by allowing
the engine to operate at peak efficiency.  Changing the oil and oil
filter reduces the wear on the pistons and cylinders and limits the
amount on worn metals that may be introduced to the exhaust stream. 
Maintaining efficient spark plugs reduces the potential for inefficient
combustion and reduced efficiency, preventing higher emissions. 
Inspecting the belts and hoses ensures that the engines cooling and
electrical systems are operating, therefore eliminating the burning of
oil and ensuring that the electrical systems are functioning as
intended.

Intervals for checking, inspecting and replacing the oil and oil filter,
spark plugs, hoses, and belts vary with engine makes and models,
application, location, and other factors, therefore making it difficult
to define specific maintenance intervals that would be represent the
operation of the best controlled engines.  However, EPA must promulgate
specific requirements pursuant to section 112(d) of the CAA and the
information indicates that there are commonalities in maintenance
interval frequencies for the best controlled engines.  Based on the
information provided, EPA believes that the work practices below are
what the best controlled existing stationary non-emergency SI engines
less than 100 HP are currently doing and for that reason the MACT floor
for these engines except 2SLB engines is work practices as follows:

Change oil and filter every 1,440 hours of operation or annually,
whichever comes first, except that sources can extend the period for
changing the oil if the oil is part of an oil analysis program as
discussed below and none of the condemning limits are exceeded;   

Inspect spark plugs every 1,440 hours of operation or annually,
whichever comes first, and replace as necessary; and

Inspect all hoses and belts every 1,440 hours of operation or annually,
whichever comes first, and replace as necessary.

The following work practices are what the best controlled stationary
non-emergency 2SLB engines less than 100 HP are currently doing and is
therefore the MACT floor:

Change oil and filter every 4,320 hours of operation or annually,
whichever comes first, except that sources can extend the period for
changing the oil if the oil is part of an oil analysis program as
discussed below and none of the condemning limits are exceeded;   

Inspect spark plugs every 4,320 hours of operation or annually,
whichever comes first, and replace as necessary; and

Inspect all hoses and belts every 4,320 hours of operation or annually,
whichever comes first, and replace as necessary.

Two stroke lean burn engines have a longer maintenance interval than
4-stroke engines because 2SLB engines do not have as much oil
contamination and also operate at lower speeds and temperatures so spark
plugs do not fire as frequently and fire at lower temperatures than
4-stroke engines.  Further rationale for longer maintenance intervals
for 2SLB engines in general is discussed in the section on 2SLB engines
in this memorandum.  

	As discussed above, current maintenance procedures vary from engine to
engine based on a number of factors including engine design, fuel, and
operating characteristics.  Maintaining the oil however, is, one of the
most important activities operators can perform to minimize emissions
and to ensure proper operation and performance.  

	In addition to following a set schedule for checking and replacing the
oil, it is also common that the oil is monitored through an oil analysis
program where the oil is periodically sampled to determine oil quality. 
Based on the oil sample that is extracted, an oil analysis can be
performed that can indicate if it is time to replace the oil or if the
existing oil has not reached condemning limits it can continue to be
used.  Based on the analysis a decision can be made whether to drain and
replace the oil or if the oil change interval can be extended if the
properties of the oil are within acceptable limits.  Appropriate
parameters and condemning limits that would indicate oil degradation and
the presence and quantity of contaminants varies.  However, EPA has
determined that the parameters that would most appropriately indicate
the oil quality are the total acid number (TAN), viscosity, and water
content.  The TAN is an indication of the acidity of the oil and the
viscosity of the oil is a measure of how well the oil flows and these
parameters are, along with water content, measures of the condition of
the oil.  If the following levels below as measured through an oil
analysis program are exceeded, EPA has determined that an oil change
must be performed:

TAN increases by more than 3.0 milligrams (mg) potassium hydroxide per
gram (KOH/g) from the TAN of the oil when new; or

viscosity of the oil changes by more than 20 percent from the viscosity
of the oil when new; or

percent water content (by volume) is greater than 0.5. 

	No other regulatory options beyond the MACT floor were identified as
appropriate for existing stationary non-emergency SI engines below 100
HP.  Therefore, MACT for HAP emissions is equivalent to the MACT floor
for these engines.   

Emergency SI Engines	

	For existing stationary SI emergency engines located at major sources,
EPA determined it is not feasible to prescribe or enforce an emission
standard because the application of measurement methodology to this
class of engine is impracticable due to the technological and economic
limitations.  This is consistent with decisions made for existing
stationary emergency CI engines, which EPA finalized requirements for on
March 3, 2010 (75 FR 9674).  Emergency engines typically only operate
during emergencies or during periods of routine testing and maintenance.
 EPA determined that application of the emissions measurement
methodologies during either of these periods is not practicable.  It is
impracticable to test emissions from stationary SI emergency engines
during periods of routine testing and maintenance using the test
procedures specified in the rule because it would increase the required
number of hours of operation of the engine beyond the routinely
scheduled reliability testing and maintenance operation, thereby
increasing emissions.  While emergency engines have periods of operation
for scheduled maintenance and reliability testing, those periods are
usually several hours shorter than the number of hours that would be
required to run the necessary emissions tests under 40 CFR part 63,
subpart ZZZZ.  It is also impracticable to apply the testing
methodologies required in this rule to test the stationary engines
during periods of emergency operation because emergencies are unplanned
events and implementation of the procedures specified in 40 CFR part 63,
subpart ZZZZ require advance planning before tests are conducted.  In an
emergency, the owner/operator does not have the advance planning time
necessary to implement 40 CFR part 63, subpart ZZZZ.  In addition, it
would be costly to test existing stationary SI emergency engines at
major sources.  EPA estimates that there are close to 1,600 existing
stationary SI emergency engines from 100 HP to 500 HP at major sources
that are subject to this rulemaking.  The cost for testing these engines
could be as high as $3 million.  

For these reasons, work practices are appropriate and justified for this
group of stationary engines because the application of measurement
methodology is not practicable due to technological and economic
limitations.  Consequently, work practices are the MACT floor for
existing stationary emergency SI engines located at major sources.  

Again, in order to determine the work practices for stationary emergency
engines at major sources, EPA reviewed information obtained from
different manufacturers and operators of SI engines.  For the same
reasons as discussed above for existing stationary non-emergency SI
engines less than 100 HP at major sources, EPA has determined that
maximum achievable control, based on the work practices of the best
controlled emergency engines, is to maintain and replace the following
stationary engine components:  oil and oil filter, spark plugs, hoses,
and belts.  EPA discussed above the effect that maintaining these
parameters have on HAP emissions.  

As stated, intervals for checking, inspecting and replacing these
components vary from engine to engine and determining specific
maintenance intervals that would be represent the operation of the best
controlled emergency engines is challenging.  However, EPA must
promulgate specific requirements pursuant to section 112(d) of the CAA
and the information indicates that there are commonalities in
maintenance interval frequencies for the best controlled engines.  Based
on the information provided, EPA believes that the below maintenance
practices are what the best controlled existing stationary emergency SI
engines are currently doing and for that reason, the MACT floor for
these engines is maintenance practices as follows:

Change oil and filter every 500 hours of operation or annually,
whichever comes first, except that sources can extend the period for
changing the oil if the oil is part of an oil analysis program as
discussed below and none of the condemning limits are exceeded;   

Inspect spark plugs every 1,000 hours of operation or annually,
whichever comes first, and replace as necessary; and

Inspect all hoses and belts every 500 hours of operation or annually,
whichever comes first, and replace as necessary.

The changing of oil and the oil filter for stationary emergency engines
is more frequent on an hourly basis than for non-emergency engines
because of the nature of operation of these engines, which is for
standby and intermittent use, and thus requires less hourly use over the
same period of time, and oil quality is reduced over time even during
periods when the engine is not used.  

	Emergency SI engines also have the option to use an oil analysis
program to determine if it is time to replace the oil or if the existing
oil has not reached condemning limits it can continue to be used.  The
provisions of the oil analysis program are the same discussed above for
non-emergency SI engines less than 100 HP.

 No other regulatory options beyond the MACT floor were identified as
appropriate for existing stationary emergency SI engines at major
sources.  Because these engines are typically used only a few number of
hours per year, the costs of emission control are not warranted when
compared to the emission reductions that would be achieved.  The cost
per ton estimates for stationary emergency SI engines can be found in
the memorandum entitled “Cost per Ton of HAP Reduced for Existing
Stationary SI RICE” in the rulemaking docket (EPA-HQ-OAR-2008-0708). 
Therefore, MACT for HAP emissions is equivalent to the MACT floor for
these engines.

Black Start Engines

	Black start engines are used solely to start up combustion turbines. 
They operate for very short durations and have the same issues as
emergency SI engines based on their unique and limited operation. 
According to information received during the public comment period,
black start engines typically operate no more than 10 minutes at a time
and only operate during emergencies or during periods of high demand
(see for example EPA-HQ-OAR-2008-0708-0088 and 0129).  The short time of
operation makes testing of black start engines using the required
procedures impracticable.  Therefore, work practices are the MACT floor
for existing stationary black start engines located at major sources and
are as follows:  

Change oil and filter every 500 hours of operation or annually,
whichever comes first, except that sources can extend the period for
changing the oil if the oil is part of an oil analysis program as
discussed below and none of the condemning limits are exceeded;   

Inspect spark plugs every 1,000 hours of operation or annually,
whichever comes first, and replace as necessary; and

Inspect all hoses and belts every 500 hours of operation or annually,
whichever comes first, and replace as necessary.

As with stationary emergency SI engines, no other regulatory options
beyond the MACT floor were identified as appropriate for existing
stationary black start engines at major sources.  The limited operating
time also makes applying aftertreatment to black start engines not
effective.  In addition, these engines operate a few hours per year,
making further regulation of these engines economically impractical. 
Therefore, MACT is equivalent to the MACT floor for these engines.

4.0	REQUIREMENTS FOR ENGINES AT AREA SOURCES

Under CAA section 112(d)(5), EPA may elect to promulgate standards or
requirements for area sources "which provide for the use of generally
available control technologies or management practices by such sources
to reduce emissions of hazardous air pollutants."  Additional
information on generally available control technologies or management
practices (GACT) is found in the Senate report on the legislation
(Senate report Number 101-228, December 20, 1989), which describes GACT
as:

. . . methods, practices and techniques which are commercially available
and appropriate for application by the sources in the category
considering economic impacts and the technical capabilities of the firms
to operate and maintain the emissions control systems.

 

Determining what constitutes GACT involves considering the control
technologies and management practices that are generally available to
the area sources in the source category.  EPA also considers the
standards applicable to major sources in the same industrial sector to
determine if the control technologies and management practices are
transferable and generally available to area sources.  In appropriate
circumstances, EPA may also consider technologies and practices at area
and major sources in similar categories to determine whether such
technologies and practices could be considered generally available for
the area source category at issue.  Finally, as EPA has already noted,
in determining GACT for a particular area source category, EPA considers
the costs and economic impacts of available control technologies and
management practices on that category.  

	For existing stationary SI engines less than or equal to 500 HP, EPA is
requiring management practices.  This determination is consistent with
comments received on the proposed rule, as well as other information
submitted to EPA post-proposal.  Comments EPA received on the proposed
rule indicated that EPA had underestimated the cost of emission controls
and overestimated how many engines were already using these controls. 
Engine owners/operators have indicated that most of these smaller area
source engines are not equipped with the control technologies required
to meet these limits.  For example, the American Petroleum Institute
(API) said that the estimate of 4SRB engines currently equipped with
add-on controls that EPA used for the proposal (80 percent), was greatly
overestimated.  The Gas Processors Association indicated that few, if
any, engines below 500 HP are currently equipped with add-on controls. 
Several comments received on the proposed rule supported the use of
management practices where EPA proposed that for certain engines, and
further recommended that EPA establish management practices for other
engines at area sources.  Commenters indicated that the management
practices EPA proposed are generally available, although they did have
comments on the maintenance intervals. More information on the
management practice recommendations submitted by commenters is
summarized in the response to comments document for the final rule,
available from the rulemaking docket.  EPA reevaluated the cost impacts
associated with establishing numeric emission limitations for these
engines and determined that the cost impacts would be unreasonable for
most engines given the expected emission impacts both with and without
the expectation of use of emission control technologies.  Specific costs
for each engine type are provided in the sections that follow.   

Based on this information, EPA determined that management practices for
these stationary SI RICE less than or equal to 500 HP located at area
sources of HAP are generally available and cost effective and these
procedures will ensure that emissions are minimized and engines are
properly operated.  EPA believes that requiring management practices
instead of specific emission limitations and/or control efficiency
requirements on the majority of existing stationary SI engines at area
sources alleviates concerns regarding costly and burdensome requirements
for rural sources and other area sources. 

Similarly, as discussed below, for engines above 500 HP, EPA determined,
based on its reevaluation of the cost impacts associated with
establishing numeric emission limitations for emergency engines, black
start engines, 2SLB engines and landfill and digester gas engines, that
the cost impacts would be unreasonable for these engines given the
expected emission impacts both with and without the expectation of use
of emission control technologies.  EPA also determined that management
practices are generally available for these engines.

Therefore, EPA is finalizing management practices for area source
engines that are existing stationary non-emergency 2SLB engines,
existing stationary non-emergency 4SLB less than or equal to 500 HP,
existing stationary non-emergency 4SRB engines less than or equal to 500
HP located at area sources of HAP, existing stationary non-emergency
landfill and digester gas engines, and  existing emergency stationary SI
engines.  Finalizing management practices for most existing stationary
SI engines at area sources minimizes the burden of the final rule,
particularly on small businesses and individual owners and operators.  

For existing non-emergency 4SRB engines greater than 500 HP at area
sources and non-emergency 4SLB stationary engines greater than 500 HP at
area sources, EPA determined that it is appropriate to set numerical
emission limits, which are expected to be met using emission control
technologies.  Additional discussion and the basis for EPA’s final
determination are provided in the sections that follow.

Non-Emergency 2SLB

For existing stationary non-emergency 2SLB engines, EPA determined that
management practices are generally available.  EPA looked at
promulgating further requirements beyond management practices for
non-emergency 2SLB engines at area sources.  The first option EPA looked
at was having a CO emission limit for these engines based on emission
levels expected without using add-on controls.  EPA looked at the costs
associated with this option, which includes the cost of performance
testing, monitoring, recordkeeping and reporting.  These costs are
estimated to be more than $3,000 on an annual basis per engine.  On a
cumulative basis, the yearly compliance cost would be close to $35
million.  However, a CO emission limit based on what a 2SLB engine could
achieve without oxidation catalyst would not result in any emissions
reductions beyond what would occur with proper management practices. 
EPA believes the costs associated with this option are unreasonable
given there would be no emissions reductions achieved.  

The second option EPA looked at was going beyond management practices
for non-emergency 2SLB engines at area sources by requiring emission
limits based on levels expected using oxidation catalyst.  Although
add-on controls are technically feasible for these engines located at
area sources, EPA does not believe oxidation catalyst is generally
available for 2SLB engines.  In addition, control costs are high and it
is possible to achieve reasonable controls using management practices. 
For example, the cost per ton of HAP removed associated with requiring
oxidation catalyst control on a 250 HP engine is $224,000.  For a 500 HP
engine, the cost per ton of HAP removed is $128,000 and for a 1,000 HP
engine, the cost is $80,000 per ton of HAP removed.  Information on how
EPA estimated the cost per ton for oxidation catalyst on 2SLB engines
and for specific costs for different size 2SLB engines, please refer to
the memorandum “Cost per Ton of HAP Reduced for Existing Stationary SI
RICE,” available from the docket (EPA-HQ-OAR-2008-0708).  EPA
determined that it is not appropriate to go beyond management practices
for existing non-emergency 2SLB engines.  Management practices represent
what is generally available among such engines to reduce HAP, and the
practices will ensure that emissions are minimized and engines are
properly operated.  Therefore, going beyond management practices is not
justified and for existing stationary non-emergency 2SLB engines EPA is
requiring management practices.  

Regarding what management practices are required, EPA has determined
that maintaining and replacing the following stationary engine
components is generally available management practice:  oil and oil
filter, spark plugs, hoses, and belts.  In order to determine the
specific intervals for management practices for stationary non-emergency
2SLB engines at area sources, EPA reviewed information obtained from
different manufacturers and operators of SI engines.  

Two stroke lean burn engines have a longer maintenance interval than
4-stroke engines because 2SLB engines do not have combustion blow-by
gases entering the crankcase due to the engine configuration and
therefore do not have as much oil contamination from the combustion
blow-by gases.  The 2SLB engines also operate at lower speeds and
temperatures than 4-stroke engines, consequently the spark plug does not
fire as frequently and fires at lower temperatures than 4-stroke
engines.  Therefore, 2SLB engines should have longer maintenance
practice intervals than 4-stroke engines and consequently EPA has
determined that the proper interval for stationary non-emergency 2SLB
engines is every 4,320 hours of engine operation or annually, whichever
comes first.  Intervals for checking, inspecting and replacing the oil
and oil filter, spark plugs, hoses and belts vary with engine makes and
models, application, location, and other factors.  This makes it
difficult to define specific maintenance intervals that would be
representative of every possible operating scenario.  However, EPA must
finalize specific management practices.  Based on comments received on
the proposed rule and more specifically information received
post-proposal from Exterran, JW Power Company, and CSI (EJC) indicates
that a maintenance frequency of every 4,320 hours of operation is common
practice and generally available.  This specific recommendation is
supported by INGAA and API.  A maintenance interval of every 4,320 hours
of engine usage will ensure that the components remain in proper
condition and continue to perform the necessary functions to support
proper engine operation, reduce HAP, and minimize emissions. 
Specifically, EPA is requiring the following management practices:

Change oil and filter every 4,320 hours of operation or annually,
whichever comes first, except that sources can extend the period for
changing the oil if the oil is part of an oil analysis program as
discussed below and none of the condemning limits are exceeded;   

Inspect spark plugs every 4,320 hours of operation or annually,
whichever comes first, and replace as necessary; and

Inspect all hoses and belts every 4,320 hours of operation or annually,
whichever comes first, and replace as necessary.

EPA has discussed above the effect that maintaining these parameters
have on HAP emissions and believes that the above management practices
will ensure that HAP emissions are minimized.  EPA also determined that
it would be appropriate to include the option to use an oil analysis
program in the final rule.    

≤500 HP

For existing stationary non-emergency 4SLB engines less than or equal to
500 HP located at area sources, EPA determined that management practices
are generally available.  EPA looked at promulgating further
requirements beyond management practices for non-emergency 4SLB engines
less than or equal to 500 HP at area sources.  The first option EPA
looked at was having a CO emission limit for these engines based on
emission levels expected without the use of add-on controls.  EPA looked
at the costs associated with this option, which include the cost of
performance testing, monitoring, recordkeeping and reporting.  These
costs are estimated to be more than $3,000 on an annual basis per
engine.  On a cumulative basis, the yearly compliance cost would be
close to $121 million.  However, a CO emission limit based on what a
4SLB engine could achieve without oxidation catalyst would not result in
any emissions reductions beyond what would occur with proper management
practices.  EPA believes the costs associated with this option are
unreasonable given there would be no emissions reductions achieved.    

The second option EPA looked at was going beyond management practices
for non-emergency 4SLB engines less than or equal to 500 HP at area
sources by requiring emission limits based on levels expected using
oxidation catalyst.  Again, add-on controls are technically feasible for
these engines located at area sources, but control costs are high when
compared to the amount of reductions achieved.  Information on the cost
of control and the potential HAP reductions achieved with oxidation
catalyst for different size 4SLB engines is presented in the memorandum
“Cost per Ton of HAP Reduced for Existing Stationary SI RICE,”
available from the docket (EPA-HQ-OAR-2008-0708).  Requiring emission
limits on this segment of engines that would require the use of
oxidation catalyst would result in a significant burden, especially on
small businesses.  For example, in the 250 HP to 500 HP size range, 40
percent of the population consists of agricultural engines, which are
typically located at small businesses.  For larger size engines, i.e.,
those above 500 HP, engines used for agricultural purposes represent
only 14 percent of the total population.  EPA does not believe the costs
of requiring aftertreatment are reasonable and therefore, going beyond
management practices is not justified and GACT for existing stationary
non-emergency 4SLB engines less than or equal to 500 HP is management
practices.  Management practices represent what is generally available
among such engines to reduce HAP and the practices will ensure that
emissions are minimized and engines are properly operated.  EPA does not
believe that management practices would be a substantial burden on
owners and operators such as homeowners and small entities.    

EPA has determined that for existing stationary non-emergency 4SLB
engines less than or equal to 500 HP, the management practices shall be
performed every 1,440 hours of engine operation or annually, whichever
comes first, which reflects the management practices that are generally
available.  Again, intervals for checking, inspecting and replacing the
oil and oil filter, spark plugs, hoses and belts vary with different
4SLB engine makes and models, application, location, and other factors. 
This makes it difficult to define specific maintenance intervals that
would be representative of every possible operating scenario.  However,
EPA must finalize specific management practices.  Based on comments
received on the proposed rule and more specifically information received
post-proposal from Exterran, JW Power Company, and CSI (EJC),3 which is
supported by industry groups INGAA and API, indicates that a maintenance
frequency of every 1,440 hours of operation is common practice and
generally available.  A maintenance interval of every 1,440 hours of
engine usage will ensure that the components remain in proper condition
and continue to perform the necessary functions to support proper engine
operation, reduce HAP, and minimize emissions.  Therefore, EPA is
requiring the following management practices for existing stationary
non-emergency 4SLB engines less than or equal to 500 HP at area sources:

Change oil and filter every 1,440 hours of operation or annually,
whichever comes first, except that sources can extend the period for
changing the oil if the oil is part of an oil analysis program as
discussed below and none of the condemning limits are exceeded;   

Inspect spark plugs every 1,440 hours of operation or annually,
whichever comes first, and replace as necessary; and

Inspect all hoses and belts every 1,440 hours of operation or annually,
whichever comes first, and replace as necessary.

Non-Emergency 4SLB >500 HP

For existing stationary non-emergency 4SLB engines greater than 500 HP
located at area sources, EPA determined that management practices are
generally available.  EPA looked at promulgating further requirements
beyond management practices for non-emergency 4SLB engines greater than
500 HP at area sources that are operated more than 24 hours per calendar
year.  EPA considered having a CO emission limit for these engines based
on emission levels expected without add-on controls.  Compliance costs
are estimated to be more than $3,000 on an annual basis per engine and
cumulatively close to $28 million on a yearly basis.  Again, a CO
emission limit based on what a 4SLB engine could achieve without
oxidation catalyst would not result in any emissions reductions beyond
what would occur using proper management practices.  EPA believes the
costs associated with this option are unreasonable given there would be
no emissions reductions achieved.    

The second option EPA considered was going beyond management practices
for non-emergency 4SLB engines greater than 500 HP at area sources that
are operated more than 24 hours per calendar year by requiring emission
limits based on levels expected using oxidation catalyst.  EPA believes
that oxidation catalyst is readily available and feasible for all
existing stationary non-emergency 4SLB engines above 500 HP generally
regardless of location.  Further, EPA has determined that costs and
economic impacts associated with implementing HAP-reducing technologies
are reasonable and justified.  For example, the cost per ton of HAP
removed for a 750 HP engine is about $20,000 and is around $16,000 for a
1,000 HP engine.  Information on the specific add-on control costs and
cost per ton estimates can be found in the memorandum “Cost per Ton of
HAP Reduced for Existing Stationary SI RICE,” available from the
docket (EPA-HQ-OAR-2008-0708).  Also, the controls that are expected to
be used on these engines will have the co-benefit of reducing volatile
organic compounds (VOC) and CO emissions as well.  The reductions
estimated from installing controls on non-emergency 4SLB engines greater
than 500 HP at area sources are 3,500 tons of HAP, 33,000 tons of CO,
and 18,000 tons of VOC.  Based on this, EPA believes it is appropriate
to go beyond management controls for existing stationary non-emergency
4SLB engines greater than 500 HP at area sources.  Therefore, EPA has
determined that the final emission limits should be based on the use of
oxidation catalysts for existing stationary non-emergency 4SLB engines
greater than 500 HP that are located at area sources.  

To determine the final emission limits, EPA looked at the CO emissions
data from 4SLB engines less than or equal to 1,000 HP that are equipped
with oxidation catalyst control.  EPA has test results from 4 existing
4SLB engines with oxidation catalyst.  Next, EPA followed the MACT floor
approach using the upper prediction limit, which was discussed in a
separate  memorandum, to establish the concentration.  This resulted in
a concentration of 47 ppm by volume, dry basis (ppmvd) of CO at 15
percent O2.  A summary of the test data that was used to set the
concentration standard is available in Appendix B-2 of the memo titled
“MACT Floor and MACT Determination for Existing Stationary SI RICE
≤500 HP Located at Major Sources.”  Next, EPA looked at the test
results obtained during testing at Colorado State University (CSU) for
the 4SLB engines equipped with oxidation catalyst.  The data from CSU
indicate that oxidation catalysts on 4SLB engines are capable of
reducing CO emissions by 93 percent or more.  A control efficiency of 93
percent is also currently the CO percent reduction required for new and
reconstructed stationary 4SLB engines greater than 500 HP and located at
major sources that are equipped with aftertreatment under 40 CFR part
63, subpart ZZZZ.  Consequently, for existing stationary non-emergency
4SLB engines greater than 500 HP located at area sources that are
operated more than 24 hours per calendar year, the final emission limit
is 47 ppmvd of CO at 15 percent O2 or a CO reduction of 93 percent.  

Emergency 4SRB ≤500 HP

For existing stationary non-emergency 4SRB engines less than or equal to
500 HP located at area sources, EPA determined that management practices
are appropriate for GACT.  EPA looked at promulgating further
requirements beyond management practices for non-emergency 4SRB engines
less than or equal to 500 HP at area sources.  The first option EPA
looked at was going beyond management practices by having a formaldehyde
emission limit for these engines based on emission levels expected
without add-on controls.  EPA looked at the costs associated with this
option, which would include the cost of performance testing, monitoring,
recordkeeping and reporting.  These costs are estimated to be nearly
$4,000 on an annual basis per engine.  On a cumulative basis, the yearly
compliance cost would be more than $123 million.  However, a
formaldehyde emission limit based on what a 4SRB engine could achieve
without oxidation catalyst would not result in any emissions reductions
beyond what would occur with proper management practices.  EPA believes
the costs associated with this option are unreasonable given there would
be no emissions reductions achieved.

The second option considered by EPA was going beyond management
practices for non-emergency 4SRB engines less than or equal to 500 HP at
area sources by requiring emission limits based on levels expected using
add-on control technology.  The applicable control technology for
reducing HAP is non-selective catalytic reduction (NSCR), which is
technically feasible for these engines located at area sources. 
However, control costs are high for these engines.  For example, the
cost per ton of HAP removed associated with requiring NSCR control on a
250 HP engine is $167,000.  Information on the cost per ton of HAP
reduced with NSCR for different size 4SLB engines is presented in the
memorandum “Cost per Ton of HAP Reduced for Existing Stationary SI
RICE,” available from the docket (EPA-HQ-OAR-2008-0708).  Requiring
emission limits on this group of engines necessitating the use of
aftertreatment would result in a significant burden, especially on small
businesses.  As previously stated in this memorandum, in the 250 HP to
500 HP size range, 40 percent of the population consists of agricultural
engines, which are typically located at small businesses.  Although
there are co-benefits with using NSCR on 4SRB engines, EPA does not
believe that this co-benefit outweighs the other considerations
discussed above and does not justify going beyond management practices
for existing non-emergency 4SRB engines less than or equal to 500 HP at
area sources.    Management practices represent what is generally
available among such engines to reduce HAP, and the practices will
ensure that emissions are minimized and engines are properly operated. 
EPA determined that it is not appropriate to go beyond management
practices for existing non-emergency 4SRB engines less than or equal to
500 HP.  

  

 EPA does not believe the costs of requiring aftertreatment are
reasonable and therefore, going beyond management practices is not
justified and GACT for existing stationary non-emergency 4SLB engines
less than or equal to 500 HP is management practices.  EPA does not
believe that management practices would be a substantial burden on
owners and operators such as homeowners and small entities.  

EPA has determined that for stationary non-emergency 4SRB engines at or
below 500 HP, it is appropriate for the management practices to be
performed every 1,440 hours of engine operation or annually, whichever
comes first, which reflects the management practices that are generally
available.  As with 2SLB and 4SLB engines, intervals for checking,
inspecting and replacing the oil and oil filter, spark plugs, hoses and
belts vary between 4SRB engines based on different makes and models,
application, location, and other factors.  This makes it difficult to
define specific maintenance intervals that would be representative of
every possible operating scenario.  However, EPA must finalize specific
management practices.  Based on comments received on the proposed rule
and more specifically information received post-proposal from Exterran,
JW Power Company, and CSI (EJC),3 which is supported by industry groups
INGAA and API, indicates that a maintenance frequency of every 1,440
hours of operation is common practice and generally available.  A
maintenance interval of every 1,440 hours of engine usage will ensure
that the components remain in proper condition and continue to perform
the necessary functions to support proper engine operation, reduce HAP,
and minimize emissions.  Therefore, for existing stationary
non-emergency 4SRB engines less than or equal to 500 HP at area sources,
EPA is requiring the use of management practices as follows:

 

Change oil and filter every 1,440 hours of operation or annually,
whichever comes first, except that sources can extend the period for
changing the oil if the oil is part of an oil analysis program as
discussed below and none of the condemning limits are exceeded;   

Inspect spark plugs every 1,440 hours of operation or annually,
whichever comes first, and replace as necessary; and

Inspect all hoses and belts every 1,440 hours of operation or annually,
whichever comes first, and replace as necessary.

Non-Emergency 4SRB >500 HP

For existing stationary non-emergency 4SRB engines greater than 500 HP
located at area sources, EPA determined that management practices are
generally available.  EPA looked at promulgating further requirements
beyond management practices for non-emergency 4SLB engines greater than
500 HP at area sources that are operated more than 24 hours per calendar
year.  EPA considered having a formaldehyde emission limit for these
engines based on emission levels expected without add-on controls. 
Compliance costs are estimated to be almost $4,000 on an annual basis
per engine and cumulatively more than $28 million on a yearly basis. 
Again, a formaldehyde emission limit based on what a 4SRB engine could
achieve without oxidation catalyst would not result in any emissions
reductions beyond what would occur with proper management practices. 
EPA believes the costs associated with this option are unreasonable
given there would be no emissions reductions achieved.    

The second option EPA considered was going beyond management practices
for non-emergency 4SRB engines greater than 500 HP at area sources that
are operated more than 24 hours per calendar year by requiring emission
limits based on levels using aftertreatment.  Aftertreatment controls
(NSCR) for existing non-emergency 4SRB engines greater than 500 HP are
readily available and feasible regardless of location.  Non-selective
catalytic reduction, the technology applicable to 4SRB engines for HAP
reduction is generally available.  Further, costs and economic impacts
associated with implementing HAP-reducing technologies are reasonable
and justified.  The cost per ton of HAP removed from a 750 HP engine is
about $68,000 and $56,000 for a 1,000 HP engine.  Information on the
specific add-on control costs and cost per ton estimates can be found in
the memorandum “Cost per Ton of HAP Reduced for Existing Stationary SI
RICE,” available from the docket (EPA-HQ-OAR-2008-0708).  In addition,
the controls that are expected to be used on these engines will have the
co-benefit of reducing VOC, CO emissions and NOx emissions.  For
example, co-benefits of NOx reductions can be achieved at a favorable
cost effectiveness of less than $1,000/ton for a 750 HP engine and
$720/ton for a 1,000 HP engine.  EPA believes that this co-benefit adds
to the justification for establishing emission limits based on the use
of NSCR for these engines.  The reductions estimated from installing
controls on non-emergency 4SRB engines greater than 500 HP at area
sources are 1,200 tons of HAP, 64,000 tons of CO, 96,000 tons of NOx,
and 6,400 tons of VOC.  For these reasons, EPA believes it is
appropriate to go beyond management practices for existing stationary
non-emergency 4SRB engines greater than 500 HP at area sources. 
Therefore, EPA has determined that the final emission limits should be
based on the use of NSCR for existing stationary non-emergency 4SRB
engines greater than 500 HP that are located at area sources.  

	To determine the final emission limits for non-emergency 4SRB engines
greater than 500 HP located at area sources that are operated more than
24 hours per calendar year, EPA looked at the formaldehyde emissions
from 51 uncontrolled 4SRB engines and determined the average
uncontrolled formaldehyde concentration.  The average uncontrolled
formaldehyde concentration was 11.3 ppmvd at 15 percent O2.  Next, EPA
applied a 76 percent formaldehyde control efficiency to the uncontrolled
formaldehyde level.  The 76 percent formaldehyde control efficiency is
based on test results used to set the final standards for stationary
4SRB engines greater than 500 HP at major sources and is consistent with
the current requirement for these engines.  As a result, the final
emission limit for existing non-emergency 4SRB engines greater than 500
HP is 2.7 ppmvd formaldehyde at 15 percent O2 or a 76 percent
formaldehyde reduction.

Emergency SI 

For existing stationary emergency SI engines located at area sources,
EPA believes that it is appropriate to set GACT to be the same
requirements as is required for emergency engines at major sources
because the same issues that were discussed above for stationary
emergency SI engines at major sources apply to emergency SI engines at
area sources.  Again, this is consistent with how EPA treated existing
stationary emergency CI engines in the requirements finalized on March
3, 2010 under 40 CFR part 63, subpart ZZZZ.  There is no reason why the
requirements for engines located at area sources pursuant to GACT should
be different than those for engines located at major sources.  The
management practices are generally available and being located at an
area source does not prevent the engine from being maintained
appropriately and according to how engines at major sources are being
maintained.  Further, the management practices do not present an
economic burden on area source engines.  Therefore, GACT for existing
stationary emergency SI engines at area sources is the use of management
practices as follows:

Change oil and filter every 500 hours of operation or annually,
whichever comes first, except that sources can extend the period for
changing the oil if the oil is part of an oil analysis program as
discussed below and none of the condemning limits are exceeded;   

Inspect spark plugs every 1,000 hours of operation or annually,
whichever comes first, and replace as necessary; and

Inspect all hoses and belts every 500 hours of operation or annually,
whichever comes first, and replace as necessary.

As discussed above for major sources, these sources may utilize an oil
analysis program in order to extend the specified oil change requirement
specified above.  

Black Start Engines

For existing stationary black start engines located at area sources, EPA
believes that it is appropriate to set GACT to be the same requirements
as is required for black start engines at major sources because the same
issues that were discussed above for stationary black start engines at
major sources apply to these engines at area sources.  There is no
reason why the requirements for area sources pursuant to GACT should be
different than those for black start engines at major sources. 
Therefore, GACT for existing stationary emergency SI engines at area
sources is the use of management practices as follows:

Change oil and filter every 500 hours of operation or annually,
whichever comes first, except that sources can extend the period for
changing the oil if the oil is part of an oil analysis program as
discussed below and none of the condemning limits are exceeded;   

Inspect spark plugs every 1,000 hours of operation or annually,
whichever comes first, and replace as necessary; and

Inspect all hoses and belts every 500 hours of operation or annually,
whichever comes first, and replace as necessary.

Non-Emergency Landfill and Digester Gas

For existing stationary landfill and digester gas engines located at
area sources, EPA determined that management practices are appropriate
for GACT.  EPA looked at going beyond management practices for
non-emergency landfill and digester gas engines at area sources.  The
first option EPA looked at was going beyond management practices by
having a CO emission limit for these engines based on levels expected
without add-on controls.  EPA looked at the costs associated with this
option, which would include the cost of performance testing, monitoring,
recordkeeping and reporting.  These costs are estimated to be between
$3,000 and $4,000 on an annual basis per engine, depending on the engine
type.  On a cumulative basis, the yearly compliance cost would be close
to $2.5 million.  However, a CO emission limit based on what landfill
and digester gas engines could achieve without add-on controls would not
result in any emissions reductions beyond what would occur with proper
management practices.  EPA believes the costs associated with this
option are unreasonable given there would be no emissions reductions
achieved.  

The second option EPA looked at was going beyond management practices
for non-emergency landfill and digester gas engines at area sources by
requiring emission limits based on levels expected using add-on
controls.  However, add-on controls are not technically feasible for
these engines and it is possible to achieve reasonable controls using
management practices.  Therefore, going beyond management practices is
not justified and GACT for existing stationary non-emergency landfill
and digester gas engines is management practices.  Management practices
represent what is generally available among such engines to reduce HAP,
and the practices will ensure that emissions are minimized and engines
are properly operated.  

Regarding what management practices are required, EPA has determined
that maintaining and replacing the following stationary engine
components is generally available management practice:  oil and oil
filter, spark plugs, hoses, and belts.  These same components must be
maintained for the existing engines at major sources where MACT is work
practices, and EPA believes these practices are transferable and
generally available to area sources.  There is nothing preventing
existing non-emergency landfill and digester gas engines at areas from
maintaining and replacing these engine components.  

To determine the specific intervals for management practices for
stationary non-emergency landfill and digester gas engines at area
sources, EPA reviewed information obtained from different manufacturers
and operators of SI, including operators of landfill and digester gas
engines.  Based on the information reviewed, it appeared that the
management practices for landfill and digester gas engines are
comparable to those of 4-stroke engines in general.  Typically, engines
operating at landfills or that use digester gas fuels are either 4SLB or
4SRB.  Also, based on information available to EPA, the majority of
landfill gas fired engines at 4SLB engines and digester gas engines are
4SRB.  Therefore, management practices for landfill and digester gas
engines are the same as for 4-stroke engines.  Specifically, GACT for
existing stationary non-emergency landfill and digester gas engines at
area sources is the use of management practices as follows:

Change oil and filter every 1,440 hours of operation or annually,
whichever comes first, except that sources can extend the period for
changing the oil if the oil is part of
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Inspect all hoses and belts every 1,440 hours of operation or annually,
whichever comes first, and replace as necessary.

 Memorandum from Jennifer Snyder and Tanya Parise, Alpha-Gamma
Technologies, Inc.  Subcategorization of Stationary Reciprocating
Internal Combustion Engines ≤500 HP.  May 15, 2006. 
EPA-HQ-OAR-2005-0030-0012.

 Pages 80-81 of Comments on the Proposed Revisions to the National
Emission Standards for Hazardous Air Pollutants for Reciprocating
Internal Combustion Engines.  Prepared by American Petroleum Institute. 
June 3, 2009.  EPA-HQ-OAR-2008-0708-0242.2.

 Page 9 of Comments on the Proposed Revisions to the National Emission
Standards for Hazardous Air Pollutants for Reciprocating Internal
Combustion Engines.  Submitted by Gas Processors Association.  June 2,
2009.  EPA-HQ-OAR-2008-0708-0112.1.

 Memorandum from Rebecca Rentz, Bracewell and Giuliani to Melanie King,
EPA.  Spark Ignited (SI) Recommended Management Practices.  January 27,
2010.  EPA-HQ-OAR-2008-0708-0354.1. 

 Memorandum from Tanya Parise, EC/R to Melanie King, EPA.  MACT Floor
and MACT Determination for Existing Stationary SI RICE ≤500 HP Located
at Major Sources.  August 10, 2010.

 Roy, EPA OAQPS ESD Combustion Group.  January 7, 2004. 
EPA-HQ-OAR-2002-0059-0665.

 Memorandum from Melanie Taylor and Jennifer Snyder, Alpha-Gamma
Technologies, Inc. to Sims Roy, EPA OAQPS ESD Combustion Group.  January
7, 2004.  EPA-HQ-OAR-2002-0059-0665.

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