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OAR Box 1778 

Prepped by Ollie Stewart 

Document Number: 

2DII-A-5 

Docket Number: 

A-90-06 

Printed 10/28/2008 9:50:52 AM Sheet 21 of 276 
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EPA-450/2-78-006a 

Electric Utility Steam Generating Units 

Background Information for Proposed 

Particulate Matter Emission Standards 

Emission Standards and Engineering Division 

U.S. ENVIRONMENTAL PROTECTION AGENCY 

Office of Air, Noise, and Radiation 

Office of Air Quality Planning and Standards 

Research Triangle Park, North Carolina 27711 

July 1978 
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5. MODIFICATION AND RECONSTRUCTION 

5.1 GENERAt 

The terms modification and reconstruction have special meanings 

when used in new source performance standards. These terms are clarified 

in Subpart A, Part 60, Subchapter C, Chapter 1, Title 40 , Code of 

Federal Regulations. In general terms, a modification is a selected 

type of change which increases the emission of selected pollutants to 

t he atmosphere. When the alterations are limited, new source performance standards only require that increases in the emission of selected 

pollutants be prevented. In general terms, reconstruction is a change 

which is so substantial as to class the source as a new source rather 

than an altered existing source. In this case, the source becomes 

subject to all the limits of the new source performance standard. 

5.2 MODIFICATION 

5.2.1 Scope and Effect of Hodifcation Regulations 

. The term modification has special meaning when used with new 

source performance standards. According to regulations, a modification 

means any change in the method of operation of an existing facility 

which increases the amount of any air pollutant (to which a standard 

aoolies) emitted into the atmosphere by that facility or which results 

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in the emission of any air pollutant (to which a standard applies) 

into the atmosphere not previously emitted. The term modification 

is further limited by exempting selected types of changes from the 

applicability of new source performance standards. 

Normally, all that is reauired when an existing source becomes 

subject to modification regulations is that emissions of a SDecific 

pollutant after alteration be no more than they were before alteration. 

Usually, the source does not have to be equipped to comply with the 

numerical limits of the standard. Modification regulations apply to 

the pollutants of the new source standard, and apply on pollutant-bypollutant basis. In rare cases, emission of one or more pollutants 

may be less than the limit of a new source performance standard prior 

to the alteration. In this situation, an emission increase is allowed, 

up to the limit of the applicable new source performance standard. 

For examole, a source subject to modification regulations because of 

a switch from gas to coal would not have to be equipped to prevent 

particulate and S02 emission increases. For this situation, emission 

increases would be allowed up to the levels of the particulate and 

S 02 standards for coal. 

Adding an affected facility to a plant or replacing an existing 

facility within a plant would not cause other unchanged existing 

facilities within the plant to become subject to the no emission 

increase rule. When a Dlant has several existing facilities, the no 

emission increase rule does not apply to an altered existing facility 

if net plant emissions are not increased. For example, if emissions 

of pollutant A are increased by a change to facility 1 in a plant, . 

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the emission increase is allowed if emission of pollutant A from 

facility 2 is decreased by an amount eaual to or exceedinq the amount 

of increase from facility 1. 

Emission increases are allowed if such increases are caused by . 

routine maintenance, repair, and replacement. Emission increases 

are also allowed if caused by increases in production rate which can 

be accomplished without major capital expenditure. Increases in jS 

emissions caused by lonaer operating hours are also exempted from the 

rule on no emission increase. Another exemption is for the use of 

an alternative fuel or raw material if—prior to the date any standard 

becomes applicable—the existing facility was desiqned to accommodate 

that alternative use. reversion to coal, required for energy considerations as stipulated in Section 111(a)(8) of the Clean Air Act 

as amended in 1977, is not considered a modification. Emission 

increases caused by the addition or use of any system whose primary 

function is the reduction of air pollutants, are also exempt from the 

no emission increase rule. 

5.2.2 Modified Coal-Fired Steam Generators 

For the ourooses of determining if modification or reconstruction 

reflations apply or should aPDly, the coal-fired steam generator 

system is defined as including the followinq major components: 

a) Fuel burners (including coal pulverizer, crusher, stoker system) 

b) Combustion air system 

c) Steam generation system (firebox, tubes, etc.) 

d) Draft system (excluding stack) 

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The major points which define the inlets to the affected facility 

are: 

1. The inlet to the Dumps which feed water at steam qenerator 

pressure. 

2. The inlet to the bins which directly feed the pulverizer or 

stoker systems unless the bins are sized to store more than 

enough coal to operate the steam generator 72 hours at full 

load. When large bins are installed, the inlet to the affected 

facility is the outlet of the bins feeding the pulverizer 

or stoker systems. 

3. The combustion air intakes. . 

The major points which define the outlets of the affected facility 

are: 

1. -.Any steam outlet 

2. Any bottom ash outlet 

3. The outlet of the last system installed before the stack, 

such as the outlet of any induced draft fan. 

All components of the steam generator installed between these points are 

part of the affected facility except any air pollution control systems, 

such as electrostatic precipitators, mechanical collectors, baghouses, or 

scrubbers. 

Replacement of the pulverizer system of an existing coal-fired 

unit with a similar system or replacement of component parts of the 

pulverizer system with similar pares would not be considered a modification. However, replacement or redesign of the pulverizer 

system, which would substantially change the physical characteristics 

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of the pulverized coal and of the particulate emissions, may be a change 

where modification regulations aoply. 

Likewise, changes in the desiqn' of the combustion air system of an 

existinq unit that change the way combustion air is introduced to the 

combustion chamber would cause a source to be evaluated to determine if 

modification regulations should apply. Changing the combustion air damper 

settings is not a modification as long as no redesign of the combustion air 

system is involved. 

The steam generation system includes the feedwater pumps, combustion 

chamber, watertubes, economizer, and superheat and reheat sections. 

Maintenance of these components is not a modification. Major redesign of 

these parts would cause a source to be evaluated to determine if modiaffect particulate emissions. 

Redesign of the draft system, such as changing from induced draftconditions to pressurized firing, would cause an existina coal-fired source 

to be evaluated to determine if modification regulations should apply. 

Although a chanqe to a different coal might be considered a modification, these changes are exempted from modification evaluation by current 

regulations. ..£&&• 

5.2.3 Modified• .Wrftr°fias.-Fired Steam Generators 

The discussion of Section 5.2.3 is limited to modifications which 

would cause a source to become subject to particulate new source performance 

standard modification regulations for large coal-fired steam generators. 

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fication regulations should apply. It is doubtful that redesign of the '[{j.. 

feedwater system, the economizer, or the superheat or reheat sections would 

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Alterations which might cause an existing oil or gas-fired steam 

generator to become subject to particulate modification regulations for 

coal-fired steam generators are alterations involving a switch from gas or 

oil to coal. Current regulations provide that if the oil or gas-fired 

source is already designed to fire coal, a switch to coal does not cause 

the source to become subject to coal-fired steam generator particulate 

modification regulations. In addition, Section 111(a)(8) of the Clean Air 

Act as amended in 1977, exempts from the modification provisions of the 

Act certain sources switching from oil or gas to coal. The latter category 

of sources is described in general terms as sources required to switch to 

coal under Section 2(a) of the Energy Supply and Environmental Coordination 

Act of 1974. (The reader is cautioned to seek competent legal advice, such 

as from the Office of Enforcement and General Counsel, U. S. Environmental 

Protection Agency, Washington, D.C, before assuming that a source switching 

from oil 'or gas to coal is exempted from the modification provisions of the 

Clean Air Act). 

Sources switching from oil or gas to coal which are not otherwise 

excepted by U. S. Environmental Protection Agency regulations or by law 

would be subject to particulate new source performance standard modification 

regulations. Because oil and gas-fired steam generators characteristically 

emit less particulates than coal-fired steam generators, a switch from oil 

or gas to coat would normally increase particulate emission concentrations. 

Subpart A, Part 60, Subchapter C, Chapter 1, Title 40, Code of Federal 

Regulations describes the procedure for determining if a particulate 

emission increase has occurred. 

The cost of modifying an oil or gas-fired steam generator to fire . 

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coal may be so substantial as to class the source as a reconstructed source 

(see Section 5.3). 

Rulinqs on whether alternations of fossil fuel fired steam generators 

constitute a modification can be obtained by contacting a H. S. Environmental Protection Agency P.eqional Office of Enforcement. 

5.3 RECONSTRUCTION 

The term reconstruction has special meaning when used in new source 

performance standards. The purpose of reconstruction regulations is to 

prevent the perpetuation of existing sources. When modifications or 

replacements become so extensive as to create an essentially new source, 

the source becomes a reconstructed source and is subject to the new source 

performance standards which apply at the time of initiation of reconstruction. 

Accordinq to the provision of Subpart A, Part 60, Subchapter C, 

Chapter 1, Title 40, Code of Federal Regulations, a facility becomes a 

reconstructed source irrespective of any change in emission rate when 

a) the fixed capital cost of the new components exceeds 50 percent 

of the fixed capital cost that would be required to construct a comparable 

entirely new facility and, 

b) it is technologically and economically feasible to meet applicable 

standards. 

Rulings on whttner changes to a fossil fueNfired steam generator 

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constitute reconstruction can be obtained by contacting a U. S. Environmental Protection Agency Regional Office of Enforcement. 

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