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OAR Box 1787 

Prepped by Ollie Stewart 

Document Number: 

9DII-C-49 

Docket Number: 

A-90-37 

Printed 11/4/200810:22:20 AM Sheet 91 of 147 
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&M\-9&htfPttfct/ /Moor- eNOTE: THIS IS A PRELIMINARY STAFF OUTLINE OF A DRAFT OPTION THAT 

EPA IS EVALUATING IN PREPARATION OF A PROPOSED RULEMAKING. THIS 

INTERPRETATION IS NOT EPA GUIDANCE OR POLICY ON THE ISSUE. 

MODIFICATIONS IN SERIOUS/SEVERE OZONE NONATTAINMENT AREAS 

INTRODUCTION 

The amended Act at Sections 182(c)(6),(7) & (8) (copy 

attached) contains special provisions for applying 

nonattainment NSR to modifications at existing major 

stationary sources of volatile organic compounds (VOC) 

presumptively NOx, located in Serious or Severe ozone 

nonattainment areas. 

and 

In our upcoming Part C/D NSR rulemaking proposal, EPA 

intends to codify these new special provisions in the 

revised nonattainment NSR rules. 

EPA is evaluating several options for implementing the 

special provisions and requests input and suggestions from 

the FACA representatives on the issues. Send your comments 

by Aug. 16, 1993 to Mike Sewell, U.S. EPA, MD-15, New Source 

Review Section, RTP, N.C. 27711. 
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NOTE: THIS IS A PRELIMINARY STAFF OUTLINE OF A DRAFT OPTION THAT 

EPA IS EVALUATING IN PREPARATION OF A PROPOSED RULEMAKING. THIS 

INTERPRETATION IS NOT EPA GUIDANCE OR POLICY ON THE ISSUE. 

IMPLEMENTATION OPTION FOR EVALUATION 

STEP I "Increase in Net Emissions " from the Proposed 

Modification 

The special provisions apply to proposed modifications that 

result in an "increase in net emissions". The "de minimis" 

emissions rate specified in (c)(6) for determining NSR 

applicability is 25 tpy. 

The "increase in net emissions" calculation for a proposed 

modification includes contemporaneous decreases that are 

part of the proposed modification. 

For such net increases of 25 tpy or less, the special 

aggregation provisions of (c)(6) apply. 

For such net increases over 25 tpy, the special 

provisions of either (c)(7) or (c)(8) apply. 

The special provisions of either (c)(7) or (c)(8) apply to 

any discrete emissions unit(s) with an "increase in net 

emissions" over 25 tpy, regardless of other decreases at the 

source. For such units, the new aggregation provisions of 

(c)(6) do not apply. 

STEP II Special Aggregation Provisions of (c)(6) 

The aggregation provisions apply to proposed modifications 

with an "increase in net emissions" of 25 tpy or less. 

To determine if the proposed modification is above the "de 

minimis" cutoff, aggregate the "increase in net emissions" 

from the proposed modification with all other "net 

increases" at the source over any period of 5 consecutive 

calendar years which includes the calendar year in which 

such increase occurred. 

Previous net decreases would not count here, but may be 

creditable as internal offsets when applying (c)(7) or 

(c)(8). 

J 
NOTE: THIS IS A PRELIMINARY STAFF OUTLINE OF A DRAFT OPTION THAT 

EPA IS EVALUATING IN PREPARATION OF A PROPOSED RULEMAKING. THIS 

INTERPRETATION IS NOT EPA GUIDANCE OR POLICY ON THE ISSUE. 

If the aggregated net increase is over 25 tpy, the special 

provisions of either (c)(7) or (c)(8) apply. 

The provisions of (c)(7) apply to existing major stationary 

sources emitting <100 tpy and the provisions of (c)(8) apply 

to existing major stationary sources emitting >100 tpy. 

STEP III "Modifications At Existing Sources Emitting <100 TPY" 

Section (c)(7) allows BACT instead of LAER. 

The proposed modification (or discrete units that are part 

of the modification) avoid nonattainment NSR if the 

emissions increase is offset internally at a ratio of at 

least 1.3:1. 

STEP IV "Modifications At Existing Sources Emitting > 100 TPY" 

Section (c)(8) requires nonattainment NSR for the proposed 

modification. 

As a source option, proposed modifications (or discrete 

units that are part of the modification) may be exempt from 

LAER if the emissions increase is offset internally at a 

ratio of at least 1.3:1. 

This optional exemption is only for LAER, the remaining 

nonattainment NSR requirements still apply. 

General NSR offsets should be obtained in addition to 

the internal offsets. 
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Clean Air Act as Amended (1990) 

Sections 182(c)(6), (7) & (8) 

(6) De minimis Rule — The new source review provisions 

under this part shall ensure that increased emissions of volatile 

organic compounds resulting from any physical change in, or 

change in the method of operation of, a stationary source located 

in the area shall not be considered de minimis for purposes of 

determining the applicability of the permit requirements 

established by this Act unless the increase in net emissions of 

such air pollutant from such source does not exceed 25 tons when 

aggregated with all other net increases in emissions from the 

source over any period of 5 consecutive calendar years which 

includes the calendar year in which such increase occurred. 

(7) Special Rule for Modifications of Sources Emitting Less 

than 100 Tons — In the case of any major stationary source of 

volatile organic compounds located in the area (other than a 

source which emits or has the potential to emit 100 tons or more 

of volatile organic compounds per year), whenever any change (as 

described in section 111(a)(4)) at that source results in any 

increase (other than a de minimis increase) in emissions of 

volatile organic compounds from any discrete operation, unit, or 

other pollutant emitting activity at the source, such increase 

shall be considered a modification for purposes of 

section 172(c)(5) and section 173(a), except that such increase 

shall not be considered a modification for such purposes if the 

owner or operator of the source elects to offset the increase by 

a greater reduction in emissions of volatile organic compounds 

concerned from other operations, units, or activities within the 

source at an internal offset ratio of at least 1.3 to l. If the 

owner or operator does not make such election, such change shall 

be considered a modification for such purposes, but in applying 

section 173(a)(2) in the case of any such modification, the best 

available control technology (BACT), as defined in section 169, 

shall be substituted for the lowest achievable emission rate 

(LAER). The Administrator shall establish and publish policies 

and procedures for implementing the provisions of this paragraph. 

(8) Special Rule for Modifications of Sources Emitting 

100 Tons or More — In the case of any major stationary source of 

volatile organic compounds located in the area which emits or has 

the potential to emit 100 tons or more of volatile organic 

compounds per year, whenever any change (as described in 

section 111(a)(4)) at that source results in any increase (other 

than a de minimis increase) in emissions of volatile organic 

compounds from any discrete operation, unit, or other pollutant 

emitting activity at the source, such increase shall be 

considered a modification for purposes of section 172(c)(5) and 

section 173(a), except that if the owner or operator of the 
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source elects to offset the increase by a greater reduction in 

emissions of volatile organic compounds from other operations, 

units, or activities within the source at an internal offset 

ratio of at least 1.3 to l, the requirements of section 173(a)(2) 

(concerning the lowest achievable emission rate (LAER)) shall not 

apply. 
SPECIAL MODIFICATION PROVISIONS FOR 

SERIOUS & SEVERE OZONE NONATTAINMENT AREAS 

SEC. 182(c)(6),(7), & (8) 

Applies to modifications at existing major 

stationary sources of VOC and NOx 

Significance level for modifications, or 

discrete unit(s), is > 25 tpy 

Opportunities to avoid Part D NSR review or 

LAER if internal offsets are obtained 
STEP I - "INCREASE IN NET EMISSIONS" 

FROM THE PROPOSED MODIFICATION 

• Sum increases and decreases from the 

proposed modification to calculate the 

"increase in net emissions" 

- if sum is 25 tpy or less, netting provisions of 

(c)(6) apply 

- if sum is > 25 tpy, provisions of (c)(7) or (c)(8) 

apply 

• For discrete unit(s) with "increases in net 

emissions" > 25 tpy, regardless of any 

decreases at other units, the provisions of 

(c)(7) or (c)(8) apply 

PtCAl 
STEP II SUMMING "NET INCREASES" 

• Sum all "net increases" at source over a 5 

year contemporaneous period 

• Significance level is > 25 tpy 

• Contemporaneous period is 5 consecutive 

calendar years which includes the calendar 

year when increase will occur 

• For significant increases 

- (c) (7) applies to existing major sources 

< 100 tpy 

- (c) (8) applies to existing major sources 100 

tpy or greater 

CO 
KEY ISSUE 

CREDITING DECREASES 

"Current" Netting Option 

- sum all creditable increases and decreases 

during the contemporaneous period 

"New" Netting Option 

- only sum "net increases" during the 

contemporaneous period 

- creditable net decreases are available as 

internal offsets 
STEP III 

SEC. 182(c)(7) PROVISIONS 

MAJOR SOURCES LESS THAN 100 TPY 

BACT applies instead of LAER 

Part D NSR does not apply to the 

modification, or any discrete unit(s), if 1.3:1 

internal offsets are obtained 

r 
STEP IV 

SEC. 182(c)(8) PROVISIONS 

MAJOR SOURCES 100 TPY OR GREATER 

Part D NSR Applies 

As an option, LAER does not apply to the 

modification, or any discrete unit(s), if 1.3:1 

internal offsets are obtained 

- Remaining Part D NSR provisions still apply 

/fcf 3 It, 
«• ^ 

KEY ISSUE 

OFFSET REQUIREMENT FOR LAER OPTION 

General Part D offset requirement is: 

- at least 1.2:1 for Serious ozone areas 

- at least 1.3:1 for Severe ozone areas 

Does 1.3:1 internal offset required when 

avoiding LAER satisfy the General offset 

requirement? 

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