UNITED STATES ENVIRONMENTAL PROTECTION AGENCY

Office of Air Quality Manning and Standards

Research Triangle Park, North Carolina 27711

JAN 2 0 1984

MEMORANDUM 

SUBJECT: Averaging Times for Compliance 

With VOC Emission Limits - SIP Revision Policy 

FROM: John R. O'Connor, Acting Director 

Office of Air Quality Planning a Standards (MD-10) 

TO: Director, Air and Waste Planning 'Division 

Regions 11-IV, VI-VIII, X 

Director, Air Management Division, Regions 1, V, IX 

The purpose of this memorandum is to clarify the Agency's policy regarding emission time 

averaging for existing sources of volatile organic compounds (VOC's). Numerous State 

Implementation Plan (SIP) revisions, both broad regulations and source-specific changes, have 

been submitted which provide for compliance determinations by time averaging" emissions of 

VOC for periods exceeding 24 hours. These requests and the following policy on this subject 

were discussed extensively at a recent meeting attended by those Regional Offices which have the 

most pending actions (Regions 1, III, IV. V); the Office of Air Quality Planning and Standards; 

and the Office of General Counsel. This policy represents the consensus of the meeting attendees. 

The objective of EPA's national VOC emissions control program is the timely attainment 

and maintenance of the national ambient air quality standard (NAAQS) for ozone. SIP revisions 

and other regulatory actions relating to VOC control must maintain the integrity of this basic 

objective. There should be assurances that VOC emission control is reasonably consistent with 

protecting this short-term ozone standard. Further, since SIP's and associated VOC control 

programs contemplate the actual application of reasonably available control technology (RACT), 

regulatory actions that incorporate longer term averages to circumvent the installation of overall 

RACT level controls cannot be allowed. 
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CurrentAgency guidance specifies the use of a daily weighted average for VOC 

regulations as the preferred alternative where continuous compliance is not feasible. An example 

might be where a facility operates in a batch manner with multiple lines and various products. 

Reference ii made to the December 8, 1980. Federal Register (copy attached) where can 

coating operators are all allowed to -bubble- several production lines and average emissions over 

a 24-hour time period. 

The preferred daily weighted average alternative may not be feasible in all cases. Where 

the source operations are such that daily emissions cannot be determined or where the application 

of RACT for each emission point (line, machine, etc.) is not economically or technically feasible 

on a daily basis, longer averaging times can be permitted under certain conditions. In determining 

feasibility, consideration might be given, for example, to the extent to which modifications can be 

made to testing, inventory, or record keeping practices in order to quantify daily emissions. Also, 

variability or lack of predictability in a source's daily operationmight be considered as well as 

availability of control technology or the physical impediment or restriction to control equipment 

installation. In order to allow longer than daily averaging in SIP regulations, the following 

conditions or principles must be honored: 

1. Real reductions in actual emissions must be achieved, 

consistent with the RACT levels specified in SIP's or the 

control technique guidelines (CTG's). These limits are 

typically expressed in terms of VOC per unit of production 

(a qualitative such as lbs VOC/gal coating). Where it is 

not feasible to specify emission limits In such terms, 

emission limits per unit of time can be approved provided 

that: 

a. The mission limits reflect typical (rather than potential 

or allowable) production rate and operating hours. These 

emission limits must truly reflect emissions reductions 

consistent with RACT and are not simply an artificial 

constraint on potential emissions. 'This must be 

supported in the SIP revision by historical production 

and operation data. 

b. Nonproduction or equipment downtime credits are not 

allowed in the emission limit calculation unless a 

Federally enforceable document specifically restricts 

operation during these times. Such credit must be based 

on real, historical emissions. 

2. Averaging periods must be as short as practicable and in no case 

longer than 30 days. 

3. A demonstration must be made that the use of long-term averaging 

(greater than 24-hour averaging) will not jeopardize either ambient 

standards attainment or the reasonable further progress (RFP) plan 

for the area. This must be accomplished by showing 
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that the maximum daily increase in emissions associated with long-term averaging is 

consistent with the approved ozone SIP for the area. 

4. Sources in areas lacking approved SIP's, or in areas with 'approved SIP's but showing 

measured violations, cannot be considered for longer term averages until the SIP has 

been revised demonstrating ambient standards attainment and maintenance of RFP 

(reflecting the maximum daily emissions from the source with long~-term averaging). 

Meaningful short-term (i.e.,, daily) emission caps are desirable especially for sources 

subject to large fluctuations in emissions. The use of a daily cap (equal to or less than current 

average emissions on a daily basis) that limits short-term emissions to RACT equivalent levels 

would meet the above objective of ensuring VOC control that is consistent with attaining the 

MARS for ozone. 

States have the primary responsibility to show adherence to the above principles and, to do 

so, must include the following information (in detail) in all SIP revision requests that seek VOC 

averaging times greater than 24 hours: 

1. The VOC limits specified in an enforceable form with appropriate compliance dates. 

2. A description of the affected processes and associated historical production and 

operating rates. 

3. A description of the control techniques to be applied to the affected processes such as 

low solvent and waterborne coating; technology and/or add-on controls. 

4. The nature of the emission control program whether a bubble, a regulation change, a 

compliance schedule, or some other form of alternative control program. 

5. The method of record keeping and reporting to be employed to demonstrate 

compliance with the new emission limit requirement and to support the showing that 

the emission limit is consistent with RFP and the demonstration of attainment. 

Each EPA Regional Office shall have the primary responsibility for determining the 

approvability of application requests. However, in order to assure Regional consistency. 

coordination with the Office of Air Quality Planning and Standards staff is encouraged during the 

initial development of any single "time average' SIP revision or regulation. Also, all SIP revisions 

involving long-term averaging must be proposed in the Federal Register with an explanation of 

how the principles listed above have been satisfied. 
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Should there be any questions on this policy. please call Tom Helms (FTS 629-5526) or 

Brock Nicholson (FTS 629-5516). 

Attachment 

cc: Barbara Bankoff 

Ron Campbell 

Jack Farmer 

Mike Levin 

Ed Reich 

B. J. Steigerwald 

Darryl Tyler 

Peter Wyckoff 

Chief, Air Branch, Regions I-X 

Regional Administrator, Regions I-X