1 Greenridge Lane #2 

Lincoln, MA 01773 

October 20, 2005 

Department of Environmental Protection 

Bureau of Waste Prevention 

One Winter Street 8th Floor 

Boston, MA 02108 

Attn: Robert Donaldson 

Subject: Comments on Proposed 310 CMR 7.06(l)(c) Opacity Rule 

I appreciate the opportunity to provide comments on the proposed 310 CMR 7.06(l)(c) Opacity 

rule. 

Overall the rule reflects a reasonable balance between the goal of optimizing opacity emission 

control and the need to establish limits that are achievable. The use of 6-minute block averaging 

to report opacity emissions is also supported, as it provides an averaging time that is more 

consistent with the behavior of opacity than the specifications in 310 CMR 7.06(l)(a) and (b), 

avoiding designating unavoidable instantaneous spikes as excess emissions. The 6-minute block 

period is also consistent with the averaging time used in federal opacity monitoring rules 

There are, however, several minor revisions to the rule being requested in an effort to simplify 

implementation requirements and make them more consistent standard monitoring practices. 

More generally, with regard to rule implementation, it is felt that conformance with this proposed 

rule should not involve more onerous compliance requirements (i.e. more frequent Method 9 

testing or more elaborate deviation tracking) than is applicable to the larger utility boilers subject 

to 310 CMR 7.06(l)(a) and (b). Rule procedures should be kept as simple as feasible to facilitate 

proper implementation. Compliance provisions in several recent Air Plans designed to 

implement the substantive content of a previously proposed version of this opacity rule were 

significantly more complex than warranted by the nature of the opacity emission issue or were 

needed to ensure proper conformance with proposed opacity limits. 

More specific requested revisions to the proposed rule are detailed below. 

Section 7.06(l)(c)(l)b. 

1. Requirement that Two Excepted Opacity Incidents Occur within the Same Hour: It is 

requested that 7.06(l)(c)l .b be revised to eliminate the requirement that the two excepted 

elevated opacity incidents occur within a single hour. The basic intent of this exception, to 

allow any boiler up to (2) two opacity incidents > 27% in a calendar quarter during special 

operating conditions, seems appropriate, as opacity emissions are very sensitive to 

combustion conditions, and even proper operating practices may not be sufficient to avoid an 

occasional excursion under all circumstances. Unanticipated changes in the combustion 

process, as well as startups and shutdowns, can produce unavoidable transient conditions 

resulting in brief periods of elevated opacity no matter how well boiler operation is 

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maintained. Also, the need to minimize 02 to promote NOx control makes operating shifts 

more susceptible to minor air/fuel imbalances that can produce opacity spikes. 

The designation of two exceptions as a base case seems reasonable, since a source whose 

operating demands make it more susceptible to opacity excursions may elect to install a 

datalogger and take advantage of the additional exceptions provided in 7.06(l)(c)(l)c, which 

seems appropriate. 

However, there does not seem to be any reason to require that the two elevated incidents > 

27% provided under 7.06(l)(c)(l)b occur within the same 60 minute period. Limiting the 

two eligible incidents > 27% to lie within a 60 minute period seems overly restrictive, and 

somewhat arbitrary. 

Particularly at startup, the combustion process is variable, and transient conditions may occur 

at any time. Oftentimes such transients accompany the placement of each burner into service; 

and the sequencing of individual burner lite-offs could easily extend over more than an hour, 

particularly as efforts to reduce opacity may include a slower ramping up during startup. 

More generally, due to the largely random nature of such transients, it does not seem 

appropriate to confine the two allowed general exception excursions to a single 60 minute 

period. 

2. Applicability of Exceptions: it is suggested that language be added to 7.06(l)(c)(l)b 

clarifying that the two elevated incident exception is applicable on an individual boiler basis. 

The current 7.06(l)(c)(l)b language is silent on this issue, and could be interpreted to indicate 

that the two exceptions are allowed per facility not per boiler, which does not seem consistent 

with the intent of this provision. Similar clarifying language should be added to 

7.06(l)(c)(l)c. 

Section 7.06(1 VcfflLk. 

The limited targeted exceptions provided in 7.06(l)(c)l .c are strongly supported, however minor 

refinements and clarifications are requested. 

1. Number of Allowed Elevated Incidents: It is requested that 7.06(l)(c)l .c include an 

Alternative Minimum (Floor) number of allowed elevated incidents between 27% and 60%, 

in addition to the basic restriction of 0.1% of operating time. The types of operating 

conditions requiring use of the exceptions described in paragraph 7.06(l)(c)l.c. (e.g. startup, 

shutdown, load change, etc.) occur most frequently for limited use boilers. This is one 

instance in which more operating time does not correspond to a larger need for an exception 

A suggested value for this Alternative Floor is eleven (11) elevated incidents per quarter, 

which corresponds to about half of the theoretical maximum number of elevated incidents 

that would be allowed for a unit operating continuously (i.e. there are approximately 21,900 

6-minute periods in a quarter, and 0.1% of 21,900 = 22 allowed elevated 6-minute periods 

for a continuously operating unit). 

With this refinement, the language in 7.06(l)(c)l.c would be revised to specify that the 

number of elevated incidents greater than 27% but less than 60% per calendar quarter during 

special conditions cannot exceed one-tenth of one percent (0.1%) of the total 6-minute block 

averages, or 11 per quarter, whichever is less restrictive. 

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2. Numeric Data Reduction System: the requirement for the Numeric Data Reduction System to 

have a printout capability should be expanded to allow output of opacity data to an electronic 

file. I do not believe all data loggers can be directly attached to a printer. In any case, it may 

be more convenient to download data from the logger to a computer from which printouts of 

6-minute block values can then be generated. 

It is requested then that the first sentence of 7.06(l)(c)l .c be revised to state "For a facility 

equipped with a visible emission monitor with a numeric data reduction system that can 

printout or output to an electronic file individual block averages etc." (suggested new text is 

in bold). 

3. Criteria for Approving Use of the Exceptions in this Provision: The 7.06(l)(c)l,c. text 

indicates that the DEP "may" approve the exceptions specified in this provision. It is 

requested that this language be clarified to indicate that the 7.06(l)(c)l.c exceptions will 

normally be approved, if consistent with the approved Plan of Good Operating Practices 

(POGOP). 

4. Definition of "One-Hour": It is requested that the all references to "one-hour" in 7.06(l)(c) 1 .c 

be revised to specify "one block hour". In this context, block hour means clock hour. 

The evaluation and aggregation of data on a block hour basis is consistent with the standard 

configuration of most "numeric data reduction" devices, such as CEMS, Also most emission 

standards specify compliance on a block hour basis. It is recognized that, in theory, 

aggregation of data on a block hour basis represents a slightly less conservative compliance 

approach than aggregation over 60 minutes beginning at the first elevated incident, but in 

practice the number of occasions on which three incidents would occur within a 60 minute 

period but not in the same block hour would be minimal. The benefit of avoiding the need 

for customizing the configuration of a monitoring system, with its accompanying opportunity 

for improper implementation, is felt to be more important than the slight increase in 

conservativeness gained by performing 60 minute aggregations on a rolling basis. 

5. Interface of 7.06(l)(c)l.b and 7.06(l)(c)l.c Exceptions: It is suggested that language be 

added to 7.06(l)(c)l.c to clarify mat the exceptions provided in 7.06(l)(c)l.b and 

7.06(l)(c)l.c are not mutually exclusive. A source that chooses to install a visible emission 

monitor with numeric reduction system and use the opacity exceptions described 

7.06(l)(c)l.c, should still be eligible to use the exceptions provided under 7.06(l)(c)l.b. 

6. Applicability of Exceptions: it is suggested that language be added to 7.06(l)(c)(l)c 

clarifying that the allowed exceptions are applicable to each individual boiler at a facility -

see related Comment 2 for 7.06(l)(c)l.b 

Section 7.06(l)(cU.d 

1. Compliance Method: The language in paragraph 7.06(l)(c) 1 .d. should be clarified to indicate 

that compliance with 7.06(l)(c) opacity limits may be demonstrated either through Method 9 

testing or by use of a certified opacity monitor, however a source is not required to use their 

visible emission monitor as a direct compliance monitor unless such a requirement is 

contained in an existing 7.02 Air Plan approval. 

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Even the large utility boilers in Massachusetts, which are subject to the provisions of Sections 

7.06(l)a and b, and which are equipped with PS-1 certified opacity monitors mandated by the 

federal Acid Rain Program (40 CFR 75), are not required to use these opacity monitors for 

direct compliance, unless such a requirement is contained in a 310 CMR 7.02 Plan Approval. 

In contrast, the industrial boilers that would qualify for applicability under Section 7.06(l)(c) 

are typically equipped with non-PS-1 smoke sensors, which are required under 310 CMR 

7.04(2). It would, therefore, be inequitable and inappropriate to designate the opacity 

measurement devices on boilers choosing to conform to the Section 7.06(l)(c) provisions as 

compliance monitors. They should be designated as indicator monitors, with deviations from 

the Section 7.06(l)(c) limits being reportable under the Operating Permit (Title V) Program, 

but these deviations would not automatically be considered excess emissions. 

It should be noted that opacity monitors subject to PS-1 certification must be located in 

accordance with specific siting criteria, are subject to stringent design criteria, as well as 

initial certification testing, none of which is required for a smoke sensor under 310 CMR 

7.04(2). Also, PS-1 opacity monitors are typically calibrated daily, and may have quality 

assurance audits conducted on a quarterly basis, none of which is typically done for a smoke 

sensor. 

Thus, neither the accuracy of the smoke sensors, nor the regulatory provisions in 310 CMR 

7.06(1) justifies a requirement to use opacity monitors as direct compliance monitors under 

Section 7.06(l)(c). 

Section 7.06(1 Vc)2.d 

1. Duration and Frequency of Special Condition Events: The language in paragraph 

7.06(l)(c)2.d should be revised to clarify that the description of the "duration" and 

"frequency" of startup, shutdown, soot blow, and other special events presented in the Plan of 

Good Operating Practices is a qualitative characterization, not a quantitative analysis. 

Since most of the "special conditions" associated with elevated opacity incidents are the 

result of transient combustion conditions whose duration cannot be fully controlled and 

whose frequency is likely to depend on facility process demands and other unpredictable 

circumstances, it is not feasible to quantitatively specify the duration or frequency of these 

events. For example, the frequency of load shifts and even of startups, in an industrial 

facility, will vary depending on process demands. The duration of load ramping will be 

affected by the severity of swings in load demand. Fuel switching frequency may be a 

function of changes in fuel costs and/or fuel availability. And certain opacity generating 

events such as burner trips are totally unpredictable. Even soot blowing schedules may be 

adjusted based on the duration boiler operation and/or any upward trends in opacity 

emissions. 

However, it is also recognized that the operational roles of boilers within a facility may differ 

(i.e. units may be base loaded, shoulder units, peaking units, etc.), and expected frequencies 

and durations of the special conditions producing elevated opacity excursions can be 

differentiated to some extent based on these operational roles. Therefore it seems appropriate 

for the POGOP to provide a general descriptive characterization of the expected frequency 

and duration of these special conditions consistent with the normal operational role of a 

boiler, but such descriptions should not be required to include quantitative specifications. 

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Section 7.06m(c)2.f 

1. Specification of Emission Limits for Special Conditions: This provision (7.06(l)(c)2.f) 

should be deleted. 

The opacity excursions excepted under 7.06(l)(c) are produced by transient, off-design 

combustion conditions that are not well behaved, stable or repeatable. As a result, past 

emission trends displayed during these special condition events are only an approximate 

predictor of future emissions behavior. Uncertainties inherent in such non-routine transient 

events makes historical data a less than reliable basis from which to extrapolate specific 

opacity emission maxima. Slight changes in the combustion process or operating 

circumstances, or even the normal gradual wear of hardware components, might affect 

conditions sufficiently to amplify transient opacity spikes, and result in new maximum. 

For these reasons, it does not seem appropriate to require that specific opacity limits be 

identified from the historical data set used to develop the Plan of Good Operating Practices 

(POGOP). That data set should be adequate to justify the designation of the types special 

conditions giving rise to opacity excursions, as required in 7.06(l)(c)2.e, but is unlikely to be 

adequate to appropriately assign specific emission limits for each special condition. 

The upper limit of 60% specified 7.06(1 )(c)l.c, then, should be applicable to excursions for 

any special condition designated and justified in the POGOP. No requirement to identify 

alternative emission limits should be included in this 7.06(l)(c) rule. 

Conformance with the POGOP should ensure that sources do not use the exceptions under 

7.06(l)(c)l.c as a basis for relaxing existing opacity controls. The POGOP will contain 

operating procedures designed to maintain proper control of opacity emissions. To reinforce 

this idea, the Opacity Air Plans approvals could include language making it explicit that the 

7.06(l)(c)l.c exception should not be construed as an emission standard, but rather the source 

has the obligation to make all reasonable efforts to meet the 7.06(l)(c) opacity standard of 

15%/27% at all times to the extent feasible. 

Section 7.06(l)(c>4 

1. Deviations: It is requested that a sentence be added at the end of this Section indicating that 

"opacity excursions > 27% that qualify as allowed exceptions under 310 CMR 7.06(l)(c)l.b 

and 7.06(l)(c)l.c shall not be considered deviations under the Operating Permit". 

Overall 310 CMR 7.06(l)(c) Plan Approval Comments 

1. Status of Previous Opacity Plan Approvals: Opacity Air Plan approvals were issued to 

several Massachusetts sources implementing provisions of a previously proposed version of 

7.06(l)(c). Since the proposed regulation that was the basis for these existing opacity Air 

Plans has been superceded by the current 7.06(l)(c) proposal, it seems appropriate that those 

Opacity Air Plans be automatically terminated immediately once the 7.06(l)(c) rule has been 

finalized, unless a source should request that their existing Air Plan approval remain 

effective. A complex array of implementing provisions were included in these existing 

Opacity Air Plans approvals that may no longer be appropriate or applicable, and therefore it 

would seem preferable to formulate a new Air Plans permit to operationalize the final 

7.06(l)(c) rule, rather than attempting to modify the existing Air Plans. 

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It is also requested that a source, whose Plan of Good Operating Practices (POGOP) was 

previously approved by MADEP, be allowed to immediately comply with the provisions of 

the 7.06(l)(c) rule once it is promulgated final, in lieu of remaining subject to any existing 

Opacity Air Plans. Such an approach would permit an expedited conversion to the new rule 

for sources that have already implemented approved opacity control and monitoring 

practices. 

Thank you for your consideration of these comments. 

Sincerely: 

A 

Bob Machaver 

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