Summary	of	Interagency	Working	Comments	on	Draft	Language	under	

EO12866/13563	Interagency	Review.		Subject	to	Further	Policy	Review.

Environmental Protection Agency (EPA): Draft Guidance

Control Techniques Guideline for the Oil and Natural Gas Sector

RIN 2060-ZA22

General Comments

1) Reviewer recommends making any conforming changes to the CTGs that come about 

based on comments on the Oil and Gas NSPS rulemaking.

EPA Response:

We are making any appropriate conforming changes to the CTG that came about based on 

comments on the Oil and Gas NSPS.

2) Reviewer recommends providing clarity in relation to how the CTGs and the voluntary

EPA programs are consistent and that companies that take voluntary actions that comply

with EPA’s programs will not be required to take additional action that would be counter 

to the voluntary program. 

EPA Response:

We are soliciting comment on this.

3) Reviewer recommends that RACT technologies explicitly include flexibility to include 

technologies in addition to OGI—especially as new technologies emerge that provide 

similar or increased performance at reduced cost--e.g. infrared absorption based 

technologies, continuous monitoring systems, and unmanned sensing systems. Suggested 

language could be: “...OGI and other sufficiently tested monitoring technologies that 

demonstrate equivalency or superiority to the technical capabilities of current OGI 

technologies.” This language (or similar) should accompany all specifications of OGI 

technologies.

EPA RESPONSE:

The draft guidelines provide recommendations for air agencies to consider in determining 

RACT. Air agencies can use the recommendations in this guideline to inform their own 

determination as to what constitutes RACT in their particular nonattainment areas. We are 

aware of several types of technologies that may be appropriate for fugitive emissions 

monitoring. In the preamble to the NSPS, we are requesting comment on whether there 

are other fugitive emission detection technologies for fugitive emissions monitoring and 

details related to these technologies. However, we cannot recommend or allow the use of 

these emerging technologies until we have evaluated detailed information on topics such 

as detection capability; an equivalent fugitive emission repair threshold to what is required 

in the proposed rule for OGI; the frequency at which the fugitive emissions monitoring 

surveys should be performed and how this frequency ensures appropriate levels of fugitive 

emissions detection; whether the technology can be used as a stand-alone technique or 

whether it must be used in conjunction with a less frequent (and how frequent) OGI 
Summary	of	Interagency	Working	Comments	on	Draft	Language	under	

EO12866/13563	Interagency	Review.		Subject	to	Further	Policy	Review.

monitoring survey; the type of restrictions necessary for optimal use; and the information 

that is important for inclusion in a monitoring plan for these technologies.

4) Reviewer recommends that EPA should propose allowing flexibility to enable the use of 

continuous emissions monitoring systems and mass flow rate thresholds for compliance. 

Reviewer notes that a mass flow rate (scfh) is preferable to a concentration measurement 

(ppm), which is a less accurate measurement of leaks since it does not consider the impact 

of atmospheric conditions, such as wind or background methane. 

EPA RESPONSE: 

The CEMS technology is not used to determine the presence of fugitive emissions nor 

does EPA believe that CEMS are appropriate to be used in this case. Fugitive emissions 

are inconsistent by nature and come from various emissions points. CEMS are typically 

used on a source emission stack (e.g. boiler). 

5) Reviewer recommends that EPA consider alternative approaches to conducting leak 

surveys that are more akin to approaches taken by Colorado and Wyoming. Concerns 

with the proposed approach include:

a. Many studies have shown a skewed distribution for emissions related to leaks and 

that the occurrence of such leaks is often random and difficult to predict, which 

suggests that more frequent surveys may be necessary to identify and repair the 

largest leaks. 

b. The proposed structure for determining the frequency of surveys may create a 

disincentive for companies to find leaks because not detecting a leak for two 

consecutive surveys would reduce the frequency (and costs) of future surveys.

EPA Response:

a. We are soliciting comment, in the NSPS, on the use of Method 21, which is one of 

the options that Colorado allows in Rule 7; however, we are concerned with the 

ambiguity of the “other Division approved instrument based on monitoring device or 

method” provision. There are no operational requirements to ensure that leaks can 

consistently be found during monitoring with such an instrument. In addition to 

Method 21, we are soliciting comment on other potential leak detection approaches. 

In the NSPS, we are also soliciting comments on the use of other emerging 

technology for fugitive emissions monitoring. 

b. EPA shares these concerns. In effort to ensure that fugitive emissions will be found 

when using OGI, we are proposing that all OGI operators develop fugitive emission 

monitoring plans. This plan includes daily instrument checks, determination of 

maximum wind speed during monitoring along with other specific parameters that 

ensure that leaks will be found. The monitoring plan would also require proof of 

inspection (i.e. still images of components during monitoring survey). The plan would 

require record keeping and reporting requirements to ensure compliance. We 

therefore believe that the methodology for surveying, repairing, and reporting 

fugitives is sufficient and that the OGI is optimized if all the parameters are met. 

Appendix I. of the model rule provides details of the monitoring plan requirements.
Summary	of	Interagency	Working	Comments	on	Draft	Language	under	

EO12866/13563	Interagency	Review.		Subject	to	Further	Policy	Review.

Specific Comments

1) Reviewer recommends changing the assumed price for natural gas from $3.50/ mcf to 

$4.00/mcf in Table 4-3. A market price for natural gas of $3.5/mcf is inconsistent with 

the market price assumed on page 5-13 of this document and with the proposed NSPS, 

which assumes $4/mcf. 

EPA Response:

We have corrected the price for natural gas in Table 4-3.

2) Reviewer requests clarification regarding the following text on page 5-6:

“Although we have additional data available on fugitive emission from 

compressor stations, including data from the Measurement of Methane Emissions 

from Natural Gas Gathering Facilities and Processing Plants: Measurement 

Results study published in 20151, the data sets for gathering and boosting 

facilities had skewed distributions. In the study data set, 30 percent of gathering 

facilities contributed 80 percent of the total emissions, and gathering facilities 

emitted, on average, yielded higher emission than would be calculated with the 

factor used in this analysis. Therefore, for gathering and boosting station 

reciprocating compressors, we used the same methane emission factor used in the 

2011 NSPS TSD.”

Reviewer notes that the logic underlying this statement is unclear (there also seems to be 

grammatical problems with the second sentence). The text seems to be saying that recent 

research indicates that the distribution of emissions is skewed and greater than previously

thought. Yet, a decision is made to use an emissions factor based on less current 

information. Is EPA trying to make the point that their estimated benefits of the rule are 

conservative? Please clarify.

EPA Response:

For gathering and boosting station reciprocating compressors, we used the methane 

emission factor used in the 2011 NSPS TSD because factors for this source are not 

available in the GHG Inventory.

The above language will be replaced with:

For gathering and boosting station reciprocating compressors, the 2011 NSPS TSD 

emissions factors were used because they are considered to be the best representative

emissions factors at this time. 

 

1 Mitchell, Austin L. et al. Measurements of Methane Emissions from Natural Gas Gathering Facilities and 

Processing Plants: Measurement Results. Environ. Sci. Technol. 2015, 2119-3227.