# Mandatory Greenhouse Gas Reporting Rule: EPA’s Response to Public Comments

Subpart DD: Electric Transmission and Distribution Equipment UseNovember 8, 2010 Subpart DD—Response to Comment Document 2 FOREWORD

This document provides responses to public comm ents on the U.S. Environmental Protection Agency’s (EPA’s) Proposed Mandatory Greenh ouse Gas Reporti ng Rule: Additional Sources of Fluorinated GHGs: Subpart DD, Electric Transmissi on and Distribution Equipment Use. EPA published a Notice of Proposed Rulemaking in the Federal Register (FR) on Ap ril 12, 2010 (75 FR 18652). EPA received comments on this proposed rule via mail, e-mail, and at a public hearing held in Washington D.C. on April 20, 2010. Copies of all comments submitted are available at the EPA Docket Center Public Reading Room. Comments letters and transcripts of the public hea rings are also available electronically through http://www.regulations.gov by searching Docket ID EPA-HQ-OAR-2009-0927.

EPA prepared this document in mult iple sections, with each secti on focusing on a different broad category of comments on the rule. In light of the large number of comments received and the significant overlap between many comments, this document does not respond to each comment individually. Rather, EPA summarized and provided a single response to each significant argument, assertion, and question contained within the totality of comments. Within each comment summary, EPA pr ovides in parentheses

one or more lists of Docket ID numbers for commenter s who raised particular issues; however, these lists are not meant to be exhaustive, and EPA does not indi vidually identify each and every commenter who made a certain point in all instances, particularly in cases where multiple commenters expressed essentially identical arguments.

EPA’s responses to comments are ge nerally provided immediately fo llowing each comment summary. In some cases, EPA provided responses to specific comments or groups of similar comments in the preamble to the final rulemaking. Rather than r epeating those responses in this document, EPA has referenced the preamble.

Comments were assigned to specific section of this document based on an assessment of the principal subject of the comment; however, some comments inevitably overlap multiple subject areas.November 8, 2010 Subpart DD—Response to Comment Document 3 

### Table of Contents

1. Definition of the Source Category ......................................................................................... 4

1.1 Definition of a Facility—Track 1 ..................................................................................... 4

1.2 Definition of a Facility—Track 2 ..................................................................................... 4

1.3 All-in Provision and Boundary between Electricity Generation Facility and T&D Facility—Track 1 .................................................................................................................... 10

1.4 All-in Provision and Boundary between Electricity Generation Facility and T&D Facility—Track 2 .................................................................................................................... 11

1.5 Installation of Electrical Equipment at Electric Power Systems—Track 2 ................... 13

1.6 De Minimis Exemption for Sealed-pressure Equipment—Track 1 ............................... 13

1.7 De Minimis Exemption for Sealed-pressure Equipment—Track 2 ............................... 14

1.8 Other (Definition of Source Category) ......................................................................... 16

2. Reporting Threshold ........................................................................................................... 17

2.1 Threshold Analysis—Track 1 ....................................................................................... 17

2.2 Other (Reporting Threshold)........................................................................................ 18

3. GHGs to Report—Track 1 .................................................................................................. 19

4. Detailed GHG Emission Calculation Procedures/Equations ............................................... 20

5. Monitoring and QA/QC Requirements ................................................................................ 21

5.1 Frequency of Weighing Cylinders—Track 1 ................................................................ 21

5.2 Frequency of Weighing Cylinders—Track 2 ................................................................ 22

5.3 Accuracy and Precision of Scales—Track 1 ................................................................ 23

5.4 Accuracy and Precision of Scales—Track 2 ................................................................ 24

5.5 Frequency of Scale Calibration ................................................................................... 25

5.6 Other (Monitoring and QA/QC Requirements)—Track 1 ............................................. 25

6. Data Reporting Requirements—Track 1 ............................................................................. 26

7. Other Subpart DD Comments – Track 1 ............................................................................. 28

8. Other Subpart DD Comments – Track 2 ............................................................................. 29 Appendix A – List of Commenters Sorted by Submission Number ............................................ 30November 8, 2010 Subpart DD—Response to Comment Document 4 

### 1. Definition of the Source Category

1.1 Definition of a Facility

— Track 1

Relevant Bin Number 4.1.1

Comment Summary 1.1-a: Two commenters (0407 and 0639) suppor ted the concept of a reportingfacility as an entire transmission and distribution system rather than an individual building, such as a gasinsulated substation.

Response 1.1-a: EPA appreciates the commenters’ support of the proposed definiti on of a facility.

Comment Summary 1.1-b: One commenter (0608) sought clar ification on how to determine the boundary of a facility if numerous electric power retail companies have a common owner. The

commenter asked if the common owner should be cons idered one facility, or whether each individual electric power retail company should be considered a separate facility.

Response 1.1-b: The final rule clarifies that the facility boundary is based on a physical collection of equipment that functions as an integrated unit between two specified points: (1 ) the point(s) at which electric energy is obtained by the facility from an el ectricity generating unit or a different electric power transmission or distribution entity that does not hav e a common owner and (2) the point(s) at which the customer(s) or another electric power transmission or distribution entity that does not have a common owner receives the electric energy. Therefore, num erous electric power retail companies would only be considered one reporting facility if they are electr ically linked through transmission and distribution lines in a continuous manner without being separated by electric power entities with a different owner.

It should also be noted that for purposes of the reporti ng threshold, if distinct facilities have a common owner and the total nameplate capacity of all t he facilities with the common owner exceeds 17,820 pounds, then each facility must report emissions even if the nameplate capacity of an individual facility is less than 17,820 pounds.

Comment Summary 1.1-c: Commenters 0624, 1021, and 1080 st ated that reporting should be corporate-level to ensure that the largest potential emitters of SF 6 are covered by the rule as well as to ensure accurate reporting. The co mmenters argued that corporate-level reporting will minimize the burden among owners and operators of electric power systems in determining what collections of electrical equipment constitute each electric power system.

Response 1.1-c: See the Subpart DD Final Preamble, Section III, “Summary of Comments and Responses” for EPA’s response on corporate-level reporting.



### 1.2 Definition of a Facility

— Track 2

Relevant Bin Number 4.1.1

Comment Summary 1.2-a: EPA requested comment on whether it would be appropriate to use the Regional Greenhouse Gas Initiative (RGGI) definiti on of a transmission and/or distribution entity for assistance in defining an electric power system facility. RGGI defines a transmission and/or distribution entity as ‘‘the assets and equipment used to transmi t and distribute electricity from an electric generator

to the electrical load of a customer. Includes all re lated assets and equipment located within the service territory of the entity, defined as the service territory of a load-servicing entity specified by the applicable state regulatory agency.” Commenters 0075, 0086, 0088, 0109, and 0133 did not think the RGGI definition is appropriate for use in the definition of a facility for Subpart DD. Commenter 0075 considered the EPA definition more “specific a nd definitive.” Commenter 0088 cons idered EPA’s proposed definition to be generally more consistent with national indust ry standards than the RGGI definition.November 8, 2010 Subpart DD—Response to Comment Document 5 Response 1.2-a: EPA appreciates the comments regarding the ap propriateness of the RGGI definition of

a transmission and/or distribution entit y. EPA did not incorporate the RGGI definition into the definition of a facility for this subpart due to the ambiguity involv ed with the definition and the lack of support of the RGGI definition among commenters.

Comment Summary 1.2-b: Six commenters (0075, 0088, 0097, 0098, 0115, 0128) generally agreed with the system-wide facility concept contained in EPA’ s proposed definition of an electric power system facility. Commenter 0075 noted that it is reflective of the way the commenter has reported emissions

under EPA’s SF6 Emission Reduction Partner ship for Electric Power Systems.

Response 1.2-b: EPA has retained the system-wide facility conc ept as part of the facility definition for this subpart.

Comment Summary 1.2-c: EPA proposed the following as part of the language relating to the definition of a facility: “Reporting by the elec tric power system would comprise all gas-insulated equipment located between the point of generation and the point at which the ultimate customer receives the electricity.” Commenters 0075 and 0088 requested that the reference to “ultimate” customer be removed from the language since many utilities and electric power provi ders do not provide electric power directly to the ultimate consumer, but rather to a different utility or electric power provider. Commenter 0075 explained that removing the word “ultimate” from the physical de scription of an electric power system would clarify that there might be numerous distinct facilities from the point at which electric power is generated to the point at which electric power is provided to the ultimate consumer.

Response 1.2-c: EPA acknowledges that the pr oposed language would not be appropriate fo r cases in which an electric power entity provides electricity to another electric power entity rather than the ultimate

retail customer. EPA has removed refer ence to the “ultimate customer” in the final rule and has clarified that the downstream boundary of the facility is “the poi nt(s) at which the customer (s) or another electric power transmission or distributi on entity that does not have a comm on owner receives the electric energy.”

Comment Summary 1.2-d: Commenter 0083 stated that the propos ed language describing electric power systems as equipment “operated as an integr ated unit by one electric power entity or several entities that have a single owner" could be interp reted to mean that one parent company would have to report emissions for all its subsidiaries, which would not be desirable for the commenter given its ownership structure. The commenter explained that it is a subsidiary company with its own board of directors that is distinct from its parent co mpany’s other subsidiaries, and thereby thought each subsidiary should be allowed to report separately.

Response 1.2-d: : The final rule clarifies that the facility boundary is based on a physical collection of equipment that functions as an integrated unit between two specified points: (1 ) the point(s) at which electric energy is obtained by the facility from an el ectricity generating unit or a different electric power transmission or distribution entity that does not hav e a common owner and (2) the point(s) at which the customer(s) or another electric power transmission or distribution entity that does not have a common owner receives the electric energy. Therefore, numerous subsidiaries would only be considered one reporting facility if they are electrically linked th rough transmission and distribution lines in a continuous manner without being separated by electric power entities with a different owner. . See Subpart DD Final Preamble, Section III, “Summary of Comments and Responses” for EPA’s additional discussion of the final Definition of a Facility language.

Comment Summary 1.2-e: Seven commenters (0083, 0087, 0097, 0098, 0101, 0127, 0133) argued that reporting should be based on the ownership of equipment (frequently referred to in comments as corporate-level reporting) to ensure accurate reportin g, reduce ambiguity regarding what collections of equipment constitute facilities, and reduce the over all burden of reporting. Commenters 0083, 0087, andNovember 8, 2010 Subpart DD—Response to Comment Document 6 0133 considered the term “operated as” in the proposed definition of a facility to be ambiguous since the operation of electrical equipment can mean many different things. Commenter 0083 thought that “operated as” could be interpreted to mean the per formance of maintenance activities and argued that the entity responsible for performing maintenance ac tivities on equipment should not be responsible for reporting emissions from that equipment since the ent ity has no power to make decisions regarding the purchase or replacement of the equipment.

Commenter 0087 acknowledged that corporate-level r eporting can lead to ambiguities if there are multiple owners of equipment. To avoid this potential ambiguity in multiple-owner situations, commenters 0087 and 0101 suggested that reporting be based on whichever owner is responsible for the maintenance of the equipment.

Commenter 0133 stated that “corporate reporting would allow an entity to determine quickly and accurately what equipment should be counted toward the reporting threshold (that which it owns) and then report fully the emissions related to that equi pment (based on service and maintenance records). It also would eliminate any confusion that may be caus ed by introducing operational relationships into the

definition of ‘elect ric power system’.”

Commenter 0133 agreed with EPA that the entity re sponsible for equipment service and maintenance activities is most capable of accurate data collecti on and compiling, but the commenter argued this notion supports reporting based on ownership since the owners have the obligation to service and maintain their equipment.

Response 1.2-e: See the Subpart DD Final Preamble, Section III, “Summary of Comments and Responses” for EPA’s response on corp orate-level reporting. To avoi d confusion, EPA has removed the term “operated as” from the definiti on of facility. The definition of facility in the final rule refers to equipment that “is owned, serviced, or maintained by a single electric power transmission of distribution entity (or multiple entities with a common owner).” Th e phrase “owned, serviced, or maintained” as used in the definition of facility is not intended to allo w or suggest segmenting portions of a system for the purpose of avoiding General Provisions (40 CFR 98.2 - 98.4), the reporting requirements that are applicable to all owners and operators associated with the facility.

Comment Summary 1.2f: Commenters 0127 and 0133 interpreted the definition of a facility proposed by EPA to mean that a single facility constitutes all generation, transmission, or distribution assets that are operated as an integrated unit even if different companies are responsible for the generation, transmission, and distribution of t he electricity. The commenters expr essed concern that the proposed facility definition will lead to confusion and inaccura te emission reports if numerous companies have to

share data in order to calculate emissions.

Response 1.2-f: To avoid confusion, EPA has removed the te rm “operated as” from the definition of facility. Instead, the definition refers to equipmen t that “functions as” an integrated unit, and that is owned, serviced, or maintained by a single electric power transmission or distribution entity. The final rule clarifies that the facility boundary is based on a ph ysical collection of equipment that functions as an integrated unit, that is owned, serviced or mainta ined by a single electric power transmission or distribution entity (or multiple entities with a commo n owner), and that is located between two specified points: (1) the point(s) at which electric energy is obtained by the facility from an electricity generating unit or a different electric power transmission or distribution entity that doe s not have a common owner and (2) the point(s) at which the customer(s) or anot her electric power transmission or distribution entity

that does not have a common owner receives the electr ic energy. Therefore, numerous electric power retail companies would only be considered one reporting facility if they are electrically linked through

transmission and distribution lines in a continuous manner without being separated by electric power

entities with a different owner.

Comment Summary 1.2-g: Commenter 0096 requested that report ing be required by whichever entity directly owns and operates a collection of equipment. The commenter elaborated as follows, “For example, at a power plant where most of the switchya rd is owned by a local distribution company (LDG), the LDG would report on the equipment that it oper ates as part of its overall T&D system SF 6 reporting.November 8, 2010 Subpart DD—Response to Comment Document 7 To the extent that the power plant operator manages any SF 6 containing equipment at the same power plant, the power plant operator would report SF 6 emissions from any equipment that it manages at the facility as part of its power plant facility-level reporting. However, the power plant operator would only report SF 6 emissions for equipment it owns as part of it s facility report if the facility would otherwise exceed the 25,000 tonne Mandatory Reporting Rule (MRR) reporting threshold for the facility.”

Response 1.2-g: The commenter’s proposal may be suitabl e for certain ownership and operational relationships. However, the definition of a facility for this subpart must be applicable to scenarios in which there are multiple owners or complex ownership and operational relationships involved with specific pieces equipment. EPA’s final definition of a fac ility is based on a physical collection of equipment located between two specified points, where the equipment is owned, serv iced, or maintained by a single electric power entity (or multiple entities with a common owner). Per the Gener al Provisions (40 CFR 98.2 - 98.4), the reporting requireme nts are applicable to all owners and operators associated with the facility. See Subpart DD Final Preamble, Secti on III, “Summary of Comment s and Respon ses” for additional discussion of the final Definition of a Facility language.

Comment Summary 1.2-h: Commenter 0098 recommended the following edits to EPA’s proposed facility definition:

EPA proposes to define the facility as follows: For purposes of this sub part, “facility” means an electric power system. Electric power system means the collection of SF 6 - and PFC-insulated equipment linked through electric power transmiss ion or distribution lines and operated as an integrated unit by one electric power entit y or several entities that have a single owner.

The commenter did not indicate why this edit should be made.

Response 1.2-h: One of EPA’s intentions of the proposed la nguage was to avoid situations where a parent company divides several subsidiary companies into separate facilities even though the subsidiary companies are located next to each other and operate electrical equipment that is interconnected by lines. Therefore, EPA used language to clarify that in this scenario, the electrical equipment throughout the subsidiary companies would be considered as part of a single facility. See Subpart DD Final Preamble, Section III, “Summary of Comments and Responses” for additional discussion of the final Definition of a Facility language.

Comment Summary 1.2-i: Commenter 0101 indicated that EPA as sumed a single electric power company always owns and operates all transmi ssion and distribution equipment from the point of generation to the point at which customers ultimately receive electricity. The commenter noted that in some cases the owner of a piece of equipment is diffe rent from the operator of that piece of equipment, and the commenter is concerned that under the propo sed definition of a facility, double-counting of emissions might occur from both the owners and operators of a piece of equipment reporting SF 6 emissions from the equipment.

Response 1.2-i: EPA acknowledges that the trans mission and distribution equi pment from the point of generation to the point at which customers ultimate ly receive electricity is not always owned and operated by a single electric power entity. EPA has clar ified the boundaries of a Subpart DD facility in the final rule, and notes that there may be more than one di stinct electric power system facility located from the point at which electricity is generated to the point at which the ultimate customer receives the electricity. See Subpart DD Final Preamble, Se ction III, “Summary of Co mments and Resp onses” for additional discussion of the final Definition of a Facility language and clarification of reporting obligations.

Comment Summary 1.2-j: Commenter 0101 argued that the following activities listed in the Monitoring and QA/QC requirements of 40 CFR §98.304 are not possible for an owner that does not operate or maintain a substation to conduct: (1 ) Ensure purchases from bulk gas distributors, Original Equipment Manufacturers, and off-site recycling are accounted for, (2) Ensure all cylinders are consistently weighed on certified scales, and (3) Provide proof that all sca les are certified using NIST-traceable standards.November 8, 2010 Subpart DD—Response to Comment Document 8 Response 1.2-j: Per the General Provisions (40 CFR 98.2 - 98.4), the reporting requirements are applicable to all owners and operators of a facility, but is up to the owners and operators to designate a representative who will be responsible for certifying, signing, and subm itting GHG reports to EPA. This means that the owner, operator, or some combinati on of the two can conduct the monitoring and QA/QC measures listed in 40 CFR §98.304 for the facility.

Comment Summary 1.2-k: Commenter 0109 supported the “operation” differentiation between electric power systems in the definition of a facility pr oposed by EPA and noted that it will be reporting on an “operation basis” under other subparts of the rule.

Response 1.2-k: EPA appreciates the commenter’s support of t he proposed definition of a facility. EPA did propose defining the facility boundaries on the basis of operation. However, due to the myriad relationships and operational structures among owners and operators of electric power systems as well as other issues raised by comment ers, it was necessary to revise the facility definition to no longer differentiate facility boundaries solely on the basis of equipment operation. The definition now refers to equipment that is “owned, serviced, or maintained by” a single entity. To avoid confusion, EPA has removed the term “opera ted as” from the definition of facility. T he definition of facility in the final rule refers to equipment that “is owned, serviced, or ma intained by a single electric power transmission of distribution entity (or multiple entities with a co mmon owner).” The phrase “owned, serviced, or maintained” as used in the definition of facility is not intended to allow or suggest segmenting portions of a system for the purpose of avoidi ng General Provisions (40 CFR 98.2 - 98.4), the reporting requirements that are applicable to all owners and operators as sociated with the facility. See Subpart DD Final Preamble, Section III, “Summary of Comments and Responses” for additional discussion of the final Definition of a Facility language.

Comment Summary 1.2-l: Commenter 0115 requested flexibility in the EPA proposed definition of a facility “with respect to ownership, geographic service territories and business structure.” The commenter explained that there are multiple transmission assets located geographically within the boundaries of its service territories that it operates and maintain s but does not own. The commenter would like the definition to “allow for segregation of assets by ownership or by operating entity in the event future operating practices and agreements with these third parties provide for a mechanism to segregate the affects these third-party assets have on [the commenter’s] overall emissions.”

Response 1.2-l: EPA acknowledges that flexibility in the definition of an electr ic power system facility to segregate electrical equipment based on either ownership or operational control might provide

convenience to certain SF 6 equipment users under certain conditions. However, it is essential that the definition of a facility for this subpart clearly identif y which collections of equipment constitute a facility and the points at which a facility begins and ends. This is essential because given the complex owner and operator relationships in the industry, allowing flexibility to define a facility differently depending on the situation encountered would greatly increase t he risk of double-counting, underreporting, and/or confusion regarding the bo undaries of a facility. To avoid confusion, EPA has removed the term “operated as” from the definition of facility. The definition of facility in the final rule refers to equipment that “is owned, serviced, or maintained by a single electric power transmission of distribution entity (or multiple entities with a common owner).” The phrase “owned, serviced, or maintained” as used in the definition of facility is not intended to allow or sugg est segmenting portions of a system for the purpose of avoiding General Provisions (40 CFR 98.2 - 98.4), the reporting requirements that are applicable to all owners and operators associated with the facility. See Subpart DD Final Preamble, Section III, “Summary of Comments and Responses” for additional discussion of the final Definition of a Facility language.

Comment Summary 1.2-m: Commenter 0119 suggested t hat “EPA clarify the applicability of the rule to clarify that ‘electric power syst ems’ are owned by electric distribution companies and that these companies would be responsible for reporting any emissions.”November 8, 2010 Subpart DD—Response to Comment Document 9 Response 1.2-m: Per the General Provisions (40 CFR 98.2 - 98.4), the reporting requirements are applicable to all owners and operators of a facility, an d it is up to the owners and operators to designate a representative who will be responsi ble for certifying, signing, and submitting GHG reports to EPA. Furthermore, the owners of electric power system facilities are not limited to electric distribution companies; there are myriad types of entities that can own an electric power system facility. For more information on the types of entities that can be considered owners of electric power syst em facilities as well as which entities are responsible for reporting emissions, please see Subpart DD Final Preamble, Section III, “Summary of Comments and Responses.”

Comment Summary 1.2-n: Commenter 0120 suggested that the sy stem boundary in the final rule include all equipment operated by a single owner , regardless of whether or not the equipment is electrically linked through lines. The commenter noted that it currently has a single unified information collection protocol for the three “affiliates” it operates even though the “affiliates” are not linked through lines. The commenter stated that having to report emi ssions for the three affiliates separately would be an incremental burden since it would necessitate establishing multiple information collection systems.

Response 1.2-n: EPA acknowledges that in cert ain cases, it may be more convenient for affiliate companies to compile a single set of emission estimates and submit one report to EPA through a common owner. However, EPA examined a variety of r eporting levels for Subp art DD and concluded that the facility definition must be based on a physical colle ction of equipment to avoid issues associated with corporate-level reporting (or reporting based solely on a common ownership). These issues include the complexity of corporate ownership structures, the potential for double-counting emissions when there are multiple owners associated with an electric power system, and the challenges of tracking and monitoring emissions for a facility over time if there are changes in the ownership. For more information on the EPA’s examination of options for defining a facilit y for Subpart DD, see Subpart DD Final Preamble, Section III, “Summary of Comments and Responses” as well as the TSD, located here: www.epa.gov/climatechange/emis sins/ghgrulemaking.html

Comment Summary 1.2-o: Commenter 0133 argued that the joint obligation for reporting between owners and operators in §98.3 will be confusing in practice if applied to Subpart DD since owners and operates are not equally capable of measuring emissions or defining clear facility boundaries for the source category. The commenter stated that in order to avoid confusion and inaccurate emission reports, EPA needs to clarify “how this joint repo rting obligation would be structured.”

Response 1.2-o: The details of the joint reporting obligat ion between owners and operators are provided in the General Provisions (40 CFR 98.2 - 98.4). Ac cording to the General Provisions, the reporting requirements are applicable to all owners and operator s of a facility. But it is up to the owners and operators to designate a representative who will be responsible for certifying, signing, and submitting GHG reports to EPA. Therefore, the owners and oper ators of a facility can coordinate in measuring emissions and confirming the facility boundary if t hey are indeed “not equally capable of measuring emissions from a facility or defining clear facility boundaries.”

Comment Summary 1.2-p: Commenter 0088 was supportive of how EPA’s proposed definition of a facility recognized the physical interconnection and operational interdependence of system components, but was concerned about EPA’s assertion that “regardless of the role that operation or ownership plays in the final source category definition, the obligation to report will apply to both owners and operators.” The commenter thought this could lead to double-countin g of emissions. Commenter TRANS-DC-04 (2010) also expressed concern that holding both owners and operators of electric power systems responsible for

SF 6 may lead to double-counting of emissions.”

Response 1.2-p: The details of the joint reporting obligat ion between owners and operators are provided in the General Provisions (40 CFR 98.2 - 98.4). Ac cording to the General Provisions, the reporting requirements are applicable to all owners and operator s of a facility. But it is up to the owners and operators to designate a representative who will be responsible for certifying, signing, and submitting GHG reports to EPA. Since the designated representative is selected by an agreement binding on all theNovember 8, 2010 Subpart DD—Response to Comment Document 10 owners and operators of the facility, then the des ignated representative should be fully capable of ensuring that the facility emission s were measured properly and that emissions were not double-counted.

Comment Summary 1.2-q: Commenter TRANS-DC-04 (2010) thought that in certain cases, the myriad of ownership and operational relationships for elec tric power systems across regions and companies might not be “amenable” to reporting at the system-wide level.

Response 1.2-q: The mass-balance monitoring methods for subpart DD, which are based on the IPCC Tier 3 method of measuring emissions from electric power systems, require monitoring of emissions for an entire electric power system and are not conducive for measuring emissions for a specific piece of equipment or single substation within a larger elec tric power system. Given the myriad ownership and operational relationships in the el ectric power system industry, EPA acknowledges that coordination might be required among distinct owners and operators in order to ensure that emissions are measured accurately and reliably. For more information on EPA’ s rationale for system-wide reporting, please see

the TSD located here: www.epa.gov/climatechange/em issins/ghgrulemaking.html



### 1.3 All-in Provision and Boundary between Electricity Generation Facility and T&D Facility

— Track 1

Relevant Bin Number 4.1.1.1

Comment Summary 1.3-a: Twelve commenters (0407, 0455, 0584, 0597, 0618, 0624, 0661, 0725, 1021, 1080, 1566, 1741) requested clarification and/or expressed concern ov er the general reporting requirement located in §98.2(a)(2) that any subpart D electric generating unit facility above the reporting threshold would be required to report emissions for all source categories that are located at the facility, including SF 6 emissions under subpart DD.

Five commenters (0407, 0584, 1021, 1080, 1741) stated that including SF 6 emissions from electric equipment in subpart D facility emission reports c ould lead to double-counting of emissions since facilities in subpart DD might encompass electrical eq uipment that is located at a subpart D facility.

Response 1.3-a: Based on the concerns expressed by co mmenters, EPA has made alterations to the Reporting Threshold language in §98.301 so that a subpart D electric generating unit facility would only be required to report emissions associated with the Electrical Transmission and Distribution Equipment Use source category if the amount of SF 6 and PFC-insulated equipment within the subpart D facility exceeds the reporting threshold for subpart DD, which is 17,820 lbs of SF 6 and PFC nameplate capacity. EPA expects that in general, the subpart D facility will not independently meet this threshold and thus is unlikely to incur the reporting obligation and the risk of double-counting emissions. For more information, please see the Subpart DD Final Preamble, Section III, “Su mmary of Comments and Respon ses.”

Comment Summary 1.3-b: Seven commenters (0407, 0455, 0597, 0624, 1021, 1080, 1741) argued that it would be very difficult to accurately measure SF 6 emissions from only electrical equipment at a electric generating unit that is part of an integrated utility since the SF 6 stocks that services this equipment are often stored and tracked in a central storage area fo r the integrated utility. In this scenario, the SF 6 stored at the central storage areas would be used to serv ice equipment throughout the integrated transmission and distribution system, not just a single electric gene rating unit. These commenters noted that the massbalance is only an efficient and effective method for m easuring emissions at the system-level and not for a single physical location such as an electric generating unit facility.

Response 1.3-b: As explained in section §98.301

- Reporting Threshold of the final rule

, Subpart DD emissions occurring at an electric generating unit (EGU) facility woul d only need to be reported if the nameplate capacity of the SF 6 and PFC insulated equipment at the facility exceeds the subpart DD threshold of 17,820 pounds of nameplate capacity. EPA does not expect that many EGU facilities will

have this much SF 6 and PFC-insulated equipment. If an EGU does exceed the subpart DD threshold,November 8, 2010 Subpart DD—Response to Comment Document 11 then conducting mass-balance emissions monitoring at th is facility, as required by subpart DD, should be a similar process and similar burden as conducting the mass-balance monitoring methods for non-EGU facilities. For more information, please see the Subpart DD Final Pr eamble, Section III, “Summary of Comments and Responses.”

Comment Summary 1.3-c: Commenters 0624, 1021, and 1741 specific ally requested clarification on reporting responsibilities be tween different owners in certain cases where subs tations are “co-located” with electricity generation facilities. As explained by commenter 0624, “If co-located substations and other supporting infrastructure included SF 6 -containing equipment owned by the same electric generating facility owner, then it appears that t he proposed rule would require any SF 6 emissions to be included in the reporting by the generating facility owner. However, if the substation and other supporting infrastructure is owned by another entity (i.e., not t he owner of the generating facility), it is unclear who would be responsible for reporting any SF 6 emissions emanating from the co-located substations and other supporting structure, the owner of the generating facility or the owner of the SF 6 -containing equipment.”

Response 1.3-c: According to the General Provisions (40 CFR 98.2 - 98.4), the reporting requirements are applicable to all owners and operators of a facilit y (although the actual emission report is certified, signed, and submitted to EPA by t he representative designated by the owners and operators of the facility). If the SF 6 insulated equipment co-located at an electric ity generating unit is part of a subpart DD electric power system facility, then the owners and operators of the electric power system facility would report emissions for that equipment. In the case of an electricity generating unit that must report subpart

DD emissions for SF 6 -insulated equipment co-located at the facili ty (note that this would only be required if the EGU had more than 17,820 pounds of SF 6 and PFC insulating equipment located within its facility), the emissions report for the EGU facility would need to include emissions for any SF 6 insulated equipment located within the facility, regardless of whether the owners and operat ors of the EGU are the same as the owners and operators of the SF 6 -insulated equipment. See subpart A §98.2-98.4 and subpart D §98.301 for more information.

Comment Summary 1.3-d: Commenters 0624, 0479, and 0547 sought clarification on whether a Subpart DD facility that falls above the threshold woul d be required to report emissions from a source category that is located at the same site as the Subpart DD facility. Commenters 0624 and 0479 asked whether a Subpart DD facility would be required to re port emissions from combustion sources on site if under the same ownership control and, if so, whethe r there would be any emissions or heat input size threshold for determining applicability. Commenter s 0624, 0479, and 0547 recommended that portable equipment or generating units designated as emergency generators should be exempted from Subpart DD facility emission reports.

Response 1.3-d: The facility definition for subpart DD (see 40 CFR §98.307) is unique from the definition of a facility used in other subparts (see General Provis ions, 40 CFR 98.2 - 98.4) in that the electric power system facility only encompasses electric tran smission and distribution equipment and servicing inventory insulated with or containing SF 6 or PFCs. The electric power system facility does not include co-located emission sources. However, per Genera l Provisions 40 CFR 98.2 - 98.4, the facility must report for all applicable source categories listed in Table A—3 and Table A—4 of subpart A that are triggered by the facility..



### 1.4 All-in Provision and Boundary between Electricity Generation Facility and T&D Facility

— Track 2

Relevant Bin Number 4.1.1.1

Comment Summary 1.4-a: Seven commenters (0088, 0096, 00 97, 0126, 0127, 0133, TRANS-DC-04 (2010)) requested clarificat ion and/or expressed concern over the general reporting requirement located in § 98.2(a)(2) that any subpart D electric generatin g unit facility above the reporting threshold would beNovember 8, 2010 Subpart DD—Response to Comment Document 12 required to report emissions for all source categori es that are located at the facility, including SF 6 emissions under Subpart DD. The co mmenters argued that this would le ad to ambiguities in reporting responsibilities and impose an unreasonable burden wh ile only capturing a relatively small amount of

emissions.

Commenters 0096 and 0126 requested a de minimis exception for SF 6 -insulated equipment for electric generating unit emission reports. Commenter 0096 stated “in the case of power plants, that a de minimis exemption from SF 6 reporting should be explicitly allowed fo r the power plant facility since the vast majority of SF 6 is typically used in T&O applications that will be reported on by LOCs as part of their system-wide reporting of SF 6 . As an alternative, simplified engineering estimation techniques should be

allowed at facilities with de minimis SF 6 emissions. Overall, in the context of the magnitude of CO 2 emissions from power plants, SF 6 emissions are negligible. As an example, we estimate that SF 6 emissions at the largest fossil plant operated by [the commenter] that SF 6 emissions were less than 0.1% of the facility's total GHG emissions in 2008.” Commenter 0126 recommended either a complete de minimis exception or a separate threshold of 17,820 lbs of SF 6 nameplate capacity at the electric generating facility to trigger SF 6 emissions reporting.

Commenter 0097 cited the complexity of electric generation and electricity transmission ownership structures as a major impediment to accounting for SF 6 emissions from switchyards at electricity generation facilities and recommends the following: “1. Require transmission and distribution entities to report SF 6 emissions for the equipment that it owns within the switchyard, and 2. Require electric generation facility entities to report SF 6 emissions for the equipment that it owns within the switchyard. However, EPA should identify SF 6 emissions as de minimis compared to stationary combustion greenhouse gas emissions on site, and permit the use of alternative calculation methodologies (such as engineering calculations) to estimate the emissions of SF 6 containing equipment rather than the mass balance methodology.”

Commenter 0098 supported the general recommendations from commenter 0097, but offered slightly different recommendations: “1. Require transmission/ distribution and electric generating entities to separately report SF 6 emissions for the equipment that they own within the switchyard, and 2. Allow electric generation facilit y entities to report SF 6 emissions for the equipment that it owns within the switchyard/contiguous power block with utilization of alternative calculation methodologies (such as engineering calculations) to estimate the emissions of SF 6 containing equipment rather than the mass balance methodology. EPA should identify SF 6 emissions as de minimis compared to stationary combustion greenhouse gas emissions on-site. (A lso, keep the 17,820 pound minimum by reporting entity.) Reporters should be allowed the option to repo rt per mass balance where the incoming inventory and the returning bottles are weight certified by the s uppliers/recyclers. Suppliers of equipment or bottles must supply certified gas weight to the purchaser 3. Electric generation facilities and T&D entities that are owned by the same parent company but operated as distinct companies should be allowed to report at the distinct company level.”

Response 1.4-a: EPA agrees that reporti ng subpart DD emis sions as part of subpa rt D facility emission reports would, in most cases, only capture emissions that are minor and/or already captured as part of a subpart DD facility emission report. However, in some cases there might be considerable SF 6 emissions that occur at an EGU facility that would not be accounted for if subpar t D facilities were not required to report any subpart DD emissions that occur. To ba lance the risk of unaccounted emissions with the burden associated with reporting s ubpart DD emissions for distinct EG U facilities, EPA is only requiring that subpart D facilities include subpart DD emission s in their emission reports if the total nameplate capacity of SF 6 and PFC containing equipment located within that facility exceeds 17,820 pounds.

In terms of the reporting responsibility for SF 6 -insulated equipment located at an EGU facility, the General Provisions (40 CFR 98.2 - 98.4) dictate that the reporting requirements are applicable to all owners and operators of a facility (although the actual emission report is certified, signed, and submitted to EPA by the representative desi gnated by the owners and operator s of the facility). If the SF 6 insulated equipment co-located at an electricity generating unit is part of a subpart DD electric power system facility, then the owners and operators of the electric power system fa cility would report emissions for that equipment. In the case of an electricity generating uni t that must report subpart DD emissions for SF 6 -November 8, 2010 Subpart DD—Response to Comment Document 13 insulated equipment co-located at the facility (i.e., an EGU with more than 17,820 pounds of SF 6 and PFC insulating equipment located within its facility) , the emissions report for the EGU facility would need to include emissions for any SF 6 insulated equipment located within the facility, regardless of whether the owners and operators of the EGU are the sa me as the owners and operators of the SF 6 -insulated equipment. See subpart A §98.2-98.4 and subpart D §98.301 for more information.



### 1.5 Installation of Electrical Equipment at Electric Power Systems

— Track 2

Relevant Bin Number 4.1.3

Comment Summary 1.5-a: Five commenters (0081, 0094, 0096, 0097, 0125) recommended that a Subpart DD facility should not be responsible for em issions from new equipment being installed at the Subpart DD facility until the equipment has been transfe rred to the equipment user by the electrical equipment manufacturer. Commenter 0081 recomme nded that the point of transfer be when the equipment has been “received, insp ected, and accepted by the utility and the title has been transferred.” Commenter 0096 stated that “regarding GIS equipm ent assembled on-site by a manufacturer, [the commenter] requests that the manufacturer be responsible for any SF 6 reporting up until the point in time that the end user takes final acceptance of the equipm ent (i.e., at the point in time when the end user confirms that all contract agreements have been me t and takes ''final delivery" of the completed GIS equipment). For shipped, pre-assembled GIS equipment, the end user should take responsibility for SF 6 reporting at the point in time at which the title for the equipment transfers to the end user.” Commenter 0125 recommends the point of transfer be defined as “t he point when the equipment warranty is activated or when the title is transferred or another such point described in the contract between the customer and the equipment manufacturer or third party.”

Response 1.5-a: EPA has confirmed that some equipment is not installed by the purchaser of the equipment. For example gas insulated substations ar e typically assembled by the manufacturer onsite and it can take several months to complete assembly, inspection, and final acceptance and commissioning. For this reason, gas accounting is best done by the entity t hat is commissioning the equipment and handling the gas that will be inst alled into the equipment.EPA agrees with the commenters that the Subpart DD facilities should not be responsible for reporting emissions from new equipment being installed (or from the installation proce ss itself) at the Subpart DD facility until the title to the equipment has been transferred to the equipment us er by the electrical equipment manufacturer. EPA has included the following langu age in Subpart DD §98.302

— GHGs to report: “For acquisitions of equipment containing or insulated with SF 6 or PFCs, you must report emissions from the equipment after the title to the equipment is transferred to the el ectric power transmission or distribution entity.”



### 1.6 De Minimis Exemption for Sealed-pressure Equipment

— Track 1

Relevant Bin Number 4.1.4

Comment Summary 1.6-a: Eight commenters (0407, 0479, 054 7, 0624, 1021, 1080, 1569, 1741) requested clarification on whether there is a de mi nimis exception for hermet ically sealed-pressure equipment that is not intended to be serviced during its lifetime. Seven commenters (0407, 0479, 0547, 0624, 1021, 1080, 1741) specifically argued for a de minimis exception in the context of the Data Reporting Requirement Nameplate capacity of equipment containing SF 6 . Commenters 0407 and 1741 noted that a de minimis exception only for the to tal system-wide nameplate capacity reporting requirement would not exclude hermetically sealed-p ressure equipment from being captured in the massbalance emissions monitoring method since the system -wide nameplate capacity is not an input to the mass-balance equation.

Commenter 1569 argued for a general de minimis ex ception throughout Subpart DD. In addition to arguing for a de minimis exception for hermetically sealed-pressure equipment, commenter 1569 also argued that any equipment with less than 15 pounds of nameplate capacity should be exempted from all Subpart DD inventory and emissi on reporting requirements.

Commenter 1741 suggested that if there is no de mi nimis exception for hermetically sealed-pressure equipment, there should be an option for facilities to esti mate the internal volume for a typical piece ofNovember 8, 2010 Subpart DD—Response to Comment Document 14 sealed-pressure equipment within different equipmen t categories, and then use the internal volumes to assume a maximum nameplate capacity amount for equipment within each category.

Response 1.6-a: EPA concurs that the burden associated with performing a bottom-up assessment to determine the nameplate capacity of each piece of s ealed-pressure equipment within an electric power transmission and distribution facility is high when compared to the benefits of performing such an assessment. As a result, EPA has excluded sealed-pressure equipm ent from the data reporting requirement for total facility-wide nameplate capacity existing as of the beginning of the year. However, the potential for emissions from sealed-pressure equipment due to catastrophic events or equipment disposal still makes it important to document emissions from sealed -pressure equipmen t, especially for facilities that specialize in electricit y distribution. EPA has clarified that SF 6 arriving inside newly acquired sealed-pressure equipment must still be included as part of the SF 6 acquisitions input of the massbalance equation, and sealed-pressure equipment that is new or retired must still be considered as a change to the nameplate capacity in the mass-balance equation.

For the purpose of determining which equipment mu st be included in the overall nameplate capacity threshold, EPA considers it more ap propriate to distinguish equipment based on whether it is hermetically sealed rather than whether it is above or below a specified nameplate capacity threshold (such as 15 pounds as suggested by commenter 1569). This is because it can be burdensome to obtain the exact nameplate capacity of relatively small distribution equip ment whereas it is generally straightforward to determine whether the equipment is sealed-pressure equipment. Distinguishing equipment based on whether it is sealed-pressure or closed-pressure re duces the potential error associated with determining whether a piece of equipment should be included in the system-wide nameplate capacity estimate. Sealed pressure equipment generally contains anywhere from a few ounces to 15 pounds of SF 6

.



### 1.7 De Minimis Exemption for Sealed-pressure Equipment

— Track 2

Relevant Bin Number 4.1.4

Comment Summary 1.7-a: Ten commenters (0075, 0083, 0086, 0096, 0097, 0098, 0109, 0120, 0126, 0133) recommended a de minimis exception for hermetic ally sealed-pressure equipment in the Subpart DD source category. Commenters 0075 and 0083 noted t hat emissions from this type of equipment are very low—except in the case of catastrophic failu re—and that the equipment does not typically require servicing or recharging of SF 6 over its operational lifetime.

Commenter 0075 asserted that “including this equipment in the definition of a ‘facility’ simply complicates reporting and verification with essentially no added benefit or value to the reporting rule or the compilation of total SF 6 emissions.”

Since hermetically sealed-pressure equipment is non-serviceable, Commenter 0083 recommended excluding the equipment by using the following language in §98.302—GHGs to Report: “You must report

total SF 6 and PFC emissions (including emissions from fugi tive equipment leaks, installation, servicing, equipment decommissioning and disposal, and from storage cylinders) from the following types of

serviceable equipment: (a) Gas-insulated substations (b ) Circuit breakers (c) Switchgear (d) Gasinsulated lines (e) Electrical transformers.”

Commenter 0086 recommended three options for redu cing the burden associated with inventorying hermetically sealed-pressure equipment for the §98.302 Data Reporting Requirement for system-wide nameplate capacity of equipment containing SF 6 . The three recommended options provided by commenter 0086 were as follows: “(1) establish a de-minimus capacity for specific equipment below which the equipment would be exempt from the invent ory requirements, (2) clarify that, after an initial inventory, smaller pieces of equipment do not need to be included in annual inventories, or (3) for smaller equipment, such as switches, allow affected entitie s the option of estimating the volume of small equipment and assuming a maximum nameplate amount of SF 6 for each one.”

Commenters 0094 and 0096 recommended excluding “sma ll distribution equipment, containing less than 35 pounds of SF 6 ” from reporting. Commenter 0094 did not think that tracking small equipment isNovember 8, 2010 Subpart DD—Response to Comment Document 15 efficient, and notes that while approximately 43% of its circuit breakers have less than 35 lbs of SF 6 , distribution equipment accounts for only 2% of its total SF 6 emissions.

Commenter 0120 recommended a de minimis exception for equipment containing less than 15 pounds, or a complete reporting exception for all distribution equipment. Commenter 0133 recommended a de minimis exception for sealed-pressure equipment in the context of the §98.302 Data Reporting Requirement for system-wide nameplate capacity of equipment containing SF 6 , and noted that this would not exclude hermetically sealed-pr essure equipment from being captured in the mass-balance emissions monitoring method since the system-wide nameplate capacity is not an input to the mass-balance equation.

Response 1.7-a: Comments regarding the inclusion of sealed-pressure equipment in reporting requirements that were received a fter EPA’s second Subpart DD proposal in 2010 were very similar to the comments received in EPA’s first Subpart DD pro posal from 2009. Please see Response 1.6-a or Subpart DD Final Preamble, Section III, “Summary of Comments and Re sponses” for EPA’ s response.

Comment Summary 1.7-b: Commenter 0096 thought that tracking of SF 6 from hermetically sealedpressure equipment “would be better performed by upstream reporting of SF 6 by original equipment manufacturers (OEMs) where it would be much easier for OEMs to report a complete picture of small sealed equipment sold in the United States.” Commenter 0097 supports this notion by stating that hermetically sealed-pressure equipment is a case where “upstream regulation of SF 6 is more effective, specifically at the original equipment manufacturer.”

Response 1.7-b: Under Subpart SS

— Electrical Equipment Manufacture and Refurbishment and Manufacturing of Electrical Components, OEMs must monitor emissions that occur from the manufacture of sealed-pressure as well as include sealed-pres sure equipment in their data reporting requirements. However, this does not render the inclusion of sealed-pressure equipment in subpart DD reporting requirements unnecessary. The potential for emissi ons from sealed-pressure equipment due to catastrophic events or equipment disposal still makes it important for electrical equipment users to document emissions from sealed-pressure equipment, es pecially for Subpart DD facilities that are highly involved in electricity distribution. While emission s from sealed-pressure equipment must be monitored by Subpart DD facilities, EPA has removed the requi rement for including seal ed-pressure equipment as part of the data reporting requirement for total fa cility-wide nameplate capacity existing as of the beginning of the year.

Comment Summary 1.7-c: Commenter 0109 provided separate recommendations for three different types of sealed pressure equipment: transmission, distribution

— SF 6 gas insulated, and distribution

— SF 6 gas insulated/interrupting. The commenter thought it was reasonable for sealed-pressure transmission equipment to be included in reporting since the typical mass of SF 6 in each piece is between 5 and 18 pounds, and “there are facilities with a good quantity of devices (typically identified as circuit switchers) yielding significant nameplate capacity.” The commen ter stated that the “inter rupting type” used in distribution applications has not been available in the U.S. for many years, and should only be included in reporting if this type of equipment represents more than 0.5% of total nameplate capacity. Lastly, the commenter stated that reporting on “distribution equipment with SF 6 as an insulating gas at very low pressure (typically less than 1 atmosphere)” would be a significant issue since this equipment holds such

small amounts of SF 6 and the “administrative burden of estima ting the nameplate capacity and tracking this distributed distribution equipment is extremely high.”

Response 1.7-c: EPA appreciates the commenter’s detailed deli neation of the various types of sealedpressure equipment as well as the commenter’s thoughts on the appropriateness of including each type of sealed-pressure equipment in the Subpart DD report ing requirements. Due to the need for simplicity in knowing when to include a piece of equipment in t he reporting requirements as well as the potential for emissions from sealed-pressure e quipment used for electricity distribution, EPA is requiring that SF 6 arriving inside all types of newly acquired sealed-pres sure equipment must still be considered as part of

the SF 6 acquisitions input of the mass-balance equation, and all types of sealed-pressure equipment that is new or retired must be considered as a change to the nameplate capacity in the mass-balance equation. But in an effort to reduce the overall burden for affected enti ties, EPA has excluded all types ofNovember 8, 2010 Subpart DD—Response to Comment Document 16 sealed-pressure equipment from the data reporting requirement for tota l facility-wide nameplate capacity existing as of the beginning of the year.



### 1.8 Other (Definition of Source Category)

Relevant Bin Number: 4.1

Track 1

Comment Summary 1.8-a: Two commenters (0612, 1741) request ed clarification on exactly what equipment is included in the Subpart DD source category. Commenter 0612 specifically requested

clarification on whether scientific research equipment that contains SF 6 would be included in the electrical equipment regulated in Subpart DD. Commenter 1741 sou ght clarification on whether processes that use

SF 6 as a testing gas would be regulated in Subpart DD.

Response 1.8-a: The Subpart DD source category includes all SF 6 and PFC insulated equipment and servicing inventory that is used within an electric power system. For a definition of the electric power system facility, see Subpart DD §98.307-Definitions. If the SF 6 -insulated equipment and servicing inventory discussed by the commenters are used with in an electric power system, then the equipment and servicing inventory would be covered under Subp art DD even if the equipment is not listed in §98.307-Definition of the Source Category.

The subpart A General Provisions (40 CFR 98.2 - 98 .4) do exclude research and development activities from being covered by the source categories provid ed in the rule. Research and development activities are defined in subpart A as those activities conduct ed in process units or at laboratory bench-scale settings whose purpose is to conduct research and development for new processes, technologies, or products and whose purpose is not for the manufacture of products for commercial sale, except in a de

minimis manner.

Track 2

Comment Summary 1.8-b: Commenter 0109 explained that the use of SF 6 in transformers is not widespread due to largely unsuccessful experimental trials using SF 6 insulated transformers. The commenter recommended that due to the high administr ative burden for tracking and reporting this nonswitchgear equipment, EPA establish “a minimum thresh old on quantity to trigger reporting (i.e. 2 or more transformers).”

Response 1.8-b 

### : Although the use of SF 6 in electric power transformers might not be as widespread as

SF 6 use in other types of electrical eq uipment, there is still the potential for SF 6 emissions from SF 6 - insulated transformers that are actively in use in the United States today. Furthermore, SF 6 -insulated transformers are marketed to electrical equipment user s in the United States, and it is unclear how much of this equipment will be utilized in the future. Due to the potential for emissions from electric power transformers currently in use as well as the potential for an increase in the use of these transformers, EPA is not providing reporting exceptions for SF 6 -insulated transformers in the Subpart DD source
category.November 8, 2010 Subpart DD—Response to Comment Document 17 

### 2. Reporting Threshold

Relevant Bin Number 4.2

Track 1

Comment Summary 2-a: Commenter 0413 questioned why EPA “appears to be requiring reporting of very minor SF 6 gas emissions when nameplate capacity ex ceeds 17,820 pounds, while a larger emission from electrical equipment with lower SF 6 nameplate capacity equipment will be unreported.”

Response 2-a: The 17,820 pound threshold was developed as a nameplate-based approximate of the 25,000 metric tons of CO 2 equivalent threshold. The nameplate capacity equivalent to a 25,000 metric

ton of CO 2 equivalent was estimated using dat a reported by Partners in EPA’s SF 6 Emission Reduction Partnership for Electric Power Systems. EPA’s threshold analysis show ed that the 17,820 pound nameplate capacity threshold would cover a small percent age of the total electric utilities in the United States (approximately 10%) while covering a large percentage of annual SF 6 emissions from electric power systems in the United States (approximately 83 percent). A nameplate capacity-based threshold was chosen because it allows pot ential sources to determine whether they are above or below the threshold much quicker than if the sources had to m easuring emissions for this determination, thereby reducing the burden for the industry as a whole. While it is possi ble that a facility with less than 17,820 pounds of nameplate capacity has greater SF 6 emissions than a facility with greater than 17,820 pounds of nameplate capacity, EPA’s analysis concluded that nameplate capacity is strongly correlated with SF 6 emissions, more so than other parameters like high-v oltage transmission miles. For more information on EPA’s threshold analysis, please see the TSD located here: www.epa.gov/climatechange/emis sins/ghgrulemaking.html

Comment Summary 2-b: Commenters 0551, 0479, and 0547 agreed with the 17,820 pounds of SF 6 nameplate capacity threshold proposed by EPA for subpart DD. Comment ers 0479 and 0547 noted that it allows potential sources to quickly determine whether they are covered.

Response 2-b: EPA appreciates the comment ers’ support of the r eporting threshold.



### 2.1 Threshold Analysis—Track 1

Relevant Bin Number 4.2.1

Comment Summary 2.1-a: Commenter 0413 stated that “no peer review scientific evidence exists to link nameplate capacity with actual SF 6 gas emissions or leakage.” The commenter disagreed with EPA’s method for calculating the 17,280 pounds of SF 6 nameplate capacity threshold for subpart DD. Specifically, the commenter co nsidered the use of 1999 weig hted utility leak rates of SF 6 to be inaccurate since utilities currently emit SF 6 at lower rates than they did in 1999. The commenter thought a “more rational assumption would be leakage rates well below 1% annually.”

Response 2.1-a: The relationship between nameplate capacity (how much SF 6 equipment contains when full) and the amount of SF 6 emissions that occur from equipment is not perfect; other factors such as equipment age and geographic location can hav e an impact on emission s. Nonetheless, EPA’s analysis showed that nameplate capacity is a strong correlate to SF 6 emissions and stronger than other potential correlates such as high-voltage transmissio n miles. EPA used 1999 weighted leak rates from 42

Partners of EPA’s SF 6 Emission Reduction Partnership for Elec tric Power Systems (1999 was the first year that the Partnership received data) because it is assumed that utilities who have not participated in the Partnership activities have not achieved the emission reductions from 1999-2008 that have been achieved by Partners, and it was essential that a non-emissions bas ed threshold be conservative enough to ensure that sources emitting more than 25,000 metric tons of CO 2 equivalent were covered by the

threshold. EPA does not consider the leakage rates of “well below 1% annually” to be a rational assumption since the average Partnership leak rate s have never been below 4% since the inception of the Partnership.November 8, 2010 Subpart DD—Response to Comment Document 18 

### 2.2 Other (Reporting Threshold)

Relevant Bin Number 4.2.2

Track 1

Comment Summary 2.2-a: Commenter 0547 stated that “EPA s hould recognize that nameplate capacity inventory of in-service po wer systems is achievable for distinct facilities such as substation sites but would be virtually impossible for most power sy stems in the transmission and distribution lines system.”

Response 2.2-a: EPA is assuming the commenter is stating t hat it would be virtually impossible for an entity that transmits and distributes electricity to determine the entire system-wide nameplate capacity of all equipment within its electric transmission and di stribution system. Contrary to the opinion of the commenter, many electric power entities in EPA’s SF 6 Emission Reduction Partnership for Electric Power Systems have provided system-wide namepl ate capacity estimates to EPA for all SF 6 -insulated equipment within the system except sealed-pressu re equipment used for electricity distribution.

Comment Summary 2.2-b: Commenter 1569 remarked that “There are some pieces of electrical equipment that do not list the capacity of SF 6 in pounds on the nameplate, but rather give the pressure of

SF 6 in the system in pounds per squa re inch (psig). It is our recomm endation that the EPA establish a set protocol to use to calculate the weight of SF 6 in the equipment based on a set pressure and temperature when the weight is not explic itly listed on the nameplate.”

Response 2.2-b: EPA understands that in some cases the capacity of a piece of equipment is not clearly affixed to the equipment itself. In these cases, EPA re commends contacting the or iginal manufacturer of the equipment, who should be able to provide the nameplate capacity of the equipment.

Track 2

Comment Summary 2.2-c: Commenter 0126 stated that “EPA is proposing to add electric power systems to the list of "all-in" sour ce categories in 40 CFR 98.2(a)(1). The reason for EPA's proposal is that electric power systems have a production capaci ty or gas consumption threshold rather than a CO 2 e emission threshold. Sources in the "a ll-in" category must report emissions from all source categories for which calculation methodologies are provided in any s ubpart of the rule.” The commenter questions why EPA would abandon the concept of a CO 2 e emission threshold for SF 6 and PFC that existed in 2009 (for the initial proposal) and instead “consider in its current proposal a production capacity or a gas consumption threshold.”

Response 2.2-c 

### : The 17,820 pound nameplate capacity thre shold for Subpart DD proposed in 2010 was the same threshold as proposed in 2009. The reason EPA is listing Subpa rt DD as an “all-in” category is because the threshold for Subpart DD is capacity-based rather than a CO 2 e emission threshold. EPA notes that if a facility contains either an “all-in” source category listed in §98.2(a)(1) or a source category listed in §98.2(a)(2) that triggers the 25,000 metric ton of CO 2 e threshold, the facility must report for all applicable source categories listed in Table A—3 and Table A—4 of subpart A that are triggered by the facility. But EPA also notes that an electric power system facility (as specifically defined in subpart DD) only encompasses electric transmission and distributi on equipment and servicing inventory insulated with or containing SF 6 or PFCs; as such, the electric power system facility boundaries do not extend to emission sources other than the electric transmission and distribution equipment and servicing inventory.November 8, 2010 Subpart DD—Response to Comment Document 19 

### 3. GHGs to Report

— Track 1

Relevant Bin Number 4.3

Comment Summary 3-a: Commenter 0661 asked “EPA to clar ify whether PFCs are based on nameplates or whether mass balances can be used to assess PFC emissions.”

Response 3-a: PFC emissions must be measured in the exact same manner as SF 6 emissions using the mass balance monitoring methods provided in §98.302.

Comment Summary 3-b: Commenter 1569 noted that sometimes SF 6 is emitted or destroyed due to a lightning strike or fire, and recommende d that EPA exempt emissions of SF 6 from a force majeure event, or at least establish a separate reporting section for those cases.

Response 3-b: Emissions of SF 6 that occur from a force majeure event are not exempted from the Subpart DD reporting requirements. The mass-balan ce monitoring methods required for Subpart DD are designed for a system-wide emis sions measurement and are not conducive for use in measuring emissions occurring from specific events affecting specific pieces of equipment. The commenter should note that the purpose of the Mandatory Reporting Rule is to collect emissions data; the rule does not penalize facilities based on the quantity of their emissions.November 8, 2010 Subpart DD—Response to Comment Document 20 

### 4. Detailed GHG Emission Calculation Procedures/Equations

Relevant Bin Number 4.4

Track 1

Comment Summary 4-a: Commenter 0096 requested that EPA allow for flexibility for “higher quality, direct measurement data when available” in pl ace of the proposed mass-balance method. The commenter stated that the objective of EPA’s proposed regulation can be “best accomplished by looking

at the amount of SF 6 added to equipment which would equate to loss of SF 6 as emissions. For example, a company may have the actual weight of SF 6 added to equipment during the year based on actual SF 6 use which is a far better measure that simply look ing at a mass balance for that year. The use of SF 6 may be determined by the weight difference between the amount SF 6 purchased (full bottle) and the remaining amount of SF 6 in an empty bottle of SF 6 . In other cases a company may actually weigh the

amount of SF 6 gas added to each piece of equipment.”

Response 4-a: The monitoring methods required by Subpart DD to measure SF 6 emissions are based on the IPCC Tier 3 method pr ovided in the peer-reviewed 2006 IPCC Guidelines for National

Greenhouse Gas Inventories. The Tier 3 mass balance method is considered by IPCC to be the most accurate method for measuring SF 6 emissions from electric power sy stems. Observing the amount of SF 6 that is charged into leaky equipment might be a useful tool for estimating emissions from a specific piece of equipment, but this direct measurement complete ly overlooks potential em issions that can occur elsewhere within an electric power system. For exampl e, if a circuit breaker is decommissioned from the electric power system and the SF 6 within the breakers is vented into the atmosphere, the direct measurement method described by t he commenter would not capture t hese emissions. Another example of emissions that would not be captured using the commenter’s method would be emissions that occur from a faulty cylinder valve.

Track 2

Comment Summary 4-b: Commenter 0096 argued that the mass-balance formula should not include annual nameplate capacity changes since these changes have “no bearing on the amount of SF 6 used during the year.” The commenter st ated that instead of using the a nnual change in nameplate capacity, “a single system capacity value, such as the st art of the year capacity, should be used in the SF 6 leak

rate formula.”

Response 4-b: The annual nameplate capacity change is essential to include in the mass-balance monitoring methods for Subpart DD in order to measure emissions accurately. The mass-balance method works by systematic ally accounting for all SF 6 uses within the system. The amount of SF 6 that cannot be accounted for by the electric power system is equal to the emissions during the year since the

unaccounted for SF 6 was not recorded as being used in a non-emissions context (such as the SF 6 being sent offsite for recycling or added to the storage in ventory). Assessing the changes in nameplate capacity plays an integral role in accounting for SF 6 gas uses. For example, if new equipment is purchased during the year and the equipment is filled with SF 6 stocks from the user’s storag e inventory, then the nameplate capacity of the new equipment must be used to reconcile the amount of SF 6 that was withdrawn from inventory, otherwise the amount of gas withdrawn from the storage inventory would register as an

emission.November 8, 2010 Subpart DD—Response to Comment Document 21 

### 5. Monitoring and QA/QC Requirements

Relevant Bin Numbers: Section 4.5

Track 1

Comment Summary 5-a: Commenter 0608 stated that it is very difficult to weigh the amount of SF 6 in gas carts with on board storage vessels to an accuracy of 1 percent. This commenter’s current practice is to estimate the weight of gas carts with onboar d storage vessels using engineering calculations. Commenter 0608 noted that the “weighing method is based on a pivoting table single point measuring system and removal of individual cylinders from the gas carts is difficult.” The commenter also explained that large carts are also used that have non-removable tanks on trailers; the proposed rule would require the weighing of the entire trailer, which would not yield an accurate measurement of gas because of “other materials such as compressor fluid and filt er material which vary overtime.” The commenter requested “a more pragmatic approach that tracks it s current business practice: (1) cylinders should be weighed at the beginning and end of each reporting period; 2) the weight of SF 6 in gas carts with onboard storage vessels may be calculated using the curre nt methodology; and (3) the manufactured supplied and installed weighing system in gas carts with onboard SF 6 cylinders should be permitted. By allowing [the commenter] to continue its current practices, US EPA would reduce the reporting burden and still achieve its aim of gathering emissions data.” Commenter 0608 also explained that this approach is consistent with methods provided for under the Climate Registry Protocol for reporting SF 6 emissions from Electricity Transmission and Distribution systems.

Response 5-a: After assessing concerns among numerous reporters about the proposed scale accuracy requirements, EPA eased the scale accu racy requirement from a relati ve requirement of 1% of true weight to an absolute requiremen t of +/- 2 pounds of true weight. In addition, EPA has removed the proposed requirement in §98.306 (b)(2) for weighi ng storage cylinders as t hey enter and leave the storage inventory and clarified that the QA/QC requir ements for scale accuracy and calibration apply only to cylinders returned to the gas supplier and cylinders weighed at the beginning and end of each year for the beginning and end-of-year storage inventory. EPA also examined the use of engineerin g calculations and alternative techniques other than scale weighing for determining SF 6 weight. Due to the unreliability of the most commonly used engineering calculations for weighing gas, such as using temperature and pressure readings, EPA determined that such methods are not suitable for the Subpart DD mass-balance monitoring methods, which rely on highly accurate in puts. For more information on the potential issues with using engineering calculations to determine the weight of SF 6 , see comment response 5.1-b. For more information on the necessity for highly accura te mass-balance inputs, see comment response 5.2-

a.



### 5.1 Frequency of Weighing Cylinders

— Track 1

Relevant Bin Numbers: Section 4.5, 4.5.1, and 4.5.3

Comment Summary 5.1-a: Ten commenters (0455, 1021, 0608, 0624, 0618, 1566, 0902, 0479, 0547, 1645) disfavored EPA’s propos ed requirement of weighing gas cylinder s each time they leave and enter storage. Commenter 1021 noted that EPA does not explain what purpose weighing cylinders leaving and entering storage in addition to the weighing of cylinde rs at the beginning and the end of every year would

serve.

Commenter 0455 asserted that “ weighing cylinders twice each time they are used, ‘as they are leaving and entering storage,’ would result in a significant increase in worker hours.” Commenters 0455, 0624, 0618, and 1566 suggested that SF 6 cylinders could be monitored by taking initial measurement of SF 6 stored in containers, combined with the submission of records tracking subsequent SF 6 . This approach, they stated, would be less cost ly than monitoring requirement proposed in §98.304(b)(2).

Commenters 0479 and 0547 are concerned about t he potential administrative burden and health and safety issues associated with frequent cylinder weighing by substation personnel, and preferred a standardized approach that relies on SF 6 vendors and recyclers to provi de weighing services of the delivered cylinders and residual gas upon return of the cylinder. These commenters believed that SF 6November 8, 2010 Subpart DD—Response to Comment Document 22 vendors and recyclers are bette r prepared to report this information, as they already employ procedures to weigh cylinders using scales that are routinely maintained and calibrated.

Commenter 0902 noted that the “rule as written will require employees to manually lift and weigh each

tank of SF 6 in order to gather the information needed in t he reporting process. Because a full tank of SF 6 weighs over 200 lbs., increased handling of cylinders co uld increase risk of worker injury.” Commenter

0902 favored the use of alternate methods of info rmation gathering, stati ng that, “although current technology requires weighing gas cylinders to obtain an accurate measurement of SF 6 usage, future reporting need not be limited to this inherently unsa fe method of information gathering. An alternate

method of data collection that meets the stated accu racy requirements will allow reporting methods to keep pace with advances in technology.”

Commenters 1645 and 0608 favored the approach us ed under the existing voluntary program between electric power systems and EPA. Commenter 1645 noted that, “although the interim weighing of cylinders as they are used, handled, and relocated may have inter nal inventory value to the user, this information is not necessary for accurate annual reporting, and can add significantly and unnecessarily to an organization’s labor burden and book keeping requ irements, if mandated by the reporting rule.” Commenter 0608 asserted that individual cylinder weighing is impractical and questionably cost effective given that at each facility, cylinders ma y leave and enter storage 20 times per year.

Response 5.1-a: EPA agrees that the b enefit of weighing SF 6 gas cylinders as they enter and leave inventory does not justify the costs of performing this activity. EPA has removed this requirement from § 98.306 (b)(2) and clarified that the QA/QC requirements for scale accuracy and calibration apply to cylinders returned to the gas supplier and cylinders weighed at the beginning and end of each year for the beginning and end-of-year storage inventory.

Comment Summary 5.1-b: Commenter 1566 suggested that instead of weighing cylinders to track the quantity of contained SF 6 , the pressure of the gas could be measured using a standard pressure gauge and the mass calculated using the ideal gas law. Co mmenter 1566 noted, “considering the relatively de minimis greenhouse gas emissions resulting from use and handling of SF 6 , this method of tracking the

SF 6 content in cylinders in lieu of weighing cylinders should be sufficient.”

Response 5.1-b: Measuring the amount of SF 6 in cylinders using temperature and pressure calculations is not an adequate method for weighing SF 6 cylinders in the context of mandatory reporting since SF 6 in a cylinder can be in both a gaseous and liquefied state, thereby making pressure readings unreliable. For example, in cases where gas extraction from the cylinder has cooled the temperature of SF 6 liquid in the cylinder to the point where it will no longer vaporize, a zero PSIG pr essure reading could be read from the cylinder when there is still SF 6 remaining as a heel in the cylinder.



### 5.2 Frequency of Weighing Cylinders

— Track 2

Relevant Bin Numbers: Section 4.5, 4.5.1, and 4.5.3

Comment Summary 5.2-a: Four commenters (0133, 0097, 00 98, 0083) disfavored EPA’s proposed requirement of weighing gas cylinders each time they leave and enter stor age. Commenters 0133 noted that EPA does not explain what purpose weighing cylinders leaving and entering storage in addition to the weighing of cylinders at the beginning and the end of every year would serve.

Commenters 0097 and 0098 were concerned about th e potential administrative burden and health and safety issues associated with frequent cylinder weighing by substation personnel, and preferred a standardized approach that relies on SF 6 vendors and recyclers to provi de weighing services of the delivered cylinders and residual gas upon return of the cylinder. These commenters believed that SF 6 vendors and recyclers are bette r prepared to report this information, as they already employ procedures to weigh cylinders using scales that are routinely maintained and calibrated.

In regards to administrative burden, Commenter 0083 explained that while a spreadsheet maintained by one person may be appropriate for smaller or densely devel oped utilities, it is not feasible for a companyNovember 8, 2010 Subpart DD—Response to Comment Document 23 with transmission operations spanning large geographic areas, which would instead require expensive software upgrades that can take months or years to install.

Response 5.2-a: EPA agrees that the b enefit of weighing SF 6 gas cylinders as they enter and leave inventory does not justify the costs of performing this activity. EPA has removed this requirement from § 98.306 (b)(2) and clarified that the QA/QC requirements for scale accuracy and calibration apply to cylinders returned to the gas supplier and cylinders weighed at the beginning and end of each year for the beginning and end-of-year storage inventory.

Comment Summary 5.2-b: Commenters 0097 and 0098 were in favor of EPA permitting the use of best available estimation methodologies in the first reportin g year to limit the administrative burden on industry to weigh each SF 6 cylinder, which would allow facilities flexibility in report ing using a combination of internal engineering calculations and/or purchase records.

Response 5.2-b: EPA understands that it might be difficult for some entities to employ the monitoring, data reporting, and QA/QC requirements by the beginning of 2011. Therefore, facilities may use best available monitoring methods during 2011 to the ext ent provided in §98.3(d)(1) through (d)(2), with the date changes specified in the final rule. For more information, see §98.303(a) of the final rule.



### 5.3 Accuracy and Precision of Scales

— Track 1

Relevant Bin Numbers: Section 4.5.2

Comment Summary 5.3-a: Six commenters (0902, 1021, 0618, 0624, 1566, 0608) disagreed with the proposed scale accuracy language at §98.304(b)(l), that states, "cyli nders returned to the gas supplier are consistently weighed on a scale that is certified to be accurate and precise to within 1 percent of the true weight", and "If the gas supplier weighs the residual gas, obtain from the gas supplier a detailed monthly accounting, within 1 percent, of residual gas amounts in the cylinders returned to the gas supplier" and at §98.304(b)(2), that states, "Cylinders shall be weighed on a scale that is certified to be accurate within 1 percent of the true weight."

Commenters were concerned about t he cost of scales requiring this level of accuracy and the need to purchase several of them for each site where cylin ders are stored. Commenter 0902 stated that they will have to purchase multiple scales at each location, which span thousands of transmission miles. This commenter was concerned about the cost of a scale of this accuracy, which is around $1,200 and the
need for several scales, which would result in the expenditure of thousands of dollars.”

Commenter 1012 remarked that given the expense of highly accurate scales and the associated workerhours with repeated weighing and scale recalibrat ion, EPA should explain “why its chosen methodology—the mass balance approach—does not pr ovide sufficient information for reporting purposes such that the additional burden of fr equent, highly accurate weighing is justified.”

Commenters 0618, 0624, and 1566 were also concer ned about the need to purchase and maintain numerous high-accuracy scales at each facility storing SF 6 cylinders, which is costly for monitoring “what translates to ‘de minimis’ quantities of GHG emissions.”

Commenter 0902 appreciated the necessity for accu rate reporting but believed that a one percent accuracy requirement is arbitrary and unnecessa rily burdensome on the industry. Commenter 0902 explained that a one percent requirement will vary greatly within the report ing process. “A scale that is one percent accurate for a full 220 pound tank of SF 6 will not be one percent accurate for a tank containing only a couple pounds of residual gas being returned to the supplier.” Commenter 0902 suggested a maximum variance in pounds rather than a percentage of the true weight. “A requirement that scales be accurate within two pounds, which is one percent of a full SF 6 tank, will reduce the financial burden on affected companies while still pr oviding accurate reporting.” This commenter explained that “designating a variance in terms of pounds establishes a clearly defined limit, and will result in more consistent and accurate reporting.”

Response 5.3-a: The 1 percent accuracy requirement was proposed by EPA becaus e the mass-balance method for measuring emissions requires accurate i nputs, and the overall unce rtainty of the emissionNovember 8, 2010 Subpart DD—Response to Comment Document 24 estimate rises significantly as the potential inaccu racy of each input increases. However, EPA also recognizes that the price of scales does increase as the accuracy of the scale increases and that many electric power entities do not currently use scales that are accurate to within 1 percent of the true weight.

In order to balance the reporting burden with the nee d for accurate mass-balance inputs, this Final Rule requires the accuracy and precision of scales used to weigh cylinders to be based on pounds, within +/- 2 pounds of true weight.

EPA deemed the +/- 2 pound ac curacy requirement to be an appropriate accuracy level based on a sensitivity analysis using mass-balance emission estima te data from four different size Partners from

EPA’s SF 6 Emission Reduction Partnership for Electric Po wer Systems. The sensitivity analysis involved testing the effect of five different scale accuracies on the relative uncertainty of the emissions estimates (on a 95% confidence interval). The five scale accura cies tested included: 1% (r elative), 2% (relative), 1 pound (absolute), 2 pounds (absolute), and 1% of full scale at 330 pounds (absolute). Assuming 2% uncertainty in the nameplate capacity parameters of the mass-balance formula (which are not measured using scales), the 2 pound scale accuracy requirement resulted in a range of relative uncertainties among Partners between 1% and 4.4%. The analysis also showed that the 1% relative scale accuracy resulted in a range of relative uncertainties between 0.5% and 4.1%, and the 5% relative scale accuracy resulted in a range of relative uncertainties between 2.6% and 6.5%. The complete sensitivity analysis can be found here: www.epa.gov/clim atechange/emissins/ghgrulemaking.html



### 5.4 Accuracy and Precision of Scales

— Track 2

Relevant Bin Numbers: Section 4.5.2

Comment summary 5.4-a: Commenter 0083 stated that they will hav e to purchase multiple scales at each location, which span thousands of transmissi on miles. This commenter was concerned about the cost of a scale of this accuracy, which is aroun d $2,000 and the need for several scales, which would result in the expenditure of thousands of dollars. T he commenter appreciated the necessity for accurate reporting but believed that a one percent accuracy requirement is arbitrary and unnecessarily burdensome on the industry. Commenter 0083 reco mmended amending §98.304(b)(1) and (2) as

follows:

“(1) Ensure that cylinders returned to the gas supplier are consistently measured by a method certified to be accurate and precise within 2 pounds, and are recalibrated per the manufacturer's specifications. Either measure residual gas (the amount of gas remaining in returned cylinders) or have the gas supplier measure it. If the gas supplier measures the residual gas, obtain from the gas supplier a detailed monthly accounting, within 2 pounds, of residual gas amounts in each cylinder returned to the gas supplier.

(2) Ensure that procedures are in place to measur e all cylinders as they ar e leaving and entering the electric power system. Cylinders s hall be measured by a method certified to be accurate and precise within 2 pounds and shall be recalibrated at the frequency specified by the manufacturer.”

Commenter 0902 explained that a one percent requirement will vary greatly within the reporting process. “A scale that is one percent accurate for a full 220 pound tank of SF 6 will not be one percent accurate for a tank containing only a couple pounds of residual ga s being returned to the supplier.” Commenter 0902 suggests a maximum variance in pounds rather than a percentage of the true weight. “A requirement that scales be accurate within two pounds, which is one percent of a full SF 6 tank, will reduce the financial burden on affected companies while st ill providing accurate reporting.” This commenter explains that “designating a variance in terms of pounds establishes a clearly defined limit, and will result in more consistent and accurate reporting.”

Commenter 0133 remarked that given the expense of highly accurate scales and the associated workerhours with repeated weighing and scale recalibrat ion, EPA should explain “why its chosen methodology—the mass balance approach—does not pr ovide sufficient information for reporting purposes such that the additional burden of fr equent, highly accurate weighing is justified.”

Response 5.4-a: Please see Response 5.3a for EPA’ s response to this comment.November 8, 2010 Subpart DD—Response to Comment Document 25 

### 5.5 Frequency of Scale Calibration

Relevant Bin Numbers: Section 4.5.1 and 4.5.2

Track 1

Comment Summary 5.5-a: Three commenters (0568, Email-034-1, and 1645) did not support a calibration frequency that requires annual recalibra tion or the minimum frequency specified by the manufacturer, whichever is more frequent. Commenter 0568 advocated removing the phrase, “whichever is more frequent” found at § 98.304(b)(2) because removing this phrase “will allow for the purchase of a higher quality scale that may not require recalibration as often as once a year, and will not provide an incentive for the regulated entity to purchas e a lower quality scale and replace it yearly.” This commenter stated that “the current wording of the Proposal encourages this practice because the cost of replacement for scales can be less than the cost in time and money of recalibrating scales.” Commenter Email-034-1 recommended this change because the ca libration cycle of the scales they intend to purchase is every 3 years.

Response 5.5-a: EPA agrees that scale recalibrati on in accordance with manu facturer specifications is

sufficient and that the incremental costs associated with annual recalibration (when the manufacturer’s specified calibration is less frequent) are not justified. EPA has retained the require ment that recalibration occur in accordance with manufacturer specificati ons but removed the requirement for a minimum of

annual recalibration.

Track 2

Comment Summary 5.5-b: Three commenters (0083, 0109, 0115) did not support a calibration frequency that requires annual recalibration or the minimum frequency specified by the manufacturer, whichever is more frequent because of cost and l ogistical reasons. Commenter 0083 stated that “the manufacturer of the scale is better equipped t han the EPA to determine the minimum maintenance requirements for their own product. Annual certificat ion is costly, time consuming, and most notably unnecessary.”

Response 5.5-b: Please see Response 5.5-a for EPA’ s response to this comment.



### 5.6 Other (Monitoring and QA/QC Requirements)

— Track 1

Relevant Bin Numbers: Section 4.5.3

Comment Summary 5.6-a: Commenter 1062 “supports the Tier 3 mass-balance protocol as being adequate as long as good QA/QC procedures are utili zed. It is important that reporting methods and verification be consistent nationally.”

Response 5.6-a: EPA appreciates the support of the comm enter. §98.303 and §98.305 of Subpart DD provide numerous QA/QC and data reporting require ments to ensure that data reported to EPA is accurate and complete.November 8, 2010 Subpart DD—Response to Comment Document 26 

### 6. Data Reporting Requirements

— Track 1

Relevant Bin Numbers: Section 4.7

Comment Summary 6-a: Commenter 0413 said that “EPA is seeking excessively detailed and redundant information regarding electrical equipment containing SF 6 gas.” The commenter states that “the amount of information sought create s a reporting requirement for use of SF 6 gas not its emissions into the atmosphere. This new regulation of ‘use’ is unauthorized and unnecessary as EPA's data showing significant reduction in SF 6 emissions from 1990 to 2007. Congress only authorized reporting of

SF 6 gas emission and did not authorize a complex regulatory system for regulating the use of SF 6 gas.”

Response 6-a: The system-level mass-balance monitoring methods required by Subpart DD are considered the most accurate and complete method for measuring SF 6 emissions for an electric power system because the method captures emissions that occur anywhere within the system by tracking system-level SF 6 use. This comprehensive monitoring met hod is important because an electric power system can span thousands of miles, and emissions can occur from a wide variety of causes throughout the electric power system including improper gas handling, leaky equipment, and faulty cylinder valves. While facilities are required to track and document SF 6 gas use within the system to yield accurate inputs for the mass-balance formula, EPA is not regulating how or when SF 6 can be used by the facility. For more information on the selection of monitoring methods for Subpart DD, please see the TSD located here: www.epa.gov/climatechange/ emissins/ghgrulemaking.html For a further detailed response on the amount of information required to be reported on U.S. greenhouse gas emissions, please see the 2009 Response to Comments Volume 13 – Content of the Annual Reportdocument, comment EPA-HQ-OAR2008-0508-0604.1 excerpt 5 (p. 1-2).

Comment Summary 6-b: Commenter 0413 stated that due to the amount of data reporting requirements required for Subpart DD, “EPA is seeking to create a significant amount of paperwork for utilities, which have successfully and significantly reduced SF 6 emissions” from 1990 to 2007.

Response 6-b: Through the mandatory reporting rule, EPA is seeking to collect accurate and comprehensive greenhou se gas emissions data to inform polic ymaking. EPA values the progress made under the Partnership in reducing emissions, but this does not obviate the need for mandatory reporting. There are large electric power sy stems that have not participated in the voluntary Partnership, and the emissions estimated through the voluntary Part nership have not undergone the QA/QC requirements necessary to ensure they are reliable enough to inform policymaking. While compiling and reporting

emission data does involve a burden to affected entities, EPA has attempted to minimize the burden as much as possible while still insuring that emission s data is accurate, complete, and verifiable.

Comment Summary 6-c: Commenter 0413 stated that the reporti ng requirement for total system-wide nameplate capacity is excessively detailed because “t here should be no need to report if the equipment is no longer in service.”

Response 6-c: The data reporting requirements for Subpart DD require reporting the nameplate capacity of equipment containing SF 6 and the nameplate capacity of equipm ent containing PFC existing at the beginning of the year (not including hermetically se aled-pressure switchgear). For purposes of compiling the system-wide nameplate capacity value, facilities should only include equipment that is energized. Equipment that is not in service but still contains SF 6 should be treated as a part of the storage inventory.

Comment Summary 6-d: Commenters 0902 and 0568 requested clarification on whether the SF 6 inside partially-filled electrical equipment that has been purchased but not yet installed should be considered as part of the mass-balance input §98.306(h) "SF 6 with or inside new equipment purchased in the year" or the input §98.306(g) "SF 6 stored in containers at the beginning and end of the year.” Commenter 0568 also requested clarification regarding whether t he nameplate capacity of this equipment should be recorded as new nameplate capacity acquired during the year (if the equipment is not yet installed at the end of the year).November 8, 2010 Subpart DD—Response to Comment Document 27 Response 6-d: SF 6 that is inside partially-filled electrical equipment that has been purchased by the facility (i.e., the title has been transf erred to the facility) but is not ye t installed should be counted as part of the mass balance input §98.306(h) "SF 6 with or inside new equipment purchased in the year" as well as the mass-balance input §98.306(g) "SF 6 stored in containers at the beginning and end of the year” (assuming the equipment still has not been in stalled by the end of the year).

Comment Summary 6-e: Commenter 1645 argued that the number of transmission miles for a facility, as requested in the data reporting requirements of Subpart DD, is not a good metric for correlating with nameplate capacity and SF 6 emissions. The commenter thought a better metric for evaluating “SF 6 emission intensity” would be the number of SF 6 breakers within an electric power system facility. The

commenter noted that the amount of SF 6 emissions associated with transmission miles is largely dependent on the geographic region of t he country and whether the transmission miles are located in rural or urban areas within specific geographic regions.

Response 6-e: EPA acknowledges that the amount of SF 6 used per transmission mile varies depending on the geographic region where the tr ansmission lines occur. However, EPA’s analysis indicated that transmission miles still correlates strongly with nam eplate capacity and SF6 emissions, albeit not as strongly as the correlation between nameplate capacity and SF 6 emissions, and therefore EPA is requiring transmission miles as a data reporting requirement. (For more information on EPA’s threshold analysis, please see the TSD located here: www. epa.gov/climatechange/emissins/ghgrulemaking.html.)

The number of SF 6 breakers within an electric po wer system facility could also provide useful information. However, due to the wide-variety of circuit breaker sizes and vintages, which can hold drastically different

amounts of SF 6 , there is limited usefulness to simply kn owing the total number of breakers within an electric power system fac ility. Therefore, EPA is not requiring this value as a data reporting requirement.November 8, 2010 Subpart DD—Response to Comment Document 28 

### 7. Other Subpart DD Comments – Track 1

Relevant Bin Numbers: Section 4.10

Comment Summary 7-a: Commenter 0212 stated that the nameplate capacity approach for Subpart DD does allow utilities to quickly determi ne whether they must re port, but does not allow utilities to get credit for reduced emissions, which may be possible even as nameplate capacity increases. The commenter

asked whether EPA has a mechanism to address this going forward. Commenter 0902 suggested that “EPA adopt an incentive program to encourage continued em ission reductions and to offset the additional reporting costs under the mandatory reporting rule. Ut ilization of tax or other financial incentives will provide a business case for companies to aggressively pursue reduction of SF 6 emissions.”

Response 7-a: The purpose of the Mandatory Reporting Rule is to collect accurate and comprehensive data on the amount of greenhouse gases emissions from various sources to help inform policymaking.

EPA does not have a mechanism for providing financial incentives for greenhouse gas emission reductions through the Mandatory Reporting Rule be cause such incentives would be outside the scope of

the rule.

Comment Summary 7-b: Commenter 0555, after reviewing the mechanisms for the use of SF 6 in electrical equipment, “applaud[s] EPA for a substantial document, and agree that the general methodology for SF 6 emissions from electric power systems is feasible.”

Response 7-b: EPA appreciates the support from the commenter.

Comment Summary 7-c: Commenter 1569 agreed that greenhouse gas emission reports for Subpart DD should be submitted on an annual basis since more frequent reporting using the mass-balance

emission measurement methods could result in errors.

Response 7-c: EPA appreciates commenter’s su pport of annual reporting.November 8, 2010 Subpart DD—Response to Comment Document 29 

### 8. Other Subpart DD Comments – Track 2

Relevant Bin Numbers: Section 4.10

Comment Summary 8-a: Commenter 0075 noted that “the proposed rule does not address the small quantities of SF 6 used as a tracer for leak detection in pressu rized systems, such as nuclear power plant

boiler tubes.”

Response 8-a: EPA appreciates the commenter’s concern about other uses of SF 6 that are not covered by the rule. The purpose of the Mandatory Reporting Ru le is to collect greenhouse gas emissions data from significant sources without subjecting small sources to a repo rting burden. EPA is not currently aware of significant SF 6 emissions occurring from its use as a tracer gas for leak detection in pressurized systems, but will continue to exam ine whether significant greenhouse gas emissions occur from sources not currently covered by the Mandatory Reporting Rule.

Comment Summary 8-b: Commenter 0128 supported EPA’s inclus ion of fluorinat ed greenhouse gas reporting provisions for electric transmission and di stribution use and thought it will enhance the overall accuracy of EPA’s greenhouse gas reporting rule and help the ag ency move towards a “truly comprehensive inventory of national GHG emissions.”

Response 8-b: EPA appreciates the support from the commenter.November 8, 2010 Subpart DD—Response to Comment Document 30 

### Appendix A – List of Commenters Sorted by Submission Number

Submission No. Commenter Organization

EPA-HQ-OAR-2009-0 927-0075 Kenneth Boyd Southern Company

EPA-HQ-OAR-2009-0 927-0081 Kenneth Boyd Southern Company

EPA-HQ-OAR-2009-0 927-0083 Deborah Boyle Oncor

EPA-HQ-OAR-2009-0 927-0086 Pamela F. Faggert Dominion Resource Services, Inc.

EPA-HQ-OAR-2009 -0927-0087 Ho lly Propst Western Business

Roundtable

EPA-HQ-OAR-2009 -0927-0088 Carol Whitman National Rural Electric Cooperative Association

EPA-HQ-OAR-2009-0 927-0094 Alexander G. Taft National Grid

EPA-HQ-OAR-2009-0927 -0096 Bruce D. Alexande r Exelon Corporation

EPA-HQ-OAR-2009-0927 -0097 Michael Bradley The Clean Energy Group

EPA-HQ-OAR-2009-0927 -0098 Rayburn L. Butts Nextera Energy, Inc.

EPA-HQ-OAR-2009-0927 -0101 Scott Davis Arizona Public Service

EPA-HQ-OAR-2009-0 927-0109 McCabe Americ an Electric Power

EPA-HQ-OAR-2009-0 927-0115 Michael B. McNulty ITC Holdings

EPA-HQ-OAR-2009-0927 -0119 Rob Rouse The Dow Chemical Company

EPA-HQ-OAR-2009-0927 -0120 Ruthanne Calabrese Northeast Utilities

EPA-HQ-OAR-2009 -0927-0125 Eric Hsieh National Electric Managers

Association

EPA-HQ-OAR-2009-0927 -0126 Wesley McNealy Pepco Holdings, Inc.

EPA-HQ-OAR-2009-0 927-0127 Gregory Ry an DTE, Energy

EPA-HQ-OAR-2009-0 927-0128 Pamela Campos Environmental Defense

Fund

EPA-HQ-OAR-2009-0927 -0133 Quinlan Shea Edison Electric Institute

EPA-HQ-OAR-2008-0508 -0212 Emily Fisher Edison Electric Institute

EPA-HQ-OAR-2008-0 508-0407 Michael Stroben Duke Energy Corporation,

EPA-HQ-OAR-2008-0 508-0413 Environmental Task Force

of the Northwest Public

Power Association

EPA-HQ-OAR-2008 -0508-0455 De bra Jezouit Class of '85 Regulatory Response Group

EPA-HQ-OAR-2008-0508 -0479 Michael Bradley The Clean Energy Group

EPA-HQ-OAR-2008-0508 -0547 Wesley McNealy Pepco Holdings, Inc.

EPA-HQ-OAR-2008 -0508-0551 De laine Shane Metropolitan Water District of Southern California,

EPA-HQ-OAR-2008-0 508-0555 Kyle Pistor NEMA

EPA-HQ-OAR-2008 -0508-0568 Rita Hayen American Transmission Company LLC

EPA-HQ-OAR-2008-0508 -0584 Nicole McInto sh Consumers Energy

EPA-HQ-OAR-2008-0 508-0597 Angila Re therford Vectren

EPA-HQ-OAR-2008-0 508-0608 Linda Sullivan National Grid

EPA-HQ-OAR-2008-0508 -0612 Andrew Lawrence De partment of Energy

EPA-HQ-OAR-2008-0 508-0618 Vincent Brisini RRI Energy, Inc.

EPA-HQ-OAR-2008-0508 -0624 Joseph Miakisz FPL Group

EPA-HQ-OAR-2008 -0508-0639 Scott Davis Arizona Public Service Company

EPA-HQ-OAR-2008-0508 -0661 J.P. Blackford American Public PowerNovember 8, 2010 Subpart DD—Response to Comment Document 31 Submission No. Commenter Organization

Association

EPA-HQ-OAR-2008-0 508-0685 Helen A. Howe s Exelon Corporation

EPA-HQ-OAR-2008-0508 -0725 John McManus Am erican Electric Power

EPA-HQ-OAR-2008-0508 -0902 Deborah Boyle On cor Electric Delivery

EPA-HQ-OAR-2008-0508 -1021 Quinlan Shea Edison Electric Institute

EPA-HQ-OAR-2008-0 508-1062 Matthew Frank State of Wisconsin

EPA-HQ-OAR-2008-0508 -1080 Kelly Carmichael NiSource

EPA-HQ-OAR-2008-0 508-1566 Robbie LaBor de Cleco Corporation

EPA-HQ-OAR-2008-0508 -1569 Patricia Meehan Ne w York Power Authority

EPA-HQ-OAR-2008-0 508-1645 S outhern Company

EPA-HQ-OAR-2008-0508 -1741 Pamela Faggert Dominion

EMAIL-034 Steve Lowder Bonneville Power

Administration

Trans-DC-04 Dan Chartier Edison Electric Institute