MOUNTAINWEST PIPELINE, LLC — Warning Letter

12022053WL_Warning Letter_05102022_(21-200067)_text.pdf, page 1Official PDFWARNING LETTER OVERNIGHT EXPRESS DELIVERY May 10, 2022 Ms. Colleen Larkin Bell President and Chief Executive Officer Mountainwest Pipeline, LLC 333 South State Street P. O. Box 453360 Salt Lake City, Utah 84145 CPF 1-2022-053-WL Dear Ms. Larkin Bell: From June 2 through 4, 2021, a representative of the Pipeline and Hazardous Materials Safety Administration (PHMSA) pursuant to Chapter 601 of 49 United States Code inspected Dominion Energy Questar Pipeline, LLC (Dominion Questar) Leroy Storage’s procedures for Underground Natural Gas Facilities in Salt Lake City, Utah. As a result of the inspection, it is alleged that you have committed a probable violation of the Pipeline Safety Regulations, Title 49, Code of Federal Regulations (CFR). The item inspected and the probable violation is: 1. § 192.12 Underground natural gas storage facilities. (a)… (b) Depleted hydrocarbon and aquifer reservoir UNGSFs. (1) … (2) Each UNGSF that uses a depleted hydrocarbon reservoir or an aquifer reservoir for natural gas storage and was constructed on or before July 18, 2017, must meet the provisions of API RP 1171 (incorporated by reference, see §192.7), sections 8, 9, 10, and 11, and paragraph (c) of this section, by January 18, 2018, and must meet all provisions of paragraph (d) of this section by March 13, 2021. Dominion Questar failed to meet the provisions of API RP 1171, Section 9. Specifically, Dominion#

12022053WL_Warning Letter_05102022_(21-200067)_text.pdf, page 2CPF 1-2022-053-WL Questar failed to demonstrate that it had determined its defined threshold levels based on well integrity evaluation and from risk assessment in accordance with API RP 1171, Section 9.3.2 (Section 9.3.2). Section 9.3.2 states in part, “The operator shall monitor for presence of annular gas by measuring and recording annular pressure and/or annular gas flow. The operator shall evaluate each annular gas occurrence that exceeds operator- or regulatory-defined threshold levels determined from well integrity evaluation and from risk assessment. The operator should test wellhead seals when annulus pressure is detected and where injectable packing and/or test ports are present.” During the inspection, Dominion Questar identified that its threshold level for annular gas occurrences was 1400 psig. Upon PHMSA’s request, Dominion Questar was not able to provide an adequate analysis of why their threshold pressure was this high. Therefore, Dominion Questar failed to meet the provisions of Section 9.3.2 regarding determination of its defined thresholds for annular gas occurrences. Under 49 U.S.C. § 60122 and 49 CFR § 190.223, you are subject to a civil penalty not to exceed $239,142 per violation per day the violation persists, up to a maximum of $2,391,142 for a related series of violations. For violation occurring on or after May 3, 2021 and before March 21, 2022, the maximum penalty may not exceed $225,134 per violation per day the violation persists, up to a maximum of $2,251,334 for a related series of violations. For violation occurring on or after January 11, 2021 and before May 3, 2021, the maximum penalty may not exceed $222,504 per violation per day the violation persists, up to a maximum of $2,225,034 for a related series of violations. For violation occurring on or after July 31, 2019 and before January 11, 2021, the maximum penalty may not exceed $218,647 per violation per day the violation persists, up to a maximum of $2,186,465 for a related series of violations. For violation occurring on or after November 27, 2018 and before July 31, 2019, the maximum penalty may not exceed $213,268 per violation per day, with a maximum penalty not to exceed $2,132,679. For violation occurring on or after November 2, 2015 and before November 27, 2018, the maximum penalty may not exceed $209,002 per violation per day, with a maximum penalty not to exceed $2,090,022. We have reviewed the circumstances and supporting documents involved in this case and have decided not to conduct additional enforcement action or penalty assessment proceedings at this time. We advise you to correct the item identified in this letter. Failure to do so will result in Dominion Energy Questar Pipeline, LLC being subject to additional enforcement action. No reply to this letter is required. If you choose to reply, in your correspondence please refer to CPF 1-2022-053-WL. Be advised that all material you submit in response to this enforcement action is subject to being made publicly available. If you believe that any portion of your responsive material qualifies for confidential treatment under 5 U.S.C. 552(b), along with the complete original document you must provide a second copy of the document with the portions you believe qualify for confidential treatment redacted and an explanation of why you believe the redacted information qualifies for confidential treatment under 5 U.S.C. 552(b). 12022053WL_Warning Letter_05102022_(21-200067)_text Page 2 of 3#

12022053WL_Warning Letter_05102022_(21-200067)_text.pdf, page 3CPF 1-2022-053-WL Sincerely, Robert Burrough Director, Eastern Region, Office of Pipeline Safety Pipeline and Hazardous Materials Safety Administration 12022053WL_Warning Letter_05102022_(21-200067)_text Page 3 of 3#