NTSB Safety Recommendation P-19-004

NTSB safety recommendation P-19-004.

TO THE PUBLIC SERVICE COMMISSION OF MARYLAND, THE COMMONWEALTH OF VIRGINIA STATE CORPORATION COMMISSION DIVISION OF PUBLIC UTILITY REGULATION, AND THE PUBLIC SERVICE COMMISSION OF THE DISTRICT OF COLUMBIA: Oversee the replacement process for the mercury service regulators that Washington Gas has in service.

Priority: CLASS II

Overall Status: Open - Acceptable Response

Issued Date: 2019-06-10

Synopsis: On August 10, 2016, at 11:51 p.m., eastern daylight time, a 14-unit apartment building, located at 8701 Arliss Street, in the unincorporated community of Silver Spring, in Montgomery County, Maryland, partially collapsed due to a natural gas-fueled explosion and fire. The explosion and fire also heavily damaged an adjacent apartment building, 8703 Arliss Street, which shared a common wall with building 8701. As a result of this accident, 7 residents died, 65 residents were transported to the hospital, and 3 firefighters were treated and released from the hospital. The damage from the accident exceeded $1 million. The following are safety issues in this accident: • the location and inspection of service regulators within a structure • the inspection of the gas meter assembly • the notification of the natural gas odor to Washington Gas Light Company • the detection of natural gas through odorants and methane

Probable Cause: The National Transportation Safety Board determines that the probable cause of the explosion in building 8701 of the Flower Branch apartment complex was the failure of an indoor mercury service regulator with an unconnected vent line that allowed natural gas into the meter room where it accumulated and ignited from an unknown ignition source. Contributing to the accident was the location of the mercury service regulators where leak detection by odor was not readily available.

Keywords: Hazmat

Ntsbnumber: DCA16FP003

Report Number: PAR-19-01

Addressee Name: State of Maryland, Public Service Commission

Addressee Status: Open - Acceptable Response

Addressee Acronym: PSC

Addressee Organization Type: S-State Government

Communication Date: 2019-06-10

Communication Type: Transmittal Letter

Communication Contents: The National Transportation Safety Board (NTSB) is an independent federal agency charged by Congress with investigating every civil aviation accident in the United States and significant accidents in other modes of transportation—railroad, highway, marine, and pipeline. We determine the probable cause of the accidents and issue safety recommendations aimed at preventing future accidents. In addition, we carry out special studies concerning transportation safety and coordinate the resources of the federal government and other organizations to assist victims and their family members affected by major transportation disasters. We are providing the following information to urge your organization to act on the safety recommendations in this letter because we believe your organization can help reduce the risk of future accidents. For more information about NTSB and our recommendation process, please see the attached one-page summary. On April 24, 2019, the NTSB adopted its report, Building Explosion and Fire, Silver Spring, Maryland, August 10, 2016, NTSB/PAR-19/01. The details of this accident investigation and the resulting safety recommendations may be found in the attached report, which can also be accessed at http://www.ntsb.gov. As a result of this investigation, the NTSB identified the following safety issues: • The location and inspection of service regulators within a structure. • The inspection of the gas meter assembly. • The notification of the natural gas odor to Washington Gas Light Company. • The detection of natural gas through odorants and methane. Accordingly, the NTSB makes the following safety recommendations to the Public Service Commission of Maryland, the Commonwealth of Virginia State Corporation Commission Division of Public Utility Regulation, and the Public Service Commission of the District of Columbia. Additional information regarding these recommendations can be found in the noted sections of the report. • Following Washington Gas’s successful completion of Safety Recommendation P-19-009, audit and verify the performance of Washington Gas’s mercury service regulator replacement program, including its recordkeeping. (P-19-003) (See section 2.3.9.) • Oversee the replacement process for the mercury service regulators that Washington Gas has in service. (P-19-004) (See section 2.3.10.) The NTSB is vitally interested in these recommendations because they are designed to prevent accidents and save lives. We would appreciate a response within 90 days, detailing the actions you have taken or intend to take to implement these recommendations. When replying, please refer to the safety recommendations by number (for example, P-19-003). We encourage you to submit your response to correspondence@ntsb.gov. If your reply exceeds 20 MB, including attachments, please e-mail us at the same address for instructions on how to send larger documents. Please do not submit both an electronic copy and a hard copy of the same response.

Addressee Acronym: PSC

Addressee Organization Type: S-State Government

Communication Date: 2025-05-19

Communication Type: Staff-Level Communication

Communication Contents: In an informal meeting on May 19, 2025, MD PSC informed us that the agency is continuing the work described in its previous letter regarding Safety Recommendations P-19-3 and -4. We look forward to receiving your next update.

Addressee Acronym: PSC

Addressee Organization Type: S-State Government

Communication Date: 2019-09-09

Communication Type: Official Correspondence

Communication Contents: -From Jason M. Stanek, Chairman: I am in receipt of your correspondence on June 10, 2019, regarding the National Transportation Safety Board's ("NTSB") report on the Building Explosion and Fire, Silver Spring, Maryland, August 10, 2016, NTSB/PAR-19/01 . I appreciate the efforts of the NTSB investigators and the NTSB Board Members in determining the event's probable cause, findings, and recommendations. The Maryland Public Service Commission also appreciated the opportunity to be a formal party to this investigation. Upon review of the NTSB report, the Commission accepts its two assigned recommendations: (1) Following Washington Gas's successful completion of Safety Recommendation P-19-009, audit and verify the performance of Washington Gas's mercury service regulator replacement program, including its recordkeeping. (P-19-003) (2) Oversee the replacement process for the mercury service regulators that Washington Gas has in service. (P-19-004) On September 5, 2019, the Commission ordered the Washington Gas Light Company (Washington Gas) to file an implementation plan proposal for NTSB recommendations (P-19-009, P-19-010, P-19-011, P-19-012, P-19-013) by October 7, 2019, which includes details regarding the scope, prioritization, schedule, and cost projections for the plan. (See In the Matter of an Investigation of Washington Gas Light Company Regarding a Building Explosion and Fire in Silver Spring, Maryland on August 10, 2016, Case No. 9622, Order No. 89248 (Sept. 5, 2019).) The proposed plan should also address potential implementation risks that could be encountered and any risk mitigation actions contemplated. Upon review of the proposal filed by Washington Gas, the Commission will determine what additional steps, if any, are necessary before approving the implementation plan. I have enclosed a copy of the Commission's order for your review. Following approval of an implementation plan, the Commission will order Washington Gas to file an annual report on the status of its implementation plan in a format to be developed with input from Commission Staff. This annual report will also discuss instances where implementation of the NTSB recommendation to relocate interior service regulators is infeasible due to obstructions (P-19-013). Finally, the Commission's Engineering Division will be responsible for providing oversight and auditing of the performance of Washington Gas's mercury service regulator replacement program, including its recordkeeping (P-19-003) and the replacement process for the mercury service regulators that Washington Gas has in service (P-19-004). To accomplish this, Commission Staff will supplement its existing Pipeline Safety Program2 field and records inspection processes with procedures targeted to Washington Gas's implementation of the NTSB recommendations. Commission Staff will report its audit findings annually following Washington Gas's filing of its implementation status report. Please let me know if you have any concerns regarding the Commission's implementation of our assigned recommendations.

Addressee Acronym: PSC

Addressee Organization Type: S-State Government

Communication Date: 2020-02-25

Communication Type: Official Correspondence

Communication Contents: We note that, on September 5, 2019, the Maryland PSC ordered Washington Gas to file an implementation plan proposal for the recommendations that we issued to Washington Gas in our report on the Silver Spring accident (P-19-9 through -13) by October 7, 2019. The proposed plan that Washington Gas develops will address potential implementation risks and the mitigations to address these risks. After this plan is approved, the Maryland PSC plans to order Washington Gas to file an annual report on the status of its implementation plan. Finally, we note that your Engineering Division will oversee and audit Washington Gas’s mercury service regulator replacement program, including its recordkeeping. To accomplish this, you will supplement your existing pipeline safety program field and records inspection processes with procedures targeted to Washington Gas’s implementation of our recommendations. You plan to update us annually about your audit findings after Washington Gas files its implementation status report with you. This annual report will also discuss instances where Washington Gas’s compliance with Safety Recommendation P-19-13 (to relocate interior service regulators outside) is not feasible. On September 9, 2019, Washington Gas sent us a letter describing its response to Safety Recommendations P-19-9 through -13. Washington Gas reported that it expected to complete actions in response to Safety Recommendations P-19-9 and -10 by December 31, 2019. The actions that you described in your letter will satisfy Safety Recommendations P-19-3 and -4. We note that you plan to follow and report to us about Washington Gas’s compliance with Safety Recommendation P-19-13 and instances where compliance with this recommendation is not feasible. Although Safety Recommendations P-19-3 and -4 do not discuss your auditing and verifying Washington Gas’s compliance with Safety Recommendation P-19-13, we commend your plans to follow Washington Gas’s actions. Pending auditing and verification of Washington Gas’s mercury service regulator replacement program until it is completed, Safety Recommendations P 19 3 and 4 are classified OPEN--ACCEPTABLE RESPONSE.

Addressee Name: Commonwealth of Virginia, Corporation Commission, Division of Public Utility Regulation

Addressee Status: Open - Acceptable Response

Addressee Acronym: VSSC

Addressee Organization Type: S-State Government

Communication Date: 2019-06-10

Communication Type: Transmittal Letter

Communication Contents: The National Transportation Safety Board (NTSB) is an independent federal agency charged by Congress with investigating every civil aviation accident in the United States and significant accidents in other modes of transportation—railroad, highway, marine, and pipeline. We determine the probable cause of the accidents and issue safety recommendations aimed at preventing future accidents. In addition, we carry out special studies concerning transportation safety and coordinate the resources of the federal government and other organizations to assist victims and their family members affected by major transportation disasters. We are providing the following information to urge your organization to act on the safety recommendations in this letter because we believe your organization can help reduce the risk of future accidents. For more information about NTSB and our recommendation process, please see the attached one-page summary. On April 24, 2019, the NTSB adopted its report, Building Explosion and Fire, Silver Spring, Maryland, August 10, 2016, NTSB/PAR-19/01. The details of this accident investigation and the resulting safety recommendations may be found in the attached report, which can also be accessed at http://www.ntsb.gov. As a result of this investigation, the NTSB identified the following safety issues: • The location and inspection of service regulators within a structure. • The inspection of the gas meter assembly. • The notification of the natural gas odor to Washington Gas Light Company. • The detection of natural gas through odorants and methane. Accordingly, the NTSB makes the following safety recommendations to the Public Service Commission of Maryland, the Commonwealth of Virginia State Corporation Commission Division of Public Utility Regulation, and the Public Service Commission of the District of Columbia. Additional information regarding these recommendations can be found in the noted sections of the report. • Following Washington Gas’s successful completion of Safety Recommendation P-19-009, audit and verify the performance of Washington Gas’s mercury service regulator replacement program, including its recordkeeping. (P-19-003) (See section 2.3.9.) • Oversee the replacement process for the mercury service regulators that Washington Gas has in service. (P-19-004) (See section 2.3.10.) The NTSB is vitally interested in these recommendations because they are designed to prevent accidents and save lives. We would appreciate a response within 90 days, detailing the actions you have taken or intend to take to implement these recommendations. When replying, please refer to the safety recommendations by number (for example, P-19-003). We encourage you to submit your response to correspondence@ntsb.gov. If your reply exceeds 20MB, including attachments, please e-mail us at the same address for instructions on how to send larger documents. Please do not submit both an electronic copy and a hard copy of the same response.

Addressee Acronym: VSSC

Addressee Organization Type: S-State Government

Communication Date: 2025-04-25

Communication Type: Staff-Level Communication

Communication Contents: In an informal meeting on April 25, 2025, we learned that the Division of Utility and Railroad Safety continues to monitor Washington Gas’s mercury service regulator replacement project. We look forward to your next update.

Addressee Acronym: VSSC

Addressee Organization Type: S-State Government

Communication Date: 2019-09-06

Communication Type: Official Correspondence

Communication Contents: -From Judith Williams Jagdmann, Chairman: This letter is in response to your June 10, 2019 letter regarding the National Transportation Safety Board's ("NTSB") April 24, 2019 report entitled Building Explosion and Fire, Silver Spring, Maryland, August JO, 2016, NTSB/PAR-19/01 ("Report"). The Virginia State Corporation Commission ("SCC") commends the NTSB for its detailed investigation and Rep01i concerning the Maryland incident. Further, and as you suggest in your letter, it is vital that we take the steps necessary to reduce the risks of such future accidents. To that end, the Report makes the following recommendations to the SCC as well as the Maryland and District of Columbia regulatory commissions: 1. Following Washington Gas's successful completion of Safety Recommendation P-19-009, audit and verify the performance of Washington Gas's mercury service regulator replacement program, including its recordkeeping (P-19-003) (see Report section 2.3.9). 2. Oversee the replacement process for the mercury service regulators that Washington Gas has in service (P-19-004) (see Report section 2.3.10). Your letter also requests that the Commission respond detailing actions it has taken, or intends to take, to implement said recommendations. The SCC's Division of Utility and Railroad Safety ("Staff') has spoken with Washington Gas (''Company") officials on multiple occasions regarding the Report's recommendations assigned to the Company. Based on the Company's commitments and agreements made during these conversations, the Staff plans to implement the two recommendations assigned to the SCC as follows: The Company has agreed to identify all personnel performing mercury service regulator replacement work on their daily crew/personnel location notices. The Company has agreed to provide information where mercury service regulators may be involved in pipeline replacement projects or large construction projects. The above-mentioned location and project notices will allow the Staff to incorporate these locations into our existing risk-based field inspections. During risk-based field inspections, the Staff will check for proper operator qualifications and adherence to Company procedures and code requirements. In closing, the SCC and its Staff are committed to monitoring the implementation of the important safety recommendations documented in the NTSB Report. We will keep NTSB apprised should we encounter any difficulties in carrying out this critical mission.

Addressee Acronym: VSSC

Addressee Organization Type: S-State Government

Communication Date: 2020-02-24

Communication Type: Official Correspondence

Communication Contents: We note that you will incorporate recordkeeping audits and reviews of Washington Gas’s mercury service regulator replacement program into your current general pipeline safety code compliance inspections. Washington Gas will provide quarterly reports detailing specific metrics measuring its mercury service regulator program progress. In addition, Washington Gas will identify all personnel performing mercury service regulator replacement work and will provide information where mercury service regulators are involved in pipeline replacement projects or large construction projects. This information will enable you to incorporate these locations into your existing field inspections, during which you will check for proper operator qualifications and adherence to procedures and code requirements. Taking these actions while the mercury service regulator replacement program is in progress will satisfy these recommendations. Pending the Virginia SCC’s continued auditing and oversight of Washington Gas’s mercury service regulator replacement program, Safety Recommendations P 19 3 and 4 are classified OPEN--ACCEPTABLE RESPONSE. Please update us at ExecutiveSecretariat@ntsb.gov on your progress toward implementing these recommendations, and do not submit both an electronic and a hard copy of the same response.

Addressee Name: District of Columbia, Public Service Commission

Addressee Status: Open - Acceptable Response

Addressee Acronym: DC PSC

Addressee Organization Type: L-Local Government

Communication Date: 2025-04-24

Communication Type: Staff-Level Communication

Communication Contents: On April 24, 2025, DCPSC informed us that the agency is continuing the work described in its previous letter regarding Safety Recommendations P-19-3 and -4. We look forward to receiving your next update.

Addressee Acronym: DC PSC

Addressee Organization Type: L-Local Government

Communication Date: 2019-06-10

Communication Type: Transmittal Letter

Communication Contents: The National Transportation Safety Board (NTSB) is an independent federal agency charged by Congress with investigating every civil aviation accident in the United States and significant accidents in other modes of transportation—railroad, highway, marine, and pipeline. We determine the probable cause of the accidents and issue safety recommendations aimed at preventing future accidents. In addition, we carry out special studies concerning transportation safety and coordinate the resources of the federal government and other organizations to assist victims and their family members affected by major transportation disasters. We are providing the following information to urge your organization to act on the safety recommendations in this letter because we believe your organization can help reduce the risk of future accidents. For more information about NTSB and our recommendation process, please see the attached one-page summary. On April 24, 2019, the NTSB adopted its report, Building Explosion and Fire, Silver Spring, Maryland, August 10, 2016, NTSB/PAR-19/01. The details of this accident investigation and the resulting safety recommendations may be found in the attached report, which can also be accessed at http://www.ntsb.gov. As a result of this investigation, the NTSB identified the following safety issues: • The location and inspection of service regulators within a structure. • The inspection of the gas meter assembly. • The notification of the natural gas odor to Washington Gas Light Company. • The detection of natural gas through odorants and methane. Accordingly, the NTSB makes the following safety recommendations to the Public Service Commission of Maryland, the Commonwealth of Virginia State Corporation Commission Division of Public Utility Regulation, and the Public Service Commission of the District of Columbia. Additional information regarding these recommendations can be found in the noted sections of the report. • Following Washington Gas’s successful completion of Safety Recommendation P-19-009, audit and verify the performance of Washington Gas’s mercury service regulator replacement program, including its recordkeeping. (P-19-003) (See section 2.3.9.) • Oversee the replacement process for the mercury service regulators that Washington Gas has in service. (P-19-004) (See section 2.3.10.) The NTSB is vitally interested in these recommendations because they are designed to prevent accidents and save lives. We would appreciate a response within 90 days, detailing the actions you have taken or intend to take to implement these recommendations. When replying, please refer to the safety recommendations by number (for example, P-19-003). We encourage you to submit your response to correspondence@ntsb.gov. If your reply exceeds 20MB, including attachments, please e-mail us at the same address for instructions on how to send larger documents. Please do not submit both an electronic copy and a hard copy of the same response.

Addressee Acronym: DC PSC

Addressee Organization Type: L-Local Government

Communication Date: 2019-09-09

Communication Type: Official Correspondence

Communication Contents: -From Willie L. Phillips, Public Service Commission, Chairman: This letter is in response to the National Transportation Safety Board (“NTSB”) June 10, 2019 letter, urging the Public Service Commission of the District of Columbia (“Commission”) to act on the safety recommendations provided in the letter and NTSB’s April 24, 2019, Report (“Report”) related to the 2016 accident in Silver Spring, Maryland. The NTSB explained that it is vitally interested in these recommendations because they are designed to prevent accidents and save lives. The NTSB provided five (5) recommendations to the Washington Gas Light Company (“Washington Gas” or “Company”) and requested that the Commission take the following two (2) actions: • Following Washington Gas’ successful completion of Safety Recommendation P-19-009, audit and verify the performance of Washington Gas’ mercury service regulator replacement program, including its recordkeeping. (P-19-003) (referencing Section 2.3.9 of the Report.); and • Oversee the replacement process for the mercury service regulators that Washington Gas has in service. (P-19-004) (referencing Section 2.3.10 of the Report.) Following NTSB’s request, the Commission initiated an investigation into Washington Gas’ compliance with the five (5) NTSB recommendations and how the recommended actions could best improve safety in the District of Columbia (“District”) (See Formal Case No. 1157, Order No. 19982, Attachment A). Through this formal investigation, the Commission will oversee Washington Gas’ implementation of the NTSB recommendations. To facilitate our investigation, by Order No. 19982, we directed Washington Gas to file a detailed implementation plan (“Plan”) outlining the replacement process for mercury service regulators and summarizing the specific actions to be completed in response to the NTSB recommendations, the deadlines for completion, and associated cost estimates. (See Plan, Attachment B). Washington Gas timely submitted its Plan, and as directed, provided implementation details for each NTSB recommendation, specifying preliminary timelines and cost estimates.1 Washington Gas reported that it is considering the following major improvements, in addition to some already completed actions: • Update its work management system and Operations and Maintenance Manual and expand its supervisors’ auditing responsibilities; • Add additional vent connection checks in its required inspection process; • Complete an expedited mercury regulator replacement program (“Program”), targeting replacement of identified mercury regulators for multi-family dwellings within five (5) years and for non-multi-family dwelling within ten (10) years of the Program start; and • Track and report its progress to the Commission. The Commission is reviewing the details of Washington Gas’ Plan and will take further action, as necessary, and may hold a hearing on this subject in the first quarter of Fiscal Year 2020. In addition, the Commission is committed to the safety of District residents and will continue to work toward further improvement of the safety and reliability of the gas distribution system in the District. Given the importance of this matter, the Commission will apprise the NTSB of any material developments in the implementation of the five (5) NTSB recommendations and provide our final order on the Commission’s investigation into this matter. Please do not hesitate to contact me should you have any questions.

Addressee Acronym: DC PSC

Addressee Organization Type: L-Local Government

Communication Date: 2019-08-30

Communication Type: Official Correspondence

Communication Contents: LETTER FROM WASHINGTON GAS TO THE DC PUBLIC SERVICE COMMISSION: Letter from Cathy Thurston-Seignious, Supervisor, Administrative and Associate General Counsel, Washington Gas to Brinda Westbrook-Sedgwick, Commission Secretary, Public Service Commission of the District of Columbia: Formal Case No. 1157 [Washington Gas Implementation Plan] Pursuant to Order No. 19982, issued by the Public Service Commission of the District of Columbia in the above-referenced proceeding, Washington Gas Light Company hereby submits for filing its Implementation Plan to address the National Transportation Safety Board’s safety recommendations. Please feel free to contact me, if you have questions regarding this matter.

Addressee Acronym: DC PSC

Addressee Organization Type: L-Local Government

Communication Date: 2020-08-20

Communication Type: Official Correspondence

Communication Contents: -From Willie L. Phillips, Chairman: This letter is in response to the National Transportation Safety Board (“NTSB”) February 24, 2020 letter, requesting the Public Service Commission of the District of Columbia (“Commission”) to update the NTSB on the safety recommendations provided in NTSB’s April 24, 2019, Report (“Report”) related to the 2016 accident in Silver Spring, Maryland. The NTSB explained that it is vitally interested in these recommendations because they are designed to prevent accidents and save lives. The NTSB provided five (5) recommendations to the Washington Gas Light Company (“Washington Gas” or “Company”) and requested that the Commission take the following two (2) actions: • Following Washington Gas’ successful completion of Safety Recommendation P-19- 009, audit and verify the performance of Washington Gas’ mercury service regulator replacement program, including its recordkeeping. (P-19-003) (referencing Section 2.3.9 of the Report.); and • Oversee the replacement process for the mercury service regulators that Washington Gas has in service. (P-19-004) (referencing Section 2.3.10 of the Report.) As I discussed in my letter to NTSB on September 9, 2019, the Commission initiated an investigation into Washington Gas’ compliance with the five (5) NTSB recommendations and how the recommended actions could best improve safety in the District of Columbia (“District”) (See Formal Case No. 1157, Order No. 19982). Through this formal investigation, the Commission will oversee Washington Gas’ implementation of the NTSB recommendations. On August 14, 2020, the Commission issued Order No. 20608 (see Attachment A) which, inter alia, approved Washington Gas’ updated implementation plan (“Plan”). By Order No. 20608, the Commission has established oversight measures to review the relocation and replacement of mercury regulated meters in the District of Columbia. Additionally, where relocation outside and/or replacement is not possible the Commission has established additional oversight to review proper venting procedures. The Commission is committed to the safety of District residents and will continue to work toward further improvement of the safety and reliability of the gas distribution system in the District. Please do not hesitate to contact me should you have any questions.

Addressee Acronym: DC PSC

Addressee Organization Type: L-Local Government

Communication Date: 2020-02-24

Communication Type: Official Correspondence

Communication Contents: We note that you initiated an investigation of Washington Gas’s compliance with the recommendations that we issued to it as a result of our Silver Spring accident investigation (P 19 9 through -13), and, through this formal investigation, you will oversee Washington Gas’s implementation of the recommendations. We further note that you directed Washington Gas to file a detailed implementation plan outlining the replacement process for mercury service regulators and summarizing the specific actions to be completed, the deadlines for completion, and associated cost estimates. Washington Gas submitted its plan and provided implementation details for each of our recommendations, specifying preliminary timelines and cost estimates. We understand that you are reviewing Washington Gas’s plan and will take further action if needed. These actions will satisfy the recommendations. Pending your continued auditing and oversight of Washington Gas’s mercury service regulator program, Safety Recommendations P 19 3 and 4 are classified OPEN--ACCEPTABLE RESPONSE. Please update us at ExecutiveSecretariat@ntsb.gov on your progress toward implementing these recommendations, and do not submit both an electronic and a hard copy of the same response.

Addressee Acronym: DC PSC

Addressee Organization Type: L-Local Government

Communication Date: 2020-10-28

Communication Type: Official Correspondence

Communication Contents: We are aware that you initiated an investigation into Washington Gas’s compliance with the recommendations that we issued as a result of our Silver Spring accident investigation (Safety Recommendations P 19-9 through -13), and, through this formal investigation, you will oversee Washington Gas’s implementation of the recommendations. We note that you have now received, reviewed, and approved Washington Gas’s updated mercury service regulator replacement program. We are pleased that you have established oversight measures to review mercury service regulator relocation and replacement and to review proper venting procedures where relocation outside is not possible. Pending your continued auditing and oversight of Washington Gas’s mercury service regulator replacement program, Safety Recommendations P-19-3 and -4 remain classified OPEN--ACCEPTABLE RESPONSE. Please update us at ExecutiveSecretariat@ntsb.gov on your progress toward implementing these recommendations, and do not submit both an electronic and a hard copy of the same response.