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Safety Recommendation Details

Safety Recommendation P-19-010
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
Recommendation: TO WASHINGTON GAS LIGHT COMPANY: Revise your procedures and field forms to require technicians to verify the integrity of vent lines following the testing of indoor service regulators throughout the Washington Gas network.
Original recommendation transmittal letter: PDF
Overall Status: Open - Initial Response Received
Mode: Pipeline
Location: Silver Spring, MD, United States
Is Reiterated: No
Is Hazmat: No
Accident #: DCA16FP003
Accident Reports: Building Explosion and Fire
Report #: PAR-19-01
Accident Date: 8/10/2016
Issue Date: 6/10/2019
Date Closed:
Addressee(s) and Addressee Status: Washington Gas (Open - Initial Response Received)

Safety Recommendation History
From: Washington Gas
Date: 9/9/2019
Response: -From Adrian Chapman, President and Chief Executive Officer, WGL (Washington Gas Light): We are completing related changes to our Work Management System and expect to have this recommendation implemented by December 31, 2019. For additional detail, please see the attached submissions to the District of Columbia, Maryland and Virginia public utility commissions. Consistent with Washington Gas's commitment to operating a safe and reliable system, we propose to undertake the above actions as enhancements to the safety of our system and consistent with our regulatory obligation as a safe and prudent operator. Nothing in this letter or in the proposed actions to be taken should be misunderstood as agreement with the NTSB's determination of probable cause in this matter.

From: NTSB
To: Washington Gas
Date: 6/10/2019
Response: 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 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 Washington Gas Light Company. Additional information regarding these recommendations can be found in the noted sections of the report. • Throughout the Washington Gas network, implement an audit program to verify the data on the service forms used to determine the location and condition of mercury service regulators to ensure the accuracy of this safety-critical data. (P 19 009) (See section 2.3.9.) • Revise your procedures and field forms to require technicians to verify the integrity of vent lines following the testing of indoor service regulators throughout the Washington Gas network. (P-19-010) (See section 2.3.5.) • Establish a time frame with specific dates and milestones for the replacement of mercury service regulators throughout the Washington Gas network that recognizes the need to expedite this program and that prioritizes multifamily dwellings where mercury service regulators are located inside the property. (P-19-011) (See section 2.3.10) • Install all new service regulators outside occupied structures. (P-19-012) (See section 2.3.10.) • Relocate existing interior service regulators outside occupied structures whenever the gas service line, meter, or regulator is replaced. In addition, multifamily structures should be prioritized over single-family dwellings. (P-19-013) (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-19-009). We encourage you to submit your response to 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.