To: PIPELINE OPERATORS and EXCAVATION STAKEHOLDERS
SUBJECT: URS SAFETY ALERT: Underground Utility Separation- Gas pipelines vs. Electrical power infrastructure
In recent weeks Staff of the Commission’s Division of Utility and Railroad Safety’s Damage Prevention and Pipeline Safety sections have discovered multiple occurrences of electrical power and gas distribution facilities being less than 12” of radial separation as required from each other and absent of any approved shielding devices.
In one instance of improper separation, multiple arc faults occurred from the electrical power facility resting within six inches of a medium density polyethylene (“MDPE”) plastic commercial service line. Eventually, the multiple arc faults resulted in the electrical service burning a hole into the live MDPE service line creating a gas leak and evacuations of a significant commercial area.
About 12:25 a.m. on July 7, 1998, a natural gas explosion and fire destroyed a newly constructed residence in the South Riding community in Loudoun County, Virginia.
This incident was investigated by multiple safety partner agencies including the VA SCC and the National Transportation Safety Board (“NTSB”.) Below is an excerpt from the NTSB’s report PB2001-916501 PAR-0101 (available here.):
“A family consisting of a husband and wife and their two children were spending their first night in their new home at the time of the explosion. As a result of the accident, the wife was killed, the husband was seriously injured, and the two children received minor injuries. Five other homes and two vehicles were damaged.
The National Transportation Safety Board determines that the probable cause of the accident in South Riding, Virginia, was the corrosion and subsequent overheating and arcing at a splice in one of the conductors of the triplex electrical service line, which, because of inadequate separation [emphasis added] between the electrical conductors and the gas service line, led to the failure of the gas service line and the subsequent uncontrolled release of natural gas that accumulated in the basement and was subsequently ignited. Precipitating the electrical service line failure was damage done to the electrical service line during installation of the gas service line and/or during subsequent excavation of the electrical line.”
In response to this incident, the Commission adopted separation standards in Case PUE-2000-0662 and furnished a report to the Governor and General Assembly on December 28, 1999.
It is extremely concerning the rising number of electrical separation issues with gas pipelines being discovered by Staff in the field. Staff is therefore requesting that pipeline operators and excavation stakeholders:
- Take the information in this URS Safety Alert and disseminate within their organizations, including all contractors, and perform additional training and familiarization with all separation standards, but particularly those involving electrical and gas facilities (12” radial separation.)
- Operators and excavation stakeholders are encouraged to report the discovery of improper separation immediately to the utilities in question regarding the use of contact information on their 811 ticket.
- Staff also requests to report those separation issue to the Division’s Damage Prevention Section via its DPA-1 form found here.
Additional information regarding Utility Line Separation requirements is contained in Virginia’s Professional Excavator Manual is available here .
Information regarding Utility Line Separation can be found here.
Should you wish to discuss the matter further please feel free to contact our Damage Prevention and Pipeline Safety sections. Very respectfully your partners in safety,
Utility Damage Prevention Pipeline Safety
Carl Dale Scott Marshall
Damage Prevention Program Manager Pipeline Safety Program Manager