pipeline Accident Report

Natural Gas Explosion and Fire

South Riding, Virginia
July 7, 1998

NTSB Number PAR-01-01
NTIS Number PB2001-916501

Executive Summary

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. 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.

Probable Cause

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 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.

The safety issues identified during this investigation were (1) the adequacy of standards for minimum separation distances between gas service lines and electrical service lines and (2) the lack of a requirement for the installation of excess flow valves. As a result of this investigation, the Safety Board issues two recommendations to the Research and Special Programs Administration (RSPA) and one recommendation each to the Edison Electric Institute, the National Rural Electric Cooperative Association, the American Power Association, and the U.S. Department of Agriculture’s Rural Utilities Service.