By Charles Koval
One night, a couple feet underground outside an American home, the gas flowing in a service line began to escape through a puncture adjacent to a newly installed mailbox. A man and woman inside the home were watching the news. Their children were playing. Then, suddenly, without warning . . . nothing happened.
A simple and inexpensive device called an excess flow valve (EFV) kicked in, stopping the gas flow. There was no explosion, no fire, no injury or loss of life.
As a petroleum engineer and pipeline specialist for the NTSB, I know that the most important pipeline safety advance in recent decades has been the establishment of the national one-call 811 number. But EFVs may be the next most important life-saver, especially for homeowners.
Gas companies install an EFV in a service pipeline where it meets the main line. The EFV shuts off the gas flow in the service line when it exceeds the normal flow rate; excess flow often indicates that gas is escaping the service line through a puncture or sever, potentially leading to an explosion or fire.
I’ve been working a long time to encourage the progress that came to fruition late last year regarding EFVs. The Pipeline and Hazardous Materials Safety Administration (PHMSA) quietly completed an important achievement and, in the process, closed an NTSB recommendation. PHMSA issued a rule expanding the use of EFVs to new or renewed service lines leading to almost all small commercial businesses and multi-residence buildings.
It’s taken decades to achieve this result. In all, the NTSB has made 24 safety recommendations related to EFVs.
When I came to the NTSB in 1990, the agency had already been endorsing EFVs for 20 years, beginning with recommending a shutoff valve after research that came out of a 1970 safety study.
I worked on accident after accident that may have been prevented by EFVs. Most of my work between 1990 and 1994 involved single-family residences, but many multi-residence accidents were just as horrible, if not worse. The incidents occurred in large cities like Tulsa, Oklahoma, and St. Paul, Minnesota, and in smaller towns like St. Cloud, Minnesota; Montezuma, Indiana; and Cliffwood Beach, New Jersey. I can still remember my first NTSB supervisor expressing exasperation that this simple and elegant solution was not in wider use.
Then came June 9, 1994. At about 6:45 that evening, a 2-inch-diameter steel gas service line that had been exposed during excavation separated at a compression coupling about 5 feet from the north wall of John T. Gross Towers, an 8-story retirement home. The escaping gas flowed underground toward Gross Towers, passed through openings in the building foundation, entered the mechanical room through the floor vents, and migrated to other floors.
A resident smelled the gas, as did a workman onsite, who told his foreman. The foreman called the gas company and the housing authority, then had other employees locate and shut off the gas line valve inside the towers. But at 6:58 p.m., the built-up natural gas in the building ignited and exploded; a second explosion followed 5 minutes later. The accident killed one person and injured 66—and it could have been much worse. Many residents were not in the building on the early summer evening of the disaster.
A humble EFV could have shut off the gas flow into Gross Towers. After the explosion, the NTSB recommended that PHMSA’s predecessor agency require that all gas distribution operators inform all customers of the availability of EFVs. After many years, the agency did so. Meanwhile, fatal accidents continued—all potentially preventable with EFVs.
Then, in 1998, the NTSB was called to the site of an explosion and fire at a single-family home in South Riding, Virginia.
A man, woman, and their two children were spending their first night together in their new home. The family retired at about 10:30—the children to the upper level of the house, and, because not all of their furniture had arrived, the parents to the first-floor study. Shortly after midnight, the house exploded and was engulfed in flames. The children were thrown out of the house and onto the lawn, suffering minor injuries. The parents fell into the basement as the first floor collapsed. The father was able to crawl to safety, badly burned; the mother did not escape and died as a result of her injuries.
Again, an EFV could have prevented the tragedy.
Following this accident, the NTSB recommended that PHMSA require EFVs in all new and renewed gas service lines, regardless of customer classification, when operating conditions were compatible with readily available valves. PHMSA first required only that single-family homeowners be notified of the availability of the valve and be allowed to pay for it themselves. Then, in 2009, PHMSA changed the rule, requiring EFVs to be installed on almost all new and renewed service pipelines to single family homes. Finally, on October 14, 2016, PHMSA expanded the safety requirement to include most new and renewed service pipelines for multi-residential and commercial applications, closing one chapter in EFV history—and with it, an outstanding NTSB recommendation.
My first NTSB supervisor is no longer with us, but even years ago, he could imagine the broad use of EFVs that he did not live to see. Sometimes it takes a long time to normalize safety. Too often, it takes a highly visible accident—or several of them—to draw attention to a problem. Solutions often come a little bit at a time, or a long time afterward, without any fanfare.
But for now, and well into the future, for many businesses and homes nationwide, if a service line fails, nothing will happen. These homes and businesses are a little safer today because PHMSA and the gas industry acted on NTSB’s EFV recommendations.
Charles Koval is a Petroleum Engineer and Pipeline Specialist in the NTSB Office of Railroad, Pipeline and Hazardous Materials.
 The service line does not need an EFV if it: 1. does not operate at or above 10 psig all year, 2. has previously had contaminates, 3. could interfere with necessary operation or maintenance activities, or 4. is not commercially available to the operator.