The bulldozer was clearing land outside a day care center in Hapeville, Ga., when it broke open a buried 1-inch pipeline. The escaping gas ignited into a fireball that killed nine people, including seven children settling down for their afternoon naps.
That was 1968. Since then, there have been at least 270 similar accidents across the country that could have been prevented or made less dangerous by a valve that cuts off leaking gas and costs as little as $10-$15 for homes and small businesses and $200-$300 for larger buildings, an Associated Press investigation found.
Yet nearly 90 percent of the nation's gas service lines aren't fitted with the valves. Despite persistent government recommendations, the gas industry has argued that they are unreliable and cost too much to install — $207 million over 50 years in one industry-commissioned study, more than $1 billion in another estimate.
In the meantime, the accidents continued: Since Hapeville, at least 67 people have been killed and more than 350 hurt in accidents where the valves could have helped but weren't installed. Six people were killed in a Minnesota store blast in 1972. A 25-story Manhattan building was destroyed in 1974, injuring 70 people. Four people died and six buildings were leveled in an explosion in 1998 in St. Cloud, Minn.
"There were lives lost that did not need to be lost," said Robert Hall, deputy director of the National Transportation Safety Board, which is responsible for investigating pipeline accidents.
The NTSB recommended the valves 16 times, but only in 2009, under pressure from Congress, was a rule approved — to make the devices mandatory only on lines leading to new, single-family homes. Now, regulators are considering expanding that to new or replaced pipelines serving millions of multifamily homes and commercial buildings. And the utilities are objecting.
"NTSB has made excess flow valves some kind of holy war where they think everything should have a valve on it," said Don Stursma, an official at the Iowa Utilities Board who sits on an advisory board to the Pipeline and Hazardous Materials Safety Administration.
Pipeline agency officials say they will decide whether to push ahead with the new rules sometime next year.
The valves are designed to trip automatically when there is a break in a service line, the narrow-diameter pipes that serve individual homes and businesses. A sudden rush of escaping gas pushes a small, spring-loaded stopper inside the valve, plugging the line.
Without them, gas can leak unchecked into a building or house, pooling until an ignition source — turning on the stove, a pilot light in the water heater, even an electrical spark from a cellphone — triggers an explosion or fire.
The most complete government records, covering 2004 to the present, showed 187 accidents that potentially could have been avoided or mitigated, according to the AP's review.
That includes 148 cases the U.S. Transportation Department said could have been averted or diminished if valves were in place. The department released details on those accidents in response to a public records request from the AP. Applying the agency's criteria, the AP found 39 more. Another 84 cases were identified by NTSB investigators or mentioned in Transportation Department studies.
There are more than 66 million natural gas service lines in the U.S., but only about one in 10 had excess flow valves, according to the government's most recent data. Almost 46 million new service lines have been installed since 1970 — about 39 million without excess flow valves. That's about 39 million "missed opportunities," as Hall put it.
The federal pipeline safety agency, which sets pipeline rules, announced last year that it was considering requiring the valves for multifamily dwellings and commercial buildings. The agency believes the 2009 mandate for safety valves on single-family homes "only partially addressed" the NTSB's recommendations, agency spokeswoman Jeannie Layson said in a written statement.
Before the agency decides whether to go ahead with new rules, officials want to survey companies about how much it might cost them to place excess flow valves on service lines for buildings along with new, single-family homes, Layson said.
Manufacturers and utilities say the cost per valve could be as low as $10-$15 for homes, retail businesses and restaurants. For larger buildings, such as large commercial or small industrial businesses and institutional buildings such as libraries, the cost can climb to $200-$300, according to GasBreaker Inc., a Pennsylvania-based manufacturer.
Government and industry estimates on overall costs have varied greatly:
— In 1974, consultants to the Transportation Department said installing valves on new lines was not only economically and technically feasible, but would improve public safety. They recommended more study, however.
— In 1991, an industry-commissioned study put the price tag at $207 million over 50 years to outfit new and renewed lines, an estimate that included the price of the device, its installation and the potential cost of digging up pipes to repair bad valves.
— In 1995, when Congress was debating whether to mandate the valves, an industry executive estimated the cost would top $1 billion. The proposal was dropped.
All sides in the debate agree that installing the valves retroactively would be too expensive. But NTSB's Hall said industry resistance has blocked the valves' installation even on new service lines where costs would be largely limited to the price of the device.
The American Gas Association and several other industry groups warn there are still too many unknowns, including how the valves would function in large-scale settings where demand for gas could jump in different seasons.
The association said a federal pipeline safety agency study "grossly understates the economic, technical, and operational complexities" of broadening the valves' use to large-volume customers such as hotels, restaurants and hospitals.
The association would support valves on certain larger customers that draw a fixed amount of natural gas, vice president Christina Sames wrote. She cautioned against a broader mandate, saying that schools, hospitals, restaurants and some apartments that can draw varying amounts of gas are "critical" customers where an inadvertent trip of a valve would threaten safety or hurt business.
Hall said excluding such customers would leave unprotected those places more likely to have large concentrations of people, raising the potential for greater damage in an accident.
The dispute over valves for service lines comes amid a broader debate over pipeline safety sparked by a 2010 explosion in San Bruno, Calif. that killed eight people and a blast last year in Allentown, Pa., that killed five. Those accidents also triggered calls for emergency shut-off valves, but they involved larger pipelines not covered in the government's proposed service line rules.
Individual utilities said they should be trusted to decide when and where to install the service line valves. A device manufacturer, however, said some utilities' reluctance stems from a lack of experience with the devices.
"We have sold millions of these and, if these problems were a reality, we as a manufacturer would be called to task on them," GasBreaker CEO John McGowan Jr. said.
San Francisco-based Pacific Gas & Electric Co., one of the nation's largest gas companies, has installed excess flow valves on fewer than 3 percent of its 3.4 million service lines, government data from 2011 shows.
Anthony Earley, PG&E's CEO, said he objects to widespread use of valves because customers can be inconvenienced if gas is shut off in response to a false trigger. "Once you trip a gas valve and shut off gas, you can't just turn the gas back on," he said.
The company plans to install additional valves on new or replaced lines for single-family homes in the coming years.
Steve Miner, a manager of operations at Vermont Gas Services, said the valves are impractical at schools or hospitals because they can limit gas flow, possibly "starving" large boilers or furnaces that need a steady flow to run properly. Beyond those cases, Miner said, he would have "no problem" with expanding the mandates.
"I think they are the best thing out there," Miner said. "I'm the one who has to go on these emergency calls and it's a nice feeling when you know the (excess flow valve) is on that service."
So the debate continues, and so do the questions of those who lost loved ones.
When a crew of cable installers in St. Cloud, Minn., struck a downtown gas line in 1998, the pipe leaked for 39 minutes until something ignited the gas. A pizzeria, apartment units, a law office and a bar were destroyed. Among the dead was Robert Jacobs, a gas company worker and father of two.
"I would think putting those valves on lines going to apartments or businesses would be very important, but the companies say it's too expensive," said his wife of 23 years, Jean Jacobs. "But how do you put a price tag on a life?"
Follow Garance Burke on Twitter at http://twitter.com/garanceburke
AP reporter Matthew Brown can be reached at mbrown(at)ap.org