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.