But Los Angeles officials have chosen to continue with construction of a new high school over an abandoned oil field even though it may be releasing methane, hydrogen sulphide and other gases.
A citizens' commission narrowly agreed to finish building the Belmont Learning Complex, even though protective safeguards may double the record pound;96 million ($153m) already spent on the school.
Commission members said the safeguards would be cheaper than abandoning the project and beginning again somewhere else.
The building is needed to ease overcrowding in existing schools that has become so bad that a student representative, Anna Fernandez, told commission members that an imperfect school was better than none. "We will take the risk," she said, backed up by 200 of her classmates.
The debacle has already dragged on for a decade, and authorities say the school could take at least another five years to finish. Meanwhile, the existing school serving the neighbourhood has 5,000 students - so many that some do not have desks. More than 2,400 children are bused to schools in other sections of the city.
But critics argue that the Los Angeles school district is not qualified to monitor and maintain the sophisticated equipment needed to prevent explosive or toxic gases from collecting in the building.