Under roadways, neighborhoods and business districts across the United States, there's a massive system of pipelines carrying natural gas.
Thursday, the safety mechanisms or procedures that are supposed to make sure that the fossil fuel is delivered safely somehow failed in the Merrimack Valley.
The breakdown led to dozens of explosions and fires in Lawrence, Andover and North Andover. One young man was killed and several people were injured. Numerous buildings were damaged or destroyed.
For more on how natural gas is delivered and what might have gone wrong, WBUR's Sharon Brody spoke with Christina Sames. Sames is the vice president of operations and engineering at the American Gas Association, the industry group that represents natural gas companies.
This segment aired on September 14, 2018.