Washington Gas officials declined to answer questions about the study, but Eric Grant, the utility’s vice president of corporate relations, issued a statement saying that it maintains “rigorous inspection programs, operating procedures and record-keeping protocols. Washington Gas practices exceed the leak detection and repair procedures that are required by code, enforced by federal agencies and overseen by each state’s public service commission.” The statement said the company has 13,000 miles of distribution mains and more than 940,000 service lines in its system.

Betty Ann Kane, chairman of the District’s Public Service Commission, said there has never been an explosion of leaking natural gas in her eight years on the panel. Under orders from the commission, Washington Gas is aggressively replacing older cast-iron mains and a type of pipe coupling that has leaked elsewhere, she said.