it is a large underground gas leak unclearstown sullivan square she said is lackly killing the plants and trees. they disproportionately contribute to the methane we see from the natural gas leaks. reporter: a few miles away at washington and causeway street. right along the freedom trail, sits a narrow pipe shooting more than 20 feet to the sky and releasing and dispersion natural gas leaking from the 100-year-old craft pipe below. it is just one of the more than 70,000 gas leaks reported as of the end of last year. >> you could have an accident there. you could have admission of gas right there. fuge financial cost. the state cannot say how much but one federal report says rate payers across the country paid at least $20 billion during the 11-year period for all the leaking gas. >> heard ka-boom. the explosion due to the natural gas leak back in 2014 to the dorchester neighborhood and erupted into a three-alarm blaze injuring a dozen people. lein safety concern, but envirnlallists are also alarmed at the damage they say is being done to the atmosphere by the methane being released.