All of the Skippack Township residents who had left their homes Sunday night because of a foul odor were set to spend the night at home Tuesday, after investigators conducted more monitoring and found improved conditions in houses.
"The levels are significantly lower," Skippack Township Fire Company Chief Haydn Marriott said Tuesday.
On Sunday, 151 households in the Fairlawn Court development were evacuated after residents of one house reported smelling a bad odor.
An initial reading in the basements of that house and others indicated the presence of the potentially harmful compound hydrogen cyanide. The chemical, investigators had said, was coming from sump pump pits in the basements.
Later, investigators said that the meters they used gave a wrong reading and that there was no hydrogen cyanide. Water samples from sump pump pits sent to labs at the Pennsylvania Department of Environmental Protection and the U.S. Environmental Protection Agency concluded that the chemical that had caused the bad smell was gasoline.
Officials from local, state, and federal environmental agencies used different meters to recheck the levels Tuesday, Marriott said. Investigators still didn't know how the gasoline got into the sump pump pits.
As of Monday night, all but two households had returned home. Marriott said those two families told him that they planned to sleep in their own beds Tuesday night.
Montgomery County property records show that an old gas pipe was placed underground decades ago, long before the development was built. Marriott said that pipe was for natural gas, not the liquid gasoline found in water samples.