Good to be back home again

Problems with an aging underground electrical cable drove several families from their homes this spring, but NStar officials and residents of Allston Street in Charlestown now are confident that their troubles are behind them.

Electrical fires that broke out at different points in an underground line on March 3 and April 27 created unsafe levels of carbon monoxide in two buildings. In the latter case, residents of a three-story house were forced to spend a week in hotels while the carbon monoxide lingered in the building.

Mike Durant, a spokesman for NStar, said both incidents apparently stemmed from malfunctions in the same electrical line. He suggested that the protective lining to that cable might have been damaged by water from heavy rainfall.

"We had a lot of rain, and because this happens so rarely, this is the only thing we can look at as a catalyst," he said. "The line has been replaced, and whatever caused the problem underground has been addressed."

The first incident occurred on a Saturday morning at 3 Allston St. According to Durant, carbon monoxide produced by the fire seeped into homes through the ground.

Once power was shut off, carbon monoxide dissipated to a safe level after several hours and residents were allowed to return to their homes.

The troubled stretch of electrical line was replaced, but on the morning of April 27, a resident in the basement unit of 19 Allston St. called to report an odor of smoke.

Kara Lammi , who lives on the second floor with her fianc e, Warren Shepherd, said she learned of the leak when Boston fire fighters knocked on her door to tell her she would need to evacuate the house.

"They told us it was a carbon monoxide problem," she said. "They let us back in for a few minutes to grab some things, but after that the people from NStar told us we would need to check into hotels."

The Boston Fire Department deduced from an air-quality test that the level of carbon monoxide gas in the home was extremely unsafe.

According to Durant, the protocol for dissipating a concentration of carbon monoxide usually involves cutting the power to the affected line and using pipes to vent ground near the buried line. This time, dangerous levels of carbon monoxide lingered for seven days.

"The gas did not dissipate out of ground even though we did what was called for," said Durant. "The levels in mostly the basement remained elevated longer than anyone expected they could."

As dangerous amounts of the gas lingered, NStar enlisted a geologist to examine the site. The company also ripped up asphalt in front of four homes along the street and even removed topsoil in an effort to vent the gas.

"When we took the asphalt off, the [carbon monoxide] level started to drop pretty quickly," said Durant. "That gave us the idea that this was the right step."

Durant said that even before the March incident, work had begun to replace the aging electrical line. That was confirmed by neighbors, who said crews have been working on the street since last summer .

The stretch of line that caused gas to leak into the homes at 3 and 19 Allston St. has now been replaced, and residents of 19 Allston St. were allowed to return home on May 4.

Lammi said the ordeal was an inconvenience, particularly because many hotels were full for conventions and graduations.

"I was a little nervous to come back, but the health department checked out the building and they said it was fine," she said after returning home. "The whole thing was a pretty big inconvenience, not knowing from night to night if we could go back. I'm glad it's over."