Suburban stink still a mystery

PECO is still trying to determine what led to more than a thousand complaints of gas odors over the weekend, mostly in Montgomery and Delaware Counties.

More than 400 reports were received just by 4 p.m. Saturday, including from customers in Bucks and Chester Counties, and the problem continued into Sunday morning.

PECO followed up on every report without discovering a leak or other source.

"We didn't identify any issues in the natural gas distribution system," said spokeswoman Jackie Thompson. "... We monitor the system for volume and pressure, and we didn't find any issues from a distribution system perspective."

A chemical release into the air from a single source, like a factory or fire, was unlikely.

Not only did the reports cover a huge area, but "the customers were smelling the natural gas odor from inside their homes," said PECO spokeswoman Cathy Engel Menendez.

One possibility: Somehow too much mercaptan -- the chemical added to odorless natural gas to give a smell -- got into the system.

Such cases are rare, said Engel, who had heard that a similar episode happened about 15 years ago, when a Delaware utility added too much mercaptan. Because natural gas supplies are networked, complaints came in from PECO customers in Chester County.

In July 1987, news reports documented a similar case. Because of faulty pipeline, workers in Chester had to inject mercaptan manually, and they overdid it, according to The Philadelphia Inquirer.

"A flood of customer complaints," primarily in South Philadelphia and Delaware County, sent "scores of utility work crews into a state of emergency readiness," the newspaper wrote.

Philadelphia Gas Works did not get any complaints over the weekend, according to spokeswoman Melanie McCottry.

Contact staff writer Peter Mucha at 215-854-4342 or pmucha@phillynews.com. Follow @petemucha on Twitter.