Federal investigators, responding to a fatal gas explosion in
The conditions described by Susan M. Coughlin, then-acting chairwoman of the National Transportation Safety Board, were similar to those found by investigators looking into the cause of the Feb. 9 natural gas blast in Allentown that killed five people.
"The Allentown infrastructure contains many miles of ... cast-iron gas and water mains installed in the late 1800s and early 1900s that have likely been weakened by corrosion," Coughlin wrote in a letter referring to a 1990 gas explosion about a mile from the recent blast site.
The NTSB only had the authority to recommend that UGI replace the pipeline most likely to fail, and UGI acted on those recommendations, reporting in 1996 that it was undertaking a systematic replacement program. Since then, UGI spokesman Dan Adamo said Tuesday, the company has replaced 120 miles of cast-iron pipeline throughout its 14-county Pennsylvania service area -- an average of eight miles a year.
Adamo could not say what portion of those 120 miles of replacement pipe is in Allentown. The gas utility still has 79 miles of cast-iron gas mains in Allentown, he said.
The state Public Utility Commission on Tuesday also could not say how much pipeline was replaced in Allentown.
Coughlin's 1992 letter makes plain the NTSB's concern that old cast-iron lines were a growing threat in Allentown. In the 51 years between 1925 and 1976, she wrote, two significant gas explosions occurred in Allentown, killing 10 and injuring 24.
Between 1976 and the date of the letter, July 10, 1992, a period of 16 years, two more gas explosions occurred. Three people were killed, 23 injured and 11 homes were destroyed or damaged in those blasts, Coughlin wrote.
Since her letter, six gas explosions have occurred in Allentown, killing seven people and injuring 83. Most of the injured were in the 1994 blast at Gross Towers seniors apartment complex. Those six explosions were caused by excavator and contractor error as well as deteriorating pipelines.
The circumstances of the 1990 event and the most recent blast have some similarities. In the Feb. 9 blast, investigators have focused on a cracked section of 83-year-old cast-iron pipe at 13th and Allen streets.
In 1990, a deteriorating water line caused an 87-year-old cast-iron pipe to weaken and crack. Escaping gas seeped into a home at 423 N. Fifth St. and ignited, killing one person and injuring nine. The NTSB found that the gas pipe's failure was "inevitable," even without the leaking water main, because the old cast-iron pipe was "fully" corroded.
Despite the link to a leaking water main, the NTSB blamed UGI for the explosion, saying it failed to monitor its system and replace pipeline before it was dangerously corroded.
In addition, other stresses identified in Coughlin's letter -- including heavy traffic, cracked pavement and soil movement -- continue to weaken aging utility lines.
UGI's response to the 1990 blast, federal records show, satisfied the NTSB. The safety board deemed UGI's plan to carry out a program identifying and replacing the riskiest pipelines an "acceptable action" in 1997 and closed that part of the case.
The NTSB record also indicated satisfaction with recommendations that UGI train local first responders to deal with gas issues safely; complete a prospective gas surveillance system that collects information on gas leaks, system abnormalities and corrective actions; and document the location of underground voids, or sinkholes, with the city of Allentown.
The city, however, did not respond to the NTSB recommendation that it work with UGI and other excavators in documenting the location of voids. As of 2002, NTSB said, it had not heard from the city, and it closed that portion of the report "unacceptable action/no response received."
Michael Moore, a spokesman for Mayor
In a related development, an NTSB spokesman confirmed a statement made by NTSB Chairwoman Deborah Hersman last week that the agency would not be on the ground in Allentown for this investigation because of a lack of manpower.
The NTSB, Hersman said, would not be able to investigate a January explosion in
"It has been a particularly bad year for pipeline accidents," she told reporters in a briefing leading up to a hearing in
NTSB spokesman Ted Lopatkiewicz said the safety board has four pipeline inspectors who are already examining accident sites in California, Illinois, Florida, Michigan and Texas. The NTSB has asked the PUC to investigate on its behalf, Lopatkiewicz said.
"The Public Utility Commission is heavily trained to handle investigations of this type," said PUC spokeswoman Denise McCracken, adding that PUC gas safety inspectors have "extensive" training under the
"We have received similar requests in the past from the NTSB to handle investigations," McCracken said. "On several occasions, we also have worked alongside NTSB during investigations and have a working history with them. We have worked start-to-finish with them and have proven our ability to determine cause of incidents and make recommendations."