The increased pressure overwhelmed the aging gas line system in Lawrence, Andover, and North Andover, setting off fires and explosions that damaged 121 structures, killed one person in a home explosion, and left two dozen injured, according to the preliminary report.
The report put the fault on Columbia Gas of Massachusetts, which had developed and approved the work package that resulted in the disaster, the report said.
“Columbia Gas developed and approved the work package executed on the day of the accident. The work package did not account for the location of the sensing lines or require their relocation,” the report said.
The problems started on the afternoon of the catastrophe in South Lawrence at an intersection where Columbia Gas workers were performing a “pipe-replacement project,” the NTSB said.
Report sites over pressurization as trigger in deadly Massachusetts gas line explosion | TheHill
The preliminary findings on the Sept. 13 explosions and fires, which hit Lawrence, Andover, and North Andover, were released Thursday by the National Transportation Safety Board.
“The contracted crew was working on a tie-in project of a new plastic distribution main and the abandonment of a cast-iron distribution main,” the NTSB said. “The distribution main that was abandoned still had the regulator sensing lines that were used to detect pressure in the distribution system and provide input to the regulators to control the system pressure. Once the contractor crews disconnected the distribution main that was going to be abandoned, the section containing the sensing lines began losing pressure.”
As the pressure “dropped about 0.25 inches of water column (about 0.01 psig), the regulators responded by opening further, increasing pressure in the distribution system,” the NTSB said. “Since the regulators no longer sensed system pressure they fully opened allowing the full flow of high-pressure gas to be released into the distribution system supplying the neighborhood, exceeding the maximum allowable pressure.”
The agency said that moments before the explosion, “the Columbia Gas monitoring center in Columbus, Ohio, received two high-pressure alarms for the South Lawrence gas pressure system: one at 4:04 p.m. and the other at 4:05 p.m. The monitoring center had no control capability to close or open valves; its only capability was to monitor pressures on the distribution system and advise field technicians accordingly. Following company protocol, at 4:06 p.m., the Columbia Gas controller reported the high-pressure event to the Meters and Regulations group in Lawrence. A local resident made the first 9-1-1 call to Lawrence emergency services at 4:11 p.m.”
Columbia Gas is working to replace all of the affected piping with “new high-pressure plastic mains with regulators at each service meter,” according to the NTSB.
More than 20 people were injured, and thousands of residents were displaced from their homes and lost power.
In a statement, Joe Hamrock, president and CEO of NiSource Inc., parent company of Columbia Gas of Massachusetts, said the company is fully cooperating with the review.
The incident killed an 18-year-old man, sent 21 people to the hospital, and damaged 131 buildings, completely destroying at least five homes, according to the NTSB.
“As a party to the NTSB investigation, we are prohibited from discussing or speculating on the cause of the incident or facts related to it until the NTSB has completed its work,” Hamrock said. “However, we can say that, because safety is our top priority, in the hours immediately after the incident we suspended similar work and enhanced procedures related to our low pressure systems. We saw these as responsible steps to take in the aftermath of the incident and while the facts were being gathered.”
Hamrock said the company remains “focused on three key areas: Taking Care of People: We continue to work with state and local leaders and a broad network of community partners to meet the needs of the people affected by this incident and to keep them fully informed as the recovery effort moves forward. Ensuring Safety: All of our actions are driven by our commitment to the safety of our customers, our communities and our employees. Regaining Trust: We are working to restore gas service as quickly as possible and are committed to taking the steps needed to re-earn the trust of our customers, communities, and public officials.”
Minutes before the fires and explosions occurred, the Columbia Gas monitoring center in Columbus, Ohio, received two high-pressure alarms for the South Lawrence gas pressure system: one at 4:04 p.m. and the other at 4:05 p.m. But the report found the monitoring center had no control capability to close or open valves; its only capability was to monitor pressures on the distribution system and advise field technicians.
He said he’s “very proud of the strong, dedicated team driving the restoration effort in the streets and homes of Lawrence, Andover, and North Andover. We continue to expect completion by November 19th.”
BOSTON (AP) — Over-pressurized natural gas lines were the source of deadly explosions and fires that rocked communities north of Boston last month, the National Transportation Safety Board said Thursday.
The five-page, preliminary report found that utility workers contracted by Columbia Gas had failed to account for critical pressure sensors as they replaced century-old cast-iron pipes in Lawrence on Sept. 13.
That omission caused high-pressure gas to flood the neighborhoods distribution system at excessive levels, triggering more than 80 explosions and fires across the city, as well as neighboring North Andover and Andover.
One person was killed and about 25 others were injured in the ensuring chaos. The gas explosions also damaged 131 structures and destroyed five homes. Thousands of homes and businesses are still without natural gas service as Columbia Gas replaces some 50 miles (80 kilometers) of gas pipeline.
At 4:06 p.m., the Columbia Gas controller reported the high-pressure event to the Meters and Regulations group in Lawrence, five minutes before a local resident made the first 911 call to Lawrence emergency services.
The work is about one-third complete, and the company says all customers should have gas service by Nov. 19.
Joe Hamrock, president of NiSource, Columbia Gas parent company, said in a statement that it is prohibited from comment or speculating on the cause of the incident until the federal investigation is complete.
But he noted that in the hours immediately after the incident, the utility company suspended similar work elsewhere and improved its procedures around low-pressure gas systems like the one in Lawrence.
We saw these as responsible steps to take in the aftermath of the incident and while the facts were being gathered, Hamrock said.
U.S. Sen. Edward Markey, a Massachusetts Democrat, said its still not clear how Columbia Gas could have allowed the disaster to happen, whether it could have been prevented and whether the company was adequately prepared to respond to a disaster on that scale.
The release of the preliminary report raises more questions than answers, said Markey, who, along with Democratic U.S. Sen. Elizabeth Warren, has been reviewing the companys internal procedures following the explosions.
The National Transportation Safety Board, in its report, says the disaster was rooted in failures at the planning stages of the Lawrence pipeline project, which was developed and approved by Columbia Gas.
The agency said the work package didnt account for regulator sensing lines, which it says are used to detect pressure in the distribution system so that regulators can control system pressure.
Federal investigators also noted that the utilitys monitoring center in Columbus, Ohio, received two alerts registering high pressure in the Lawrence system just minutes before the explosions.
The Ohio facility isnt able to close or open valves remotely but quickly relayed the high-pressure report to field technicians in Massachusetts, the report said.
Local utility officials shut down the impacted regulator within about a half an hour, and closed the critical gas distribution values about three hours later, according to the report.
The next stage of the federal investigation will look at coordination between the emergency responders and Columbia Gas and an analysis of the companys engineering, design and construction plans, according to the report.
Gov. Charlie Baker, meanwhile, said the state Department of Public Utilities will hire an independent evaluator to assess the safety of the states pipelines. It has ordered all natural gas pipeline operators in the state to review their procedures on pressure regulation, overpressure protection, energizing new and replacement pipelines, and tie-ins involving high pressure to low pressure distribution systems.