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.
Preliminary report details cause of Merrimack Valley gas explosions
“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.
LAWRENCE, Mass. (AP) — Federal investigators are confirming overpressurized natural gas lines were the source of the deadly explosions and fires in communities north of Boston last month.
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.”
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.
“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.”
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.”
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