Dive Brief:

• The Massachusetts Department of Public Utilities (DPU) has ordered Columbia Gas to halt all non-essential work on its pipeline system until at least Dec. 1 as it assesses the company's pipeline system and its operations practices following a deadly series of explosions last month.
• The DPU is also in the process of hiring an independent evaluator to assess pipeline infrastructure throughout the state, "out of an abundance of caution," a state official said.
• Both decisions followed preliminary findings by the National Transportation and Safety Board (NTSB) that the overpressurization of Columbia's pipeline system was caused by bad work orders transmitted to a work crew contracted by Columbia Gas.

Dive Insight:

Massachusetts' gas customers have been on edge following September's tragic accident, as human error is apparently to blame in a pair of incidents.

The NTSB's preliminary findings point toward mistakes made by the utility, so the DPU has called a halt to all work by Columbia Gas. That comes at roughly the same time regulators also halted all work by National Grid when it reported an overpressurization incident of its own.

The moratorium on work by Columbia Gas "will not impede the emergency restoration services in the Merrimack Valley and allows the DPU to approve additional work upon request by the company," the Massachusetts Office of Energy and Environmental Affairs (OEEA) said in a statement.

In the aftermath of the September explosions, Gov. Charlie Baker, R, put Eversource Energy in charge of recovery after concluding Columbia Gas was not prepared to address the issue.

The DPU "is in the process of hiring an Independent Evaluator to assess, out of an abundance of caution, the safety of pipeline infrastructure throughout Massachusetts," according to Peter Lorenz, a spokesman for OEEA. 

The NTSB preliminary assessment found the overpressurization happened after a Columbia Gas-contracted work crew was performing a pipe replacement project in South Lawrence, Mass., working on a tie-in project of a new plastic distribution main and the abandonment of a cast-iron distribution main.

The abandoned distribution main "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," according to the NTSB. 

As pressure dropped in the abandoned main, system regulators increased pressure in the distribution system and allowed "the full flow of high-pressure gas to be released into the distribution system supplying the neighborhood, exceeding the maximum allowable pressure."

The system over-pressure killed one person, sent 21 to the hospital, damaged 131 structures and destroyed five homes.

National Grid is also restricted in the work in can perform, after an overpressurization incident that resulted in service being shutoff for some time. The utility said the incident was brief, no customers were evacuated, and the mistake was corrected within a few minutes. The moratorium will remain in place until National Grid's safety practices have been reviewed.