The Sierra Club says a new natural gas pipeline to Cape Cod could carry double the gas of the old lines, conflicting with public goals to reduce the use of fossil fuels.
But the pipeline owner disputes the idea that the new line — set to replace two pipes attached to the underside of the Bourne and Sagamore bridges — would increase gas capacity on the Cape.
Here’s how Sierra Club Massachusetts does the math: It calculates that replacing the two 10-inch-diameter pipes with a single 18-inch-diameter pipe increases the area of a cross-section of the piping by 62 percent. Then, the group adds the effect of two other things it says happen with a larger pipe: reduced friction against pipe walls and higher pressure used to pump the gas.
“The bigger the pipeline, the less wall friction there is, so the more gas can actually flow through it more easily,” said Eva Morgan, energy organizer at Sierra Club Massachusetts. “So your efficiency goes up. … And so with some very simple calculations, you can get to two times the current capacity.”
The U.S. Army Corps of Engineers has ordered the pipes moved to accommodate the replacement of the Bourne and Sagamore bridges, which it owns. The new pipeline will tunnel under the Cape Cod Canal at a location between the bridges.
Algonquin Gas Transmission, owned by Canadian energy company Enbridge, uses the pipeline to deliver gas to National Grid on the Cape. The pipeline feeds a downstream distribution system that is not expanding as part of this project.
Enbridge denies that the project would increase the capacity of the pipeline.
As evidence, spokesperson Melissa Shurburne cited limits written into the pipeline’s current federal permits, rather than how much the new pipe is capable of carrying.
“Natural gas pipelines are designed, permitted, and operated within specific capacity limits established through a rigorous regulatory process,” she said in an email. “We cannot simply increase the amount of gas flowing through a pipeline beyond its approved capacity.”
She declined a telephone interview and did not answer a question seeking to differentiate between the legally permitted capacity of the pipeline and the amount of gas it would be physically capable of carrying in the future.
The Federal Energy Regulatory Commission approves pipeline capacity based on engineering, safety, and other regulations, she said.
The Massachusetts Department of Transportation has agreed to reimburse Algonquin the full $302 million relocation cost, with the expectation that the old pipe and metering stations will be removed from the Sagamore Bridge well in advance of the start of construction of the new bridge in late 2027 or early 2028.
The Sierra Club contends that the reimbursement translates into taxpayers funding a future boost in profits for Enbridge.
“They're essentially profiteering off of taxpayer dollars, because they don't have to assume any of the risk of the expansion, and they can then sell that increased capacity for gas in the future,” Morgan said.
She said using more “fracked gas” on the Cape, now or in the future, does not align with the state’s goal to achieve net zero greenhouse gas emissions by 2050, or with the goals of the Regional Policy Plan prepared by the Cape Cod Commission.
“Increasing that capacity is both not good for the Regional Policy Plan goals and also just generally harmful for Cape Cod and Cape Codders,” she said.
Sherburne, of Enbridge, maintains that capacity would not be increased. She said a larger diameter pipe is necessary to offset pressure losses along the route.
“This helps maintain the necessary operating pressure and delivery capability throughout the system, particularly at the extremities of the system where pressure impacts are most pronounced,” she said.
A subcommittee of the Cape Cod Commission is scheduled to hold a hearing on the pipeline Oct. 28 at 5 p.m. at the Veterans Memorial Community Center in Bourne.
A Department of Transportation official said moving the pipeline is a prerequisite for construction of the new Sagamore Bridge to begin.
