Are pipelines safe in limestone?
This map, taken from a July 2014 official Williams response to federal regulators, shows the proposed route of the Atlantic Sunrise pipeline superimposed over Lebanon County’s karst belt (highlighted in blue). (Photo: Public domain)
(Undated) — Lebanon Pipeline Awareness member Michael Schroeder had a sinking feeling when he learned that a new natural gas pipeline would go through the county’s band of limestone-rich karst geology.
The Atlantic Sunrise pipeline extends from north to south across the face of sinkhole-prone land near Annville — a section of Lebanon County that already receives stress from vibrations at Fort Indiantown Gap, the Pennsy Supply quarrying operation, the busy Norfolk Southern train track and heavy traffic on Route 422, Schroeder said.
Atlantic Sunrise builder Williams admits that karst geology requires extra precaution, and geologists say risk is involved in any development that disturbs limestone and creates more opportunities for acidic water to break down the sedimentary rock, creating sinkholes.
Proceed with caution
However, Helen Delano, a geologic scientist at the Pennsylvania Department of Conservation and Natural Resources, said safe construction can take place on karst geology if proper precautions are taken to deal with the inherent risk.
“Here be dragons, but it’s not, ‘don’t ever go here safely.’ It’s, ‘if you really need to go here, spend extra money to go here safely,’” Delano said.
In Virginia, where 20 counties have pipelines likely over karst geology, karst-related problems “appear to be an insignificant percentage” of overall pipeline problems, according to the Virginia Cave Board.
Pipeline representatives also said history demonstrates that pipelines can be built safely in porous geology. Jeff Shields — a spokesman for Sunoco, which is building the Mariner East 2 pipeline through Lebanon County that will skirt the southern edge of the county’s karst belt — says he isn’t aware of a disaster caused by a pipeline in a karst area even though Sunoco has been moving liquids via pipeline since the 1930s.
Unlike Mariner East 2, the Atlantic Sunrise pipeline will only transport natural gas, not liquids. Williams has techniques for ensuring the safety of pipelines in karst geology and has already committed to using stronger steel and thicker pipes than required by regulators, spokesman Christopher Stockton said.
Jim Lolcama, a hydroecology expert for KCF Groundwater Inc., said there are special environmental and geotechnical concerns when building in sedimentary rock. However, there are building practices that make pipelines safe in porous geology, and the industry is heavily regulated to ensure it is done correctly, he said.
“You just have to be super careful, and you have to hire people who understand that particular animal,” Lolcama said.
Schroeder isn’t convinced that the plans are fail-safe. Even if the pipeline companies attempt to be as safe as possible, sinkholes can pop up at any moment in unexpected places, he said.
“It’s inherently unpredictable, and nature has a way of doing its own thing and not conforming to human desires,” he said.
Delano said it is possible that a sinkhole could occur somewhere unexpected, but sinkholes can be generally anticipated if a company both utilizes existing survey maps of sinkholes and examines carefully each property on which it’s building.
Spreading contamination
The biggest concern is that in the unlikely event of a leak, highly permeable rocks would allow a contaminating liquid like natural gas to spread more quickly, according to Lolcama and the Virginia Cave Board.
Within karst zones, the likelihood that a leak would easily spread varies greatly by location, said Sam Earman, an associate professor of geology at Millersville University. Some karst structures facilitate a rapid path for contaminated substances to reach the water table, but fractures and cavities in sedimentary rock can also keep groundwater inside their paths, thus causing wells to be less at risk for contamination, Earman said.
If a leak were to occur, the natural gas liquids in Sunoco’s pipeline would become gaseous because they would no longer remain sufficiently pressurized to be liquefied. Therefore, they would not spread like a liquid through rock, Shields said.
More ammunition for at least one side of the debate could come any day, when FERC releases an environmental impact study that is expected to touch on the risk of the Atlantic Sunrise pipeline to the karst formation. The study will be made available for at least 30 days of public comment and a series of public meetings throughout the length of the pipeline route will be held before it is finalized, said Ann Pinca, president of Lebanon Pipeline Awareness.
The Lebanon County commissioners also sent a letter to FERC in September requesting an additional “in-depth study” on the impact of the Atlantic Sunrise pipeline on sinkhole-prone areas in North Annville, South Annville and South Londonderry townships.
This article comes to us through a partnership between WITF and Lebanon Daily News.
Sometimes, your mornings are just too busy to catch the news beyond a headline or two. Don’t worry. The Morning Agenda has got your back. Each weekday morning, host Tim Lambert will keep you informed, amused, enlightened and up-to-date on what’s happening in central Pennsylvania and the rest of this great commonwealth.
