|Geologist Says Feds Made “Incredible Error” Ignoring Huge N.Y. Salt Cavern Roof Collapse
In the 1960s, a 400,000-ton block of rock fell from the roof of an old salt cavern in the Finger Lakes region of New York — a cavity that new owners now want to reopen and use to store highly pressurized natural gas.
The Midwestern energy company that seeks a federal permit for the storage project has denied knowing the roof failure ever happened. And the Federal Energy Regulatory Commission (FERC), which is poised to rule on the company’s permit application, has never publicly acknowledged the event.
But a Houston geologist hired by lawyers for opponents of the project characterized the omission by Arlington Storage Co. and FERC as “an incredible error” that heightens safety concerns about the project next to Seneca Lake, less than three miles from the Village of Watkins Glen, population 1,860.
“Clearly, Arlington’s application and FERC’s conclusions are compromised by this error,” H.C. Clark wrote in a Jan. 15 letter that is now part of FERC’s public record in the case.
In the letter, Clark, who holds a Ph.D. in geophysics from Stanford and taught the subject for years at Rice University, analyzes a “400,000-ton fault block cavern roof failure” and rock faults surrounding the cavern. Clark draws on a series of long-suppressed reports written more than 50 years ago by a geologist for the company that then owned the cavern.
The fallen chunk of rock — roughly four times as massive as the U.S.S. Nimitz supercarrier — now sits on the floor of the cavern, leaving an unsupported rock roof roughly the size of a football field. The roof collapse created an irregular cavity that may soon hold pressurized methane drawn from natural gas wells in nearby northern Pennsylvania.
Both federal and state regulators are responsible for scrutinizing all plans for underground storage of volatile hydrocarbons. Salt cavern storage presents not only risks of human error in operating a complex industrial site, but also two categories of geologic risk: cavern collapses and leaks.
Geologic risks are slight in regularly-shaped cavities surrounded by pure salt, which is nearly impermeable. But when the cavity is highly irregular in shape and its boundaries are made up of more complex elements, including heavily faulted shale rock, risks can rise substantially.
When salt cavern accidents do occur, they can be devastating. Major fires and explosions struck at salt caverns holding LPG in 1980, 1984, 1985 and 1992, killing or seriously injuring people in three of those cases. Catastrophic accidents hit salt caverns holding compressed natural gas in 2001, 2003 and 2004.
More recently, in August 2012, the sudden collapse of a salt cavern wall near Bayou Corne, La., 75 miles west of New Orleans, has created a 26-acre sinkhole. The crisis is nowhere near resolved because energy companies store natural gas, liquid butane and various chemicals in adjacent salt caverns.
Several hundred residents who were forced to evacuate immediately have not been able to return to their homes in a year and a half. The state of Louisiana is now offering to buy out dozens of them as it copes with the latest threat: the buildup of explosive gases in the local aquifer.
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