A panel of experts and several studies are at odds over the distance at which heat from an ignited liquefied natural gas (LNG) tanker would pose a hazard to the public, according to a Government Accountability Office report released Wednesday. The agency called on the Department of Energy (DOE) to expand the issues under review in a current study to resolve this uncertainty and others.
"Understanding and resolving the uncertainties surrounding LNG spills is critical, especially in deciding on where to locate LNG facilities...While there is general agreement on the types of effects from an LNG spill, the results of [study] models have created what appears to be conflicting assessments of the specific consequences of an LNG spill, creating uncertainty for regulators and the public," said the GAO report, which was requested by several House lawmakers.
The GAO reviewed six studies of LNG hazards and interviewed 19 recognized experts in LNG hazard analysis. The studies' conclusions on the distance at which 30 seconds of exposure to LNG-generated heat could burn people varied, ranging from less than one-third mile to about 1 1/4 mile. A 2004 study conducted by Sandia National Laboratories, a DOE research lab in Albuquerque, NM, concluded that the most likely distance for a burn is one mile, a guideline used by the Federal Energy Regulatory Commission and the U.S. Coast Guard in setting the one-mile exclusion zones around LNG facilities and tankers in the event of a major spill and fire.
The study variations occurred because researchers had to make modeling assumptions since there are no data for large LNG spills, either from accidental spills or spill experiments, the agency said.
While the majority of GAO's panel of experts agreed that the most likely public safety impact from an LNG spill is the heat impact of a fire, there was some disagreement about the heat impact distances. Seven of the experts believed Sandia's distance of one mile was "about right," while eight experts were evenly split as to whether the distance was "too conservative" or "not conservative enough." Four experts did not respond to the question.
The experts, however, did concur that explosions are not likely to occur in the wake of an LNG spill unless the LNG vapors are in confined spaces, and that some hazards, such as freeze burns and asphyxiation, do not pose a problem for the public.
"We are recommending that DOE incorporate into its current LNG study the key issues identified by the expert panel," including large fire phenomena, cascading tank failure, large-scale spill testing on water and large-scale fire testing, the GAO report said. "We particularly recommend that DOE examine the potential for cascading failure of [multiple] LNG tanks" in the event of a terrorist attack or disaster. A typical LNG tanker has five LNG storage tanks and holds 125,000 cubic feet of LNG chilled to -260 degrees Fahrenheit. A single tank failure could potentially cause additional tanks to fail and leak, the report noted..
The GAO also urged DOE to focus on the heat effects from large-pool fires, rather than relying on hypothetical estimates based on much smaller fires that are not representative. Sandia National plans to carry out such research later this year.
"Although LNG tankers have not been subject to a catastrophic accident or attack, we need to ensure regulators are making decisions with a large enough margin of safety to account for the threats in the post-9/11 environment," said House Energy Committee Chairman John Dingell (D-MI), who was among the lawmakers requesting the GAO report. He said the committee plans to conduct hearings to ensure that DOE is conducting the research needed to make sound siting decisions for LNG terminals.
"LNG shipments do have an excellent safety record, evidenced by the fact that more than 40,000 tankers have delivered LNG over 47 years without a major spill," said Rep. Joe Barton of Texas, the ranking Republican on the panel. While "that's good news," he said "GAO's recommendation for continued research on the theoretical impact of a major spill is only prudent."
But Rep. Edward Markey (D-MA) was more critical. "It's very troubling that our knowledge about the potential public safety consequences of a terrorist attack on these vessels is not better," said Markey, a committee member whose district includes the nation's only urban LNG import terminal, the Distrigas facility in Everett, MA.
"The GAO...reports that a study the Energy Department recently commissioned to address large-scale LNG fires only looks at three of the top 10 issues that the experts believe need to be addressed, and that this DOE study won't include any examination of one of the most serious accident scenarios that experts believe could cause the most damage -- a cascading failure of the LNG tanks on these vessels. I believe the Energy Department needs to expand its current LNG study immediately so that it examines all of the top LNG safety issues that GAO has identified," he noted.
The GAO report coincides with a projected 400% increase in LNG imports over the next decade, according to the House panel. To respond to the expected influx of imports, U.S. energy companies have submitted 32 applications at FERC to build new LNG terminals in 10 states and five offshore areas, the GAO report said. As of October 2006, the Commission had approved 13 of the applications.
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