Tankers provoke disaster fears
Publication: Portland Press Herald
By Larry David Hansen
Staff Writer
ELIOT – For nearly one-quarter of his 73 years, Wilbur (Johnny) Morgridge has sat calmly and watched huge oil and gas tankers navigate past his home along the Piscataqua River.
Often, vacationers run onto his property to see the spectacle. The ground trembles, the ship’s shadow swallows neighborhood homes, while newcomers to the experience become awestruck admirers.
“They think it’s beautiful,” Morgridge said. “One time, an elderly couple from Massachusetts was jumping up and down as a tanker went by. Then, they came up to me and offered me $300,000 for my place.”
The sight of tankers, many longer than two football fields, also impresses David Brown. But as the new director of the Maine Emergency Management Agency (MEMA), Brown feels another emotion: concern for public safety.
Brown’s business is predicting and preparing for catastrophes. He fears a catastrophe could result from an accident involving what he believes is the most dangerous hazardous material transported up the Piscataqua River: liquid petroleum gas, used as propane.
The fact that four to 18 million gallons of liquid petroleum gas (LPG) is transported at any one time up the second-fastest tidal basin in the country unnerves Brown. He sees the snakelike power of the Piscataqua River, the shoreline populations of Kittery, Eliot, and Portsmouth and Newington, N.H., and wonders what could happen if, for instance, an LPG vessel ran into one of the three bridges, causing a leak.
Brown fears an explosion. Experts say a major explosion of one LPG tanker could bring down Interstate 95. The United States Coast Guard LPG Hazard Assessment chart states that if 21,000 tons of LPG leaked through an eight-inch hole in a vessel and encountered a flame, fire would rise 210 feet in the air, and anyone within 510 feet would be endangered.
The chart also projected that if a tanker with 3.3 million gallons of LPG completely exploded, the “flame length” would be one-quarter of a mile, and anyone within 2.7 miles could be endangered.
Brown, in his fifth month as MEMA director, wants to make sure that the emergency response of Maine and New Hampshire can handle such a catastrophe.
“I just want to assure myself that there are emergency plans for these LPG tankers,” he said. “If I can assure myself then I can assure the Maine citizens.
“LPG is not a horrible, horrible thing,” he said. “It’s a danger, just like a lot of other things in our world. I just want to be sure we know what the risks are, and how to handle them.”
‘Table-top’ drill
Brown is hoping that his confidence in the emergency plans will come on Sept. 19. That day, about three dozen public safety officials from Maine and New Hampshire will sit down for the half-day “table-top” drill to test safety and evacuation response to a hypothetical tanker accident on the Piscataqua River. This scenario, not yet revealed, may involve any one of the several hazardous materials moved down the river.
Among these hazardous materials are asphalt, fuel oil for Pease Air Force Base, heating oil, kerosene, and sodium hydroxide.
LPG is not the most common material transported. Of the 195 tanker vessels on the Piscataqua River in 1986, only 11 hauled LPG, according to Lt. Commander Dennis Sande, of the U.S. Coast Guard Marine Safety Office in Portland.
But Brown, as Maine’s chief guardian of public safety, is more concerned with LPG than the others.
Fred Brann, oil and hazardous materials specialist for the Maine Department of Environmental Protection, said LPG has two dangerous elements. Upon leakage, LPG, which is heavier than air, will immediately become a vaporous gas before settling to the ground. If an accident happened, and a major leak dispersed a cloud of propane into the air, Brann said, people could suffocate and die.
The other danger, far more spectacular, is what Brann refers to as a BLEVE (boiling liquid expanding into a vapor explosion). A BLEVE occurs when an outside source of heat, such as fire, heats the container to the point of an explosion.
“If a BLEVE occurred under Interstate 95, the bridge would probably be blown up,” said Brann. “But the probability of a BLEVE is extremely slight, otherwise we would never allow it (transport of LPG).”
BLEVEs are extremely rare, and none involving an LPG carrier has been known to occur in this country, Brann says. And there has never been an LPG accident on the river in which the public was endangered, according to Sande, executive officer of the U.S. Coast Guard’s Marine Safety Office, responsible for monitoring all seaway activity from Portsmouth to Canada.
“It (a BLEVE) simply can’t happen,” said Lawrence Heffron, senior vice president for Sea-3, the Newington company that is the only seaport facility north of Providence that imports LPG.
Safety measures
The tankers that carry LPG are equipped with elaborate safeguards to prevent such incidents.
The tankers, from 500 to 700 feet in length, contain three to four compartments that act like thermos bottles. The separate compartments reduce the hazards of a leak. If a leak occurred in one compartment, that puncture would not directly affect the containment of the other compartments.
These containers, usually low-carbon steel, are surrounded by several feet of insulation. About 123 inches of either perlite or urethane usually covers the compartments. And a constant stream of nitrogen, circulating within the two to four feet of “dead space” next to the outer shell, acts as another layer of insulation.
The nitrogen also prevents air from entering in the event of a rupture to the tanker’s outer shell. If the containers were exposed to the air, the liquid fuel could boil into a vapor.
The pressurized compartments keep the liquid at about -44 degrees Fahrenheit.
Surrounding the volatile LPG, the outer shell of the tanker is made of a thick steel mixture that has the strength to withstand the low temperatures and pressure.
“An LPG tank has to be airtight,” said Lt. Brian Conaway, chief of the emergency response branch for the Coast Guard’s Marine Safety Office. “It can’t lose pressure. It can’t lose temperature; otherwise it will turn into a vapor. Then we would have a problem.”
Coast Guard officials say the chances of a serious incident affecting the public are extremely remote. Conaway said if a leak ever did occur, the ship would either be pushed back to sea or firefighters would spray the leak with water to disperse the vapor, thus removing any possibility of an explosion.
“When the vapor cloud is dispersed, it can’t support any type of combustion,” Conaway said.
The Coast Guard, with authority over the tanker movement, is responsible for initiating any emergency plans in case of an incident. Its plan, the LPG Vessel Movement and Emergency Contingency Plan, is accompanied by the Piscataqua River Disaster Plan, developed by surrounding communities.
Importer’s plan
Sea-3 also has developed its own emergency procedures plan.
The Coast Guard becomes involved before the ship enters the mouth of the river. Coast Guard inspectors meet the vessel when it is anchored about two miles at sea. A pre-entry inspection begins, as officials check gauges to make sure the pressurized tanks keep the liquid at its cold cryogenic state.
Then, the Coast Guard clears about a two-mile stretch of the Piscataqua River so no craft will hinder the LPG movement. This river evacuation is conducted only for LPG vessels.
Tugboats, along with two Coast Guard escort boats, meet the LPG tanker as it enters the river mouth. The caravan then begins to meander up the winding river, passing under three bridges before docking at Sea-3’s facilities a mile upstream.
When the liquid has been pumped into Sea-3’s 19-million-gallon capacity tank, from four to 24 hours after docking, the vessel is escorted back to sea.
During this entire process, Coast Guard officials stay aboard the vessel. And all area fire department officials have been alerted to the LPG movement, according to George Pierce, deputy chief of the Portsmouth Fire Department.
Pierce said his department has had practice drills dealing with LPG scenarios on the river. But for many public safety officials, Sept. 19 will be the first time they will be involved in a hazardous materials exercise that includes about 35 public safety agencies from Maine and New Hampshire.
“I haven’t seen one of these in my seven years here,” said Lionel J. Lamontange, director of the York County Civil Emergency Preparedness.
Drills of this type were much more common during the 1970s, according to Dick Holt of Portsmouth Navigation, the only tug boat company on the Piscataqua River.
MEMA’s David Brown hopes next month’s drill will give him the confidence he wants for the emergency plans of this river. Having discovered a few errors in various emergency plans around the state during the historic April flood, the new director of MEMA has learned never to have confidence in an emergency plan until it has been tried.
“I want to see it (the plan), read it. Then I want to test it, and see the test,” Brown said.