A propane leak at the Logan Township Municipal Building construction site Wednesday morning led to adjustments for students at two nearby schools and warnings that nearby residents should stay indoors.
The leak occurred about 7:30 a.m. when a 1,000-gallon pressure tank of liquid propane being moved across a parking lot by forklift rolled from a pallet, breaking a valve, Fire Chief Reynold D. Santone Jr. said.
The rush of propane that boiled out triggered a spring-loaded safety shutoff, but moisture on it froze instantly because of intense cold generated by the release, blocking the shutoff plunger, Deputy Fire Chief Tim Hileman said.
About 10 percent of the gas escaped the tank, which was about 85 percent full, officials said. The gas flowing out hugged the ground because it is heavier than air.
While officials didn't detect gas with meters downhill and downwind in western Hileman Heights or Pleasant Village, police and firefighters went door-to-door to issue residents a warning to stay indoors, Lakemont Fire Chief Tom Sral said.
The gas is highly flammable and at concentrations between 2.2 percent and 9.5 percent can explode with a spark, Hileman said.
If the gas reached a critical concentration in a house, a light switch or other power source could have set it off, Santone said.
Altoona Fire Department Hazardous Materials Response Team members had hoses near the tank ready to spray water to disperse the gas if necessary, Hileman said.
With the help of construction workers, the hazardous materials team righted the horizontal cylinder. Using special gloves that protect against frostbite, they removed a shattered plastic cap that obscured the plunger and tapped it with a nonsparking beryllium mallet, Santone said.
That broke the frozen material loose, the rush of propane cleared it away and the plunger sealed itself, officials said.
The incident drew firefighters from all five Logan Township departments, the city and Pinecroft; police from the township, the city and Altoona Area School District; and the Blair County Emergency Management Agency.
Duncansville, Geeseytown and Hollidaysburg fire companies were on standby, Sral said.
The school district diverted buses on the way to Pleasant Valley Elementary School, sending students to the high school auditorium until about 9:15 a.m., when emergency agencies said the crisis was over.
Students were back at Pleasant Valley before 10 a.m., district spokesman Tom Bradley said. He said the district's emergency notification system alerted parents to the situation after 8:15 a.m.
Students at Bishop Guilfoyle High School were moved to the front of the school, Acting Principal Timothy Lucko said.
Propane boils at minus 40 degrees - its temperature as it escapes a pressurized tank where it is in liquid form, said Jeff Shaffer, president of the Pennsylvania Propane Gas Association.
Cooling occurs because when pressure goes down, so does temperature.
Workers at the construction site used the propane for heat, construction supervisor Ralph Thompson of Lawruk Builders said. They were moving the tank because they don't need it now that the heat is on in the building.
Staff Writers Walt Frank and Mark Leberfinger contributed to this story.
