On the northern edge of the Majestic Star Casino construction site, crews are using a crane to pluck 60-foot steel beams from the snow-covered ground.
In the process, they are unearthing a mystery from the 1920s.
The beams are visible from Reedsdale Street and the West End Bridge off-ramp to the North Shore. They form a tight grid and are buried deep, with only the top 5 feet protruding above the ground.
The beams once were part of a "deep foundation system" often used to stabilize heavy structures on unstable land, said Burton Holt, technical operations manager with Ackenheil Engineers of Banksville.
But what structure did the beams support?
According to local historians, engineers and Tribune-Review research, the beams might have formed the foundation of a large iron gas tank that exploded in 1927.
The blast, reported at the time as the largest gas explosion in the world, killed 26 people, leveled much of the North Side and damaged buildings as far as 20 miles away.
"A terrific, deafening explosion ... brought terror and tragedy to Manchester and adjoining North Side districts," wrote the authors of Story of Old Allegheny City, published in 1941 by the Allegheny Centennial Committee. "As houses collapsed and chimneys toppled, brick, broken glass, twisted pieces of steel and other debris rained on the heads of dazed and shaken residents who had rushed into the streets from their wrecked homes."
Workers discovered the grid of beams in early January as they cleared the site, said Ted Howard of Independence Excavation, an Ohio firm that has been contracted for the casino's construction.
The discovery did not surprise workers.
"At a site like that, finding pilings is not unusual," said Ed Fasulo, project manager for PITG Gaming, which owns Majestic Star. "They're support pilings. For what, they did not know."
Holt, who is not part of the casino construction but reviewed photos of the beams, said they might have supported the gas tank.
"Given the number and close spacing of the piles, the previous structure was probably heavily loaded," he said. "I can't tell if the piles supported the gas tank, but it is a possibility."
He added that corrosion suggests the beams are 50 to 100 years old.
In addition, the beams are in the exact location of one of three gas tanks on the Reedsdale lot that exploded in 1927, according to maps from the time.
On Wednesday morning -- the day crews removed the first beam at the construction site -- David Grinnell, chief archivist at the Senator John Heinz History Center, hunched over a map from the 1920s.
A white sheet of paper had been pasted over the section of the map showing the Reedsdale lot. But the paper was thin enough to see through.
On the original map were three circles. Below one, just east of Fontella Street -- the exact location of the unearthed beams -- were the words: "Iron Gas Tank. Damaged. To be removed."
Grinnell then opened a map prepared by the Pittsburgh Regional Planning Association and City Planning Commission as part of their 1954 North Side Study. It showed that a building had been erected on the lot.
That building was a U.S. Steel subsidiary's warehouse. It was razed in 1994 after the Gateway Clipper owners purchased the land, said Terry Wirginis, who runs the riverboat company.
Grinnell said the warehouse could have been built on top of the old gas tank foundations.
U.S. Steel spokesman John Armstrong said it is impossible to determine if the beams were part of the warehouse construction. But he added that a warehouse -- as opposed to a production facility -- would not have needed a platform for heavy machinery or any other large objects.
Still, no one could say for sure that the beams were part of the gas tanks.
"But it's quite interesting," said Christine Davis, an urban archaeologist in Verona who worked on land surveys for the builders of PNC Park and Heinz Field.
"If this is the site of the gas explosion, that would be the type of historical site that should be documented," she said. "It would be wonderful documentation, and we could do it quickly."
Fasulo said there are no plans to stop pulling the beams from the ground.
Howard, of Independence Excavation, said there was no survey done on the land, but that the beams must be removed because part of Majestic Star buildings will be built on the site.
Uprooting the beams should take at least 10 days, he said. By Thursday afternoon, 25 of the 250 beams had been removed.
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