When the old Liberty Memorial Bridge gets dropped in the Missouri River in a few weeks, it won't go out with a big bang.

The out-going will be more of a quick burn, followed by a big splash.

Contractors have yet to finalize a date when demolition of the bridge will begin, but it will likely start within the first 10 days of October.

Joel Myers of Lunda Construction, the main contractor for the new bridge, said by freeze-up, people won't know it was ever there.

The old bridge was completed in 1922 and formally dedicated Sept. 18, on the 50th anniversary of the founding of Bismarck.

It was christened Liberty Memorial Bridge to honor North Dakota soldiers who served in World War I.

Back then, about 12,000 people attended the dedication, which spanned three days in Bismarck and Mandan, and celebrated with parades, dances and even a pageant.

Mike Kopp of the North Dakota Department of Transportation said the old bridge was designed to last 50 years.

"So here we more than 80 years later; it's really quite something," Kopp said.

Kopp said rust took its toll in places on the old bridge and of all things, pigeon droppings, very high in uric acid, hastened the corrosion process.

Myers said the actual demolition will be done by a subcontractor, DemTech out of Wyoming.

But before that, what ever can be pulled, pried and parted from the existing structure will be done ahead of time.

A different subcontractor, Total Construction from Inver Grove Heights, Minn., is in charge of dismantling what it can before the remainder is dropped in the Missouri.

The railings, sidewalks and decks will be removed and hauled off for salvage before the actual trusses and supports beams are virtually burned through.

"They are taking off everything that can be taken off," he said.

Myers said the demolition charges, known as "shaped charges," are affixed to strategic points on the structure and when detonated, literally burn through the up to half-inch thick steel in a matter of seconds.

Shaped charges are also used in the oil and gas industries as well as for military applications in armor-piercing bombs.

Myers said the west third of the bridge will be the first to go, followed by the middle.

He said there will a break while a temporary road into the river itself is removed, before the east third of the bridge comes down.

"It will come down in three different shots." Myers said. Each section, as it comes down, will be about 480 feet in length.

When the bridge does drop into the water, Kopp said a 165-ton crane, floated on a barge, will have 24 hours to remove the debris.

The concrete piers in the river itself will have to be removed as well.

Holes have already been drilled where charges will be set; when set off, the piers will be fractured.

From there, Myers said a hydraulic breaker will be used to demolish what remains.

There will, however, be a portion of the old piers that will remain submerged under water.

Kopp said the piers must be removed to an elevation of 1613 feet, about 10 feet below the current level of the river.

(Reach reporter Brian Gehring 250-8254 or brian.gehring@bismarcktribune.com.)