In about a week and half, a landmark that has stood watch over the Missouri River for more than 80 years will disappear from the landscape.

The final two truss spans of the old Liberty Memorial Bridge, opening in 1922, will be dropped into the Missouri River at 10 a.m. Oct. 29.

Mike Kopp, North Dakota Department of Transportation spokesman, said workers with Total Construction, the Minnesota contractor on the new bridge, and Demtech, the Wyoming demolition contractor, are making final preparations to drop the two spans.

The west span on the Mandan side of the river was demolished with 43 pounds of explosives at 10:07 a.m. Oct. 6.

Onlookers crowded both sides of the river to get a glimpse.

Because of the large crowds expected for the final blast, residents should be aware of road closures during and leading up to the final blast, Kopp said.

"The concrete bridge deck and secondary members have been removed," he said.

Workers are in the process of making the pre-cuts on the main support sections where charges are to be set.

For public safety, law enforcement will be enforcing a 1,000-foot safety zone around the area.

"Some flying debris may be possible with the detonation of the final two spans," Kopp said.

Both River Road and the recreational trail along River Road on the Bismarck side of the river will be closed the morning of blast.

Kopp said River Road will also be closed for several days leading up to the Oct. 29 blast date.

Beginning early next week, the road will be closed as contractors remove portions of the concrete east approach of the old bridge.

Kopp said River Road will remain closed until near the end of the month.

"In the interest of public safety, the recreational trail along River Road will also be closed during part of the time in which the east approach bridge is removed, approximately one or two days early next week," Kopp said.

Anticipated work for next week includes: forms stripped from west approach and median barriers; removing dockwall and dock from west staging area; beginning of restoring staging area to original condition; texturing last sections of bridge deck; installing median rail; wiring pier lights and overlook lights; and touch up paint and texturing concrete surfaces.

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