The Kansas Turnpike Authority plans to blast one of its original Kansas River bridges Nov. 15, dropping the steel structure into the water for removal and eventual salvage.

The second of the two bridges would be blasted Nov. 19.

The authority announced its tentative blasting plans Monday afternoon, now that turnpike traffic has been switched onto a new bridge that crosses the river at the northern edge of Lawrence.

All of the work is part of a $130 million project to replace the bridges, overhaul two interchanges and make other changes to handle increased traffic loads and prevent maintenance problems and rising expenses in the future.

Blasting the bridges originally had been expected to occur sometime in December, but crews have been efficient in removing concrete from the existing spans, said Lisa Callahan, a turnpike spokeswoman. Officials now expect to be ready to push the button on the first round of explosives the afternoon of Nov. 15, a Sunday.

According to the tentative schedule, the second span would be dropped the morning of Nov. 19, a Thursday. A third blast would be expected sometime in early December.

Officials caution that the plan remains preliminary.

“It’s still iffy on exactly what the dates will be, and certainly no times have been set just yet,” Callahan said. “They won’t blast or do demolition until all the concrete’s gone. It’s dependent on the removal of the concrete. It’s both weather dependent and how it (concrete removal) goes.”

The bridges were built in 1955, a year before the turnpike opened. Officials have said that the structures are reaching the ends of their functional lives.

While traffic no longer travels on either original bridge, turnpike officials won’t be taking any chances during blasting. As crews count down to demolition, law-enforcement personnel will be expected to create a rolling blockade for traffic on either side of the river — slowing vehicles so that none are on the new bridge as an old one is going down.

Likewise, for safety precautions, officials will prohibit onlookers from getting within 1,000 feet of either bridge as blasting approaches.