Part of an original Kansas River bridge along the Kansas Turnpike is scheduled to be blasted at 12:30 p.m. Sunday, marking the first of three explosive events connected to a $130 million reconstruction project.

The first blast targets a section of the bridge that used to carry traffic heading east through the northern edge of Lawrence. The section’s concrete deck already has been removed, and what’s left behind — a 250-ton lattice of steel beams — will be cut with 100 pounds of directional charges.

The steel framework will fall 15 to 20 feet onto a sand work surface below, then moved aside to be recycled. A second blast is set for 10 a.m. Thursday. And then the remaining bridge sections to the west — stretching across the water and onto the west bank — will be scheduled for blasting sometime in December.

Spectators will be barred from getting within 1,000 feet of the bridges leading up to and immediately following the blasts.

Anyone wanting to watch the blasts is asked to gather in the city’s Burcham Park, which is along the river and can be entered from Second and Indiana streets. Walkers can enter the park using a half-mile natural trail from Constant Park, northeast of Sixth and Tennessee streets.

Others will be able to follow the action from off-site: LJWorld.com plans to stream video of the blast live, from Burcham Park.

The original bridges are being removed, now that turnpike traffic has been steered onto a new bridge. Once the original bridges — built in the 1950s — are gone, crews will start building a second river bridge in their place.

During the blasts, traffic will be prohibited from traveling on the new bridge. The Kansas Highway Patrol will lead temporary “rolling roadblocks” along the turnpike near Lawrence, slowing traffic to 30 mph or 40 mph to keep traffic away and give crews time to be sure the bridge is clear of debris.

Also to be closed leading up to the blasts: the entrance ramp for eastbound traffic at Exit 202, and the entrance ramp for westbound traffic at Exit 204.

“Safety is our number one concern,” said Lisa Callahan, a turnpike spokeswoman.

The blasts are part of an ongoing project to replace the river bridges, overhaul interchanges and make other changes along the turnpike as it runs along the northern edge of Lawrence. The entire project is scheduled for completion by the end of 2011.