Two hundred fifty-one feet down, another 251 feet to go.

Today’s successful dropping of a 250-ton section of original Kansas River bridge along the Kansas Turnpike now has officials turning their attention to 10 a.m. Thursday, the anticipated time for detonating another 6 pounds of explosives to cut through the rusted steel structure.

“This went great,” said Rex Fleming, the turnpike’s project engineer, at the blast site Sunday afternoon. “We’re ready to do it again.”

More than 150 onlookers crowded into parking lots, under shelters and up against trees Sunday in Burcham Park to observe the first bridge blast. It’s all part of an ongoing $130 million project for the Kansas Turnpike Authority, which is replacing its 55-year-old river bridges, overhauling two Lawrence interchanges and making other upgrades through the end of 2011.

Jeremiah Seibel, 11, watched the blast with his mom, dad and 4-year-old brother. He said the explosion didn’t differ all that much from the firecrackers he’d seen obliterate plastic cups.

“It’s just bigger,” he said. “I just knew it’d be awesome.”

Officials moved up today’s scheduled blast time in anticipation of a break in the rainy weather arriving in the Lawrence area about noon. The first drops of rain started dotting Lawrence pavement about 7:30 a.m. today, and a few hours later were soaking the entire town — including the 250 tons of steel set to be dropped by detonation. The decision came just before 11 a.m., as officials observed a break in Emporia. The new 12:15 p.m. time was set at 11:50 a.m.

Officials had been expecting rain all along. The only question was how much rain would come, and whether a break would arrive.

The turnpike’s lanes needed to be dry enough to keep pavement safe for traffic to slow down during “rolling roadblocks” led by the Kansas Highway Patrol on either side of Lawrence as blast time approached.

The explosion left no debris on the new Turnpike bridge. Turnpike traffic was stopped in both directions for the explosion. Soon after, traffic resumed.