Three walls must be replaced at Riverside School after the building was slammed by an out-of-control vehicle, according to an engineering analysis conducted Friday.

Brad Kiehl, an architect with the DLR Group in Overland Park, said a structural engineer with the firm concluded a pickup truck driven into a classroom late Wednesday at Riverside caused more than $100,000 damage to walls and contents.

However, he said, the building’s roof was sound enough to permit classes to continue at the 125-student school.

“Three outside walls will have to be rebuilt,” Kiehl said.

He said decisions about saving cracked-but-stable interior walls on the one-story brick-and-block building would have to be made after work on the exterior got under way.

For now, the hole left by the truck has been boarded over.

Law enforcement reports say Tristan Westphal, 23, Lawrence, was driving the pickup that ran a stop sign and slammed into the school late Wednesday night. Officials said alcohol consumption may have been a factor in the crash. Westphal was transported to Kansas University Medical Center in Kansas City, Kan., for treatment. He was listed in fair condition Friday.

It was the second time in two years that the special-education classroom at Riverside has been struck by a vehicle.

Randy Weseman, superintendent of Lawrence public schools, said the district would examine Riverside to determine whether special precautions need to be taken to guarantee the safety of students and teachers.

“Maintaining student safety is at the top of my list,” he said. “I don’t want to leave that to guesswork.”

He said installation of concrete safety barriers would be one option explored by district staff.

“Given that this is the second incident, that’s a discussion we’ll be having,” Weseman said.

Riverside Principal David Theilen proposed that the city install “rumble” strips on Riverridge Road to alert motorists of the stop sign in front of the school on North Iowa Street.

But the city’s traffic engineer said the strips were rarely used in urban areas and might not effectively deter drivers having trouble with the stop sign at Riverridge and North Iowa.

“It’s hard to design facilities to deal with impaired drivers,” said David Woosley, city engineer. “Rumble strips are useful to people who are aware of what they’re doing.”

Weseman said Riverside’s location on North Iowa, a street traveled by large trucks day and night, would be a factor in a continuing study by the DLR Group of Riverside and all other district facilities.

“Given where that sits on the road, that’s very different from all our other schools,” Weseman said.