A motorist barreled through the intersection of Highway 128 and Tubbs Lane outside Calistoga early Tuesday, hitting a rock wall, the California Highway Patrol reported.
The driver, Heather Marie Oleary, 31, of Penngrove, was taken to Queen of the Valley Medical Center in Napa with major injuries, the CHP said.
Her passenger, Kameron Oleary Booker, 3, sustained moderate injuries and was also taken to the Queen, the CHP said.
The CHP arrested the driver, who was not wearing a seat belt, for investigation of DUI. Investigators said the child was not properly restrained in a child safety seat.
The collision occurred at 12:35 a.m. Oleary's car was westbound on Tubbs when it drove through the intersection with Highway 128 at a high rate of speed, failing to stop at the stop sign, the CHP said.
The southbound lane of Highway 128 was partially blocked for a time.
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