Engineers spent the past few days inspecting the area and decided Wednesday night the bridge wasn't safe.
Dozens of people had to leave their cars and wait for the CHP to shuttle them home.
"I go up there twice a day to spend time with my horse, so it's inconvenient, but I understand the bridge needs to be fixed and that's most important," said Rona Schiffman, who frequently uses the bridge.
The CHP is out helping residents Thursday morning, and the County Public Works Department hopes to finish fixing the bridge by the end of the week.
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