The mural, which was completed in October, is painted on a wall on state Route 94 near the Home Avenue off-ramp. Friday morning it was covered from end to end with graffiti scrawled in purple spray paint.
The painting is protected by a special coating that protects it from vandalism. Caltrans crews cleaned about half of the mural Friday afternoon using power washers.
They plan to finish the cleanup over the next few days.