Caltrans says it's seen an increase in graffiti along Highway 99 from Atwater to Livingston.
Several of the new sound walls that were decorated with mountain mosaics are now covered in spray paint.
Taggers have also targeted underpasses in the area ... along with a very visible duplex just off the Highway. Caltrans say it's becoming increasingly expensive to cover the vandalism.
The Highway Patrol says it can be difficult to catch taggers because they do their work at night and then run off. But they're asking the public to call 9-1-1 if they see any vandals in action.