Franky Boy Arborvitae.....brown on one side
We are seeing a lot of damage to conifers from the long hot summer not only this year but also the past several years. This puts stress on the tree or shrub making it susceptible to pests or diseases. The University of Pennsylvania has a page on Arborvitae Diseases which you might want to read. Oregon State also has a page, Leaf Browning and Shedding on Arborvitae which might also be helpful. I am unable to diagnose your arborvitae’s problem from photos. I suggest that you take photos and a physical sample of the browned or dead branches into the Yamhill County Extension Office at 2050 NE Lafayette St. in McMinnville. There the Master Gardeners will be able to examine the branches and leaves/needles under a microscope. They are open Monday through Friday from 9:00 to 4:00. Good luck with your Franky Boy arborvitae. It looks like a nice shrub.