They do look like they are Chamaecyparis lawsoniana, making water molds likely. Why was that ruled out, testing showed none present?

If you stick new trees in there without knowing what, specifically killed these then you might have problems with the replacements as well.

The forestry extension agent did take samples of branches and leaves/needles and determined it wasn't root rot however I tend to think different. Now, I think there are other species of Chams and trees that are resistant to root rot and I'm thinking of planting a range of trees such as native hemlocks, spruces, maybe some deodars, coast redwoods, even pacific wax myrtle and bamboos. A bunch of stuff that would grow quickly and provide privacy. Not an easy spot to irrigate and maintain so much of the stuff would be left on their own so looking towards a fall planting. Any other ideas are appreciated. Thanks bboy for the comment.

are you below the trees... ken

yes Ken, the yard and rest of gardens are below the trees and the dog pen is within the trees. It's difficult to tell from the following photo but the trunk of the trees are behind the fence and shrubs. We noticed the browning of the branches last year and consulted with the forestry & extension offices plus an arborist who then trimmed the noticable branches from view. Now this year the back side of the tree(s) is going brown up to the top as pictured in the first post. The trunks of the trees are quite large and impressive hence our apprehension for total removal plus the loss of privacy etc. Yet, I feel it may be time for a demise and that is why I'm seeking suggestions for fast growing and hardy trees. This picture was taken in ApriI. hope this answers your question.

I'm out of my element giving advice to someone in Oregon,
but Douglas Fir and Western Red Cedar would seem interesting to me if I lived way up there. Spruces would also be marvelous. Can the Coastal Redwoods survive that far north?
And I would absolutely have to have an Alaskan Cypress. There are several cultivars of it that might be interesting for a specimen tree in addition.
So many choices for someone in your area. Didn't even get into pines. And Larches, isn't there a Western Larch? I get to choose between Eastern Red Cedar and Ashe Juniper. Luckily Arizona Cypress also does well here. Well best of luck on your choices.

Good suggestions! I did plant a couple baby firs this spring and we have Western Red Cedars as well. Also Coast Redwoods are planted in other areas of our yard. Thanks for the ideas.