20 year old evergreens dying from bottom up - slow death

Thank you Cheryl.

I believe it's more than that and it could be water needs, they grow in moraine type soil. The thing is, one started, then the one next to it and it is slowly passing along. If I thought it was a pests, I do have a pesticide licence. I see some in the forests and they seem to be like mine and in a group are dying from the bottom.

I have an article from Colorado somewhere and can't put my fingers on it right now, but it sort of made sense. I have cut 3 down and will replace them with cedars. I have thousands of cedars and a backhoe so I can put big ones in and hope for the best. I live on a busy road and these trees were my noise and privacy buffer.