Plan review requires engineering on Pole Building portion of project

Hello, I used to work with AutoCAD to add fire alarm plans to existing building plans and want to build an out building on my property in Clayton, WA. I drew up plans with the available information I could obtain and found when I went to submit for a permit that the portion of the building that was “post frame construction” requires engineering approval and stamp. The portion of the building that is conventional construction with foundation and frame does not require engineering approval as it falls under existing prescriptive codes that must be met. Not realizing that I was going to have a challenge in obtaining a permit I had previously worked with a lumber yard and truss company in North Idaho with my plans and purchased all of the 6” X 6” X 20’ timbers, the trusses, 2” X 8” X 12’ roof purlins, joist hangers, 7/16” OSB roof sheeting, roof metal for the pole building and a 12’ Wide X 14’ high coil garage door (purchased used). I am hoping with your help that you can use the drawings and information that I am providing you to provide engineered plans for the pole building structural portion and allow me to utilize the materials that I have purchased as they are not returnable. I will be able to provide all of the additional support drawings required for the submittals such as cover page, site plan, etc. Best regards, George Bacon