Upon due notice to all parties in interest, the Public Utility Commission shall hear and determine the cause of such injury to the land or other property adjoining such stream. When the Commission determines that such injury was caused by the driving or floating of lumber, it shall fix the compensation to be paid therefor, including expense for witnesses and a reasonable attorney fee, and render decision accordingly, which decision shall be final and a bar to any other action brought for such damages. (Amended 1959, No. 329 (Adj. Sess.), § 39(b), eff. March 1, 1961.)