Oregon Revised Statutes Public Health and Safety § 454.675

Subsurface sewage disposal systems, alternative sewage disposal systems or nonwater-carried sewage disposal facilities or parts thereof which were constructed prior to January 1, 1974, but which are not creating a public health hazard or causing water pollution shall not be required to conform to the construction standards adopted subsequent to their initial construction. However, all alterations or repairs of such systems or facilities or parts thereof shall be made in accordance with the rules of the Environmental Quality Commission.