Good idea to document determination. - Particularly if you conclude you are not subject to the rule. - Not a rule requirement. See Section 2.4 of SPCC guidance document. http://www.epa.gov/emergencies/docs/oil/spcc/guidance/2_Applicability.pdf.
The age of consent is eighteen. With parental consent, parties can marry at age seventeen with the exception that if one party does not have a parent who resides in the state and one party has been a resident in Oregon for at least six months, then no permission is necessary.
In addition, states laws establish guidelines for minors with respect to providing medical consent, entering into contracts, suing in a court of law, and other legal processes. Nebraska is unique in that the age of majority is 19 (only two other states set the limit higher than 18).