The State Engineer shall make a written decision and Order containing Findings of Fact and Conclusions of Law. Such decision and Order shall be made of record in the Office of the State Engineer and will, without further action, become the decision and Order in the case on the 15th day thereafter. Forthwith upon receipt, the State Engineer shall send a copy, by prepaid mail, to each party or his attorney.
037-8 Wyo. Code R. § 8-23