An authorization letter for HEC is a legal document which gives permission to a third person to go and attest the degrees and transcripts on your behalf. Table of Contents. 1.Executive Summary. 2. The Assured and Adequate Water Supply Rules, A.A.C. R12-15-701 et seq. The City of Phoenix notifies affected property owners that they are no longer in a floodplain area when a Letter of Map Amendment or a Letter of. The longer it takes students to finish a certificate or degree, the more likely they are to drop out of college.