Unless there are "extraordinary circumstances," the initial growth plan remains in place for three (3) years.  After the three years, the growth plan may be amended as often as necessary. T.C.A. § 6-58-104(d)(1).  Municipal or county mayors are to propose amendments to the growth plan.  The mayor proposing the amendment is to file notice of the amendment with the county mayor and mayors of all the municipalities in the county.  Upon receiving the notice, the county mayor shall reconvene or reestablish the coordinating committee within sixty (60) days.  The coordinating committee then has six (6) months from the date of its first meeting on the proposed amendment to submit its recommendation to the local governing bodies.  The amendment shall become part of the county's growth plan after being approved by the local governing bodies and the local government planning advisory committee.  The burden of proving the reasonableness of the change is on the party proposing it.