The VTS area consists of the navigable waters of the Ohio River between McAlpine Locks (Mile 606.8) and Twelve Mile Island (Mile 593), only when the McAlpine upper pool gauge is at 13.0 feet or above. [CGD 90-020, 59 FR 36324, July 15, 1994, as amended by USCG-1998-3799, 63 FR 35531, June 30, 1998]