Reedy Creek has filed Permit#: 48-00714-P with the South Florida Water Management District for a project titled Epcot Canal Modifications:

Quote Originally Posted by Permit#: 48-00714-P

Application #: 170515-17 Permit#: 48-00714-P Received Date: 15-May-2017
Issuing Office: ORL/SFWMD Application Status: Initial Review
Permit Type: Environmental Resource (Construction/Operation Modification) 30-Day Deadline: 14-Jun-2017
Project Name: Epcot Canal Modifications Project Acres: 26.83
Landuse(s): Commercial Location: Orange S30/T24/R28
Receiving Body: Reedy Creek / Lake Russell

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The project's official purpose according to the permits is to:

Quote Originally Posted by Drainage Design Summary
... reconfigure the existing canal to provide a more-contiguous area for possible future changes to parking capacity and back of house areas. A spur of the existing canal is proposed to be filled
so that a more developable area is provided.
Although vague, the new 26.83 acre construction site appears to be a first step in some sort of expansion for Epcot.

Of note, the area outlined in blue appears to be a new structure that is being speculated (but not confirmed) to be a new show building:

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The proximity of this mystery structure seems reasonably approachable from existing Guest areas and appears to explain the potential cause of the re-location of the existing canal.