Photo: Gerard O'Brien
Southern Partnership Group chairman Pete Hodgson said the rig was being used for geotechnical investigation.
It emerged last month the soils underneath the site were different types, alluvial in some areas and sedimentary in others.
''It's about trying to find more about the whereabouts and nature of the transition from the gravelly or alluvial soil from the Leith to muddy or sedimentary soil from the harbour.''
The rig would work at night, as holes had to be drilled in the cycle lane.
The work would probably be completed ''this side of Christmas''.
