The two-lane sealed road runs along the Tekapo power canal between the Tekapo A power station and SH8 but was closed in November 2008 after owner Meridian Energy Ltd discovered a slump and seepage.
The road was closed so a patch could be put in place, but has remained shut because Meridian is still monitoring the problem to find out how much seepage exists and is considering a permanent solution.
Meridian spokesman Alan Seay said monitoring equipment was in place and Meridian wanted to keep the public away from the area.
He did not know how long the canal road would remain closed.
"We want to do it once and do it right with as little disruption as possible," he said.
The slump in the canal was found in October 2008, about 8km from the Tekapo end of the canal in an area which had caused problems since the upper Waitaki power scheme was built in the 1980s.
An inspection team, including divers, identified the extent of the problem and a temporary fix using packing, lining and wire rack cages was put in place.
The remainder of the canal road, which includes the Mt Cook Salmon farm, from SH8 almost to the Tekapo B power station on the shores of Lake Pukaki, remains open.
