As the lake began to fill, increasing levels of water began to flow from the drainage channels behind the grout curtain in the right abutment, which indicated that the grout curtain was faulty. Investigations concluded that further grouting would have to be performed (which took about a fortnight) before the lake could be raised to its final level. The decision was made to allow the lake to fill to no further than the crest of the spillway while the contractors began drilling and inserting more grout.