Excavation uncovers Clyde fault

Press, 14 June 1983, Page 3

Excavation uncovers Clyde fault

PA Wellington Fault zone damage at and around the Clyde dam site has been found by the Ministry of Works and Development during excavation. Although the Ministry was aware of the general nature of the geological problems, specific patches of broken ground, fissure lines, and difficult rock strata have been uncovered during dam excavations. With excavations now almost complete, the Ministry said that by following its normal procedures of digging out “soft” rock and backfilling with concrete, the Clyde site, with all its faults, could be brought to within New Zealand earth-quake-risk standards. The dam consortium has established site offices and

is now doing some foundation work, building a plant to make concrete and arranging its sub-contracts. It is not yet ready to begin building the dam itself.

The Wellington-based head of the Ministry’s Power Division, Mr Mike Williams, said problems had been posed by geological weaknesses in the area where the dam’s right abutment will be fitted. Shears angling downwards would have to be dug out and backfilled.

“Rock is never solid,” Mr Williams said; “Every dam we have built has some sort of foundation problem, not necessarily from faulting. Clyde has an active fault closer than any other we have worked on but it is well within our standards.”