Seeing your post regarding how the dam construction was halted every Winter brought a question to my mind.
It is as follows. Have you found any reference regarding how the structure was prepared for the Winter? Was the clay area capped with more typical fill or covered to protect it; then removed in the Spring?
It occurred to me that the could be a break in continuity of the clay barrier if the cap material(if they did cap it) was not completely removed in the Spring. Seems to be a basic simple question but in the case of this project they appear to have overlooked some very simple things.
From the records, they never really stopped. They worked around the clock with night lighting. However, in certain "stages", they had to relocate the massive 76inch wide belt conveyor system to the next planned strategic location. This "relocation work" took time and created interruptions during the filling/compaction construction.
The more important factor was that certain construction layers were exposed to seasonal rains during this compaction process. Extra hydration of the fill material becomes more dense and less pervious (more resistant to waterflow) in the compaction (actually, it becomes a ratio of compaction AND consolidation from the heavy equipment).
The precise schedule timing of the seasonal rains to the large conveyor system reconstruction to the next large "section" is not specific. The only references is that the DWR construction historical documentary videos identify alignments to certain layers to certain years. (i.e. 1964 for the "hump" section in the toe axis area, 1965 of 22 million cu yds for layer 1, 1966 of 22 million cu yds for layer 2, and 1967 of 19 million cu yds for the third and final layer.
Each layer required a major deconstruction and then reconstruction of the large conveyor system.
So the seasonal rains became part of the densification of "layer" sections of the dam. The best evidential clue to these densification layers have been revealed in prior posts - as internal seepage & saturation lateral water flows align to the layer seams.