Keeping to a 1' cap without removing the gravel means we would alter the planned contour and raise the bottom 18" in one area, but dig deeper in an area where there is no gravel to get the depth. I will also discuss with the contractor removing the first foot of gravel and filling back in with clay. Removing the clay "cap" over these areas would ensure the we know more precisely the clay layer thickness and allow the layer to be better mixed.
When you have highly variable soils, you might have to deviate from the pond design plan and just take what the ground gives you in some spots.
I like your comment above. If one of your planned "deep areas" is foot after foot of gravel, then quit digging and cover it with a good clay blanket. If you do find an area of good clay, then keep digging there and make that your new "deep area" of the pond. You can then use this extra good clay where you need it.
I do not like that your clay/gravel mixture cannot roll a pencil. It is impossible to compact a clay/gravel mixture once the gravel content gets too high. As you compact, the individual pieces of gravel start to come in contact with each other. Eventually you achieve enough point contacts that the gravel creates a framework of support (like the steel girders in a modern office building). No amount of additional compaction will seal this material because you cannot crush the gravel framework. Even though the gravel pieces are touching, water can still flow through that type of network.
Keep watching your crew while they are working and grab some samples (when you safely can). Most dozer guys don't like to continually get out of the cab to check samples. However, the good ones can "feel" what they are working in with their blade.
Keep interacting with the boss, he wants to get it right the first time too!
Have fun watching your pond get built!
