1/3 cu yd sounded way too low but after researching it is a reasonable estimate for a single-rotor at that elevation.
The Ca NG has a dozen pretty new CH-47f Chinooks with a max cargo of 24,000 pounds. They may not want to get them dirty though.
There’s been no work done on either spillway today. Lake has only been lowered 8 feet.
I just used a 1/3 yard lift bucket size because it is one of the ready made sizes tower cranes use at the end of their reach. There are bigger hoppers for bigger cranes. Helicopter lift though needs to be easily snatched over and over so I would use something that is in the range of about 1/3 of their lift capacity.