I didn’t get all of the details, but they place a cache there three to four weeks before they hike through and haven’t lost one yet. They do bury it under rocks so it is not obvious to a casual passerby.
The downside to this plan is you end up carrying multiple bear cannisters.
I haven’t been there, but I have read that Onion Valley consists of a trailhead parking lot, a pack station, and a campground. Hikers have to hitchhike to Independence to get supplies.
I did contact one pack outfit to find out how much they would charge to bring in a food drop to the trail over Kearsarge Pass. They told me $500! It’s easier to hike the extra miles then cough up that much.
Snowball