Teri Barry writes: :This looks a lot like Allium peninsulare var. franciscanum, but am not sure based on the close up. I suggest you share this photo with the Herbarium group. If my educated guess is correct we have a listed plant in a location I don't think we have reported yet."
Here are some photos to give context to the photo. I now believe it was on Trail 5, not too far above San Francisquito Creek. It could even have been on Trail 1 next to the creek. See the times of these photos and their locations, and make up your own mind.
Please leave a comment if you know the ID.
I originally reported this to be on Trail 4 below the dam. I now feel it was probably on Trail 5, walking down toward the creek. Sorry, I was busy leading a group at the time and did not take notes -- or many photos.