So if you look at the pictures you can see some sand and some hardware and
footings for some structures.
If you are slightly interested in the history of Eleanor, Cherry, and Hetch Hetchy
you really want to find a copy of
"Hetch Hetchy and its Dam Railroad" by Wurm
a really really great book on the construction of the original dam, it's raising, and much more
Some of the pictures of HH Valley I think will break your heart.
Many I have not seen before.
They really raped the valley when they built the original structure.
Anyway, back to the pictures. I found in the book when they raised the dam:
"Sand for the concrete was dug from a deposit at Miguel Meadow, on the road
between Hetch Hetchy and Lake Eleanor, and carried by a three-mile aaerial
tramway to the aggregates plant at the dam."
Sand overflowed and created quite the anomoly on the land.
Check it out on Google Earth. Just look a little east of Gravel Pit Lake.
The line runs NW to SE towards O Dam.
You can really see the sand line. It turns out it is not an Alien Landing Strip.
O well... the truth is out there...