This cache IS located at the posted coordinates!! (It is a "mystery" cache because it is a challenge geocache and certain requirements have to be met before you can log your find. )
Have you ever geocached at over 8,000 ft elevation? If you have ever found a geocache at any place 8,000 ft elevation or higher, then you can log this geocache as found by listing at least one such find in your log post. It would be fun if you could list more than one if you have several, because this would give other geocachers a list of possible geocaches to go and find in order to fulfill the requirements of this challenge. Your 8k+ ft geocache can have been found at any time: it does not have to be found after the publishing date of this geocache challenge: it could have been found years before.
In your log post, please give either the geocache name or the GC number, find date if you can, and state the physical elevation of that geocache location. If you don't know the elevation, it's easy to find that using GoogleEarth: just do a search for the cache coordinates on GoogleEarth, then put your pointer on those coordinates, and it will tell you the elevation at that spot. Alternatively, you can use Geocaching Swiss Army Knife at www.gsak.net to find the elevation.
You can list the same 10k plus elevation geocaches for all 4 challenges, if you have any, or list lower elevation caches that apply to each challenge. You need not list all the caches found that fit each challenge unless you want to: I imagine some geocachers will have dozens if not hundreds which apply to some of these challenges.
Example: In addition to geocaches found over 10,000 ft and over 9000 ft, I found these over 8000 ft: Quaker Moats GCH29G 10/15/13 elev 8521, Glass Flow GCQBN3 10/15/13 elev 8321 ft, Glass Flow 2 - OBsidian Dome GC137H1 10/15/13 elev 8421 ft, Pinnacles Above GC40HH7 10/15/13 elev 8496 ft, The Ghost Town of Bodie GCJEA9 10/13/13 elev 8391 ft.
TO FIND THIS CACHE:
This geocache is located on El Toyonal Road in Orinda (it is about 5 ft from the road, and is accessible either by driving in from Orinda (in which case it's a park and grab), or walking in from Wildcat Canyon Rd. If you walk in from WIldcat Canyon Rd it's 1 mile from the parking area at the end of El Toyonal at Wildcat Canyon, where there's a gate and you need to walk in from there.