I got this info from another local rider. I think this is a good way to go and it will cut way down on trial altercations (for SoCal riders especially)
"Okay, public service announcement time.
If you ride Los Pen/DMM, you know about Cobblestone and how Lower Cobbles is now not only legitimately multiuse and open to bikes, but how the lower section of it is Closed to Horses (in exchange for the parallel section, closed to bikes). The "no horses" section includes the popular Whoops and is the scence for two recent trail alterations. Since there has been some excited chatter today over them both, I made some calls and got the facts:
1. NEW FENCES/CLOSED SECTION of Lower Cobbles.
As part of the Trails Committee agreement to designate parts of Lower Cobbles as "no horses" and the parallel section "no bikes", we and the Rangers agreed that the traffic should be "split" all the way down to the funky road crossing at the base of Lower Cobbles, where one of the new kiosks is. This means that the last ramp-up onto the little triangular mesa, then the right turn back down to Lower Cobbles (before popping up the last ramp toward the waterfalls) gets fenced off.
The fencing does three things: 1) it allows the Rangers and enviros to protect that scrubby grass that lives up on the triangular mesita, which turns out to be special grass; 2) it keeps the horses and bikes apart from one another until the kiosk/crossing point (where sightlines are huge); and 3) it completes the "deal" made for the upper and lower Cobbles multiuse designation.
The fences were put up Sunday, torn down by some evil Hot Air Balloonists (I like the sound and image of that) and then replaced today. The ramps and triangular area have been scarfed up for rehabitation. PLEASE, don't mess with these fences. Please do enjoy the tunnel-like brush trimming job done on the section of Lower Cobbles we'll now all take on our bikes.
2. ALTERATION OF THE BIG WHOOPS on Lower Cobbles.
Somebody cut "lunch box sized" hunks out of the ramps/whoops on Lower Cobbles, just below the lips of each. This wasn't the Rangers, and there is No Plan or Intent to mess with these (these are Not places for fence posts to go in), according to the Rangers, our best friends with this trail. Whoever cut those in did it without approval.
I haven't ridden them yet, but the word is, the cuts make it worse for both cruising and for catching a little air. This may be something we have to go out and FIX, I dunno yet.
Regardless, notwithstanding any wild rumors or conspiracy theories that may spring to mind upon encountering the unauthorized work on the Whoops, then the new fences blocking the old ramps... everything is as good as it can be: the fences were known and planned, and the whoops are not slated for action by The Man."