Moka: Here's what I saw Friday and Saturday:
Start to Waterman's gap: While mostly downhill, I would not categorize this as real easy. A lot of dead fall, but easily surmounted--hop over, or on and over. Constant rocks and roots and rollers (sticks, branches) mean you'll work harder than you imagined when you were sitting in your lounge chair looking at the topo map. Not only will your stabilizer muscles (esp the peroneals) be working hard, but your ocular centers and cerebellum will be working overtime as you try to race down avoiding continuous obstacles. Think going warp speed through an asteroid field. ;D
Waterman's gap to China Grade: Your primary obstacle here is the long, but not terribly steep climb to China Grade. This much up hill is not usually featured in a road marathon however. Boston? HA HA HA.
China Grade to Gazos Creek Road in Big Basin: Be careful on the fine grained sandstone areas. They aren't real grippy where wet or dirty, so you'll need to slow in places and plod (no moon dancing). The trail picks up in technicality again, being rocky in parts. As you come into Big Basin, the dead fall becomes larger necessitating a real slowdown in spots. You also hit some wet muddy patches and will probably get your feet wet at about mile 15. There is one very easily crossed small creek.
The extra 4 1/2 to 5 mile loop for the 50KM run at about midpoint (15.5 miles): start with 2 miles of uphill starting gradually on Gazos Creek Road (about 1/2 mile), then onto Dool single track (muddy and a bit steeper in spots), then on Middle Ridge dirt/rock road (exposed~~would bake in July). Then a short section with a couple of large roller coaster (steep) ups and downs. This is followed by a run down a pretty canyon on the Meteor Single track. The last part is level repeating a flat section of the Skyline to the Sea.
Gazo's Creek to Skyline to the Sea/Middle Ridge road junction: The last, shortest (about 1 mile) and easiest of three (two for marathoners) major up hill sections. Muddy in spots, not to steep and eases way off and even flattens in spots. However, may not seem so easy for those who have already logged 20 miles including 2000 feet of up and a lot of technical single track. To think, road marathoners often complain about having to climb overpasses (which they call hills).
On STTS down to Berry Creek Falls: This starts as a wonderful, flat soft, shaded slight downhill single track that you could literally fly down if 1) you still have your legs and if 2) The huge fallen redwood trees blocking the trail are magically removed by next week
. Don't count on it. You will have to slow and limbo under these suckers. I saw two before I turned around 1/4 mile down the trail. It's been years since I've last done this section, so I don't remember how technical it gets down to Berry Creek falls, but I'm sure it's not as nice as this section starts.
Berry Creek Falls to end: Last did this section last fall. I've done it a lot in recent years. The first half mile (roughly) down from the falls (to the bike lockup) has some fairly difficult single track that you'll likely find yourself walking/jogging. There is a creek crossing and I think I remember a steel I=Beam being placed there to cross over. That will slow you down. Most of the rest of the way is on dirt road. The steepest part I remember is one quarter mile downhill grade, which isn't steep at all (however, if your quads are shot when you reach it, you might disagree). No real obstacles from this point on, other than fatigue.
New events: Yesterday, it absolutely poured in Big Basin. I imagine it did so today too. While driving 236 in Big Basin, a redwood fell near the road and the top temporarily blocked the highway (this happened within minutes of us reaching the point). So, more trail blockage is likely from this storm.
Synopsis: If you are young, athletic and well trained, you'll have no problem.
Otherwise, you may wish to adjust your time expectations and just have fun (make it a run, rather than a race). Or, do the marathon instead and save your strength for the post race swim out to Ano Nuevo Island.