I hiked up to West Fuji last week, looked over at Henninger Flat, and saw some trail cuts to the North of the Henninger Flat helipad that I didn't recognize (no photo; sorry). When I got home, I looked it up. Unsurprisingly, much of the internet's knowledge of this is people on this forum talking about using this route for various purposes. Back in the day there was a road and trail in that area, and that's what I was seeing. The 1953 USGS topo still has the road and the connecting trail marked:
Armed with this information, I went to check to see if this is the fabled shortcut to Idlehour. I started up the Mt Wilson Toll Rd in the morning. The Openstreetmap data calls out a shortcut trail at one point, to cut off a lot of the switchbacks near the top. I tried it out, achieving moderate success: didn't find the trail near the bottom, but after some bushwhacking found a nice use path. This goes up steeply along some sort of water pipe, eventually topping out at one of the spur roads at Henninger. Here was an odd LA County survey marker:
The county does their own surveys in addition to the USGS ones? From this spur road I accessed an obvious fire-break-trail straight up to the helipad, thus bypassing the main part of Henninger Flat entirely. Up on top the views were grand. Apparently this was one of those rare days where not only Catalina, but Santa Barbara Island were clearly visible (Santa Barbara island at center of photo; click for original):
Walking around to the North side of the helipad, the old road cut became apparent:
I excitedly walked towards the branch point. The old road coming in from the North is completely invisible unless you know where it is, and you look for it. But once you turn off, the going is fairly clear. As a road, this thing is horrendously overgrown, and beyond impassable. But as a trail, it's decently clear, and even pleasant:
The road quickly meets and crosses Esme Canyon, and things clear up a bit on the other side. Here are old telephone poles, supposedly the same line that comes down from Panorama Point, by Muir Peak:
Getting to the end of the old road (saddle by point 2647) is straightforward. Past that point, however, things get more questionable. The saddle isn't very high above the bottom of Eaton Canyon, but it's steep, loose and heavily brushy all over. The USGS topo says that the trail is more or less a long traverse that ends up almost at Idlehour. Maybe this was true at some point, but is not at all true anymore. There IS a traverse to start with: find it by rounding the nose of the ridge as tightly as possible, staying maximally away from point 2647:
Initially this is a narrow, but well-defined-ish and clear-ish use path. Eventually it dies out, cliffs out and becomes very brushy. This means I missed a left turn. After some bushwhacking back to the West on a slightly lower level, I found the trail again; here it was steeply descending down the slope:
I then backtracked up the trail to see where I went wrong. There IS a decent-looking trail junction. The correct left turn looks like a switchback, but the trail turns to point straight down fairly quickly. In any case, you drop down to Eaton Canyon in no time. If travelling the other way, turn uphill at the "Alex Cass" tree:
Down in Eaton Canyon, there's some water, and it's generally fairly pleasant.
I'm assuming that the canyoneering business begins a bit downstream of this point. I went upstream towards Idlehour, however. It's a nice rock-hop. Don't know how hard it is with more water in the river, but it was nice and easy on this day. To exit, I took the normal Idlehour trail and Toll road. Walking down the toll road, a tiny bit below the Idlehour trail junction I noticed a NICE trail coming in from the right. Curious, I went to check it out.
This trail is being actively maintained right now: there're various trail-maintenance tools sitting around. It looks like this trail is used by the water company to service their tunnels. CrazyHermit found these and wrote them up: http://www.secretmines.com/p/blog-page.html. The tunnels themselves are being actively maintained right now in some way too (tools, materials sitting around). None of this is particularly exciting, since this is a short-ish dead-end trail. What IS interesting is that at the Esme Canyon crossing there's a solid wooden bridge:
Looking closer, this bridge was somebody's Eagle Scout project:
A bridge crossing an obscure creek at the end of a water-tunnel-maintenance trail seems like an odd choice for an Eagle Scout project, but what do I know.
