Wednesday, June 9, 2004

Green Valley, etc.

I have been busy with mathematics and home improvement for weeks now, with little time for hiking. I did manage to join Ron Gould and Catherine O'Riley for explorations in Green Valley, two weeks ago, and find myself embarassed to report that my understanding of the ditches and mines in that remarkable area was seriously flawed.

Green Valley is on the main North Fork, about a mile down from Euchre Bar, and a mile up from Giant Gap. The canyon runs about 2400 feet deep here, but is mostly notable for its unusual width. This width can be ascribed to the weak serpentine of the Melones Fault Zone, in a linear mass trending north and south, athwart the canyon. And this width has allowed great masses of young Pleistocene (Ice Age) sediments to accumulate on both sides of the river. The sediments contain gold; and there is many a mine in Green Valley.

To work these mines, sometimes set well away from the river, water was needed, and ditches were dug. There are many mines and many ditches. At the east end of Green Valley, a ledge was blasted from steep cliffs to support a wooden flume, over a part of the course of the Green Valley Blue Gravel Mine ditch. This ditch took its water from the North Fork itself, well upstream from Euchre Bar. It crossed the river between Euchre Bar and Green Valley, in the lovely gorge there, on a trestle stated, in 1876, to be 139 feet high.

So far so good. But I took it into my mind many years ago that one certain ditch, often horribly overgrown with ancient brush, and which traverses Green Valley from the east to the west, was this same GVBGM ditch. And, since this ditch did lead to the westernmost part of Green Valley, near the Pyramid, where a large hydraulic mine flanks the river, I assumed that this was the GVBGM.

I even stubbornly misread the old newspaper articles to force them to agree with this fixed idea. But as Ron and Catherine and I forced our way east on what I had always thought to be this GVBGM ditch, and passed the center of Green Valley, into the eastern region, we kept on expecting to find traces of Ron's earlier path, from last year, when he blazed a trail along the GVBGM ditch from the east, going west.

I was in the lead, and found some cut branches. "Here it is!" I exclaimed. "Here's the spot you reached last year!"

Ron arrived, and said he didn't recall ever seeing this part of the ditch. Yet someone had worked hard on clearing the brush. In a few yards we had the answer, as a vast area of garbage came into view, the remains of a marijuana growers' camp. It may have been in use last summer. A couple hundred yards farther along this same high ditch, another, similar camp befouled the landscape.

I would guess that something like many dozens of backpack loads would be required to remove the garbage from these two sites. These are new to me; there are several other garbage sites in Green Valley, closer to the river, which I had hoped to clean up this year if possible. Now the task seems insurmountable.

Ron astutely realized we were far to high above the river to be on the line of the ditch-cut-into-the-cliffs-at-the-east-end, which is certainly the GVBGM ditch. Hence the true GVBGM ditch must be below us. We followed a faint trail down through meadowy areas hemmed around by brush, where a fascinating accumulation of large boulders of rhyolite volcanic ash is found. These boulders are no part of the Pleistocene glacial outwash sediments in Green Valley, but suggest something like a landslide deposit, originating up on the canyon rim, where the "Valley Springs" rhyolite ash beds have their proper place. The landslide might have happened a hundred thousand years ago; the boulders are deeply weathered to a brownish color, rather than the raw creamy white one sees in roadcuts, etc. (for instance, see the railroad cuts a few hundred yards east of Alta, for an excellent exposure of this Valley Springs rhyolite ash).

So. We dropped down through the meadows and found the *true* GVBGM ditch, fully 150 feet in elevation below the higher ditch. I should have realized the high ditch was way too high. At any rate, we followed the GVBGM ditch west, and found that it ended near the center of Green Valley, in a tiny reservoir, from which its water was disbursed to the mine itself, down below us and out of sight.

Thus, in accord with the old newspaper articles which I had so strenuously misread for so long, the GVBGM is in the center of Green Valley, not at the west end.

We then explored some old trails in the area, including one I call the High East Trail, which was always hard to follow, even back in 1976, and now is badly covered in brush, towards the east end of Green Valley. We scouted around without success for its continuation east, then turned west, where it is relatively open, and followed it back to its junction with the main East Trail, near Joe Steiner's grave.

Then it was a long slog up the long trail. Another fine fine day in the North Fork canyon, one in which, strangely, we never reached to river itself, but wandered through vast areas of brush, rife with old trails and old ditches and new marijuana growers' camps.

I wish they'd just legalize the stuff. We'd have no more of these obscene garbage dumps.

On another front, I hear that quite a crowd of dirt bikers rode the Euchre Bar Trail last weekend, and tore it up a bit. It might be that Tahoe National Forest needs better signs indicating the OHV closure on that trail.

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