Archive for the ‘Oakland streams and water’ Category

A stroll up Indian Gulch, or Trestle Glen

28 August 2017

Once upon a time there was a thriving native encampment near the head of San Antonio Slough, tucked under bountiful oak trees in a valley with a permanent stream. Then the padres of New Spain put the natives behind walls to earn their bread with the sweat of their brows, and a generation later the Mexican rancheros converted them to secular laborers. The valley, which took on the name Indian Gulch after the Indians were gone, has remained significant. The property line between the lands of the Peralta sons, Antonio on the south and Vicente on the north, ran directly up its streambed.

On the map, the valley with its tributaries looks like a long feather, arcing across the bottom of this map from Lake Merritt (the former slough) into the hills of the Piedmont bedrock block.

Today the valley is an Eden of the suburban sort, well worth a walk for its natural and human sights. These sights do not include the stream, now called Trestle Glen Creek and mostly culverted or hidden in back yards.

The lowermost part of the valley, going up Trestle Glen Road, has a very gentle grade, taking well over a mile to climb 100 feet. The sides of the valley rise a good hundred feet on either side.

The stream here is at grade, meaning it has cut down about as far as it can. The ground it has eroded is the sediment of the Fan, not bedrock. See it here on the geologic map.

This stretch of the valley ends just past Norwood Street as we enter bedrock country.

The grade steepens slightly, and the valley walls close in a little. The power line towers in the back of this view sit on bedrock.

Two very unobtrusive footpaths lead from here to either side of the valley where you can encounter the bedrock. The one on the south side is particularly discreet; you might have better luck coming down from Park Boulevard via Elbert Street to see this exposure.

It’s your standard Franciscan metasandstone, the same stuff that was quarried in Piedmont before it incorporated in 1907. There’s also a nice exposure on Trestle Glen Road a little farther up.

By now the valley has gotten distinctly narrower and steeper. Right at the city line at tiny Valant Place, Trestle Glen Road leaves the streambed and climbs up to Park Boulevard. Seen from Valant Place, the valley is a real ravine now.

You can’t walk up the valley any farther; it’s all on private land. But from the Piedmont streets that flank the valley — Indian Road, La Salle Avenue, St. James Drive — you can catch glimpses of the living stream.

The Uptown to Montclair ramble I posted a few weeks ago goes through higher parts of Indian Gulch. But the longest stretch of the unspoiled stream, the western branch, is totally secluded in private hands. That branch is where the rancho boundary went. You can spot it from the 33 bus, on Hampton Street, if you know where to look.

So is this a glen, or is it a gulch? Both terms refer to small, steep-sided valleys with running streams in them. However, a glen is typically wooded — the word comes from the Gaelic — and implies a green, secluded place. A gulch not only has steep sides, but also a steep slope with a rushing mountain stream, and the word is widely used in the Southwest. A gulch is forbidding, but, especially in California, it’s well suited for gold panning. This valley offers both wealth and seclusion today, so I call it a toss-up.

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Well water in use

21 August 2017

Once upon a time, we used to produce a lot of our water from local wells, but for the last century we’ve retired them as the aquifers were drawn down or polluted. So I’m always surprised and intrigued to see wells still at work. This is on Willams Street in San Leandro.

The location is a big educational complex comprising John Muir Middle School, San Leandro Adult School, and Woodrow Wilson Elementary. Presumably the well is for watering the grounds, not supplying the drinking fountains.

The water is a remnant of the once-productive San Leandro Cone, a body of sediment full of groundwater supplied by San Leandro Creek. The geologic map shows it as a set of fingers radiating from Lake Chabot, labeled “Qhl.”

Qhl stands for “Quaternary Holocene levees.” The Quaternary Period includes the last 2.6 million years of Earth history, and the Holocene Epoch is the final portion of the Quaternary, the time since the glaciers last melted. I think of the Holocene as the geological present.

Levees form when floods regularly spill over a riverbank — the moment rushing floodwater leaves the river, it slows down and immediately drops most of its sediment load. Repeat this enough times and a low rise builds up on both sides of the river: a pair of levees.

The map explanation says about Qhl, “these deposits are porous and permeable and provide conduits for transport of ground water. . . . Abandoned levee systems have also been mapped.” And that explains the well water of Williams Street — the street runs right down the middle of a former course of San Leandro Creek. Here’s a closeup.

The map shows that the Qhl unit coincides with an extremely gentle rise in the ground about 10 feet high and a quarter-mile across. Natural levees are rare to see, because humans build them up higher for “flood control,” but you’ll easily see the rise if you walk away from Williams Street a couple blocks and look back at it.

So San Leandro Creek once ran this way, must be thousands of years ago. Something perturbed it enough to cut a new streambed in another direction, and this abandoned course filled in. But it still carries water underground.

The northernmost finger of Qhl in the San Leandro Cone leads to the former site of Fitchburg, where a major wellfield once supported East Oakland with groundwater.

The smaller creeks of Leona Heights

7 August 2017

Last week I lingered over Leona Creek, in the Leona Heights area, but there are three other streams in the land between Horseshoe Creek and Chimes Creek. I’ll label them on the watershed map from 1 to 3, putting the numerals where they enter culverts.

Creek 1 passes through the old Crusher Quarry grounds, now occupied by houses, so I’ll call it Crusher Creek. This is the best view I can find of its catchment, looking across Mountain Boulevard up Bermuda Avenue to the quarry’s old working face. The headwaters are to the right, and I haven’t explored there yet.

Behind me, the creek emerges in a steep gulch that passes around the old Chabot Observatory (now a school), then disappears under route 13.

At the moment it’s all dry, so I can’t tell what shape Crusher Creek’s water is in. Probably not so good, considering the amount of sulfuric acid being weathered out of the old quarry leaving all that red iron oxide behind.

Under the freeway Crusher Creek joins the orange water from the Leona Sulfur Mine, seen here where Leona Creek enters its culvert at Twitter Court.

Creek 2 comes down next to Rusting Avenue, so I’ll call it Rusting Creek. This is not to prejudice its water quality, which is good where I’ve seen it. This view shows the entrance to its culvert at Mountain Boulevard, looking up its catchment.

Higher up, just above Mountain View Avenue, the streambed displays the variety of rock that comes from the Leona volcanics, in a spectrum from nearly white and greenish-gray to dark red.

Here are two hunks of the pristine rock with a piece between them of the ocher crust that forms on top of it after centuries of weathering.

Creek 3 has a fire road up its valley, behind a gate at the end of Leona Street, that used to be called Russell Avenue, so this is Russell Creek. It’s worth an outing, as long as you park down the road and walk in quietly. However, at the top the fire road ends at a locked gate on Ridgemont Drive, and you’ll have to walk back down. I can attest that trying anything else is foolhardy.

Here’s the view down from near the top. At the lower left you can see the fire road, which ends next to the house at the far left. (Russell Avenue appears on Apple Maps, but not Google Maps. Trust Google on this one.)

The rocks exposed along the fire road show the full range of the Leona volcanics.

Close up, they’re quite colorful with their oxide skins, and there are many fine oaks and vistas along the way. This may be Oakland’s best trail you never heard of.

Finally, from Leona Road you can take a fire road to the former Leona Quarry, now called “Monte Vista Villas at Leona Quarry” and filling up with townhomes. I can’t easily describe how to access it except to recommend you take it first from the other end, at the entrance to the development next to this fine wall made of quarry boulders.

It leads along the freeway and ends at a nameless spur off of Leona Road.

The stroll is nice, if you ignore the freeway noise, and you’ll see that the hillsides here, which look so tempting from a distance or from the seat of a car stuck in traffic, are quite inaccessible. Stay on the path.

The mine drainage of Leona Creek revisited

31 July 2017

Over the years I’ve done a lot of poking around Leona Heights, the large hill looming over the south end of the Warren Freeway. You’d think I have a nice photo after all this time, but instead here’s a vertical view from Google Maps, terrain view. It shows the area between Horseshoe Creek, at the top, and the former Leona Quarry at the lower right.

The hillside is deeply eroded by several steep gullies, all of which still have running water in them at this time of year. Those fascinate me. And the satellite view of the same area shows how much of it is forest, which also fascinates me.

Most of this land is inaccessible. There’s only two fire roads, few trails, and very steep slopes well guarded by brush and poison oak. Apparently the city owns much of it.

And here’s the stream map to help with the creek names, because they’re confusing. Each of the Leona Heights gullies is interesting, and I’ll be showing them to you in coming weeks, but this week I’ll focus on the one labeled Leona Creek.

The streams in these hills all feed Lion Creek, originally named Arroyo del Leon. The rules of river names say that the name of a stream applies to the most vigorous branch, and if the stream splits into branches of the same vigor the name can be arbitrarily assigned to one branch, or none. Thus the upstream end of Sausal Creek is where Shepard Creek and Palo Seco Creek join. So on this map I’m extending Lion Creek up its northernmost branch (although it may well be that by this criterion Horseshoe Creek should be Lion Creek). People also talk about “Leona Creek,” sometimes applying the name to all of Lion Creek and sometimes applying it to the nameless creek that has the former Leona Mine on it. Because the mine site is so important, I’m giving that particular stream the name Leona Creek.

This creek once had potential. It has a nice catchment, seen here from the Merritt College parking lot toward the north end of Ridgemont Avenue. The woods are impenetrable.

But then the creek reaches the old mine.

By early last year, the mine site had been fixed up so it looked clean.

And down below the mine the stream looked pretty good.

But as of a couple weeks ago, it was back to its old trick: acid mine drainage.

What we’re looking at is yellow and orange iron oxides, precipitated out of the acidic water as it’s neutralized. They aren’t poisonous in themselves, and the water won’t eat the flesh off your fingers. But other metals are dissolved in drainage water besides iron, which are more toxic. I don’t have any chemical data from the water, so I can’t address the true hazard. But this stuff is harmful in other ways, specifically by blanketing the streambed so that living things can’t live on and in the gravel like they’re used to — insects and insect larvae, which feed other insects and birds and so on.

Acid drainage is natural in the Leona Heights, to a certain degree. The rocks hold a lot of pyrite, which oxidizes to yield sulfuric acid, so there’s always a little acid around. The mine, however, opened up the richest part of the hill and gave it access to oxygen.

The raw chemistry of pyrite oxidation is not that fast. But sulfur-oxidizing bacteria make their living by eating pyrite and pissing out acid, and the old mine is like a giant party condo for them. They won’t stop for anything short of encasing the whole hillside in concrete. And we won’t do that.