Archive for the ‘oakland hazards’ Category

Vantage Point Park

15 February 2009

vantage point park

This tiny park is at East 12th Street and 13th Avenue, on a low rise next to a lot of activity. Between here and the water—Brooklyn Basin, the innermost part of Oakland Inner Harbor—run East 8th Street, I-880, Embarcadero Street, BART and the Southern Pacific rail line, plus I’m sure a number of underground power and water lines and what not. It’s a highly concentrated lifeline corridor. Across the way is the Coast Guard base on Government Island. In the distant left corner in the 800×600 version (click the image) you can just see Alameda Island. Except for the hummock in the foreground, everything visible is made land, artificial fill, with a high water table. It was created more or less haphazardly starting a century ago, and under strong shaking a lot of old fill of this type is prone to liquefaction.

Past the left edge of this photo, a little buried creek valley running down 14th Avenue reaches the bay. It’s all filled in, too. All the crowded life lines I mentioned cross that creek bed. In the next big Hayward fault earthquake, this is a highly vulnerable spot.

I took this shot on 19 November 2008 during a walk I took the length of Oakland, from the San Leandro to the Ashby BART stations. Lots more photos from that day on my Fotothing site.

Scars

9 January 2009

eucalyptus scars

The hills south of Hiller Highlands, just across route 24, were swept bare by the 1991 fire. Anything that was there besides eucalyptus has been unable to compete, and now it’s a fire-prone monoculture. That suits eucalyptus fine—keeps down those riffraff oaks and madrone, thank you.

The hillside forest was partially cut down maybe ten years ago, then again just a couple years ago. Each wave of attack remains obvious on the landscape. Eucalyptus is like the hundred-headed Hydra in the Odyssey: every head you cut off grows two new ones in replacement. Hercules defeated the Hydra with his sword in one hand and a torch in the other, cauterizing the wound after each head he struck off.

We can only reclaim these slopes by poisoning the stumps, herbicide-haters be damned. For a successful example, see the new slopes along Skyline Boulevard between Broadway Terrace and Elverton Drive, a wedge of land belonging to the Sibley park that has been reclaimed from just this state, exposing some excellent outcrops.

Landslides

7 December 2008

landslide scarp

This fire trail in the hills is beginning to disappear downslope. The biggest mover of sediment is not erosion, it’s landslides—or mass wasting, to use the geologist’s more general term. The land is like a building in that respect: neither of them wear out, the way an ice cube melts; instead they get more and more rickety, then collapse.

This headscarp will concentrate the infiltration of rainwater at the same time it admits air underground. The comfortable stasis of the underground is now broken. The alternating wetting and drying and the rapid loading and unloading give gravity more advantages until one day it will pull the road down. Then the city will help mass wasting along by cutting a fresh track into the hillside. This will never end until the hill or humanity is gone. For us it’s just part of the cost of living.

Once you know these crescent scarps, you’ll see them everywhere in the hills.

Earthquake day

17 October 2008

cypress structure mandela gateway

October 17 always has an ominous ring to it, because of the Loma Prieta earthquake of 1989 (or “the big-enough one“). In Oakland, we were distant from the epicenter, which is just visible on a clear day in the mountains beyond San Jose. But it was on this spot where the double-decker Cypress Structure, part of the Nimitz Freeway, felt its soft ground give way and collapsed, the deadliest single place in the whole disaster. I remember riding BART into the Oakland West station (remember when they called it that?) and sensing the whole carful of riders hold its breath as the wreckage came into view.

It was an ugly, traumatizing mess for years and years. In 2005, when I took this photo from the BART station on January 28, the Mandela Gateway complex at the base of Mandela Parkway was new, landscaping along the road was under way, and the area seemed nearly finished. But if you know where to look as you ride west from the downtown stations, you can still see the curved trace of the old freeway in the lines of the buildings and lots. Earthquakes are forever.

Fire on the mountain

13 June 2008

hiller highlands fire

Yesterday there was a fairly small fire in a treacherous place, the Hiller Highlands neighborhood. There was confusion in the media accounts I saw, but here is the correct version, as you can see in this view from across the freeway this morning. The streets, from top to bottom, are Charing Cross Road, Tunnel Road, Caldecott Lane and Route 24. (A typo in the Tribune, “Charring Cross Road,” may give you grim amusement.) The blaze began on Tunnel where street work took place a few months ago, and nearly reached Charing Cross. As I shot this photo, fire crews were still combing the burn area in search of embers.

The hills love fire, and the ecosystem is adapted to it, but civilization here is not. Given that we have irreversibly encroached on the hills by permitting residential construction there, we’re stuck with the price in dollars and lives in perpetuity. Not even the next major earthquake on the Hayward fault, less than a kilometer west, will change this even though the whole neighborhood would likely burn down again, just like 1991, if it happened today.

Yesterday not an hour before the fire started, I was standing on Grizzly Peak Boulevard looking down at this part of town and sensing just how dry everything is. Instead of coming down through here, as I have before, I walked down through the Grandview neighborhood to its north. Upper Grandview is an uncanny place, having been wiped out in the 1991 fire and disneyfied since. Today I was going to visit the fire site, but I got this shot because instead I took the opportunity to try the fire road above Broadway that ends overlooking the North Oakland Regional Sports Center. If you visit the park, have a look at the fire-resistant garden there. The rocks are mapped as undifferentiated Great Valley Sequence and are mostly an undistinguished gray sandstone.

Heights and flats

6 June 2008

oakland heights

In the East Bay, the Hayward fault separates high ground and low, with a few exceptions. Oakland is an exception (so is San Leandro, Berkeley and points north). From Oakland’s southeastern extreme at Lake Chabot up to the Panoramic neighborhood, the fault generally has a few hills on its Bay side. If you ride BART and look up at the hills, the fault is almost entirely hidden. The hill Piedmont sits on is the largest body of rock west of the fault. So Oakland is not like Hayward or Union City, where the fault is quite stark.

But here on upper Dwight Way, at Oakland’s far north end, is a spot where the height/flats dichotomy is laid right out plain. (Click the photo for a 900×750 version.) This little canyon is the one just north of Claremont Canyon, and I don’t know if it has a name. Behind me is little Dwight Canyon and just to its north is Strawberry Canyon, where the Cal stadium sits. High rock hills lie above the fault, and a plain of deep sediment lies below, an area where seismic shaking is liable to cause ground liquefaction. Of course landslides could happen where I stand; the brown patch below looks like a landslide scar . . . pick your poison.

Sulfur mine creek

25 May 2008

Lion Creek drains Laundry Canyon in the Leona Heights and Crestmont neigborhoods as well as the former Leona Quarry lands. It runs through Mills College, past Evergreen Cemetery, and into the bay at 66th Avenue — it’s the stagnant creek you see from BART just north of the Coliseum.

This is one strand of its headwaters, coming out of a former pyrite mine at the end of McDonell Avenue. The local chapter of the Society for Industrial Archeology says about this mine, the Leona Heights mine, “From the 1890’s to the mid 1930’s, iron pyrite was mined here and at the nearby Alma mine. It was processed into sulfuric acid at the Stege Works of Stauffer Chemical in Richmond (and other sites).” The photo was taken in 2003; I think it’s a little better today. The orange is iron oxides, not especially poisonous, but it looks awful. As I imperfectly understand it, sulfuric acid in the drainage water drops this mineral as it is neutralized. The acid comes from sulfur-eating bacteria in the mine environment.

Yes, Oakland has its own example of the same acid mine drainage that plagues the Appalachian states and many other lands. Every place the pioneers came to, they began mining everything they could, because that was the only way to build civilization. Sulfur is essential for gunpowder, and pyrite was the readiest source. Coal came from the Contra Costa hills, mercury from San Jose and from points north, lime from the San Mateo coast (and the local shellmounds), rock of all kinds from the Oakland Hills. This place was rich in timber and pasturage, we all know, but rich in minerals too.


Follow

Get every new post delivered to your Inbox.

Join 4,030 other followers