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.

Oakland geology ramble 4: Uptown to Montclair

24 July 2017

This five-mile urban hike is more of a terrain-and-streams ramble than a bedrock ramble. It climbs over 700 feet, winding through the watersheds that freshen Lake Merritt and traversing some of Piedmont’s wildest land. Although I’ve walked the route both ways, I’ll present it here from west to east.

The route goes from the 19th Street BART station to the heart of Montclair on La Salle Avenue, where every 20 minutes the 33 bus will take you straight back to the starting point. Or vice versa.

The terrain map shows the watersheds and drainage divides along the way.

This route is just one of several good possibilities. I have a thing about views, so I favor ridge roads that thread the divides between stream valleys. There are three streams here: Pleasant Valley/Bushy Dell Creeks (Grand Avenue), Wildwood Creek (Lakeshore Avenue), and Indian Gulch Creek (Trestle Glen Road). My route follows Warfield Ridge, the divide between the first two streams. The eastern alternative would go up Longridge Road, the divide between the last two streams. And, of course, one could take the low roads that follow the three streams instead. I leave those as exercises for the reader.

For completeness’ sake, here’s the geologic map. The blue areas are bedrock and the other colors represent various bodies of sediment.

The interaction of geology and terrain adds interest to the hike, but truth be told, the elegant and extravagant residences along the way are just as attractive as the geology.

On Broadway and Grand Avenue, you tread the level ground of the late Pleistocene marine terrace (Qmt) along the foot of the Fan (Qpaf), the large body of Pleistocene alluvium that’s one of Oakland’s most distinctive geomorphic features.

To the right of the Grand Lake Theater, the tall red-and-white building stands on Warfield Ridge. Behind it is Round Top. Cut to the right of the theater and make your way to, then up Warfield Avenue. That building houses the Grandview Apartments, and it’s well named.

Warfield, as I said, is a ridge road. It goes up and down a bit, but mostly up.

If you’re like me you’ll want to catch your breath every now and then. There are views on all sides. Pause and enjoy them. To the left is Pleasant Valley.

To the right is Wildwood Valley.

And behind is where you came.

Stay on Warfield all the way to its upper end, at split-level Wildwood Avenue. Go on up Wildwood. Right after you skirt Witter Field, in the valley of Bushy Dell Creek, you’ll enter the Wildwood Creek watershed for real, and also finally encounter bedrock.

It’s humble stuff, Franciscan sandstone. But it makes good crushed stone, and it supported several quarries before Piedmont took on its current identity. Take a closer look at the terrain here.

South of the blue line, you’ll see four small gulches eroded into this rocky hillside. The third one was a rock quarry that was later made into Oakland’s Davie Tennis Stadium. The others remained unexploited and are now thickly wooded. All four have running water still, thanks to our wet winter.

I picked the route that goes through the rocky headlands between these gulches. Turn right off Wildwood to Wildwood Gardens, and wend your way through this elegant neighborhood, across the top of the Wildwood Creek watershed, to the start of La Salle Avenue. Stay on La Salle all the way to Montclair.

La Salle crosses a fairly flat part of Piedmont, then leads along the rim of Indian Gulch, the village’s greenest and most secluded district. The road then goes up the floor of the stream’s middle branch. At its intersection with Hampton Road is a newly refurbished sports park where you can (and should) refill your water bottle. Higher up this little valley is a former reservoir named Tyson Lake. You can’t get to it.

La Salle becomes pretty steep here as you climb out of the valley and crest the highest ridge at about 725 feet elevation. The change in grade is the clearest signal that the bedrock is changing, according to the map, from Franciscan sandstone to Franciscan melange. But you can’t see that, either — there are no exposures of the melange along this road.

Instead you can see the high valley of Montclair, home of the Hayward fault, as you finally start down. A walkway painted on the road helps keep the locals’ cars back. In that respect Oakland is more walk-friendly than Piedmont.

And here’s the view back from the end of the line.

The Hayward fault is mapped right on the corner of La Salle and Moraga. You’ll see the offset curbs much better on Medau Place, though, one block north.

The McKillop landslide: Ten years after

17 July 2017

In December 2006, I read a series of news stories about a landslide in Fruitvale, on McKillop Road, that took out a house and threatened two more, so I checked it out and was so impressed I wrote it up for About.com. This house was the victim.

And this was its front yard. When I revisited, last week, the three concrete steps were still there and the little pine tree next to them was over 20 feet tall.

This slump was the extension of an adjoining land failure earlier that year. In 2006 I was able to make my way across the top of that older slump and take this shot from the other side.

Nowadays the scene is well secured and overgrown with brush, but nevertheless the land is basically ruined. The city is storing some stuff there, and there are some beehives.

You can’t really fix landslide scars. On the human scale, they’re permanent. And landslides tend to feed on each other — when a portion of a slope fails, the adjoining slopes often follow. That’s the case on McKillop Road. William D. Wood Park is actually the scar of much larger landslides that have occurred, according to one report, since 1909.

The Oakland Tribune reported in 1936 after one such slide, “The property upon which the houses were built was originally filled-in ground from excavations made at the [Central Reservoir] site 15 years ago, neighbors said.” Throughout the 1940s and into the 1950s, it was routinely called the city’s worst landslide. Studies were made along with attempts to stabilize the slope, to little avail. Homeowners were putting their houses on jacks.

Everyone gave up fighting nature in the 1970s, and they made the land a park. And so far so good — here it was in 2006:

And how it looks today.

Nature may not have given up fighting us, though.