The armored shore

17 August 2020

Oakland’s shore is not what it used to be, not at all. The only hint of how it was is Arrowhead Marsh, part of the Martin Luther King Shoreline Park: a broad wetland laced with tidal creeks and vegetation for all gradations of water from fresh to salt.

And yet even Arrowhead Marsh is reputed to be an accident, formed when Anthony Chabot’s dam, under construction in the hills, had a failure that washed huge amounts of sediment down San Leandro Creek. To fans of nature this history, true or not, is scant comfort.

The geologic map (in this case the map of non-bedrock deposits in USGS Open-file Report 2006-1307) shows that every foot of Oakland’s original shore has been erased and built upon, with the small possible exception of the western tip of Adams Point.

Radio Beach at Oakland’s north edge, our nearest thing to a natural beach, exists on landfill.

Everything in the Oakland Harbor complex, from the Outer Harbor to the military grounds to the airport, is on landfill — “made land” as the old-timers called it.

Coast Guard Island is an artificial pile of Bay sediment, built with dredging spoils.

Alameda doubled its land area by dredging and piling. It’s all there on the map.

East Creek Point, the little peninsula of made land directly east of Alameda on the shore of San Leandro Bay, is a good place to contemplate this great undertaking, its aftermath and its possible futures.

Sitting here in 1852, when Oakland was first incorporated, this scene was a luxuriant marsh like that shown in the 1857 Bache map of San Antonio Creek where the Harbor is today. (The photos in this post are extra big, so click for the full experience.)

From here the view shows nothing of what once was, other than the water and the distant mountains across the Bay. The scene was a planar surface of green and blue, with added brown mudflats at low tide. There were no sharp lines between land and sea; none of the trees on the Corica Park golf course or anywhere else on Bay Farm Island; no brown hill covering a former landfill; no palms and wharves and homes — no ground at all — on the Alameda side; no riprap boulders on this side.

All the land in this view is “reclaimed” from marsh or built outright. Sandy mud was dug up from the Bay floor, crushed rock freighted down from quarries, sand and gravel carried in from excavations elsewhere, construction waste dumped on the shore. Trenches drained the marshes, removing the water to create low-lying land for development.

Even much of the water is artificial, in that it exists by virtue of dredging the Tidal Canal. From initial planning to dedication, the massive project took 28 years, every dollar intermittently funded by Congress. Here’s the canal’s east end from the High Street Bridge. An extension dug across San Leandro Bay is called Airport Channel.

Like the rest of the shore, the canal is heavily armored from end to end.

But what we have reclaimed, nature works to claim back. Around the bend from East Creek Point, the gentle Bay surf winnows out the finer grit and exposes the construction debris holding up the weedy shoreland.

The made land is wearing down, and rising sea level will accelerate the decay. There are two ways to deal with that, and both will be used as the century proceeds: more armoring, and returning the sharp shoreline to gentle transitional marsh. This restored marsh is a start. Similar projects are under way in Alameda, especially in the former military zones.

The “made water,” for its part, is filling up. The harbor needs regular dredging to stay open. That will never end as long as water flows and sediment is carried to the sea.

Finally, the made land is prone to its own problems. In this example near the west end of the High Street Bridge, the ground has settled around the water main in the last 80-plus years. Eventually something will need to be done.

It turns out that the Tidal Canal didn’t work as planned. It was supposed to allow the tide to flush through the Estuary and save the work of dredging the ship channels. That didn’t happen, but now we can’t fill it back up. What an alternate history we would have if it hadn’t been built.

Posted in Other topics | 2 Comments »

In search of McAdam’s quarry

3 August 2020

Alexander McAdam (1854?-1920s) was a minor character in Oakland’s history who left a highly visible mark in our cityscape. A Canadian farmboy who was orphaned at a young age, he came to California after apprenticing as a wheelwright, and after eight years he saved enough money to buy a farm “at the head of Thirteenth avenue,” according to a short biography by James Guinn in 1907. “He was successful in this occupation, but in the meantime had discovered a sandstone quarry on his property. Upon the sale of his farm he acquired considerable financial returns. Stone from it has been used in many of the largest buildings of Oakland, among them being the Unitarian Church, the last buildings of the deaf and dumb asylum, numerous retaining walls, and for many other purposes.”

This caught my eye because I have long thought that Oakland’s rocks were exclusively used as crushed stone. Yet here in the First Unitarian Church, ashlar blocks of genuine Oakland sandstone form the dignified cladding of this important cultural monument and civic institution, built in the early 1890s under the energetic leadership of a leading Progressive of his time, Rev. Charles Wendte.

Rev. Wendte oversaw the building project from his home across the street. The stone cladding was the costliest item in the project, and he singled it out in his memoirs: “Our employment of stone led to vexatious complications. Quarrymen were unable to deliver this material in sufficient quantities, workmen struck for higher pay in handling it. Contracts were broken or remade.”

I had to track down this stone somehow. The documentary clues are slim, and any signs of the quarry appear to be lost. But first, there is the stone itself.

It’s a fairly sound stone of an even consistency with a warm grayish-brown color and massive (i.e., absent) bedding. The block serving as a lintel over the doorway probably broke during the 1906 earthquake, when most of the cladding along Castro Street and the top of the tower collapsed. (The tower was rebuilt without any stone, a smart move.)

A closer look shows that the stone actually varies (although some of that may be substitute stone from another source, as Wendte’s wording suggests), and that a century of exposure has caused a fair amount of spalling. No wonder there were quality problems during construction.

A still closer look reveals it as a medium-grained wacke (“wacky”): a sandstone with grains no larger than a millimeter and a large component of minerals that are not quartz. The black grains are mostly biotite mica; without a microscope I’m limited in what more I can say.

It’s familiar to me. It’s not the Franciscan sandstone produced by the dozen or so quarries in and around Piedmont. I can rule that out categorically. It’s from the high hills on the far side of the Hayward fault.

All of this is consistent with the documentary evidence placing the source in Montclair. The “head of Thirteenth avenue” is where Park Boulevard, the former 13th Avenue in Brooklyn Township, meets Mountain Boulevard. It’s the intersection at the bottom of this excerpt from the 1897 topo map.

To orient (or disorient) you, here’s the same area today.

The “XII Report of the State Mineralogist,” published in 1894, said the following about McAdam’s quarry: “It is in Medos Cañon, back of Piedmont, and is a small quarry, producing sandstone for rubble and ashler [sic]. It is not worked regularly.” The official who wrote that description, a busy guy on a quick visit to cover the whole county, wrote down “Medos Cañon” when someone said “Medau’s canyon,” meaning the valley of present-day central Montclair where the dairy farm of John H. Medau once lay. I believe that if the site had been in Shepherd Canyon, his informant would have said so as that name was in wide use at the time.

All of this means that the quarry could have been a good exposure of the Redwood Canyon Formation, a wacke of Late Cretaceous age, that forms part of the east side of Montclair’s valley along the Hayward Fault. It’s the unit marked “Kr” on the geologic map, below. The lithological description of the unit, and the composition data from Jim Case’s 1963 Ph.D. thesis, are close enough to the stone in the church.

But also likely is the Shepard Creek Formation (Ksc) and even the Oakland Conglomerate (Ko), when you consider that the units are only subtly different, variable in composition and not well mapped despite the best efforts of competent geologists.

In any case, I had a good time visiting these rock units along the Montclair Railroad Trail the other day. There’s a lovely outcrop of the Redwood Canyon Formation above the trail along the route of the recently upgraded powerline, southwest of the word “grade” on the map. That warty weathered surface, reminiscent of the Incredible Hulk’s hide, is one of this unit’s distinctive features.

But the rock there’s not a good match.

Neither is the rock in the landslide at the upper end of the trail.

And just for good measure, here’s a chunk of sandstone from the Oakland Conglomerate. The material is coarser and wacke-er, but again under the 10X hand lens it’s not like the church’s stone.

Nowhere in this area, in many years of visits, have I seen a body of rock big enough and sound enough to support a quarry capable of producing ashlars — not on this side of the Hayward fault. The nearest quarry site is down Park Boulevard where the Zion Lutheran Church sits today, the former Heyland/Diamond Cañon/Bates & Borland quarry on the side of Dimond Canyon. But that produced crushed Franciscan sandstone, something quite unlike McAdam’s stone.

I can only conclude that McAdam found a lucky hillock on his farm and made the most of it, one that’s been obliterated during the waves of development since 1890. And the site of his farm is, as we say, poorly constrained. Even his life dates are fuzzy. But his accomplishments include making a profit from farming, acquiring a large home in Temescal, serving two terms on the City Council in the nineteen-oughts, and equipping an important building with a handsome exterior (despite the vexation he caused Rev. Wendte). I can’t confirm when he died or where he’s buried, so this building surely is his monument.

While I was researching this post, the papers covered a lovely story about how archeologists used advanced geochemistry to pin down the source of Stonehenge’s biggest stones, a peculiar sandstone known in Britain as sarsen. The New York Times version was my favorite writeup, and the hardcore details are in Science Advances in an open-access paper.

Posted in Oakland geology puzzles, Oakland sandstone/shale, Oakland stone | Leave a Comment »

Wellfields

20 July 2020

As I explore Oakland, I find out more about the city’s eight-decade struggle to find adequate water. When Oakland was founded in the early 1850s, wells dug anywhere that people settled, especially in the old downtown area, yielded plenty (as I noted a few weeks back). But within a decade, the laws had to be arranged so that water companies could set up shop. The law gave them the power of eminent domain — if they needed your property, they had the right to buy you out for a fair price. (Several “water companies” were founded as cover for real-estate sharks, hoping to flip their paper titles like the domain-name squatters of the 1990s.) That’s when Anthony Chabot sprang into action, founding the Contra Costa Water Company in 1866. He made his fortune with surface water: the reservoirs of Lake Temescal and Lake Chabot. This post is about some smaller companies that competed on the basis of groundwater, digging and pumping wells in the area around the Coliseum. The map below shows the major sites.


From Sands Figuers’ Groundwater study and water supply history of the East Bay Plain, Alameda and Contra Costa Counties, California, figure 20

“Captain” Robert R. Thompson was a prominent citizen of Alameda back when the city was still on a peninsula. Seeing opportunity in 1879, he founded the Artesian Water Company, bought out the existing Alameda Water Company, and started drilling highly productive wells on the 12-acre parcel where his home sat. Today the site is known as Lincoln Park, next to Thompson Avenue on High Street. It’s as pleasant a part of town as can be, but all trace of the High Street Wellfield is long gone.


Looking down Thompson Street from High Street

Thompson knew what he was doing as well as anyone did in those days. Well diggers found the best sources by the Bay shore, even out in the tidal marshes. The theory went that a wide “subterranean river bed” extended along the shore of San Leandro Bay from the south end of Alameda all the way around to San Leandro Creek. I have a better idea that I’ll expound below.

Alameda’s demand for water rose until it outstripped Artesian’s supply, and in 1887 the company acquired the Damon tract east of the Oakland city limits near the town of Fitchburg, just down the “subterranean river,” and struck enough water there that in 1888 the High Street field was shut down except for emergencies. By then Thompson had sold his company and left town. Five years later Artesian bought a much larger (and much more productive) parcel on the Bay side of Fitchburg, near the Damon Wellfield. In 1899 Artesian was acquired by the Contra Costa Water Company during the East Bay’s “water wars,” when most of the private water companies competed themselves into bankruptcy and consolidation. Contra Costa became the People’s Water Company for a while, then the East Bay Water Company, and finally a public utility, the East Bay Municipal Utility District, took them all over in 1928 and imposed the rational, dependable system we have today.

The Fitchburg Wellfield was where the Coliseum sits today. There were 51 wells lined up here along the Southern Pacific (Amtrak) right of way and another line of 19 out in the tidal marsh.

This 1912 map shows the plumbing in the Fitchburg Wellfield. It produced a good million gallons a day of “pure, fresh water” for Alameda customers.


From Figuers, figure 21

The outer line of wells (at the bottom) was within the range of the tides, so the wells were guarded by levees. In February 1909 a storm overcame the levees and sewage from the Bay contaminated the wells, giving 8700 Alameda residents instant gastroenteritis. Nobody died, but some of the victims with severe nausea, stomach pain and diarrhea may have wished they had. After things were put to rights, the wellfield produced water steadily until 1930, when EBMUD shut it down and got entirely out of the groundwater business.

Farther over, at the intersection of Jones Avenue (98th Avenue) and the Western Pacific railroad right of way (under the BART line), the Union Water Company drilled dozens of wells starting in 1910. In fact they had seven wellfields in the area, five of which fed the pumping plant in the Elmhurst wellfield, between 89th and 92nd Avenues north of G Street. Others were in Stonehurst and in San Leandro’s Broadmoor area. Together they produced about 3 million gallons a day. The Union Water Company was sold in 1921 to the East Bay Water Company.

All the old wells are long gone now, but signs of the Contra Costa, Union, People’s and East Bay water companies can still be seen in Oakland’s streets.


See them all at my Oakland Underfoot blog

So what of that subterranean river? It wasn’t nonsense, just naive. Groundwater lives in underground layers of sand and gravel that have enough pore space to let water accumulate and flow. These layers slope downward toward the Bay, which means that the lower you can tap them, the higher the water will rise in the well and the easier the work of pumping will be.

To my eye, each of these major wellfields is related to a separate creek. At High Street, the waters of Sausal Creek flow straight down to south Alameda, where the thick sands of the former peninsula soak it up.

At Fitchburg it’s the even larger flow of Arroyo Viejo.

And at Jones Avenue, it’s not clear where the water might come from until you look at the geologic map, which shows a former course of San Leandro Creek heading right toward it — the unit labeled Qhl, meaning levee deposits.

So you could call these “subterranean rivers” and not be too incorrect. See them all in one image here.

You might wonder, “If fresh water is abundant at the shoreline, could it go even farther offshore?” And yes indeed, groundwater can advance quite far past the shoreline, and in many places there are freshwater springs under the sea. No one notices them but fish and scientists, but they account for a significant fraction of the world water budget.

Acknowledgment: As it happens, Dennis Evanosky wrote a piece a few days ago about Alameda’s water supply that helped me with a few details.

Posted in Oakland streams and water | 2 Comments »

Rocks of the Bilger Quarry

6 July 2020

It’s been twelve years since I wrote about the former quarry where the Rockridge Shopping Center sits today. Except for the pond, the whole space has gotten a makeover and it’s time for a fresh look. But first, some nostalgia. Back in 2008 the 24-hour “Big Long’s” was still there. I used to shop there; it had everything.

And flanking it was the big old Safeway with more businesses between and beyond, and the bank in the far corner. I used to bank there.

All of this is now gone, and the site is under intermittent redevelopment. Decades ago this was a giant rock pit, active for more than 70 years, that for a long time was the largest rock quarry in Alameda County. It was started by the Oakland Paving Company in 1870, and the name of Frank Bilger was associated with the succession of enterprises that produced crushed rock here, so it’s usually referred to as the Bilger Quarry. (Bilger learned the trade from his father, a German immigrant, and he surely pronounced his name the German way with a hard G.)

Now the Long’s site is a big Safeway, and the old Safeway and bank buildings are part of an empty lot. Only the water-filled pit on the east side is unchanged, and the walls show no sign of decay, which is a very good thing because it’s right next to St. Mary Cemetery.

The whole quarry site occupies a small body of quartz diorite, an intrusive (meaning it didn’t erupt) igneous rock that’s unusual but not unheard-of for the Franciscan Complex. It’s mapped as the purplish blob in the center labeled “Kfgm.”

It happens to be excellent rock for industrial and engineering purposes. The Tribune in 1890 wrote, “The material used by the Oakland Paving Company is a crushed blue rock, a trap dyke that is practically indestructible, submitting without injury to the hardest usage for eight or ten years without repairs, and with proper care, such as any pavement requires, lasting three or four times longer.”

The east end of the quarry exposes the bluish stuff. This exposure, right behind the Safeway, also has flaky veins of calcite. It’s very tough — not that I’ve used a hammer on it lately, but after seeing lots of rock you get a feel for this.

The west side consists of a much lighter material, a bit coarser grained and slightly less durable.

Between them is a contact zone that I recall as being black and sheared, with mineralization that was probably iron-manganese oxides. It was covered up when the new Safeway went in and parts of the rock face were fixed up for safety. I took this photo in 2018 from the roof parking lot.

There’s chainlink netting on the rock face, just in case it decides to start crumbling onto the roadway.

You’re always cautious about building inside an abandoned quarry, because rocks don’t last forever — that’s why they’re mostly underground, covered with soil. The experts have assured us it’s OK, and I trust them pretty well. The cemetery will last a good long while, and the former California College of the Arts campus, while it looks precarious perched above the other side, has passed muster too and someday will be apartments with good views.

What continues to impress me, every time I visit, is how different Oakland used to be. Throughout the late 1800s, the cemetery on one side and the CCA site (then it was the Treadwell estate) on the other were cheek-by-jowl with this huge operation that blasted three times a day, starting at six in the morning, and employed hundreds of men in producing crushed rock. But back then, rocks were money.

Posted in Franciscan rocks, Old quarries | 5 Comments »

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