Real stone: a green case

24 July 2023

The newest building in central Oakland is the awkwardly named AC Hotel by Marriott Oakland Downtown, at Jefferson and 14th Streets. The AC chain purports to offer “hotels that reflect the soul of each city they are located in . . . a unique combination of quality, timeless European design, comfort and true authenticity.”

To me the “soul” of downtown Oakland is its collection of vintage buildings that range in age from the 1870s to today. Even our newest towers, residential and commercial, are vintage products of our interesting time. The AC Hotel offers a head and shoulders of sound 21st-century type, soft-finished metal and glass with restrained offsets and moderate height. And down at street level, it nods to its century-old peers.

I appreciate the dignified gray tone of this wall, its solidity and its variety of texture and form. But being a geologist, I always take a closer look.

This is not “true authenticity” or even plain old authenticity. It’s concrete that mimics fine-grained granite. To me it looks just as fake as the little plastic landscaping stones that cover spigots and hide spare keys. My aesthetics are just a personal taste, and I don’t blame the architects or anything. But there are other things to consider about concrete.

First let me say that I love concrete. It’s a miracle material that has transformed architecture. It’s a foundational technology and the single largest human-made substance. It has wonderful potential for artistic expression, like this example a few blocks away.

But the manufacture of cement, the binder that holds concrete together, is highly carbon-intensive. Every ton of cement adds about a ton of CO2 to the atmosphere, a ratio as bad as coal. That makes concrete a major greenhouse gas contributor and a stubborn problem to solve before we can achieve a carbon-free future.

So the question I have for architects is, why use concrete when real stone can do the same job? An enlightening article by a British structural engineer argues that stone is capable of much more than we think; for instance, prestressed stone beams can outperform concrete in strength, lightness and durability. Today concrete is cheaper than stone, but its carbon footprint is over ten times greater. A straightforward carbon tax could do much to right the balance, especially if builders and architects embrace novel uses of stone.

Take a leisurely tour of downtown Oakland, and you’ll see stone everywhere, old and new, decorative and structural. There is an interesting exception: the First Presbyterian Church, at Broadway and 26th/27th Street, an English Gothic structure built with concrete facing in the early 1910s.

The Rev. Frank L. Goodspeed promised in 1912 that “it is expected to be one of the most complete and beautiful churches on the Pacific Coast.” The church elders considered stone at the time, but concrete “cast stone” was one-third cheaper. The J. C. Henderson company of Alameda manufactured 22,000 superficial feet of ashlar panels for the exterior, plus all of the custom curved pieces, window frames and so on, “no natural stone entering into the work.” They also took pains to give it a more naturalistic look:

A noticeable characteristic of the church walls is the varied tone. Not every stone is of precisely the same color. This result was achieved in the use of two different brands of cement. Santa Cruz cement is of a very light color and was used for all of the trim and the window tracery and for a third of the ashlar. Golden Gate cement, of a dark color, was used for the remainder of the work. Additional color variation was obtained by using lime rock instead of blue rock in the trim, together with white Monterey sand and some color to give a buff shade. (Concrete, Dec. 1916, p. 181)

The AC Hotel could have used some of that truly authentic old-fashioned care.

There’s a larger conversation going on about the climate-related merits of different building materials, not just concrete and stone. Good old timber has advocates, and Oakland will have a 21st-century tower with wood framing at 1510 Webster, going up now.

Mass timber claims to be climate-friendly, sustainable and all that good stuff. That part is debatable. But its light weight and speed of construction are indisputable advantages. And maybe the building’s lobby will have some really cool stone features.

Posted in Oakland stone | 2 Comments »

Lobe 5 of the Fan: Coolidge

10 July 2023

It’s been a while since I made a close inspection of the Fan, which is the name I gave to the wide fringe of gravel hills that surrounds the Piedmont bedrock block. I’ve not just given the Fan a name, but also have assigned numbers to its different parts, as seen in this piece of the Oakland geologic map.

Today’s post is about lobe number 5, the Coolidge lobe. I’m giving it this name because Coolidge Avenue runs from its westernmost tip up its entire length. All parts of it make interesting walking.

This is where the first non-Indigenous building in Oakland’s territory was constructed in 1821, an adobe dwelling on Luís María Peralta’s royal land grant. Spanish/Mexican adobes were what inspired the “ranch-style house.” In fact, Coolidge Avenue was originally named Peralta Avenue (Oakland annexed the area in 1909 and renamed it to avoid confusion with Peralta Street in West Oakland). The ranch site is preserved today at Peralta Hacienda Historical Park. It’s possible to explore lobe 5 and appreciate why this particular site attracted Peralta.

Lobe 5 is a triangle defined by the floodplains of Sausal Creek and Peralta Creek and the bedrock of the Piedmont block. It happens to reach a higher elevation than any other lobe, over 300 feet. Here’s a closeup of the geologic map, showing the Fan’s ancient gravel as the orange unit labeled “Qpaf” (Quaternary (Pleistocene) alluvial fan and alluvium deposits).

There’s a strip of a unit labeled “Qpoaf” signifying slightly older deposits of the same type. I give this limited credence because its description is exactly the same as the other unit; I think it was mapped this way based on the topography.

I said Peralta Creek defines the edge of the lobe but in fact it cuts across it, assuming one accepts the mapping and I have no reason not to. The creek has to flow this way because it’s confined by Rettig canyon, a water gap in the bedrock ridge at the top. The digital elevation model will make this clearer I hope.

The Hayward fault runs through that slashing valley above the canyon; I described it in this post a few years ago. That means the creeks here have had a complicated history as the fault kept ripping up their headwaters and raising and lowering land. That’s a discussion for another post.

The lobe itself has a corrugated surface, a set of grooves that coalesce down near the tip of the lobe. Those are little stream valleys, which show up on the early Oakland maps as running creeks. This map is from 1884.


Peralta Creek at center, Sausal Creek at left, Courtland Creek at right. (Source)

This odd stream pattern is more evidence of an odd history, one of the puzzles posed by the Allendale flat. More practically, the lobe had a good supply of water.

Here’s a view across the middle one of these creek valleys, looking south on Delaware Street just above the freeway. (The image at the end of this post has locations of all photos.)

The edges of the Coolidge lobe are quite distinct. On the Fruitvale side, here’s the edge as seen from below on Coloma Street.

Looking down from the lobe across the Sausal Creek floodplain at E. 27th Street.

The east side of the lobe is less abrupt, but Peralta Creek cuts quite a notch through its upper end. This is the creek bed where it interrupts California Street, above the freeway.

Access is difficult, but the stream banks in this vicinity expose the material of the Fan. It’s a clayey gravel with cobbles of the Leona volcanics and other rocks from the high hills.

It’s fairly well indurated. The stream is lined with huge eucalyptus trees, easily visible from the hills and on Google Maps. I think these pose a greater risk to the neighbors than the tall exposures of this alluvium.

Here’s the eastern edge of the lobe looking down onto the Allendale flat from Salisbury Street, a block toward the Bay from Peralta Hacienda Park near the lobe’s tip.

The hacienda site was well situated in 1821. All of the surroundings was grassland, except probably some oaks and laurels along the creek, and the creek, with its essential water supply, was easily reached without high banks.

The site commanded good views of both the Peralta and Sausal Creek floodplains as well as the Bay. You can still glimpse them here if you peek between the trees and buildings as you walk around. Its location, slightly over the crest of the lobe, offered some shelter from strong Bay breezes. There was good soil for manufacturing adobe bricks and to support the kitchen garden. Presumably there were good Ohlone trails through the area. A decent landing, just half a league away to the west at the mouth of 14th Avenue Creek, served the ranch’s needs for shipping. That’s where the East Bay’s earliest secular settlement took root in the 1840s, named San Antonio and then Brooklyn.

Here are the photo locations.

Posted in Oakland geology puzzles, the Fan | 3 Comments »

Oakland’s age of groundwater

26 June 2023

I gave a presentation last week to the local chapter of the Groundwater Resources Association of California, focusing rather strictly on Oakland’s water. It was a chance to go deeper into the topic and bring up things that didn’t fit in chapters 5 and 8 of Deep Oakland. Though I mainly spoke about groundwater, I mentioned our surface water too. I said Oakland should value it for beauty, recreation and habitat and never use it for drinking again.


Oakland’s original (1869) surface water reservoir, Lake Temescal

Oakland’s “groundwater age” lasted from the city’s founding in 1852 until 1930. I can be quite certain of that latter date because the East Bay Municipal Utility District shut down all the local groundwater wells, inherited from the previous private water companies, that year.

The groundwater age was mostly a fraught time. The first settlers in Oakland, around the lower ten blocks of Broadway, all dug wells to supply their water. After a while the water table began to sink and pollutants made their way to the shallow aquifer just beneath the Merritt Sand. In 1883 Myron Wood reported, “Wells in thickly settled neighborhoods are looked upon with distrust.”

In short order, people who were lucky enough to have productive wells started small water companies serving a local clientele. The city’s first franchised water supplier was the Contra Costa Water Company, founded by Anthony Chabot and based on surface water. Chabot dammed Temescal Creek to create the little reservoir now known as Lake Temescal. It came on line in 1869. The water wasn’t very good; one early account described it as “clear, but of a deep greenish tint.” Early customers drank it only during the rainy season, relying on their wells the rest of the year and using the city water for the yard and garden. There were flat rates and no meters. Lake Temescal regularly dried up at first, and Chabot later raised the dam.

Many businesses had their own wells. Today we might picture pure water as a mountain stream, but in the old days groundwater was much preferred. Oakland’s wells yielded water that was “hard, but very clear and pure.” Wells supported manufacturers, canneries — and breweries, which I’ve marked with a “B” on this geologic map.


North to south: Anchor, Oakland Brewing and Malting, Oakland Brewery, Washington Brewery/Golden West Brewing, Becht’s Brewery, Empire Brewery, East Oakland Brewery, Brooklyn Brewery, Palace Brewery and Alameda Brewery


Golden West Brewing Company at 5th and Kirkham Streets, 1911


Oakland Brewery at 19th Street and Telegraph Avenue, 1885

Chabot’s firm next dammed San Leandro Creek to create Lake Chabot, which went into service in 1875, but every other water company relied on wells. Chabot’s company soon joined them, and for the next fifty years the water companies struggled to grow their supplies, constructing wellfields in East Oakland and farther south. At the height of the “water wars” in the 1890s, they were badmouthing, outpumping and even sabotaging each other while the city imposed low rates that pleased the citizens but drove the companies, one after the other, to bankruptcy and consolidation.


Some of Oakland’s long-gone suppliers: Contra Costa Water Co., Union Water Co., People’s Water Co., East Bay Water Co.

Oakland had enough groundwater for a small city, but not a large one. As it and the other East Bay cities grew, the water companies repeatedly hit limits imposed by pollution, saltwater intrusion, depletion and drought.

No new dams were built until times were desperate. East Bay Water Company, having absorbed nearly twenty competitors between 1876 and 1921, built San Pablo Reservoir in 1919 and Upper San Leandro Reservoir in 1926. Then East Bay MUD, created by a public vote in 1923, bought out all its assets and shut down the wellfields. The new public agency brought the first Mokelumne River water from the Sierra foothills on 24 June 1929 during a severe drought. It had finished the Pardee Dam and Mokelumne Aqueduct in the very nick of time, just a day or two before the local reservoirs were down to their last foot of muddy water.

Today the East Bay reservoirs hold water pumped in from the Sierra foothills.

Like Los Angeles, San Francisco, New York and every other great American city, we just don’t have enough of our own water to thrive. But it’s possible that we could still develop small local aquifers that were previously out of reach. They could serve for emergency use if a major earthquake were to interrupt the supply from the Mokelumne River watershed. These might be found beneath the abundant landfill that has extended Oakland far past its original shoreline. Perhaps when the harbor and airport are built up in the face of sea-level rise, we can arrange to explore the untapped groundwater beneath them. It’s part of thinking 500 years ahead.

Posted in Oakland streams and water | Leave a Comment »

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