By Frank Landis, Conservation Committee Chair & Rare Plants Chair
Since I’m working on the Cottonwood Sand Mine EIR, having just finished commenting on the De Anza Natural NOP, I figured it’s time to admit something a little weird: not all the issues I deal with in my letters are the CNPS topics of native plants, conservation, and wildfire. Here’s what happens, and here’s what I try to do about it.
Let’s talk about the Rose Canyon earthquake fault. It comes ashore in La Jolla, then crosses I-5 about 700 feet south of the junction with SR-52 by Marion Bear Park. From there it runs under or parallel to the I-5 to disappear under Old Town.
CNPS doesn’t comment on earthquake risks, because they aren’t native plants. However, if someone asks me whether it’s a good idea to build three more lanes from I-5 to the 52 east, one of the things I’m going to point out is that this proposed four-level interchange will be built right on top of the most dangerous fault in San Diego County. And next to the train line, the trolley line, a creek, and a wildlife corridor. Maybe not so smart to have so much concentrated right there?
But I’ll make those comments as a private citizen, not as the CNPS-SD conservation chair. I don’t know of an activist group that works on earthquake hazards, and when I spot an earthquake or other orphan hazard, I point it out, as a separate, non-CNPS section in the letter.
Turns out De Anza Cove is about 500 feet from the Rose Canyon Fault. And the City’s working on a programmatic EIR for the northwest corner of Mission Bay (again!). While I was commenting on that NOP, I saw the new fault maps, and grew perturbed enough to google. That’s how I found that there was a 2014 ShakeOut scenario for a major Rose Canyon earthquake, and the Mission Bay shore could be actively dangerous.
The problem is soil liquefaction: when you shake mud or sand just right, it starts acting like a liquid, and you, or your car, or a building can sink in. Once the shaking stops, you’re trapped. If there’s a big earthquake in Rose Canyon, there’s a high risk of liquefaction on all the shorelines around Mission Bay. This doesn’t mean that you shouldn’t visit Mission Bay, as the danger is miniscule on any given day. If, however, you plan to build a long-term shoreline facility, you need to deal with the liquefaction risk. Hopefully, this time City Planning will realize that it’s a problem across the entire site and analyze it up front, rather than punting the problem to individual projects. Hopefully.
Once again, I made my fault-finding comments on de Anza as a private citizen. While I’m not a geologist, I was getting my degree in environmental science at UC Berkeley in 1989 when the Loma Prieta quake hit. Soil liquefaction was a problem then, especially in San Francisco’s Marina District, and we learned about it.
Then there are sand mines, which are not my favorite things to deal with. They tend to bring out the worst in people, so I generally stick to commenting for CNPS about CNPS issues.
A bit of background: yes, there’s a lot of sand in the world. However, if you want to put that sand in Portland cement (the binder for concrete), not just any sand will do. If the sand grains are too round, they make for weak concrete. That rules out most desert sand, where the wind has tumbled the grains for untold centuries. Instead, you want sand that was washed by water, which has angular grains that lock against each other. However, unrinsed ocean sand has too much salt on it, and salt causes the kind of fascinating, concrete-rotting chemical reactions that makes buildings fall apart.
Unfortunately, the best cement-grade sand comes from rivers. Or, if you want to use a lot of energy and make a lot of noise, you can pulverize the local granodiorite into sand. So, sand mines are either in or near rivers, or they involve pulverizing hard rocks, and either way there’s noise. This is why anyone well-off enough to fight a sand mine going in next to them does so. They’re easy to hate, and whenever an EIR shows up for one, I get sucked into reading it, with others’ assuming that CNPS-SD will join the fight against.
But that’s only half the story. A house like mine has a concrete foundation, concrete patio, concrete sidewalk, and a concrete driveway. That’s around of 100 tons of concrete, about one-third of which is sand.
This is where we get into a little problem. We want to go on a building spree to build carbon neutral, infill development, more transit hubs, deal with the housing shortage, and so forth. The cheap way to do this is with a lot of concrete, and that in turn requires a lot of mined sand.
To paraphrase one anti-sand mine group, yes, we need more sand, but do we have to mine it next to them? Well, mining it in County emits about 25% or less of the greenhouse gases emitted from getting it outside the County. The further sand is carried, the more it pollutes. So, if we’re trying to cut GHGs, in county is better.
And there’s also the environmental justice component. There’s a 2017 report out (SR 240 from the California Geology Survey) that goes into the County situation. What jumps out is how many of the exhausted sand mines are on tribal land. My house may very well be on Kumeyaay sand. But other environmentalists want me to join with a bunch of reasonably well off, mostly non-Kumeyaay people, to stop sand mines being built on degraded land near them? Environmental justice is about equal treatment. If sand needs to be mined, shouldn’t everyone share the mining burden equally? Or should wealthier communities shift the burden to poorer communities and increase greenhouse gas production in doing so?
Or maybe we can use less concrete? Readapt existing coastal neighborhoods to house more people with minimal rebuilding? Drat, I’m out of space.
Anyway, this is why I prefer earthquakes to sand mines. And I prefer native plants to both.