Episode link: https://soundcloud.com/quinn-todzo/the-struggle-to-protect-the-california-coastline
Episode Transcript
California is being swallowed into the Pacific Ocean, and it
is really hard to stop or even slow down that process. With sea levels that are
rising at increasingly alarming rates, 800 miles of shear beach cliffs along
the California coastline are eroding at rates as much as 5-10 feet per year. From
houses to highways to important infrastructure, there is a lot at stake on the
edge of California, so what are we doing about it. Well, today I am going to
bring you a boots on the ground story of how we are trying to protect our coast
from erosion, and the difficulty in doing so.
Before I go any further I do want to mention that I am not
going to really talk about rock climbing in this episode. As I discussed in my
last rock behind the climb episode on Mickey’s Beach this issue is affecting
some of our crags. But, today I ask that you indulge me a bit, because I think
my small scale story of trying to protect just one guy’s house from collapsing
into the ocean will give you some perspective on the massive issue that is
trying to mitigate coastal erosion, so stay with me.
So, the project that I am working on is for a single story
home built right on the edge of a beach cliff. About 15 years ago the homeowner
constructed a shotcrete based seawall embedded into the existing bedrock to
prevent the erosion of the cliff and subsequently his house collapsing into the
ocean. About a year ago, though, my geotechnical engineering and geology
consulting firm got a call that a huge cave had formed underneath the previously
constructed sea wall.
Basically the rock that the original sea wall was constructed
on top of was more erosive than the concrete wall above, so the ocean continued
to carve into the rock underneath burrowing a 4 foot high, 80 foot wide and 26
foot deep cave underneath this guy’s house. If we had let this cave get much
deeper, it could have seriously once again endangered the house from collapsing
into the ocean. The first order of business here was to fill in the cave with
high pressure shotcrete, or concrete that you can spray out of a hose. A couple
months after the cave was infilled with shotcrete, our client secured the
permit to begin working on the construction of a new sea wall that we designed
to protect from further undercutting. This is where I came into the project.
As an engineer out in the field my primary role on a project
like this is to ensure that our design is being constructed correctly. In an
ever evolving environment like this one, I’m also the guy on the ground to point
out anything that doesn’t make sense in the design in a constructability sense
and help make changes if necessary. In my line of work there are a lot of
assumptions made when designing structures in an ever changing environment, variability
within the construction contractor, and high stakes, they tend to send someone
with engineering or geological knowledge to do the inspections, because the
directives are never simple. So that’s what brought me out.
But before I get any further, I want to take a step back and
talk about why the California coast is eroding so quickly, and traditional ways
in which people try to protect coastal bluffs. So a lot of the coastal bluffs
are made up of marine terrace deposits. These are rocks that are comprised of
sands and clays originally deposited by the ocean, and now make up the weak
sedimentary rock near the shoreline. Through millions of years of tectonic
action these marine terrace deposits have been uplifted to form the coastal
mountain ranges along the California coast. However this doesn’t explain why
the cliffs are so shear. This comes because of wave action from the ocean.
Waves constantly bombard these weak sedimentary beach cliff rock formations at
the bottom eventually causing the entire cliff to shear off. As sea levels have
risen and fell over millions of years, they have created multiple levels of sheared
beach cliffs separated by nearly flat platforms that are a result of the ocean
spreading out the collapsed material to make a terrace, hence marine terrace
deposit. All of this is to say that we have constructed a lot on top of the
flat, weak terrace deposits that are now being reconsumed by the ocean.
So how do we protect the communities and infrastructure that
we have resting on these unstable beach cliffs?
Well one idea is to get out in front of the ocean. The
primary cause for the eroding cliffs is giant waves crashing into them, so why
don’t we just take the waves, and put them somewhere else. So we’ve actually
tried this. There are structures called jetties and breakwaters which are these
barriers made out of giant rocks or chunks of concrete that extend out off the
coast perpendicular into the ocean to hopefully curb the wave action coming in.
You see these a lot near harbors. Anyway there are a number of major problems
with these structures including problems with surrounding ecology but they can
actually have a pretty negative effect on coastal erosion.
These structures can do a good job of redirecting some waves
from pounding the coastal area you want to protect, but they can also trap sand
from being able to land onshore. Now I know what you might be thinking right
now: “I hate sand. Its course, and ruff, and irritating. And it gets
everywhere.”. However, the reality is that sand is actually really great for
protecting our coastlines. A built up sand bar can act as a buffer to block waves
from running up against the cliff or at least slowing them down. So these
breakwaters and jetties can actually do more harm than good in terms of
preserving the cliffs, because they trap the sand from landing on the beach
Piggy backing off of this discussion, another solution that
has been used is to literally pump more sand onto the coastline in a process
called dredging. This process is actually very costly though to pump enough
sand in place, but is helpful in that it maintains the coast in a more natural
way than building structures.
In my opinion, one of the most effective ways to protect a
sea cliff in general is to build a riprap buttress. This is basically a pile of
giant super heavy rocks that get piled up next to a sea cliff to protect it
from getting pounded by waves. These are actually really effective in
protecting the sea cliff, but they can actually redirect waves to be more forceful
on the sea cliffs adjacent to where they are placed. Also they look like crap
and in many cases decimate any hope of having a functional beach that can be
used by the public.
That brings me back to the project I am currently working
on, a concrete based sea wall. Concrete sea walls are exactly as they sound,
vertical walls that stand between the sea cliff and ocean. In many cases
including the project I am working on this is paired with a shotcrete finish
meaning that the weak friable rock is sprayed with concrete to create a façade
that holds everything together and still kind of looks like the cliff face so
it still has the marine terrace feel to it. On top of that, these cliffs are
anchored by a series of soil nails or tie back anchors which are huge strands
of steel that are drilled into to the cliff side and tensioned to hold it in
place and protect it against a slope failure.
All of this was in place in 2005 when our client’s original
wall was constructed. And it worked. Actually pretty well. However, as I
discussed in the beginning of this episode, the ocean, not to be outdone,
actually burrowed a cave underneath the sea wall with the constant swell
forces. The rock that the old sea wall is founded upon is weaker than the
concrete wall, so the ocean found a way to still eat at the cliff side.
However, that old wall still remains hanging over where the rock used to be.
That last bit of background you need to understand going
into the project has to do with the California Coastal Commission, which is a California
state regulatory commission that regulates the land use on or near the
California coast, and oversees any development near the shoreline. This is
great in theory as it helps protect the coastline and ocean for the general public.
However, it also makes it so there are a lot of hoops you need to jump through
to get and maintain a permit to do construction like this. As I go forward with
this story, you’ll see what I mean.
Ok, now let’s get back to about a month and a half ago when
I was first brought out on the project. Our clients had just secured a 2 month
long emergency permit to go forward with the new sea wall portion of the
project. Without a ton of forethought or planning, the construction contractor
was sent out there to build this thing. After all, they just had to dig a 4’
deep ditch, put in some steel, and spray it down with shotcrete. Boom. Easy.
Right?
Eager and ready after a long car ride down to the project
site (which I’m not allowed to tell you the exact location of), I was
immediately turned around. The tide was way too high. In a project where you
trying to prevent the effects of the ocean slamming against the area where you
are building, it is likely that the work area is going to be flooded with tidal
water. And regardless of whether you think that we should have just thown on
our wetsuits and got going, nevermind how dangerous and polluting it is to
operate heavy machinery in the ocean like that, it is against our permit to work
when there are still tidal waters present in the work area.
There are very few times when the tide is low enough for us to
get out there and work, so the solution became to try to place temporary barriers
seaward of the cliff to try to extend the time that they could actually get work
done in those short windows of time when the tide is receded enough to work. Without
the barriers, they only have roughly 3 hours of time, but with the barriers they
were looking to extend that by at least a few hours.
However the idea to place temporary barriers utterly failed.
Their first temporary barrier were these giant 6 foot tall bags filled with
sand and rocks that they would drag out every single day. At the beginning of
the day carry them out via crane and bobcat loader, and every day take them
back to the staging area up on top of the cliff. This process of carrying the
giant bags of sand and rocks out and back took so long that it actually
afforded the contractor next to no time to actually work.
So, after that they decided they would try putting giant
blocks of concrete out on the beach plane and leaving them in place overnight so
that they wouldn’t have to waste so much time moving these barriers. Well, even
though these were multi ton giant blocks of solid concrete, they were no match
for high tides and large swells, and they were nearly thrown into the side of
the cliff after just one night. They were then promptly removed.
It was also during this time of experimenting with the
failed temporary barriers that the contractor also realized that their initial
plan for digging the 4’ deep ditch called the keyway was not going to work,
because of a few details that proved to be quite problematic. First, by nature
of the permit the new wall cannot extend outboard of the original 2005 alignment,
meaning that the wall can’t be constructed in front of where the old one overhangs
the cave that formed. Also, by nature of the permit anything that the
contractor chipped whether it be old concrete or the underlying rock, has to be
offhauled from the beach into a dumpster on the road.
They initially planned on using a mechanical excavator to
chip away the old overhanging shotcrete wall to then use a different attachment
on the same excavator to dig the keyway. This proved to be ineffectual because it
takes a really long time to chip and off haul the large amount of overhanging
shotcrete needed to clear an area large enough for us to work, and there was
about half of the length of the wall couldn’t even be accessed by the excavator
because it cannot track over this one section of beach area that is mainly just
rock, no sand.
I’m not sure if any of that made sense to you, but in effect
we were one month into our two month permit and had barely even broken ground. Around
this time we had a particularly excrutiating daily project meeting These
meetings had transformed from simple daily check ins to 2+ hour tirades with a
lot of yelling and finger pointing. Anyway, I remember they were discussing
another option for temporary protection from the tidal waters when I brought up
that regardless of whether or not they fart around with another shoring system
that probably won’t work and mind you doesn’t actually do anything to construct
the wall, they do have time to at least get some stuff done with a bunch of guys
with jack hammers and rock drills. Honestly it’s not really my place to comment
on the means and methods in which this project gets done, but whatever, things
were getting ridiculous.
Luckily my point was taken well, so me and the now third site
supervisor from the contractor devised a plan of attack where some workers
would go ahead and predrill some pilot holes with the rock drills to release
the confinement in the rock, and then guys with jackhammers would come through
and chip around those pilot holes to excavate the rest of the trench. We called
this method the “swiss cheese” method because the predrilling made the excavation
area look like a block of swiss cheese kinda. Anyway, this actually worked pretty
well and soon enough we were making progress, especially as they continually
sent more and more workers out to aid with the operation.
However, it may have been too little too late because the
reality is that we were only actually able to work for about 3 hours a day
maximum. In fact there have been entire weeks where the tide is too high to be
able to work at all. On top of all of that, before we could continue to
excavate downwards, each day had to be started with shoveling out all of the
sand and rocks that collect in the keyway each night. So even with the
revolutionary swiss cheese method, progress has been slow.
And that’s not all. There are still battles over the
constructability of the wall during our limited permit window. As of right now
we have a few sections of the wall mostly trenched to depth. No steel has been
placed, and no concrete has been shot and our current permit ends in a few
days.
Now you may be thinking that the contractor is to blame and
is inadequate, but the reality is that they weren’t given a whole lot of time
to prepare for this work because the permit was issued so close to the actual
start date. In fact, we have had a number of other construction contractors
check out the project and none of them have given any better ideas than what
the current contractor is doing.
Maybe you are thinking that the Coastal Commision is to
blame by instituting too many regulations and by making us jump through a lot
of hoops during the permitting process.
The reality is, though, that this project is freaking
difficult, no matter how you slice it. Lucky for us, we have a client that is
really committed financially to building this wall, because a project like this
isn’t cheap. And for what? The wall is designed to last maybe 15-20 years. All
of the prior infill, this wall which is going to take much longer than
expected, and a number of tieback anchors all for another 15 years.
Now you might be thinking to yourself is it worth it? I mean
obviously for this guy it is. He gets another 15 years in his beautiful home.
But is any coastal remediation worth it if we the public are the ones who have
to pay for it? I mean this is a stretch of 80 feet among 800 miles of bluff on
the California coast, and these 80 feet are causing a lot of smart people some big
headaches.
Well, you wouldn’t be the only one to think it’s probably
not worth trying to protect the California coast. I mean who cares if a few
rich people lose their seaside homes. Really, just say screw it and let the
ocean consume everything in it’s path. In places like Pacifica, California
which is just south of San Francisco, the 80 foot cliff is receding at such an
alarming rate that they literally had to abandon apartment buildings and homes to
demolish them before the ocean did so. I linked a couple of interesting
articles on this from 2016. Also, as many of my friends like to point out, the
Big Sur coastline in California is consistently plagued by rockfalls and
landslides that make the beautiful highway 1 impassable. It’s just cheaper and
more feasible to just roll with the punches than try to actually fix the cliff
in these areas.
But in reality there can be problems with the do nothing approach
too. I mean people aren’t just going to let their homes get destroyed without
some sort of legal battle. Most of the time when something like this happens it
is on the city or county to reposses the property that is subject to falling
into the ocean, meaning that the public has to purchase the buildings that can’t
be saved. Also it’s not like the ocean stops eating away at the cliff. I mean
there are places in California where the ocean is eroding the cliff at a rate
upwards of 5 feet per year without defenses, and sooner rather than later that will
cut past the beautiful sea side homes, and into valuable infrastructure and
more houses.
So right now, my view on this is nuanced. I think there are
certainly places that are not worth saving. Rural locations where there isn’t
too much at stake. But, in more urbanized areas it can be hard to justify going
down without a fight, and decisions should be made on a case by case basis with
engineers, geologists, and other scientists at the forefront to weigh the options.
I’m going to be honest, I’m not too sure how to close this
discussion. We are going to be faced with some really tough decisions in the
coming years concerning this coastal erosion issue and I am sure that this
podcast that you are listening to right now will not be the last you hear of
this.
But thank you so much for listening. I know this is a bit of
a divergence from the rock behind the climb but I haven’t had too much time to
climb as of late because of this project, but I promise I have more rock behind
the climb in the works. Please let me know if you liked this episode, and especially
if you are curious to hear how we finally get this wall completed, a part of
the story that I don’t even know yet. Otherwise, thank you so much for listening
and I’ll catch you on the next one
Jazzhammer out.
Links to articles and Resources
More on Coastal Protection
https://pubs.er.usgs.gov/publication/70033640
