Could fracking save Gouda?

24. Combating sea level rise with land level rise

Note: The views expressed here are the author’s own and do not reflect the views of Energy Impact Partners.

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Sea level rise depends on where you are

The way that sea level rise works is roughly the following:

1. Ocean water warms up and expands slightly, increasing the volume of the ocean. This accounts for about 40% of sea level rise.

2. Ice melts and turns into liquid water, increasing the volume of the ocean. This also accounts for about 40% of sea level rise.

3. Warmer ocean water evaporates faster, decreasing the volume of the ocean. This is a relatively small effect.

4. A warmer and wetter atmosphere rains more, increasing the volume of the ocean. This is also a relatively small effect, and it roughly balances out increased evaporation on a global scale.

5. Land near the ocean subsides — because of groundwater depletion, heavy buildings and roads built on soft land, and natural geologic processes — increasing the apparent level of the ocean. Land subsidence accounts for the last 20% of sea level rise. Your mileage may vary locally. For example, land subsidence is roughly 50% of apparent sea level rise in Venice.

So while the main story is still the ocean getting larger, it’s not the whole story. Sometimes it’s only half!

This matters because sea level rise feels like a deeply intractable problem, one of those grim facts of climate change. Even if we were to stop emitting fossil fuels today and remove all of the excess greenhouse gases from the atmosphere, we would still have this problem. The oceans have absorbed more than 90% of all heat produced by global warming, and it’s not clear how to cool them down. It’s the physical incarnation of the business truism “don’t boil the ocean.”

Land subsidence, on the other hand, is something we can do something about. We engineer land all the time! Look at Boston in 1630 vs. 1995. Look at the Raising of Chicago. Look at the Palm Islands in Dubai. Look at the Kansai International Airport in Osaka. On multiple continents over multiple centuries, we’ve decided that water should be land and made it so. In retrospect, these projects look like warm-ups for an age of sea level rise. Why would we stop now?

Gouda

Source: Cheese World

This brings us to Gouda. In addition to being a cheese, Gouda is a town of about 75,000 in the Netherlands – where they make Gouda cheese. Like much of the coastal Netherlands, it’s low-lying and prone to flooding. Famously, the Dutch have built sea walls and other water infrastructure to manage this. But Gouda is in a tougher spot than usual: it was built on soft land that is being compressed by all the stuff they’ve built on top of it, sea levels are rising, and rainfall is increasing. This has become a problem.

The New York Times covered the story in August:

Much of the Netherlands was built centuries ago on peat marsh, a spongy soil that compresses easily. In Gouda, it is constantly subsiding under the weight of the city, said Michel Klijmij-van der Laan, a city alderman who focuses on sustainability and subsidence issues.

The oldest part of the city center subsides at a rate of about 3 to 6 millimeters each year, he said, and newer parts sink by 1 to 2 centimeters, or about half an inch, a year.

“We have until 2040 or 2050 to come up with a new plan,” Mr. Klijmij-van der Laan said. “We have to find new solutions, because the solutions we’ve always used are not future proof. Just continuing to pump water out isn’t practical, because eventually it will become too expensive.”

In an effort to tackle the problem, Gouda, which has about 75,000 residents, is spending more than $22 million a year on water mitigation efforts, including daily maintenance, repairs, system upgrades and pipe replacements. Mr. Klijmij-van der Laan said that amount is expected to increase exponentially.

Now, the Dutch are some of our most successful civil engineers, so I have no doubt there will be a new plan in time. But perhaps we can give them an idea?

I like an idea called “solids injection to raise ground elevation,” or SIRGE. SIRGE is a type of subsurface engineering where you drill a well, create a horizontal fracture, and then inject solid-laden slurries into the fracture. The solids can be things like sand or woodchips, and after the intervention, they “prop” the fractures open. This is just like what we do in the oil and gas industry.¹ If you prop the fractures open wide enough, you can actually raise the ground level above it by several inches — like you’ve installed stilts for the land itself. Once you’ve done this in one well, you repeat it in an array of locations to create a network of overlapping injections that combine to raise the land in a way you desire. In principle, you can get fancy with your design or injection timing to minimize surface disturbance.

Source: Murdoch et al. Shallow Geologic Storage of Carbon to Remove Atmospheric CO2 and Reduce Flood Risk, Environ. Sci. Technol. 2023, 57, 23, 8536–8547.

SIRGE has been shown more than a few times, sometimes on purpose and other times by accident. But it’s not yet a proven technology. We had some fun in 2022 exploring a similar idea to save Venice.

Could fracking save Venice?

Is SIRGE at all feasible for Gouda? Let’s do some envelope math. The following exercise convinced me that it’s worth some more effort, but let me know what you think.

Let’s start with a few figures mentioned in the NYT article and a few educated guesses. First, geography. How much land do we need to raise? Since the city center is sinking the fastest, but clearly it’s not the only place in need of intervention, let’s make the conservative estimate that we’ll need to lift the entire town. Gouda’s land area is about seven square miles, or 4,480 acres.

How much lift do we need? For now, let’s assume that if we offset 50 years of subsidence, we’ll have bought enough time for the town to come up with something more permanent.² How much will the town sink in 50 years? Again, let’s take a conservative estimate and use the fastest-sinking part of the city. The the city center is sinking at 3-6 mm per year. Let’s call it 5 mm per year, or 0.2 inches per year. If that rate holds constant, then we’ll need to raise the land by 10 inches to buy 50 years.

That was the easy part. Now: what is an acceptable cost for this intervention? Currently, Gouda spends about $22mm per year on water mitigation. Putting a finger in the air, it seems like $500mm, or about 23x their current spend, could be a reasonable number. After all, you are undoing 50 years of subsidence. That’s half price!

But that would be the acceptable price to the town, not the cost of the project. Typical gross margins for large construction companies are roughly 5-15%. Since this is a weird one, let’s call it 20%. So the cost of the project would have to be less than $400mm or so.

Is $400mm a lot? Hard to know, we don’t often raise seven square miles by 10 inches. How do you even benchmark a number like this? Let’s normalize it by the volume of earth moved. That gives us the following math:

Cost per volume moved = Cost / (Area * Height)

Cost per volume moved = $400,000,000 / (4,480 acres * 0.83 ft) = $107,143/acre-ft

Here are our assumptions laid out in more detail:

Source: Author

About $107k per acre-foot.³ Is that a lot? Still hard to know, but let’s try and triangulate it.

First, let’s put the price in some more context. Gouda’s cheese exports are $1.7b per year. A $500mm project represents less than 30% of that total. If you were to allocated those costs over, say 10 years, it falls to less than 3% of annual cheese exports. Maybe not a bad insurance policy? Or put another way, for Gouda’s 75,000 residents, that’s about $50-60 per person per month. In reality, this would cost much less per resident because the national government or the EU would likely step in.

Second, let’s compare this cost ceiling to some other massive land-creating projects: the aforementioned Raising of Chicago, the Palm Islands in Dubai, and the Kansai International Airport. As best I can tell, the Gouda project’s maximum price tag would be about half the price of first-of-a-kind projects we’ve done to create land. Maybe not that crazy. Notably: 1) the second phase of the Kansai Airport reduced its cost per acre-foot by 70%, suggesting there is a learning curve for these kinds of projects, and 2) Chicago got the job done for two orders of magnitude less, also suggesting there’s some room under our price ceiling. But that’s another post for another day.

Source: Author

Third and finally, let’s look at what kinds of interventions $107k per acre-foot would allow. This is probably the hardest estimate to make since there’s no public cost modeling on SIRGE. Let’s think about it on a per-acre basis. What can $107k buy you? Residential water wells typically cost $3-15k and you’d typically install two per acre, so we end up with $6-30k per acre. Shallow horizontal geothermal loops for building heating and cooling are typically $4-8k per loop, and you might install four of them per acre, so shallow geothermal would run you $16-32k per acre. Both are well within $107k per acre.

But neither involves raising the land. How much deeper do you need to drill to do SIRGE? How much will fracking, solids injection, and monitoring cost? How many wells will be needed over 4,480 acres? There are still a few too many degrees of freedom to say something concrete, but it seems worth figuring out.

As a society, we’ve decided that it’s important to maintain historical places. They hold cultural value, provide tourism revenue, and in some cases, export delicious cheese. But without maintenance, they will decay. So in the same way that we’ve committed to sweeping streets and renovating buildings, we’ll also have to commit to keeping the water out. After earthquakes and fires, we rebuild things and develop new technologies to prevent future damage. Why would we treat water differently?

As one NYT commenter put it:

Source: NYT

Special thanks to Rob Moak.

Elsewhere:

• A model for reclaiming land in the Maldives

• The Real Hero of ‘Twisters’ Is Geoengineering

• The US is a natural gas superpower

Thanks for reading!

Please share your thoughts and let me know where I mess up. You can find me on LinkedIn and X.

1. There are some differences between SIRGE and regular fracking. Here are a few: 1) Oil and gas exploration happens a mile or two underground, where SIRGE is likely to be much shallower. 2) Oil and gas fracs are typically vertical, where SIRGE contemplates horizontal fracs. 3) If you use woodchips in your SIRGE campaign, they have the nice side benefit of locking carbon away underground. There are many other differences, but you get the picture.

2. Like maybe stopping sea level rise?

3. As a side note: while acre-foot reads as a comically American unit of measure, there are a few reasons it makes sense here: 1) civil engineers and farmers commonly measure water in acre-feet, 2) SIRGE does involve drilling and fracking 🇺🇸, and 3) visually, acre-feet feels more intuitive than cubic meters here; we’re raising acres of land by about a foot.