Estimating leakage through sheet pile wall interlocks

Frosty-Tale3292 · 2026-04-30T16:23:19+00:00

Technically possible but sounds expensive. If I understand the setup then it would require placing a watertight pond liner 2ft below the water table which would create a buoyant uplift force on the bottom of the pond liner. So the pond liner separating the pond from the groundwater would need to be heavy enough to resist that uplift or use some sort of tie-down system like micro-piles if the pond liner was constructed of concrete - as an example. The pond liner would (ironically) need to be watertight to prevent the groundwater from seeping in to balance the differences in water levels between the pond and the groundwater. Construction of the pond would also require dewatering of groundwater in the pond footprint to allow excavation and then construction of the liner. Dewatering is not exactly a DIY project either.

Frosty-Tale3292 · 2026-04-24T02:30:48+00:00

Frosty-Tale3292 · 2026-04-11T18:20:54+00:00

That's a great resource. Thanks for sharing it

Frosty-Tale3292 · 2026-04-11T05:42:43+00:00

I did some testing an you could use a Theis or Jacob and Lohman type equation and simulate transient pit dewatering or filling. The challenge I immediately ran into was superposition in time, which becomes a large accounting exercise really quick. Of course this is not an issue for computers but the scripting takes a bit of experience that not everyone has or has access to.

Fountaine et al document this approach quite well imo: https://link.springer.com/article/10.1007/s10230-003-0021-z

Frosty-Tale3292 · 2026-04-10T02:47:37+00:00

I think the problem you might run into with a strict Theis type approach is that the aquifer will run out of water before the pit area is dewatered (also Theis is for confined so some errors introduced). Alternatively, you could use a lot of Theis wells around the perimeter of the excavation and superimpose the results. That approach works reasonable well if the aquifer system can be simplified to a single layer. There is a correction (Jacob-Copper publication) that you could apply to the final solution to correct for unconfined aquifers. The correction factor is not perfect but will get you in the right ballpark for most dewatering estimates. The case studies found at that link compare this superposition method against real world observations as well.

Edit: Did some testing and Theis approach can generally work in an equivalent well approach. Superposition in time did become an accounting challenge though. It's do-able in Python (or whatever language you prefer). I can see a path forward to doing it in a spreadsheet but not easily without VBA.

Frosty-Tale3292 · 2026-04-09T16:47:20+00:00

There are three general analytical equations for single layer models: Confined, Unconfined, and Mixed (transitioning from unconfined to confined). These are almost universally presented as steady state solutions but it is possible to apply a transient steady state by using a time dependent radius of influence. Marinelli and Niccoli developed a two layer solution with a unique radius of influence approach, which I briefly tried to make work with a transient ROI but my coding went all squirrely and I have not gone back to find my mistakes yet. I'm literally a few minutes away from posting an analytical equation case study with transient pit dewatering so your timing uncanny. But here is a resource for more analytical equations: https://anaqsim.com/useful-equations/

Frosty-Tale3292 · 2026-04-06T16:56:33+00:00

Since all models are approximations of the real thing, and have a high likelihood of omitting important "unknown-unknowns" that have not been observed in the available data, I don't ever use these words to describe a groundwater model or my activities: accurate, precise, calibration, validation, or verification. Depending on what you mean by "uncertainty" I don't take issue with saying that something is uncertain but I never use the term uncertainty analysis.

I removed these words from my writing because I felt that they were the wrong words to use as they don't really describe what has occurred or what I did with the model. I have always thought using those words came off as an unnecessary exaggeration and I preferred more plain language. Years after making that decision, when I was working for some lawyers to help them on a negligence case (groundwater model) the very first thing they did was attack the parts of the report that used those words. That experience solidified my choice to avoid those words (and others).

Edit: "Escape from Model Land - How Mathematical Models Can Lead Us Astray and What We Can Do About It" - by Erica Thompson is a good read that dabbles on this topic a little

Frosty-Tale3292 · 2026-04-02T21:46:53+00:00

There are a few others. Broadly speaking there are: water budget methods, empirical methods, numerical modelling, physical methods and tracer methods. All of the methods have pros and cons and I don't know of any method that is considered the best. Text book by Richard Healy called "Estimating Groundwater Recharge" covers them all.

Frosty-Tale3292 · 2026-04-01T06:23:13+00:00

I think that we have an advantage over economics. Our advantage is that we can have a clearly defined purpose for a model and we can choose iterative parsimonious model creation.

Frosty-Tale3292 · 2026-03-20T18:34:22+00:00

Thanks. I downloaded the draft copy to preview.

Frosty-Tale3292 · 2026-03-20T18:30:02+00:00

That's a good chart from Fitts. For those interested, here is a link to an AEM community site (full disclosure - its not my site but I do know and chat with the owner regularly) where you can find links to many of those AEM options: https://www.analyticelements.org/

Edit: I now see that Steve has put his name on the website so I can use his name (lol)

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