r/Geotech • u/Djr215 • 8d ago

Flowing artesian wells - Monitoring installations

Hi All,

I have a number of shaft sinking schemes coming up in an area where artesian groundwater is present (+3m AGL).

Looking for some advice on groundwater monitoring installations/wells.

I plan to monitor the artesian wells to get an idea of seasonal variation, and also use them as monitoring wells for when we conduct pumping tests (dewatering/abstraction license).

Has anyone ever installed artesian wells before? The headworks need remain at or below ground level which means the wells will be pressurised. I know this is common in the oil&gas industry. I’ve just never had to do it from a geotech standpoint.

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u/Hennethh 8d ago

We either use pore water pressure sensors or sealed piezometers with pressure gauges for monitoring artesian wells

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u/Djr215 8d ago

Thanks for the response. Sealed piezometers with pressure gauges is the method I’m looking into. Do you use specialist ground investigation contractors to install these? I’ve spoken to a few of my framework GI contractors and they don’t have any experience in it.

Can sealed piezometers be installed in regular diameter geotechnical boreholes? ~150mm. How do you manage artesian flows during drilling?

What makes these schemes particularly tricky, is they are in built up areas (schools/football pitches/recreation grounds etc).

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u/Hennethh 8d ago

Artesian flow is normally managed by water ballast or increased mud weight. Had several wells done with up to 200 mm diameter. Normally we installed injection hoses to seal the room between the piezometer and the borehole wall with a suitable grout. Having a specialist firm doing the work however is a must. If the artesian aquifer is highly permeable you are more or less screwed if you can’t seal it during the drilling process because it will be extremely difficult to do so afterwards.

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u/Djr215 8d ago

Thanks. That confirms a specialist is required as our usuals drill with water flush and don’t have the kit for weighted mud/drilling fluid. It’s pretty permeable stuff (10^-5). As the head is only +3m AGL, we can always stop the flow by adding 3m of casing above ground. But you obviously can’t continue drilling like that….

Looks like I need to put together a tender pack!

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u/Key-Ad1506 5d ago

This is how its done. Have had to do it a few times on USACE and FERC dams.