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[ryansee]

Hey I am facing a sudden problem during my application of the http://dwarffortresswiki.org/index.php/v0.34:Double-slit_method for dealing with the aquifer. I was able to secure 4 zeals while digging down. and then the method stopped working and the water started pilling up. I am unsure why this happened.

Image of the problem : http://imgur.com/ORVoXb9,wcuZL1r,qRYmAy0,rWiWwwV,15JTXdH

[sal880612m]

I have never dealt with aquifers myself but it seems important to note that water can and will flow diagonally, so I can only assume that the lack of constructed walls in the corners is letting water seep in.

[ryansee]

The thing is, I followed exact same steps as I did for the z levels above it. There shouldnt be deep water in the layer below my walls. It should be draining downwards. Why isnt it draining?

[Codyo]

I haven't done crazy methods for aquifers before. I've went through aquifers by doing like a capsule kind of thing

Where I would cave in some natural stone or soil into an aquifer pool below it, which allows me to dig into the dry material like some kind safe capsule.

[Zeranamu]

I think it's because of the corners not being walled. Not 100% sure. I tend to use the cave-in method myself.

[sal880612m]

He also asked in the old version question thread and someone better versed in aquifers figured that it was because he was attempting to pierce the last layer of the aquifer in the wrong way or something like that.

[Panando]

I'm almost certain it must be because of hitting the non-aquifer layer. That's exactly what happens when water can't drain. Digging into a non-aquifer layer is an irrecoverable error short of cheating with DFhack and turning the dug out tile into obsidian—you have to restart.

AFAIK there is no in-game way to know whether a layer is aquifer bearing or not, you just have to look at it (exploiting the fact that downstairs reveal the level below without disturbing it) and check on the wiki whether that layer type it is aquifer bearing or not, but as a rule, all sands and loams are aquifer bearing, also sandstone and conglomerate are aquifer bearing. Any type which can bear an aquifer and is also under an existing aquifer layer will also be aquifer bearing itself - there is only one exception, if an aquifer tile (i.e. sandstone) intersects the caverns in such a way that it would leak into the cavern, it will have it's aquifer tag turned off. This is exceedingly rare and is of no consequence if you dig up/down stairs into the layer below for drainage, as the slit will just drain into the cavern (only the tiles which actually touch cavern are de-aquifered, the layer itself remains an aquifer in general).

[ryansee]

I figured out a way to recover , but I don't understand the one step option. I though it meant that I pause right after he digs steps

[greycat]

I'm almost certain it must be because of hitting the non-aquifer layer. That's exactly what happens when water can't drain.

Yup.  That's my diagnosis as well.  That's why the double-slit method has different steps for the final aquifer layer, vs. all the previous aquifer layers.  That's also why you MUST correctly determine, one layer at a time, whether you are dealing with the bottom-most aquifer layer, or Yet Another Intermediate Layer.  (There's a procedure on the wiki page for doing this; it entails designating an up/down staircase and then single-stepping it with the period key once the miner gets there.)

[jcochran]

I figured out a way to recover , but I don't understand the one step option. I though it meant that I pause right after he digs steps

One step means that when you designate the spot to be mined in order to look at the next layer down, you pause when the miner gets close to the tile to be mined. Then you single step as the miner is digging out the spot and as soon as he or she finishes, you inspect the revealed tile to determine if it is wet or dry. The key thing to remember....

PAUSE BEFORE THE DIGGING IS COMPLETE!!!!!

[Panando]

Yup.  That's my diagnosis as well.  That's why the double-slit method has different steps for the final aquifer layer, vs. all the previous aquifer layers.  That's also why you MUST correctly determine, one layer at a time, whether you are dealing with the bottom-most aquifer layer, or Yet Another Intermediate Layer.  (There's a procedure on the wiki page for doing this; it entails designating an up/down staircase and then single-stepping it with the period key once the miner gets there.)

Ah yes that's right, if you look at the state of the tile while the up/down stairs is still completely dry, before it's had a chance to fill with even 1z of water then you can see whether it's a wet or dry tile on the layer below.
Otoh, I find my heuristic is 100% reliable and doesn't require onestepping which I never use, it just requires memorizing what layers can bear aquifers. Admittedly it does get a bit confusing around the clays, sands, loams and other soils - but as a rule of thumb if the layer name is at least 'half clay' (clay, sandy clay, clay loam) it isn't aquifer bearing, and if it's only one third clay ('sandy clay loam') or doesn't have clay in it's name it is aquifer bearing.