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[vanatteveldt]

This post shows how to breach a 2-level aquifer with only the wagon wood using cave-ins in concentric circles. It was inspired by the wiki an threads on the cave-in method but these assume unlimited building materials, which we don't have.

The general plan is to cave in a circle (actually: rectangle outline) of soil into the first aquifer layer, dig out the center of the rectangle and pump it dry so we can channel to the second layer, and then cave in the center of the rectangle into the second aquifer level so we can dig a stair down to the rock.

With the starting wagon we can (barely) make a pump by deconstructing the wagon, building a carpenter with a log, making a block, deconstruct the carpenter, building the carpenter again with the block, building the pipe section and corkscrew, and deconstruct the carpenter again to get the block back. We don't have any additional building materials, so no constructing supporting arms, floors, etc. We can use the one block to build a temporary floor to rescue stranded miners, but that should not be needed if we do it correctly.

The schematic overview:


We assume two soil layers above two aquifer layers. The first thing to do is channel the inner ring and then the outer ring around the first cave in. It is important to start with the first ring so you can get the miner out easily. The structure is assymetric since we need to place a pump later. The trick behind the cave in method is that the soil we drop into the water will form a new wall which shuts out the aquifer.



After the first cave-in we can channel out the inner part of the first aquifer layer. Since no water can come from outside, the only water generated is from the one pillar we need to leave standing to provide support. We can then pump away the water and let in the miner to mine away the aquifer part of the pillar so no more water is produced. The pillar is now supported by a single floor. Next, we channel out the second aquifer layer and cave in the pillar by channeling away the floor. After the dust settles, you can dig a staircase in the middle of the 3x3 pillar that was dropped down. And pray that there is no third aquifer layer :-)

The step-by-step guide with screenshots

0. While the miner is mining, make the pump components as outlined above.

1. Channel out the inner ring from above to the last dry soil layer, leaving a 3x3 pillar standing.



2. BuildDig a staircase to get the dwarf back up, and then channel the outer ring, with one side 2-wide to allow for the pump. Make sure to leave one tile unchanneled for support (only on the top level)



3. Channel out the space under the ring that will be caved in and the ring around that. Make sure to leave a little bridge in the outer ring so the inner ring will be accessible later. The channeled out ring around the cave in part is there to drain the water, so it doesn't matter that one tile is not channeled out. Edit: if you're lazy / pressed for time, only dig out the outer ring on the side where the pump will be, that is more than enough to capture the water.



4. Cause the first cave in by channeling out the last tile from the top. After the cave in, the first aquifer layer should look like this:



The soil we dropped turned into the same type of soil as the aquifer, but it will not be water producing. So, if we get everything inside the new 'wall' channeled out, there won't be any new water in this part and we can move down.

5. First, channel away the inner part of the aquifer layer. Make sure to give orders row by row so you won't have stuff leftover in the middle. Leave one wall standing. The last dry layer should now look like this:
EDIT: actually, place the tile that you leave around one to the right so that it is in a corner of the 3x3. This is needed because you want to use a constructed floor to cause the second cave-in to avoid losing your miner to a tragic accident.



And the first aquifer layer looks like this:



We first need to get the water out. It will still be producing some water due to the two tiles that we couldn't channel out, but a pump can beat two aquifer tiles and as soon as the water is mostly gone we can mine the last two tiles while leaving the floor/wall/ramp above standing.

6. Build a pump on the wide part of the soil layer. In fact, you could have done this while waiting for the miner to finish channeling. Set to pump from inside out and pump manually



Once the water is down a bit mine the two tiles that were left. Once these are gone, the level will be completely drained. You can now safely stop pumping and deconstruct the pump, if desired.

7. Channel out the inner part into the second aquifer layer. Be sure to leave one tile in the outer part so we can reach the center.



8. We are now ready to cause the second cave-in.



WAIT! Don't actually do that, it might kill your miner and then you have a big problem. Instead, build a floor next to the remaining pillar, then channel out the ramp, bring the miner to safety, and deconstruct the floor with a brave volunteer:



(the screenshot is from my second failed attempt, where I forgot to channel out the ring around the 3x3, which is needed to catch the water. I dug some space behind the volunteer to increase his chances. The death rate so far is 2 out of 3, which according to trusted sources, "ain't bad". Also note that I only dug the outer trench on one side, which is quite enough to capture the water after the first cave-in before you get the miner down.)

9. After the second cave-in, the remaining water will drain into the trench around the 3x3. Once the water is mostly gone, dig a down stair in the center and dig down to the rock. You are now through the aquifer!





You have struck native gold! I knew piercing the aquifer would be worth it :-) It is now 21st of Granite. I did waste some time waiting for the 1/1 water on the 3x3 to evaporate but it turns out 1/1 water doesn't really flow into a hole, so that was unnecessary.

If you follow the method here you should be able to get a 100% success rate quite easily and be able to breach the 2 level aquifer in around 20 days. The only risk is losing your volunteer, but that is difficult to guard against. It might be good to store the pump material somewhere else to avoid them being knocked around, if you want to preserve the parts.

In retrospect, you can probably skip the floor construction as long as there is no trench behind the miner. We don't actually care that much if he dies, as long as his pick remains accessible. That should be slightly quicker.

-----

As an epilogue, here are the stories of the brave dwarves that died to bring you this information, both starting after the second cave-in.

Failed attempt #1:
And my miner was knocked into the trench and drowned. Oops. This didn't happen on my test run, I guess it is random what the cave in dust does...

Okay I don't have time to redo the whole thing now, might edit it later. Proper procedure would have been to build the supporting pillar one closer to the edge, so you can build a floor as a temporary support. Then, you can safely channel the ramp and use a replaceable peasant to remove the floor. I guess mining out some area behind the and behind the trench will also improve his survivability as being knocked back is not what killed the miner.


Edit: Failed attempt #2:
Edit: did the run again. As you can see: (1) I built a nice little floor from the deconstructed pump block, which is currently being removed by a brave volunteer, (2) I only dug out the outer channel on the side of the pump, which was more than enough to drain the water after the first cave-in (3) Just to be sure, I dug out a "volunteer landing strip" on the side of the floor to decrease the odds of the volunteer to attempt a Hudson style landing.



Unfortunately, things don't end well for our brave volunteer:



As stated before, this is quite random, I have no idea how to improve his odds. A floor higher up would cost at least three logs, which we don't have, so I guess we have to take the odds with the volunteer. Good thing we start with seven dwarfs, eh?

The bad thing is that the pump components were knocked into the trench, and we need the pump to drain out the water, or at least realize that we need to dig a drain into A2 to let the water out...



In this run, after building the (now drowned) staircase and some trenches, it is the 19th of  Granite, so that seems like a feasible end time.

[WanderingKid]

Awesomely written out, thanks vanatteveldt.  I think I get it, just need to read through it a few more times.  Much appreciated.

[doublestrafe]

That's nothing. I can pierce it with a 9-iron.

[Virodhi]

I've never quite understood this method until now, so thanks for taking the time to spell it out. 

If you have the time, I do feel that this would be a great addition to the wiki. As you say, the methods detailed there assume you have an abundance of materials (and time!), and this guide would be helpful for the times when you don't have either.

[Snaake]

Small proof-reading correction, I think you mean "dig" instead of "build" on both of the below?

...
2. Build a staircase to get the dwarf back up, and then channel the outer ring, with one side 2-wide to allow for the pump. Make sure to leave one tile unchanneled for support (only on the top level)
...
(right at the end)
After the second cave in, you can build a staircase in the center tile of the pillar and you are good to go.

In this run, the second cave in occurred on the 24th of Granite. I messed up the timing a but, the corkscrew wasn't even ready when the miner was done with step 5. So, you shoould be able to shave some days off.

Great guide though, I recently did my first cave-in aquifer pierce, would've gone along with less head-scratching had I had this.

[Merendel]

you know your method lead me to a way of doing this without the pumps although it takes a smidge longer because it requires skilling up your miner to rank 11-12 for the final bit to work.  on the up side your only required to use a single log that you cant recover because you'll need to bucket out about 49 or so(less evaporation) units of water after the second cavein.  Still I was able to get the second cavein to happen near the end of slate on a peaceful embark with the final breakthrough into stone on the 20th of felsite.

The concept is you need your miner to do a mini chickenrun manuver right in the center of where the second cavein happens.  After you drop the first cavein (actualy can do it before if you want) have your miner dig a downstair in the center of the 3x3 where the second cavein will land. After that downstair is ready dig an updown below it that will crack open the aquifer, heres the part where you need a skilled up miner. you need him to be fast enough once that first updown is dug to be able to dig another updown in the second aquifer layer.  you'll need to 1step to get the designation set on the same frame as he finishes the first stair.  I was only able to make this work half the time with a avrage agility miner at 10skill.   This lets aquifer 1 drain into aquifer 2. channle out the 8 squares surounding that stairway so aquifer 2 now has a 3x3 with a stair in the middle.  Remove from above the last few remaining aquifer blocks that are inside the first ring you droped.  with no more aquifer blocks inside the layer 1 ring the remaining water all drains into layer 2.  At this point your free to drop the last ring. 

you'll end up with an extra tile or two siting on top of your downstair unless you planed ahead and channled out the center early on in the setup.  you'll also have a pool of 3/4 water.  make your 1 bucket  and drain that down with a pond zone (I went up 1 level and had them dump back into an aquifer off to the side.  Once the water in there is down to 1's and is evaporating channle out the stair over the middle square and set a water sorce next to it and let them take a few more buckets out (they wouldn't take from it with stairs in place). use one of your remaining logs to construct a downstairs to reconnect with the updown on the now dry aquifer layer 1 and start drilling down

edit: actualy on further reflection I wonder if it would be possible to do this in a single drop thanks to the way caveins work...  If I do the chickenrun part along with removeing the 3x3 squares around it down into layer 2 like I did with this method then did a channle only 1 layer deep into the first layer I could drop a slab whole and it would pancake and form the needed rings.

edit2:
Seems to work although you'll want to drop a section large enough that one side of the outer ring is 2 wide because the cavein leaves no ramps so you'll need at least 1 extra tile in the safe area to channle a new ramp down.  Might actualy be worthwhile to drop an a fairly good sized slab into aquifer layer 1 so you can let evaporation remove the bulk of the water.   The real gold in this is 90% of the work can be done underground entierly with the remainder only really exposing your miner/workforce to flyers.

[vanatteveldt]

@Snaake, Virodhi, WanderingKid: thanks!

I did indeed mean 'dig', for some reason with staircases it always feels as the miner is creating something, but I wouldn't want to create confusion with the actual constructing of a staircase by a mason.

I will rerun the method to make sure the miner survives and post the final screenshot. Is there a "howto put something on the wiki" wiki page?

@merendel:

Huh, good one. It had never occurred to me that a miner might be able to dig quicker than the aquifer would refill. I'm not sure I follow what you do 100%, but why do you need to remove the  water from the second cave-in? Can't you leave a single tile standing in the 'moat' around the second cave in to access the inner part? Or alternatively, can't you make the first ring wider and then channel it out to give room for the water to spread out enough to access the inner ring? Edit: just saw that you posted a full walkthrough in the single pick thread. As soon as I have time I will try your method and see if I understand the necessity better. Anyway one bucket is not so bad as you still have two logs for barrels so you can preserve your food (although I'm not sure whether the vermin spiral sets in before the alcohol withdrawal that slows the miner too much for your 'chicken run'?)

[Snaake]

I'd like to point out that the discussion on how to do the pierce with minimal resources/time has been continuing in the single pick challenge thread. Merendel worked out a way where you only need 1 bucket, and 1 log for a staircase (that you can recover once you have access to stone). Stochasty further developed a version involving a "mini chicken run" of 2 up/down staircases, and plenty of draining the upper aquifer into the lower one after that, that didn't involve any surface exposure beyond your initial tunnel to going under. He only used 1 log.

I thought I'd just confirm it/try out Stochasty's method, but managed to pierce the 2-level aquifer with NO WOOD used, not even to build a temporary access floor. I'd like to extend the main credit for the drainage method to Stochasty, though, I just realized you didn't need even that one log.

[vanatteveldt]

I'd like to point out that the discussion on how to do the pierce with minimal resources/time has been continuing in the single pick challenge thread. Merendel worked out a way where you only need 1 bucket, and 1 log for a staircase (that you can recover once you have access to stone). Stochasty further developed a version involving a "mini chicken run" of 2 up/down staircases, and plenty of draining the upper aquifer into the lower one after that, that didn't involve any surface exposure beyond your initial tunnel to going under. He only used 1 log.

I thought I'd just confirm it/try out Stochasty's method, but managed to pierce the 2-level aquifer with NO WOOD used, not even to build a temporary access floor. I'd like to extend the main credit for the drainage method to Stochasty, though, I just realized you didn't need even that one log.

+1

These guys are crazy good :-). I can barely understand the method I used above. It is amazing how quickly dwarven genius can bring a thread from "single pick is impossible in a non-freezing barren aquifer embark", via "it is theoretically possible using all 3 wood but with those undead flyers it will be almost impossible" to "hey did you know that you can just pierce 2-deep aquifers with only a pick and no surface exposure?". Genius, I say!

[Merendel]

It surprised me as well when we came up with that after a few days of bouncing ideas off eachother and refining eachothers methods.  Its significantly safer than even a frozen pierce although its one dissadvantage is this technique only really works one 2 aquifer and 2 or more dry layers.   Theoreticly you could pierce more by clearing a sufficently large area through the first layer so that your dwarf was on dry ground in the center and then repeating the chickenrun in the middle to get into the 3rd layer but that would likely be a stone layer aquifer and you need a really skilled miner to pull it off.  Its iffy on if you can skillup the dwarf enough before 3 months pass and you go into booze withdrawl slowing him down to go any further than 3 deep although if you get that far you probably have a few bits of stone to work with and could just double slit from there.