Here are some videos from YouTube.
They will help you to have more idea about potahs mining.
Conceptual Potash Mine in Saskatchewan - Click here
(Athabasca Potash which was taken over by BHP last year)
Animated video - A potash mine and production plant. You can also see the shafts (headframes) here.
Building a Headframe (Shaft) at new PotashCorp Mine - Click here
You'll see how big is a headframe (shaft) and expensive to build it.
Potash mine reconnaissance - Click here
Driving a car in potash mine. They are driving in a sylvinite layer. Everywhere is potash. You'll see the hight of the mine is about 3 meters. The height of the most potash layers in Canada is around 3-4 meters. Same as ELM's potash layers which is even higer grade than in Canada.
A tour at Saskatchewan PotashCorp underground Allan Mine
- Click here
This is one of the biggest potash mine in the World. Huge!
Solution mining - Click here
And this is the solution mining technique from Western Potash Corp which is still alive as an explorer in Canada