The main worry with a Dam is that if it goes wrong, it can go very wrong.
Most of our other megaprojects have been gradual things where if any one part completely fails, it doesn't majorly affect everything else. With a dam, there's much less room for mistakes.
Oh I realize that that things could go wrong, that being a reason I stated the innovations that I felt synergized between the techs of each option. Also, the reason I kept going on and on about the mega-kilns being a likely thing in my mind. The best way to build a dam is to build it in a dry spot (water diversion channels or literally build it off to the size and then alter the river into it), then introduce the water to the premade reservoir and dam. Digging the dam also manages to generate the fill to clog up the old river bed.
That said random number generator will be random and generate numbers randomly.
Do you honestly need a Main Metal?
Why isn't Secondary Metal sufficient?
It goes like this:
Low and Behold! Magic rocks fell from the stars.... in the land of way the hell over there!
The People did proclaim... YOINK!
So now The People have magic sky rocks and almost everyone agrees they are a shiny and shinies are to be studied carefully in their shining shininess.
A magic sky rock was opened and had metal in it.
And so The People did proclaim... 'Well we are studying these sky rocks with metal bits... and we have those other rocks of metal.'
'So we shall study the magic metal sky rocks! The metal ground rocks shall be studied at the same time'.
'But those have poison metal in them!'
'So we shall study them and our health at the same time to try and figure out a way around that!'
And The People proclaimed 'Well they are indeed shiny!'
And from on high Crow did proclaim 'Shiny! Shiny are the rocks! Study them! For! They! Are! Shiny!'
Dissenting voices try and point out Stability was shiny as well... let us set things on fire... Fire is shiny!
Others pointed out the neighbors are seemingly incapable of convincing their populous that they should stay in their lands.
But the call of shiny is strong with the crow worshipers.