GEEZ, what's that for?

It's what everyone in america's getting right now .........."THE SHAFT"   Sorry i couldn't resist.

thats small compared to what some of us are getting

the shaft is to catch haevy rain fall from the local area which then let's it run away slower then just goin down the street and flooding every where..

Damn! That's one expensive 'stormwater retention pond'. What are the dimensions? How was the hole dug? Was the concrete poured top - down during construction, or bottom - up? How thick are the walls and bottom slab.

they use concrete cutting rings and just dig out from under neithe them untill they reach the depth then just put a water table holding mat in the bottom then form the floor to run off to the pump house it's about 30 meter deep the walls are a metre thick i think..

OK, I was involved in one that was 18m dia, 18m deep.  It was dug out to the bottom, 2 m at a time, a ring was cut into the soil wall, and rebar installed, and a wire mesh put on the wall, and 300mm of shot-crete sprayed over that.

Then the wall was poured from the bottom, 3 M at a time - 1m thick, 2 mats of HUGE rebar.  The floor was 1.5m thick.  a center wall was poured, it was also 1m thick.

This was for an intake structure for an irrigation project.  the divider was so they could dewater half and still have water for the land.  There was also a 70m long cast-in-place tunnel out into the water to bring the water in.

This was before my pumping days, it was all done with a crane and bucket.  If I'd have owned a pump in those days.....$$$$