Holdfast Training Services Trial Blog

My site will have one gigantic basement raft slab that covers the entire site.  There is a podium slab 6 metres higher then the buildings above that.

The basement raft slab is built in sections of varying depths.  There’s an 800mm deep section of C40/50 with 75mm cover.  There’s a 500mm thick section of C50/60 with 40mm cover (shown by shaded area below).  There’s bit with steel orthogonal to the western line of sheet piles, and there’s bits with steel orthogonal to the eastern line of piles.  There’s areas with steel at 150mm centres, there’s areas with steel at 75mm centres.  There’s steel ranging from 32mm diameter bars down to 20mm diameter.

The drainage is no better.  We’ve had a nightmare with clashes between the bottom steel and the drainage runs.  There are also areas where the drainage runs for several metres into a manhole, only to turn around and run back the other way (shown by the brown arrows).  Why doesn’t it run along the black arrow?

Believe it or not, our project was subject to a significant value engineering study where some of these issues were designed out, only to be put back in again due to continually changing client requirements.

The Arup design is a “reinforcement intent”.  The detailed design is done by the sub-contractor.  The detailed design showed the reinforcement around an ACO drain like this:

Arup OK’d it, but on seeing it built decided it wasn’t ok and made them add in additional bars.  Which they had to do around the rapidly approaching concrete.  Timely!

The drainage designer is a bloke with a beard at Arup.  The structural designer is a bloke with a beard at Arup.  The reinforcement detailer is a bloke without a beard who doesn’t work at Arup (you can’t have everything).  And they haven’t spoken to each other, thus the clashes.  We’re on a design and build JCT contract.  So all the structural designers and architects were novated to us when the contract was signed.  Therefore all of these things are our problem to solve.

We have a design manager on site.  In fact we have three.  But ultimately the drainage in the responsibility of the drainage package manager, the steel that of the structural package manager and so on.  And they haven’t spoken to each other.

To link back to a previous blog…  Communication is key is this situation.  And we’re lacking it.

So what are we going to do about it?  Well this is where I’m not too sure.  McAlpine SOPs seem to be to let them fail and say “I told you so” later.  Not sure why.  I’m sure I’ll work it out in time.