I just can't buy into it.
Why create a 130ft high spoil heap. ?
It's just makes no sense when there's so many other easier ways to get rid of the "waste".

Why not move the spoil to the area at the bottom of Waden hill or somewhere in the area nearby where the A4 runs or even in the flatter areas the other side of Silbury towards Beckhampton. ?
If it was so dry then they wouldn't even have had to cross the Winterbourne or any other wet areas to do this.
There's plenty of places where the spoil could have been taken to.
Moving this amount of "waste" would have been no problem for them, just look at the movement of stone taking place around there at the time.
The only reason i could see for them to take on such an herculean task as to make one huge pile is if the land adjoining the area of Silbury was under cultivation at the time and just couldn't be spared, i can't buy that either though.
Temple, Sacred hill i dunno what it is but i can't buy into it being a plain old spoil heap, it makes no sense.
I'm sure someone more learned than myself will see this soon and point out other reasons why the theory is, well ridiculous, sorry no disrespect meant but i just cant see it.