In message , Recliner
writes

Am I right in thinking that spoil from the HS1
tunnel was used to raise this ground level over the Olympic site?

I don't think so. Most of the tunnel boring was done during the course
of 2003, long before the Olympic bid.

Much of the material used for levelling the Olympic Park came from the
excavation needed for the main stadium, the "ground level" of which is 9
metres below the surrounding ground level.

--
Paul Terry