The holes were dug into the street for the foundations, and
concrete poured in a large block. On top of this, a steel form
has been put in place to hold the rebars and the poured cement
that will form the column holding up the arch. Looking into the
hole, the size of the concrete block is apparent. It sits on
bedrock. Notice the four holes in the block. A boring machine
drills through the four holes in the cement block, into the
bedrock. The new holes go 28' down through the bedrock. Anchors
will be installed to hold the block to the bedrock. The anchors
through the foundation into the bedrock will make the foundation
earthquake (tremblor) proof, so the arch should really be
eternal.