why dig at sippar?

Sippar is a very ancient city located in modern day Iraq. According to the Lost Book of Enki, documentation of some-kind was intentionally buried at Sippar just before the deluge..  The 9th Tablet of the Lost Book of Enki explains thus:

"To Sippar Enlil the Tablets of Destinies from Nibru-ki moved, a temporary Bond Heaven-Earth was there established.

His brother Enki Enlil then addressed, to him he was thus saying: 

However if ever the calamity might be survived, let all that had happened be remembered.  

Let us tablets of record in Sippar, in the depths of the Earth, safely bury,   Let what from one planet on another done in days to come uncovered be!

Enki his brother's words with approving accepted.  ME's and other tablets in golden chests they stored,

In the depths of the Earth, in Sippar, for posterity they buried."

 - 9th Tablet, Page 215 of the 2002 Bear & Co. Edition.