On Sat, 18 Aug 2018 17:55:43 -0700 (PDT), Davej
wrote:

I don't yet know how difficult it will be to
extract the buried ends of the 2x10's. Thanks.

You might try drilling numerous holes in the wood using a spade bit
(3/4") - overlapping each hole a little and then take a chisel to the
rest of the wood.