HOT Standby - slave does not appear to be removing wal files

All;

We're doing a migration as follows:

1) we setup a HOT standby pair

2) we did an import of a db that wan backed up via pg_dump

The pg_xlog directory has > 1700 files in it, It seems that the slave is
way behind which I get since we just imported a 55GB database but the
slave is not removing it's local pg_xlog wal files.

We actually stopped the import when the slave hit 97%  full for the file
system where we have it's pg_xlog directory mounted
after like 30minutes the file count in the slave's pg_xlog dir has not
changed.

Any thoughts per why the slave is not removing these files?

Thanks in advance