A recent issue required all users reading and writing a directory maintain the group owner.
To ensure the group owner was maintained, ACLs were set on the directories.
The first command sets the privileges on everything that is existing.
setfacl -Rm g:yourgroup:rwx /yourdirectory
The next command does the same thing, but sets the default. This means that when a new file or subdirectory is created it inherits the existing ACLs.
setfacl -Rm d:g:yourgroup:rwx /yourdirectory