How to add additional groups for apache users?

When configuring the user/group that apache runs under, does the process run only with permissions of the specified group, or also with those of which the user is a member?

For example, if Apache runs under apache:apache, and I do usermod -aG somegroup apache, will the Apache processes be able to write to the following file inside my wwwroot?

-r--rw-r-- 1 someuser somegroup 18K Sep 11 14:27 somefile.txt