Is it normal to have .svn directory under most if not all of the subdirectories? - svn add issue

Is it normal to have .svn directory under most if not all of the
subdirectories? - svn add issue

I'm new when it comes to SVN.
I suppose that there should be only 1 .svn directory under a project
directory that is under version control. For example, the hierarchy of
such project should be as follows:
projectdir/
.svn/
subdir1/
subdir2/
...
I am passed 1 project directory by a former colleague which (surprisingly)
has .svn/ directory under most of the subdirectories:
projectdir/
subdir1/
.svn/
...
subdir2/
.svn/
...
...
I need need to put this project back onto our svn server.
I wonder if it's normal to have so many .svn/ directories under those
subdirectories (I'm having issues trying to do svn add; I suspect someone
did something funny with svn in the past) or I can remove all those
subdirectories' .svn/ directory and only care about the .svn/ directory
under the root directory of my project?