The thing is that /run itself is a tmpfs, and that anything mounted to a directory under /run is therefore only an ad hoc solution. Better is to create a static mountpoint for the partition and add it to /etc/fstab.
If the partition contains only files that are owned by yourself, then I would suggest creating the mountpoint ─ as yourself, not with sudo ─ inside your $HOME, e.g. /home/basementmedia/data.
Then, run… 
lsblk -o UUID /dev/sda3
… and write down (or copy) the UUID. Then, add a record for it to /etc/fstab…
sudo nano /etc/fstab
The record would look something like this…
UUID=the-UUID-you-copied /home/basementmedia/data ext4 auto,nofail,defaults 0 0
Save the file with Ctrl+O and leave the editor with Ctrl+X. If you reboot now, then the partition will automatically be mounted to /home/basementmedia/data.