Information from Mayor Michael Watson: This bunker is used by the Maumelle Fire Department to do live burns inside. It is smoked up from fires set inside of it. It is a training facility used to practice interior fire attack scenarios; the back door was cut in to provide a secondary exit for emergencies. Original bunkers did not have the back door and are covered with earth in the rear. In the second picture the soot is visible above the front doorway also. Live burns are done several times each year in this facility.
 

More Information by Carolyn Yancy Kent can be found here:

http://encyclopediaofarkansas.net/encyclopedia/entry-detail.aspx?entryID=373

More information from the Mayor on this second bunker:

This is an actual bunker that has had both ends removed and new facades put on the front and rear. You can still see the loading platform in the front of the bunker in the concrete. The original developer of Maumelle did this renovation to show what the inside of a bunker looks like.