This is the third Penguin side mission. As with the first and second mission, you will get a call from nightwing at some point in the story, telling you that he has spotted another truck. Again you need to follow the truck and stay out of sight. Use the glide ability and the detective mode to keep an eye on them
As soon as they think they have lost you, they will start heading towards their base. Follow them and enter the hideout.
When you enter the hideout I recommend using the explosive spray on the wall near the 5 enemies. This will leave you with just 2 enemies left in the room prior to the vault room.
Once you enter the vault room, do as always, kick some goons' asses with Batman and Nightwing, enter the vault, spray some explosives on the cache and close the vault. After setting the explosives off, the achievement is yours!
If need further help, refer to the video below (video credit to: Kicknazz Games)
Hope this helps you guys :-)
Any improvements? Please let me know in the comments below!