You're browsing the GameFAQs Message Boards as a guest. Sign Up for free (or Log In if you already have an account) to be able to post messages, change how messages are displayed, and view media in posts.
Unequip your grenades and grenade jump up there. Or, over by the scaffolding you can do the same jumping technique as what you asked about. (Left side of scaffold over on the #1 valve wheel side of the arena)