May 2015, a sad time for Ingress Agents as the ability to submit new Portals was removed.
The portal submission queue was rising to unmanageable heights as there was a Medal incentive (Seer) to shotgun as many submissions as possible (Medals can also count toward level requirements after all).
Nov 2016, Operation Portal Recon is announced and Niantic invites high level Ingress Agents to help crowd source the massive submission queue backlog.
Fast-forward to today and it sounds like we’ve cleared out most the backlog and Niantic is ready for us to help them crowd source new portals!
Level Requirement
To be able to submit new portals, you must be L11 or higher. You must be L12 or higher to participate in reviewing portals via the OPR website.
Past Submissions (2012-9/2/2015)
Old portal submissions between 2012-9/2/2015 will count towards the discontinued Seer medal.
Submission Queue
It appears you start with 7 submissions available and it is assumed you will only get your available submissions back after your submission is processed via OPR. Be careful not to waste your submissions!
Update (9/28/2017)
Agents are allowed at most 7 submissions in the previous 14 days and the limit is not tied to processing the submission. For example, if you submitted 7 Portal candidates 13 days ago, tomorrow you will be able to submit 7 more.
Pokémon GO
Since Ingress Portals are the source and database for Niantics other AR titles, this means more PokéStops in Pokémon GO! If you are a Pokémon GO Trainer and haven’t checked out Ingress yet, do yourself a favor and download it now! If you manage to make it to L11 (level 11 out of 16), you can start submitting locations you think would make good Portals/PokéStops.