The breach is first area in the Cosmodrome that you encounter at the start of the game single player. To get there from a Patrol you need to go through the buildings to the right to the area called the Divide (Where the walker spawns for the public event) and then again to the right through a passageway into buildings again. Back into the Cosmodrome wall that you passed through in the story. Check this video https://www.youtube.com/watch?v=ftOFGPSEezo for the route.