Time to check Off-Route Obstruction Clearance Altitudes. These start at 3400 to 4000 feet then quickly get up to 6000. The terrain continues to rise towards 8000 feet past Scottsbluff. Uh, were not in Minnesota anymore. OROCAs, as defined by the Instrument Procedures Handbook, are for situational awareness and emergency use. While OROCAs provide standard obstacle clearance margins (1000 feet in non-mountainous areas), you cant count on them. You decide its safest to file for 8000 feet.