The pilot departed Lamar the morning of the accident. According to the pilot, the runways in Lamar were snow packed to dry and snow banks 3 to 4 feet in height lined the edges of all runways. Prior to the night landing, the pilot verified with an airport employee, that the runway lights were operational. During the landing flare to runway 26 (5,001 feet by 60 feet, asphalt) the pilot lost visual contact with the runway due to the snow banks obscuring the runway lights. The airplane landed and veered off of the runway into the snow bank. The main landing gear separated, resulting in damage to the gearbox and a bent firewall. The pilot reported no anomalies with the airplane or its systems. According to the airport manager, the fixed base operator manager, and an airport employee, the pilot reported to them that his landing lights were not functional at the time of the landing. Several Notices to Airmen (NOTAMs) had been issued for Lamar prior to the accident. These addressed 4 foot snow banks on runway 8/26, 7 foot snow banks on runway 18/36, and no braking action on runway 18/36. After the accident the airport manager issued a NOTAM with regards to obscured runway lights.