THE PILOT WAS CLEARED FOR AN ILS RUNWAY 6 APPROACH AND REPORTED THAT HE HAD THE RUNWAY IN SIGHT ABOVE THE DECISION HEIGHT. SNOW WAS FALLING. AFTER A ‘SUCCESSFUL’ APPROACH, THE AIRPLANE TOUCHED DOWN IN THE ‘TOUCHDOWN ZONE.’ SPOILERS, THRUST REVERSERS, AND BRAKES WERE APPLIED, BUT THE AIRPLANE ‘STARTED TO DRIFT TO THE RIGHT.’ THE AIRPLANE IMPACTED A SNOWBANK ON THE RIGHT SIDE OF THE RUNWAY. ITS LEFT MAIN LANDING GEAR COLLAPSED AND THE FUSELAGE KEEL BEAM WAS DAMAGED. BRAKING ACTION WAS REPORTED AS ‘NIL’ BY THE PILOT. THE RUNWAY HAD ‘TWO TO THREE INCHES’ OF WET SNOW. IT WAS CLOSED AND PLOWED IMMEDIATELY FOLLOWING THE ACCIDENT. THE TOWER CONTROLLER HAD TRANSMITTED TO THE PILOTS ‘LAST BRAKING ACTION FAIR BY A WESTWIND ABOUT 20 MINUTES AGO.’ THE ATIS INFORMATION INCLUDED ‘APPROACH LIGHTS FOR RUNWAY 6 HAVE BEEN DECOMMISSIONED.’ Probable Cause: IMPROPER PLANNING OR DECISION BY THE PILOT IN COMMAND (PIC). FACTORS RELATED TO THE ACCIDENT WERE: DARKNESS, THE ADVERSE WEATHER CONDITIONS, AND THE RUNWAY/TERRAIN CONDITION.