LGT LEFT RWY ON ROLLOUT. STUCK IN MUD.

Narrative

I WAS CAPT ON FLT SLL-GEG. AFTER BEING TOLD BY APCH CTL THAT RWY 3 AT GEG WAS REOPENED AFTER BEING SPRAYED WITH LIQUID UREA WE WERE CLRED FOR AN APCH (ILS). THE TWR RPTED 1/16 INCH SNOW COVER; BRAKING CONDITION GOOD (TAPELY 40) AND WX 500 OVCST; 3 MI VISIBILITY; LIGHT SNOW; TEMP 32 DEG/DEW POINT 28 DEG; WIND 100 DEG/06 KTS. THE FO FLEW A NORMAL COUPLED APCH; LNDG AND ROLLOUT. WHEN I TOOK CTL OF ACFT BTWN 80 KTS AND 60 KTS I NOTICED BRAKING ACTION POOR AND CONTINUED TO BRAKE PAST HIGH SPEED EXIT C (CHARLIE); WHERE I HAD PLANNED TO TURN OFF BUT MY SPD WAS TOO HIGH. I SLOWED TO NOSE WHEEL TAXI SPD (10-15 KTS) AND CONTINUED TO BRAKE TO TURN OFF AT THE END. APCHING THE END (500-1000 FT FROM END) ACFT SEEMED TO ACCELERATE AND I USED MAX BRAKING. THE BRAKING ACTION WAS NIL. TO AVOID APCH LIGHTS FOR RWY 21 I DECIDED TO TURN TO THE L AND GET TO THE RUNUP AREA THAT EXTENDS BEYOND THE END OF THE RWY (COULD SEE THE BLUE TAXI LIGHTS OUTLINING IT). I CROSSED THE SMALL DIRT AREA BTWN THE RWY AND RUNUP AREA; LET THE ACFT ROLL AND GOT THE NOSE GEAR ONTO THE CONCRETE. BECAUSE OF THE MUDDY GND THE MAIN GEAR ROLLED DOWN IN THE MUD APPROX 8 FT FROM THE CONCRETE (ALSO THE ACFT WAS HVY; 122 PAXS PLUS 18600 POUNDS OF FUEL; 146000 POUNDS LOG WT). THERE WERE NO INJURIES AND NO DAMAGE. THE ACFT RECEIVED A GASH ON THE R SIDE DURING LATER EXTRACTIONS FROM MUD. WHEN WE LANDED THE RWY WAS COMPLETELY SMOOTH AND COVERED IN SNOW (COULD NOT TELL DEPTH AT TIME). THERE WERE NO TRACKS FROM TRUCKS DRIVING ON THE SURFACE TO SPREAD UREA OR PLOW. THERE WERE NO MOUNDS ALONG RWY FROM PLOWING. A FIRE TRUCK STARTED SLIDING ON THE TAXIWAY AS HE TURNED A CORNER JUST AS WE DID. WHEN WE SAW THE TIRE TRACKS FROM THE FIRE TRUCKS AND LATER OUR TIRES WE REALIZED THAT THE DEPTH OF SNOW WAS ACTUALLY CLOSER TO 1 INCH NOT 1/16. ALSO THE RWY SLOPES DOWNHILL TO THE NE. I DO NOT KNOW OF ANYTHING I COULD HAVE DONE TO PREVENT THIS INCIDENT. WE DID NOT HAVE TO USE EMER EVACS BUT THE TAXIWAY WAS SO SLIPPERY THAT FIREMEN HAD TO HELP EACH PAX TO TAXIS THAT WERE BROUGHT OUT TO TAKE THEM TO THE TERMINAL. LATER; WHILE OUR CREW OF 3 PLTS WAS BEING TAKEN TO TOWN THE CAB DRIVER LOST CTL ON AN EXIT AND SPUN AROUND ENDING UP GOING BACKWARDS DOWNHILL.