CL65 CREW WAS UNABLE TO MAINTAIN CABIN PRESSURIZATION ON 1 PACK AFTER THE L PACK FAILED.

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WHILE AT CRUISE; WE HAD A 'L PACK HIGH PRESSURE' MESSAGE. WE COULD NOT MAINTAIN THE CABIN PRESSURE AND DSNDED DOWN TO 10000 FT MSL AND CONTINUED TO DEST. EVENT: WHILE AT CRUISE AT FL270 WE LOST THE L PACK DUE TO HIGH PRESSURE. ACTION: DUE TO LIMITATIONS; WE DSNDED TO FL250. THE CAPT RAN THE 'L PACK HIGH PRESSURE' QRH AND THE PROB WAS NOT SOLVED. EVENT: CABIN ALT WAS INCREASING AT ABOUT 700 FPM AND WAS CURRENTLY AT 4000 FT. ACTION: WE DECIDED TO PUT OUR OXYGEN MASKS ON JUST TO BE SAFE. WE DECIDED TO DSND AND ASKED CTR FOR A LOWER ALT. EVENT: WE THEN RECEIVED 3 MASTER CAUTIONS -- 'DISPLAY COOL;' 'AIR INC INOP;' AND 'CABIN PRESSURE.' WHILE DSNDING TO FL190; WE FIGURED THE CABIN WOULD NOT STABILIZED. ACTION: WE THEN ADVISED ATC WE WOULD NEED LOWER. WE WERE CLRED TO 11000 FT. I ASKED FOR 10000 FT AND WAS APPROVED. I DID AN EMER DSCNT TO 10000 FT. EVENT: AS ALL THIS WAS GOING ON; THE CAPT HAD RUN THE QRH'S FOR ALL 3 MASTER CAUTIONS. IN THE DSCNT TO 10000 FT; THE MASTER WARNING FOR CABIN ALT SOUNDED. ACTION: THE CAPT RAN THE QRH; TALKED WITH COMPANY MAINT; AND WE WERE ADVISED TO CONTINUE TO CVG. WE DID CONTINUE AT 1000 FT TO CVG WITHOUT FURTHER INCIDENT.