SEA GND CTLR DESCRIBED GAR EVENT RESULTING FROM DEV CTLR ISSUING RWY XING CLRNC WITH ACFT ON SHORT FINAL FOR PARALLEL RWY.

Narrative

I WAS WORKING GND CTL AT THE TIME. THERE WAS TRAINING ON THE LCL CTL POS; IT WAS GOOD VISUAL CONDITIONS; AND APCH CTL WERE USING VISUALS TO BOTH RWYS 16C AND 16L. THE FIRST B757 (ACFT X) HAD LANDED AND EXITED RWY 16C AT TXWY M. THE OTHER B757 (ACFT Y) WAS ON A VISUAL APCH TO RWY 16L ON SHORT FINAL (WITHIN 1/2 MI). IT HAD BEEN BUSY AND WE WERE ABOUT TO CHANGE FLOW (TO RWY 34); BUT BESIDES THE 2 ON FINAL; THERE WERE JUST A COUPLE OTHER PLANES AND NOT REALLY BUSY. I THOUGHT I HEARD THE STUDENT ON LCL CTL SAY 'CONTACT GND' (WHICH IS DONE AFTER THE ACFT HAS CROSSED RWY 16L) SO I ASKED 'DID YOU CROSS THAT GUY?' (ACFT X). HIS REPLY WAS 'I DON'T KNOW.' I THEN SAID; 'IF YOU DID; HE'LL NEVER GET ACROSS IN TIME' (FOR ACFT Y ON FINAL TO RWY 16L). I BELIEVED LCL CTL THEN TRIED TO STOP THE ACFT X FROM XING; AND IT WAS NOT GOING TO WORK. I THEN YELLED 'YOU BETTER SEND THE OTHER ACFT AROUND!' THE INSTRUCTOR TOOK OVER AND THEN SENT ACFT Y AROUND. ACFT X HAD STOPPED SHORT OF THE RWY BUT WAS PAST THE HOLD SHORT LINE; THE ONE ON FINAL JUST ABOVE THE TWR HT AS THEY EXECUTED THE GAR! THE SUPVR LISTENED TO THE TAPE AND SAID; YES THE TWR CTLR DID CROSS ACFT X! THE STUDENT IS A NEW HIRE WITH MINIMAL EXPERIENCE; THIS FACILITY HAS 10 PEOPLE IN TRAINING; 6 OF THEM ARE NEW HIRES SO THERE IS LOTS OF TRAINING GOING ON.