COMBINE GND AND LCL TWR CTLR MADE AN OPERROR WHEN HE CLRED A CESSNA 172 FOR TKOF WHEN A CESSNA 150 WAS XING THROUGH THE DEP PATH OF THE C172.

Narrative

MERRILL FIELD (MRI) HAS 2 RWYS; 6/24 AND 15/33. THE RWYS DO NOT INTERSECT; BUT THE DEP CORRIDOR FOR RWY 24 INTERSECTS WITH THE DEP CORRIDOR FOR RWY 33. I WAS WORKING LCL COMBINED WITH GND CTL. WX WAS VFR BUT TURBULENT. ACR X; A C150; HAD REQUESTED TO TAXI FOR DEP ON RWY 33; AND WAS INSTRUCTED TO TAXI TO THAT RWY. ACR Y; A C172 OPERATED AS AN AIR TAXI; REQUESTED TO TAXI TO RWY 6. I TOLD HIM THE WIND FAVORED RWY 24; AND HE ASKED; AND I INSTRUCTED HIM TO TAXI TO RWY 24. ACR Z; A C207; OPERATED AS AN AIR TAXI BY THE SAME COMPANY; REQUESTED TO TAXI TO RWY 6. I TOLD HIM THE WIND FAVORED RWY 24; BUT HE STILL WANTED RWY 6; SO I INSTRUCTED HIM TO TAXI TO RWY 6. ACR U; A C150; WAS DOING TOUCH AND GOES ON RWY 24. ACR X REQUESTED TKOF CLRNC ON RWY 33. I OBSERVED THAT ACR X WAS ON CLBOUT; PAST THE INTXN; SO I CLRED ACR Z FOR TKOF. ACR Z REQUESTED TKOF ON RWY 6; AND I OBSERVED HE WOULD NOT BE A FACTOR FOR ACR U; SO I CLRED HIM FOR TKOF ON RWY 6. ACR Y THEN REQUESTED TKOF ON RWY 24; AND I TOLD HIM TO HOLD SHORT FOR THE OPPOSING DIRECTION DEP. I SCANNED THE RWY PRIOR TO ACR Z'S DEP; AND THEN WATCHED HIM AS HE DEPARTED. AS SOON AS HE PASSED THE INTXN WHERE ACR Y WAS WAITING; I CLRED ACR Y FOR TKOF; COMPLETELY FORGETTING THAT ACR X WOULD BE A FACTOR. ABOUT 10 SECONDS LATER I REALIZED THE CONFLICT; AND TOLD ACR Y TO CANCEL HIS TKOF. JUST AS I SAID THAT HE LIFTED OFF AND SAID 'SAY AGAIN?' I TURNED MY HEAD AND OBSERVED ACR X XING THE RWY 24 DEP PATH. ACR Y WAS ABOUT 2000 FT FROM THE END OF THE RWY. A FEW MOMENTS LATER I GOT RELIEVED FROM POS AND RPTED THE OPERROR. CONTRIBUTING FACTORS: I WAS WORKING GND COMBINED WITH LCL; WHEN IT WAS NOT NECESSARY TO DO SO. I WAS BEING TOO PERMISSIVE IN ALLOWING THE DEPS THEIR REQUESTED RWYS. ACR X AND ACR Z SIMPLY REQUESTED THE CLOSEST RWY TO THEIR BASE. I DIDN'T TAKE THE WHOLE AIR TFC PICTURE INTO ACCOUNT WHEN CLRING ACR Y. I HAD 3 DEPS FROM 3 DIFFERENT RWYS; ALL AT THE SAME TIME. HUMAN PERFORMANCE CONSIDERATIONS: I WAS TRYING TO DO EVERYTHING FOR EVERYBODY; ALONE. I WAS BEING AN 'ACCOMMODATOR' INSTEAD OF A 'CTLR.' MY ATTN WAS SPREAD TOO THIN; OVER TOO MANY DIFFERENT THINGS.