Narrative:

I was working final approach for runway 35R. During this time the WX was IMC; and the airport was conducting monitored simultaneous ILS approachs. Runway 35R was closing for snow removal. I was transitioning aircraft on right downwind and both base legs from runway 35R to runway 35L. During this time aircraft a was established on runway 35L final at 11000 ft. Aircraft B; who was on right downwind at 11000 ft; was turned base too early to follow aircraft a. Upon realizing the conflict; I turned aircraft B sebound and climbed to 12000 ft. Aircraft a was descending to 10000 ft. Aircraft a now conflicted with aircraft C at 10000 ft joining the runway 34R ILS from left base. Aircraft a came within 1.78 mi of aircraft B and 100 ft. Aircraft a came within 2.1 mi of aircraft C. I believe that the runway change was untimely as there were only 2 more aircraft that could have landed on runway 35R; not delaying the snow removal; but removing the increase in complexity from having to change the downwind traffic over to runway 35L. The final radar coordinator was distraction away from the situation by a lesser priority; therefore; not helping catch the early turn to aircraft B. I had been working steady moderate to heavy traffic for 1 hour 37 mins and was getting tired and in need of a break. In the future; during unusual situations; I will stick to the rule of altitude separation is your friend.

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Original NASA ASRS Text

Title: D01 CTLR DESCRIBES A CONFLICT AT 11000 FT WHILE PROVIDING SEQUENCING VECTORS TO PERMIT CLOSING A RWY FOR SNOW REMOVAL.

Narrative: I WAS WORKING FINAL APCH FOR RWY 35R. DURING THIS TIME THE WX WAS IMC; AND THE ARPT WAS CONDUCTING MONITORED SIMULTANEOUS ILS APCHS. RWY 35R WAS CLOSING FOR SNOW REMOVAL. I WAS TRANSITIONING ACFT ON R DOWNWIND AND BOTH BASE LEGS FROM RWY 35R TO RWY 35L. DURING THIS TIME ACFT A WAS ESTABLISHED ON RWY 35L FINAL AT 11000 FT. ACFT B; WHO WAS ON R DOWNWIND AT 11000 FT; WAS TURNED BASE TOO EARLY TO FOLLOW ACFT A. UPON REALIZING THE CONFLICT; I TURNED ACFT B SEBOUND AND CLBED TO 12000 FT. ACFT A WAS DSNDING TO 10000 FT. ACFT A NOW CONFLICTED WITH ACFT C AT 10000 FT JOINING THE RWY 34R ILS FROM L BASE. ACFT A CAME WITHIN 1.78 MI OF ACFT B AND 100 FT. ACFT A CAME WITHIN 2.1 MI OF ACFT C. I BELIEVE THAT THE RWY CHANGE WAS UNTIMELY AS THERE WERE ONLY 2 MORE ACFT THAT COULD HAVE LANDED ON RWY 35R; NOT DELAYING THE SNOW REMOVAL; BUT REMOVING THE INCREASE IN COMPLEXITY FROM HAVING TO CHANGE THE DOWNWIND TFC OVER TO RWY 35L. THE FINAL RADAR COORDINATOR WAS DISTR AWAY FROM THE SITUATION BY A LESSER PRIORITY; THEREFORE; NOT HELPING CATCH THE EARLY TURN TO ACFT B. I HAD BEEN WORKING STEADY MODERATE TO HVY TFC FOR 1 HR 37 MINS AND WAS GETTING TIRED AND IN NEED OF A BREAK. IN THE FUTURE; DURING UNUSUAL SITUATIONS; I WILL STICK TO THE RULE OF ALT SEPARATION IS YOUR FRIEND.

Data retrieved from NASA's ASRS site as of January 2009 and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.