SMA X HAD LTSS NMAC WITH SMA Y. SYS ERROR.

Narrative

WHILE WORKING THE LCL CTL POS; I CLRED SMA X TO LAND RWY 36R. SMA Y ALMOST IMMEDIATELY REQUESTED TKOF RWY 36R. SINCE SMA X WAS ON DOWNWIND; I CLRED SMA Y FOR TKOF RWY 36R EXPECTING NO CONFLICT. A SMT TOUCHED DOWN RWY 36L. GND CTL STATED 'Z IS TAXIING TO RWY 36L; NEGATIVE TCA SQUAWK.' I CONFIRMED Z POS AND ASKED THE SMT WHERE HE WAS PARKING. DUE TO AIRFIELD CONSTRUCTION; IT WAS MORE EFFICIENT TO ISSUE THE SMT A 180 DEG (TO REDUCE TAXI AND COORD TIME) AND I VERIFIED HE WAS TAXIING WITHOUT DELAY VISUALLY. GND CTL ASKED IF I WOULD ISSUE THE TCA SQUAWK ON MY FREQ. I REPLIED 'AFFIRMATIVE;' AND LOOKED DOWN AT MY SCRATCH PAD AS GND CTL ISSUED THE TCA SQUAWK AND I COPIED IT DOWN. AS I STARTED TO LOOK UP; I HEARD SMA X 'PWR UP' INTO A GAR. SEARCHING FOR THE REASON; I SCANNED THE RWY AND SAW SMA Y IN HIS DEP ROLL PHASE APPROX 200 FT PAST LNDG THRESHOLD DOING APPROX 20 KTS. AS THESE OBSERVATIONS REGISTERED IN MY MIND; SMA X OVERTOOK SMA Y AT 70-80 KTS; FLYING DIRECTLY OVER SMA Y. SINCE THE SITUATION DEVELOPED UNEXPECTEDLY AND SINCE SMA X OVERTOOK SMA Y AT SUCH A RAPID PACE; IT WAS OBVIOUS AN ACCIDENT WOULD NOT OCCUR. SMA X WAS A STUDENT PLT ON HIS FIRST SOLO. I SAW NO SAFETY-RELATED REASON TO ALTER HIS FLT PATH ONCE HE PASSED SMA Y. SMA Y WAS A STUDENT PLT AND I FELT INSTRUCTING HIM TO ABORT HIS TKOF HAD THE POTENTIAL TO CAUSE MORE PROBLEMS THAN TO CORRECT THEM AND HAD NO SAFETY BEARANCE ONCE SMA X HAD PASSED HIM. SINCE SMA X DID NOT STATE 'GOING AROUND' AND I DID NOT INSTRUCT SMA X TO 'GAR;' I FEEL THAT SMA X TECHNICALLY MADE A LOW APCH; RESULTING IN LESS THAN APPLICABLE SEPARATION AS PER FAA HANDBOOK 7110.65. AN AREA SUPVR WAS WORKING GND CTL; AND I FEEL THAT THE LIGHT TFC CONTRIBUTED TO A COMPLACENT ATTITUDE ON MY PART AND; SINCE I EXPECTED NO CONFLICT; I ALLOWED MY ATTN TO BE DISTRACTED FROM THE DEVELOPING SITUATION BY THE TWIN SMT AND THE GND CTLR'S STATEMENTS AND REQUEST. ONCE SMA X PASSED SMA Y; SEPARATION DID NOTHING BUT INCREASE AND NO ACCIDENT RESULTED. I APOLOGIZED TO THE PLTS FOR MY INACTION AND THEY STATED (MORE OR LESS) 'NO PROBLEM; DON'T WORRY ABOUT IT.'