CTLR WORKING COMBINED POS OF OP (LCL-GND CTL) DURING BUSY TIME PERIOD.

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ARRIVING IN IND WE WERE HANDED OFF TO THE LCL CTLR AFTER BEING CLRED FOR THE APCH BY THE FINAL APCH CTLR. AFTER SEVERAL CALLS; THE TWR ANSWERED AND CLRED US TO LAND ON RWY 5R. AFTER LNDG WE WERE CLRED TO THE GATE AND TOLD TO REMAIN ON THE TWR FREQ (NOT UNUSUAL AT ALL) AS THINGS DID NOT APPEAR TOO BUSY AT THE TIME. AFTER APPROX 1 HR AT THE GATE WE WERE READY TO LEAVE THE GATE AS ACR X AT MID MORNING. THE GND CTLR FREQ WAS VERY CONGESTED AS IT WAS A BANK DEP TIME AND FLTS WERE CALLING SEVERAL TIMES REQUESTING TAXI. AFTER THE THIRD CALL WE WERE FINALLY GIVEN CLRNC TO TAXI TO 5L. AT THIS POINT IT BECAME APPARENT THAT ONLY 1 CTLR WAS WORKING BOTH GND AND LCL CTL. IN MY ESTIMATION AT 1 POINT HE WAS PROBABLY WORKING 10 ACFT ON THE GND AND 6 OR MORE IN THE AIR. DURING THIS TIME HE WAS LNDG AND DEPARTING ACFT ON RWYS 5L; 5R; AND 32. ALL THIS AND GND CTL IN WX RPTED AS -X; 7 OVCST 2F. WHEN WE QUESTIONED HIM AS TO WHETHER HE WAS WORKING BOTH GND AND LCL HIS REPLY WAS 'YES...IS THERE A PROBLEM?' I FELT IT BETTER NOT TO DISCUSS THIS 'PROBLEM' ON THE RADIO. I BELIEVE THAT THIS SITUATION HAD THE POTENTIAL TO BECOME A DEADLY TRAGEDY. I KNOW IT WAS A SAT MORNING AND ALL THAT BUT WITH THE EXISTING WX AND TFC CONDITIONS AT A MAJOR ARPT LIKE IND; THIS CONDITION WAS TOTALLY UNACCEPTABLE AND TERRIBLY DANGEROUS.