GA ACFT EXITS RWY AT BJC CAUSING CTLR TO ISSUE GAR TO HELI ON APCH TO PARALLEL TXWY.

Narrative

WE WERE RETURNING TO THE ARPT IN A LOCALLY-BASED ACFT AND HAD BEEN CLRED TO LAND ON RWY 29L. AFTER LNDG; WE EXITED THE RWY ON TXWY D2. WE STOPPED BECAUSE THERE WAS A HELI ON APCH TO TXWY D. THE HELI MAINTAINED ALT AND THE TWR TOLD HIM TO GO AROUND. ALTHOUGH BOTH CREW MEMBERS WERE LCL PLTS; NEITHER OF US HAD FLOWN RECENTLY AT BJC. APPARENTLY THE USE OF TXWY D FOR HELI OPS HAS BEEN ESTABLISHED IN THE LAST FEW MONTHS. THERE WAS NOTHING ABOUT THIS ON THE ATIS AND WE HAD NO WAY OF KNOWING THAT IT WAS HAPPENING. WE EXITED AT D2 TO AVOID REMAINING ON THE RWY FOR AN EXTENDED PERIOD; WHICH WOULD HAVE BEEN REQUIRED HAD WE TAXIED TO TXWY G. I BELIEVE THAT EITHER THE ATIS SHOULD ALERT PLTS TO HELI OPS OR THE TWR CTLR SHOULD HAVE REQUESTED US TO TAXI ON RWY 29L TO TXWY G. THE HELI WAS BEHIND US; AND THUS WAS INVISIBLE PRIOR TO EXIT. WE QUERIED GND CTL ON OUR WAY IN; AND (AFTER A LONG DELAY) THEY SUGGESTED THAT HAD WE WISHED TO USE TXWY D; WE SHOULD HAVE ASKED THE TWR FOR PERMISSION. THAT IS NOT SOMETHING THAT WOULD OCCUR TO A TRANSIENT PLT; GIVEN THE ARPT LAYOUT; UNLESS THEY KNEW THAT HELI OPS WERE COMMON ON TXWY D.