C560 FLT CREW; OPERATING IN AREA OF HIGH TRAFFIC VOLUME; RECEIVED TCAS RA AND RESPONDED ACCORDINGLY.

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AFTER DEPARTING AND CONTACTING DENVER DEP; WE WERE IMMEDIATELY COMMANDED TO CONTACT DENVER DEP ON 126.1 MHZ BEFORE LEVELING AT 8000 FT MSL. THERE WERE NUMEROUS VFR TARGETS N OF BJC -- MOST LEVELING AT 7500 FT MSL BENEATH THE CLASS B AIRSPACE. WX WAS ESSENTIALLY CLR; A BEAUTIFUL SUMMER DAY IN DENVER. DEN DEP ON 126.1 WAS VERY BUSY WITH TFC CONGESTION; BUT AFTER HIS CALLS TO SEVERAL OTHER VFR AND IFR ACFT HE CALLED US SAYING; 'ACFT X RADAR CONTACT; MAINTAIN 8000.' AT THAT TIME I MENTIONED TO MY CO-CAPT MY SURPRISE THAT HE HADN'T CLRED US TO A HIGHER ALT BECAUSE OF THE INDICATED CONGESTION ON OUR TCAS DISPLAY AND NO ACFT IMMEDIATELY ABOVE. I MAINTAINED 200 KTS IN LEVEL FLT AT 8000 FT AND BEGAN SLOWING FURTHER TO WHAT I PLANNED TO BE 180 KTS DUE TO THE OBVIOUS CLOSURE OF THE SEVERAL VFR TFC TARGETS AHEAD. ABOUT THE SAME MOMENT I BEGAN REDUCING PWR; WE RECEIVED OUR FIRST TCAS TFC ALERT AND SHORTLY THEREAFTER DEN DEP GAVE US AN IMMEDIATE L TURN TO 320 DEGS FROM THE ASSIGNED 360 DEGS. WITHIN SEVERAL SECONDS OUR TCASII ISSUED A RESOLUTION ALERT TO 'DSND.' FOLLOWING THE IVSI 'GREEN ARC' SMOOTHLY TO A 1500 FPM DSCNT RATE. THE RESOLUTION WAS RESOLVED WHEN WE LEVELED AT 7500 FT MSL. PASSING DIRECTLY UNDERNEATH WE NEVER SAW THE TFC WHICH PRODUCED THE RA; UNDOUBTEDLY DUE TO THE WORKLOAD OF DEALING WITH THE RA AND NUMEROUS OTHER VFR TFC TO THE N OF THE ARPT. SUPPLEMENTAL INFO FROM ACN 742828: IN MY VIEW; THIS INCIDENT WAS A TEXTBOOK EXAMPLE OF THE HAZARDS INHERENT IN MIXING HIGH PERFORMANCE IFR TFC WITH LOW PERFORMANCE VFR ACFT IN BUSY TERMINAL AIRSPACE. I DO NOT BLAME THE CTLR FOR WHAT HAPPENED. HIS WORKLOAD WAS OBVIOUSLY FAR BEYOND A URATION LEVEL AT THE TIME. OUR HIGH LEVEL OF SITUATIONAL AWARENESS AND ALERTNESS; NOTWITHSTANDING; WE STILL ALLOWED FOR AN RA. THANK GOD THE TCAS SYS WORKED THE WAY IT IS SUPPOSED TO. IN MY VIEW; WE WOULD ALL HAVE BEEN BETTER OFF IF OUR RELEASE FROM BJC HAD BEEN DELAYED UNTIL THE TFC VOLUME ALONG OUR PROJECTED FLT PATH HAD DECREASED. MUCH BETTER STILL WOULD BE A REDESIGN OF LCL AIRSPACE AND/OR ATC PROCS THAT WOULD ALLOW HIGH PERFORMANCE DEPS FROM BJC TO CLB RAPIDLY TO 10000 FT OR HIGHER; ESPECIALLY IN THE CASE OF WBOUND TFC HEADED FOR THE HIGH TERRAIN ALONG THE FRONT RANGE.