BA31 DSNDS THROUGH CLRED ALT ON APCH TO STL.

Narrative

UPON CALLING THE ARPT (STL) AND MD80 AT 2 O'CLOCK (ON BASE TO PARALLEL RWY) 'IN SIGHT;' APCH CLRED US FOR VISUAL APCH TO RWY 12L. AS WE DSNDED THROUGH 4000 FT; ATC INFORMED US THE MD80 NEXT TO US WAS OVERSHOOTING HIS FINAL AND; DID WE STILL SEE HIM? WE SAID 'NO' AS HE'D GONE UNDER US. ATC THEN CANCELED OUR APCH CLRNC AND TOLD US TO MAINTAIN 3500 FT. WE READ IT BACK AND LOOKED FOR THE MD80. WHEN WE RESCANNED BACK IN TO THE ALTIMETER IT READ 3000 FT. JUST AS WE INITIATED A CLB BACK TO 3500 FT; WE SAW THE MD80; CALLED IT; AND WERE RECLRED FOR THE VISUAL. OCCURRENCES LIKE THIS ARE A DIME A DOZEN IN THE STL TERMINAL AREA. GND CTL HAS ACFT CONTINUOUSLY XING RWYS TO AND FROM THE GATE. TWR HAS 3 PARALLEL RWYS TAKING OFF AND LNDG WHILE PERFORMING HOLD SHORT OPS ON A RWY THAT INTERSECTS ALL 3. ACFT ARE BEING CLRED FOR TKOF BEFORE THE LAST ONE HAS EVEN ROTATED TO PREVENT GARS; ETC. THE FACT WE GOT 500 FT LOW ISN'T ITSELF TO BE BLAMED ON THE ST LOUIS SIT TOTALLY; BUT IT GOES TO SHOW THAT THE SATURATED ST LOUIS TERMINAL AREA LEAVES LITTLE TO NO ROOM FOR ERROR TO PREVENT A SCARY SIT. OTHER CONTRIBUTING FACTORS COULD HAVE BEEN: 1) THE MD80 FAULT OR HIS CTLR'S LATE TURN TO CAUSE HIM TO CROSS TO OUR SIDE. 2) I HAD A NEW AND INEXPERIENCED FO THAT I FELT I HAD TO HELP ASSIST IN LOOKING FOR THE TFC (AS HE'D LOST IT) AND MISSED GIVING ME THE STANDARD ALT CALLS TO ALERT ME OF MY ALT. 3) THE TYPICAL CASE OF 'ONE GUY FIX THE PROB (FIND THE TFC); ONE GUY FLY THE AIRPLANE' BROKE DOWN!