ACFT VECTORED TO FINAL APCH INTERCEPT WAS TURNED ON CTRLINE LATE; CROSSED INTO PARALLEL RWY CTRLINE AND 2 MI BEHIND B757. RPTR'S ACFT EXPERIENCED LIGHT TURB FOR ENTIRE APCH; BUT STAYED HIGH ON GS TO AVOID THE MAJOR WAKE.

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BECAUSE OF TFC AND WX; WE HELD FOR 1 HR 40 MINS AT BOTH ENI AND PYE. SFO WAS LNDG ON RWYS 19. WHEN THE WX PASSED THROUGH; SFO WAS USING VISUALS TO RWYS 28. WE WERE GIVEN A HDG DOWN THE N SIDE OF THE BAY (100 DEGS) AND A DSCNT TO 6000 FT. APCH SAID; 'YOU ARE NUMBER 5 AFTER A B757 ON A 20 MI FINAL.' WE WERE BTWN THE SAN MATEO AND DUMBARTON BRIDGES WHEN APCH GAVE US A DSCNT TO 5000 FT AND A HDG OF 180 DEGS (THERE WERE SCATTERED CLUSTERS OF CLOUDS STILL REMAINING). APCH SAID; 'DSND TO 4000 FT; THEN SLOW TO 180 KTS. I SAW THE LIGHTS OF ANOTHER ACFT PASS BELOW AND IN FRONT OF US. APCH SAID 'RPT THE ARPT;' WHICH WE DID; AND HE SAID 'CLRED VISUAL RWY 28R AND RPT TFC FOR THE L; A B757.' THE LIGHTS AND THE TCASII SHOWED THE B757 TO BE AT 2 MI. I DIDN'T RPT THE TFC; BUT ASKED; 'HOW FAR AHEAD IS THE B757?' APCH REPLIED; '4 MI; BUT HE'S STAGGERED FOR THE L AND BELOW YOU.' I IMMEDIATELY SLOWED TO APCH SPD; AND NIBBLED AT THE B757 WAKE ALL THE WAY TO TOUCHDOWN. SEVERAL THINGS WERE WRONG: 1) WE WERE JOINED ON A B757 WITH LESS THAN LEGAL SEPARATION; AND WE NEVER RPTED HIM IN SIGHT. 2) THE 180 DEG HDG CAUSED US TO OVERSHOOT THE RWY 28R CTRLINE. 3) THE CTLR STATED THAT WE WERE 'STAGGERED;' IMPLYING THAT THE B757 WAS FOR RWY 28L. HOWEVER; THE SEPARATION OF THE RWYS (750 FT) MAKES THEM ONE RWY FOR WAKE TURB CONSIDERATIONS. ALSO; JUST BECAUSE HE WAS BELOW US IS IMMATERIAL. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: RPTR SUGGESTS WAYS TO IMPROVE ATC PROCS TO PREVENT WAKE TURB ENCOUNTERS: NOTIFY FLC ABOUT FOLLOWING B757 ACFT; FOLLOW PROPER SPACING AS PER ATC HANDBOOK INSTRUCTIONS CONCERNING SPACING; DON'T HAVE SPLIT FREQS FOR ACFT ON PARALLEL APCHS; HAVE BOTH ACFT RPT VISUAL CONTACT WITH EACH OTHER; BUT DON'T EXPECT ACFT WHICH ARE STAGGERED; ONE IN FRONT OF THE OTHER; FOR THE FRONT ACFT TO MAINTAIN VISUAL WITH ONE BEHIND THEM. RPTR SAYS IN THE FUTURE HE WILL QUESTION APCH CTLR ABOUT WHAT TYPE OF ACFT HE IS FOLLOWING.