SNA CONTROLLER VOICED CONCERN REGARDING SCT'S PRACTICE OF ROUTING VFR TRAFFIC ALONG THE SHORELINE REQUIRING SNA LOCAL CONTROLLERS TO ISSUE ALTITUDE RESTRICTIONS ON IFR DEPARTURE AIRCRAFT; LISTING SAFETY CONCERNS.

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I WAS WORKING LCL CTL ONE AND DEPARTED A LEARJET. THE ACFT WAS ON A SID ASSIGNED AN ALT OF 5000 FT. OUT OF 1500 FT; I OBSERVED A CONVERGING OPPOSITE DIRECTION VFR C172 TRANSITION ALONG THE SHORELINE AT 4500 FT. I RESTR THE LEARJET TO 4000 FT AND INQUIRED WITH SOCAL APCH. THE C172 WAS TALKING TO THE DEP SECTOR ENRTE TO SMO ARPT. THE CONFLICT ALARM WAS NOW SOUNDING. THE ACFTS' FLT PATHS CROSSED 500 FT APART. I WAS LATER ADVISED BY MY SUPVR THAT THE APCH CTRL HAD FORGET TO RESTRICT OUR DEPS. THE PROB: SNA SID DEPS ARE ISSUED 5000 OR 7000 FT. SOCAL APCH ROUTINELY TRANSITIONS VFR ENRTE ACFT THROUGH THE DEP CORRIDOR OF SNA. THIS TRANSITION RTE IS VIA THE SHORELINE; 4 1/2 MI OFF THE DEP END OF RWY 19R. THEY ACCOMPLISH THIS BY RESTRICTING ALL DEPS TO EITHER 3000 FT OR 4000 FT; NOT UNCOMMON TO CHANGE UP TO 8 TIMES IN AN HR. THIS RESTR MUST BE ISSUED TO ACFT BY LCL CTL FROM HOLDING SHORT; TAXIING INTO POS; DEP CLRNC; OR AIRBORNE. THIS IN ADDITION TO ONE OF THE MOST RESTRICTIVE PWR-BACK NOISE ABATEMENT RESTRS IN THE COUNTRY. AS YOU CAN SEE; THERE ARE MULTIPLE CHANCES FOR ERROR IN ISSUING THE RESTR; READBACK; HEARBACK; STRIP MARKING; AND IN THIS CASE FORGETTING TO COORDINATE. IT IS ONLY A MATTER OF TIME BEFORE A LOSS OF SEPARATION; NEAR MISS; OR A COLLISION. THE FIX: STOP TRANSITIONING VFR ACFT THROUGH THE DEP CORRIDOR OF ACR'S AND LARGE JET ACFT. TAKE THEM OFFSHORE AN EXTRA 3 MI. HISTORY: LAX USED TO HAVE THIS VERY SIMILAR SITUATION USING THE SAME PROCS. ULTIMATELY IN 2004-2005 THEY HAD A LOSS OF SEPARATION AT THE SHORELINE. THEY DISCONTINUED TRANSITIONING OVER THE SHORELINE. SINCE THEN WE HAVE SUGGESTED WE MUST STOP THIS PROC INCLUDING PERMANENTLY MAKING THE ALT 3000 FT. THE OFFICIAL RESPONSE WAS 'UNABLE' DUE TO INCREASED WORKLOAD TO THE APCH SECTOR; POOR SVC TO PLTS; INCREASED NOISE TO COMMUNITIES; AND INCREASED FUEL COSTS TO CUSTOMERS; AS DOCUMENTED IN AN SNA MEMO NOV/XA/05. EVEN RECENTLY IN SEP/XA/08; IT WAS BECOMING SUCH AN INCREASED PROB AGAIN THAT A SNA SUPVR DOCUMENTED ALL THE ALT CHANGES ON VARIOUS SHIFTS TO PRESENT THE INFO TO MGMNT. NO CHANGES WERE MADE.