DC10-10 ACFT ESTABLISHED ON LOC AND 24 DME AT 2500 FT ALT RECEIVED GPWS 'TERRAIN' WARNING. FLC FOLLOWED SOP AND EXECUTED EVASIVE ACTION BY CLBING 900 FT. POSTFLT REVIEW WITH ATC NOTED THE LOSS OF SEPARATION WITH ACFT XING ABOVE RPTR ACFT.

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WHILE ESTABLISHED ON LOC FOR ILS RWY 24R AT LAX ALT STABLE AT 2500 FT MSL THE GPWS 'TERRAIN' WARNING CAME ON. EVASIVE ACTION WAS TAKEN RESULTING IN A CLB TO 3400 FT MSL. ATC WAS IMMEDIATELY ADVISED OF OUR GPWS WARNING AND ALT; AFTER WHICH A CLRNC BACK TO 2500 FT AND A NORMAL APCH AND LNDG FOLLOWED ON RWY 24R AT LAX. WE WERE ADVISED TO CONTACT SOCAL APCH ON A LAND LINE. THEY ADVISED ME THAT A POSSIBLE TFC CONFLICT COULD HAVE OCCURRED WITH OVERFLYING TFC XING THE N TO THE S COMPLEX AT LAX. HOWEVER; NO TCASII CONFLICT WAS INDICATED BY US WITH ANY OTHER ACFT. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: RPTR CAPT VERIFIED THE ARR FROM OVER SMO AND DSCNT CLRNC TO 2500 FT IN ANTICIPATION OF THE USUAL TURN IN FOR THE APCH AT APPROX 10 DME. HOWEVER; THE WX WAS POOR WITH HVY RAIN SHOWERS AND LIGHT TO MODERATE TURB WHICH MAY HAVE CONTRIBUTED TO THE HVY TFC LOAD FOR ATC. THAT RESULTED IN AN EXTREMELY EXTENDED PATTERN TAKING RPTR ACFT OUT TO 24 DME. THAT RESULTED IN A GPWS FROM HIGH TERRAIN IN THAT AREA WHICH FURTHER RESULTED IN LOSS OF SEPARATION WITH AN ACFT XING ABOVE. RPTR HAD NO CHOICE BUT TO REACT TO THE GPWS APPROPRIATELY; ESPECIALLY SINCE THE WX WAS POOR AND VISIBILITY VERY LIMITED. THOUGH IT DIDN'T RELATE TO THIS RPT THE CAPT WANTED TO REGISTER HIS AS WELL AS MANY OTHER PLTS COMPLAINT ABOUT THE CIVET ONE ARR WITH THE MULTIPLE STEP-DOWN ALTS VICE FLYING THE GS. RPTR WAS ADVISED THAT WAS DUE TO AIRSPACE PROTECTED BELOW THE TCA FOR THE NUMEROUS ARPT'S IN THAT VICINITY. CAPT SAYS THAT HAVING THE STEP-DOWNS REQUIRES THE FLC REMAIN FOCUSED IN THE COCKPIT AND NOT ABLE TO ADEQUATELY SCAN FOR TFC. HE BELIEVES IT IS A SAFETY HAZARD.