ARTCC RADAR CTLR FAILED TO PROVIDE SEPARATION IN ACCORDANCE WITH LETTER OF AGREEMENT ON 2 MTR ACFT RECOVERING TO CHD.

Narrative

TWR MTR ACFT WERE RECOVERING FROM TRNING AREAS. A RECENT PROC WAS CHANGED WHICH EXTENDED THE IFR PORTION OF THE RECOVERY. DURING A REVIEW OF THE PROCS IN THE LETTER OF AGREEMENT THE OLD RECOVERY WAS STILL INSERTED WITH NO REF TO THE REVISED PROC. I CANCELLED THE MTR X DATA BLOCK WHEN I OBSERVED HIM LEAVING 8000' MSL; AS WAS THE PROC (OLD ONE) IN THE LOA. BOTH MTRS WERE PROCEEDING TO THE SAME POINT AT 7000' MSL. I TWICE ISSUED TFC TO ONE OF THE MTR Y ON THE OTHER; BUT HE DIDN'T SEE HIM UNTIL THEIR FLT PATHS CROSSED AND HE DECLARED A NEAR MID AIR. A SIMPLE UPDATING OF THE PROC IN THE LOA AND A REMINDER IN SIGHT ON THE SECTOR COULD HAVE PREVENTED THIS OCCURRENCE. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING: RPTR WAS SUPVR GETTING CURRENCY TRNING AND BINDER IN AREA DID NOT REFLECT THE NEW PROC FOR HANDLING THE RECOVERY OF THE MTR ACFT. NEW LOA WAS REVISED TO GIVE IFR SEP TO A NEW POINT; DESIGNATED AS POINT T. OLD LETTER WAS IFR SEP DISCONTINUED WHEN ACFT LEFT 8000' SINCE INCIDENT HAPPENED THE LOA IS AGAIN BEING REVISED TO BE MORE SPECIFIC AS TO WHERE IFR CANCELLED AND APPARENTLY WILL NOT BE AN AUTOMATIC CANCEL. PROX OF ACFT WAS 2.3 NM AT SAME ALT AND WAS CONSIDERED A MODERATE CONFLICT. RPTR DID GIVE TFC TO MTR Y SEVERAL TIMES; BUT HE DIDN'T SEE MTR X UNTIL SEP HAD BEEN LOST.