Narrative:

I was working approach control, the only person certified on approach on duty at the time. Approach position started to get busy--non radar. Small aircraft X was overflying from southeast V132 to V138, nwbnd at 12000', non DME. Mdt Y was inbound on V81 from south. Small aircraft Z holding at crims at 80 as mdt Y would overtake him, mdt Y was descended to 13000'. I should have had den center take mdt Y to 11000' below small aircraft X overflt at 12000', but was too late. I checked several times with center but didn't have them past each other. Told mdt Y I would have to keep him at 13000' until traffic passed the VOR. Told center north sector this. Their paths crossed at hamet intersection. Then I was thinking that V132 would pass west of horse outbnd (east) above and small aircraft X would continue nwbnd. I made a mistake as V132 crosses over horse and I didn't allow enough sep. I wasn't on top of situation and pictured something that wasn't right. The C/a went off at center. When they called later about it I had a feeling that I had made a mistake and after rechking realized that I had. No evasive action was taken. Not realized until after everything had occurred.

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Original NASA ASRS Text

Title: ACR MDT ARR DESCENDED THROUGH THE ALT OF SMA OVERFLT BEFORE LATERAL SEPARATION EXISTED RESULTING IN LESS THAN STANDARD SEPARATION.

Narrative: I WAS WORKING APCH CTL, THE ONLY PERSON CERTIFIED ON APCH ON DUTY AT THE TIME. APCH POS STARTED TO GET BUSY--NON RADAR. SMA X WAS OVERFLYING FROM SE V132 TO V138, NWBND AT 12000', NON DME. MDT Y WAS INBND ON V81 FROM S. SMA Z HOLDING AT CRIMS AT 80 AS MDT Y WOULD OVERTAKE HIM, MDT Y WAS DSNDED TO 13000'. I SHOULD HAVE HAD DEN CENTER TAKE MDT Y TO 11000' BELOW SMA X OVERFLT AT 12000', BUT WAS TOO LATE. I CHKED SEVERAL TIMES WITH CENTER BUT DIDN'T HAVE THEM PAST EACH OTHER. TOLD MDT Y I WOULD HAVE TO KEEP HIM AT 13000' UNTIL TFC PASSED THE VOR. TOLD CENTER N SECTOR THIS. THEIR PATHS CROSSED AT HAMET INTXN. THEN I WAS THINKING THAT V132 WOULD PASS W OF HORSE OUTBND (E) ABOVE AND SMA X WOULD CONTINUE NWBND. I MADE A MISTAKE AS V132 CROSSES OVER HORSE AND I DIDN'T ALLOW ENOUGH SEP. I WASN'T ON TOP OF SITUATION AND PICTURED SOMETHING THAT WASN'T RIGHT. THE C/A WENT OFF AT CENTER. WHEN THEY CALLED LATER ABOUT IT I HAD A FEELING THAT I HAD MADE A MISTAKE AND AFTER RECHKING REALIZED THAT I HAD. NO EVASIVE ACTION WAS TAKEN. NOT REALIZED UNTIL AFTER EVERYTHING HAD OCCURRED.

Data retrieved from NASA's ASRS site as of August 2007 and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.