Date: 201206
Local time of day: 1801-2400
Location: ZLC.ARTCC, UT
Flight conditions: VMC
Aircraft: A320
Operator: Air Carrier
Operating under: Part 121
Flight plan: IFR
Flight phase: Cruise
Airspace: Class E ZLC
ATC / advisory: Center ZLC
Second aircraft: Gulfstream V / G500 / G550
Reporter organization: Government
Reporter function: Enroute
Reporter qualification: Air Traffic Control Fully Certified
Anomaly: ATC Issue All Types; Deviation / Discrepancy - Procedural Published Material / Policy; Inflight Event / Encounter CFTT / CFIT
Detector: Person Air Traffic Control
Result: Air Traffic Control Issued New Clearance
Contributing factors: Human Factors
Primary problem: Human Factors

Narrative: An A320 inbound to GPI; 20 miles out was cleared to maintain 100 until ITONE cleared for 30 approach. The weather was VFR and prior to the fix requested to go to the FCA VOR that services the airport instead. At the same time; Glacier Park Tower called for a release on a departing aircraft; a G5 ready for immediate departure. I released the G5 to 090. The A320 was at 100 and now cleared to the FCA VOR. It took at least four or five attempts to insure that the A320 had the clearance. As far as I can remember the clearance was to maintain 100; but with the confusion and the situation I can't be certain. At the same time the G5 departed and with the several attempts to assure the A320 had his clearance I think the two aircraft were blocking each others communication. I noticed now the G5 had departed and was on the wrong code; Data Block not tracking. I noticed how fast he was climbing and heading towards the A320 which at the same time I noticed now was at 090 the same altitude the G5 was at; but the Data Block wasn't tracking on the G5 and at that same moment was when I noticed the A320 assigned altitude of 100 but Mode C showed at 090. At that time the A320 had the airport and terrain in sight. As far as I remember the A320 clearance was 100; with the head on situation and not talking with the G5 I turned the A320 to a 350 heading to protect for the route of flight for the G5. Made communication attempt and got a hold of G5 and asked if he could accept a 190 heading and RADAR identified him; and climbed it to get him above the A320. I turned the A320 to a 020 heading to maintain separation. The A320 was in what I thought was a 090 MEA. The A320 questioned the heading because it turned him away from the airport and towards the mountains. After the turn the A320 lost sight of the airport but had the terrain in sight and was asking for a 360 back to the airport. I knew there was higher terrain East that I was paying attention to and knew I had to turn him back to the west. At the time I hade seven miles separation with the G5 and also had vertical separation so I turned the A320 to a 280 heading back to the airport. The A320 got the airport in sight and was cleared for a visual approach. After all was over; I still had his comment in mind about getting closer to the mountains; which at the time I was 100 % sure he was in a 090 MEA. I also knew the safe altitude on the approach for his quadrant was 088. I thought the assigned 100 and when I noticed the unsafe situation of both aircraft being at the same altitude; I took immediate action to resolve it with out having time to check the overhead maps. I knew he had the terrain in sight and I knew he was at a safe alt. and I thought he was above the MEA. As I looked up after the fact; I realized I had taken the aircraft into a 097 MEA thinking that was the 090 MEA. I was protecting him from the higher MEA East that was 118; but didn't realize at the time he was in a 097; but was still under the impression he was assigned 100 and at that point. I don't know what to recommend other then not trying to do too much at the same time. There is a lot of focus on airport delays; and as controllers we try and keep things moving as fast as we can. We don't like to delay aircraft. It was a situation were it was right at that moment if we could get the departure out safe with the communication problem with the pilot and the confusion it caused and the G5 not on the right code made it into a bigger issue then it should have been.




Synopsis: ZLC Controller described a below MVA event after issuing an altitude believed to be in MVA compliance but that was in fact below required standards. The Controller listed a number of distractions as causal factors.