Light Transport; Low Wing; 2 Turbojet Eng
Air Traffic Control Fully Certified
Air Traffic Control Time Certified In Pos 1 (yrs) 7
Confusion; Distraction; Situational Awareness; Workload
ATC Issue All Types; Conflict Airborne Conflict; Deviation - Altitude Overshoot; Deviation / Discrepancy - Procedural Clearance; Deviation / Discrepancy - Procedural Published Material / Policy
Air Traffic Control Issued New Clearance; Air Traffic Control Separated Traffic; Flight Crew Requested ATC Assistance / Clarification; Flight Crew Returned To Clearance
Staffing; Procedure; Human Factors
Working Hood sector end of shift; North sector was about to go over 2 hours right as an arrival rush was incoming. Supervisor had me take in North until next crew came in to split it off again. Got busy with arrivals and departures; aircraft trying to talk same time different frequencies making me have to decipher who was calling. Aircraft X departed; was one of the cross frequencies said climbing to 10000 ft. I hadn't given anyone 10000 ft the entire session so it caught my ear in the mixed transmissions. I asked who it was and it was Aircraft X. I RADARed; they asked; verify we are assigned 10000 ft; I said negative; maintain 6000 ft. Pilot was going through 5800 said going to go through but we can go back down; I told them that's fine; maintain 7000; they read it back. A few moments later I planned to tunnel them and an aircraft under my RHO arrivals and get them out of my departure corridor; but after I turned them north to go under the arrival; I noticed they were at 7700; I immediately turned right heading 120 and told descend and maintain 7000 immediately. Pilot asked '7000?' I said affirmative; maintain 7000 immediately. Turned an aircraft off the arrival slightly just in case at 8000 until both were separated and sent back to the downwind to final. They were anywhere between 1.8 and 2 miles lateral and 400-600 ft vertically separated. The supervisor already apologized that he should not have combined sectors; bit the bullet and left North on for over 2 hrs and said he learned his lesson that maybe call tower to give more spacing on the departures instead of launching the fleet with bad timing when we have to combine sectors and busy with an arrival rush on multiple frequencies. The pilot said he was confused because the PDX1 departure does not have an assigned altitude with it like the RNAVs do and was climbing to his filed alt; so maybe 6000 ft could be added to that to avoid confusion. But at same time the Tower had given them 6000 ft at clearance and this mostly isn't an issue. If I had noticed earlier that he was busting his altitude; I would not have turned him north and would might have kept 3 miles lateral separation though they looked like they might have been heading slightly into the RHO arrival route anyways. So I missed that part too expecting him to level off at 7000.
Portland TRACON Controller reported a loss of separation due to an aircraft overshooting assigned altitude.