Date: 201909
Local time of day: 1201-1800
Location: S46.TRACON, WA
Flight conditions: VMC
Light: Dawn
Aircraft: EMB ERJ 170/175 ER/LR
Operator: Air Carrier
Operating under: Part 121
Flight plan: IFR
Mission: Passenger
Flight phase: Initial Climb
ATC / advisory: TRACON S46
Second aircraft: MD-11
Reporter organization: Government
Reporter function: Approach; Departure
Reporter qualification: Air Traffic Control Fully Certified
Human factors: Communication Breakdown; Workload; Time Pressure; Situational Awareness; Distraction
Anomaly: ATC Issue All Types; Conflict Airborne Conflict; Deviation - Altitude Overshoot; Deviation - Track / Heading All Types; Deviation / Discrepancy - Procedural Clearance; Deviation / Discrepancy - Procedural Published Material / Policy
Detector: Person Air Traffic Control
When detected: In-flight
Result: Air Traffic Control Issued New Clearance; Air Traffic Control Separated Traffic
Contributing factors: Company Policy; Airspace Structure; Human Factors; Staffing; Procedure
Primary problem: Company Policy

Narrative: I was working 7 positions combined; and reading clearances to aircraft off PAE airport because the Tower was still closed. Aircraft X was assigned runway heading and 3;000 feet. When he departed he should have been heading 160; but instead he came off on a 100 heading. I radar identified him and noticed he wasn't doing what he was told; so I gave him a 130 heading and 4;000 feet. Apparently he read back 14;000 feet. and I missed it. At the same time I was working many other positions with a full final. I questioned what he was doing and issued traffic; he called the traffic in sight and I told him to maintain visual and gave him a wake caution.First off; we need another person there in the morning. I've been telling them this for years. It is too busy that early; and we shouldn't be working that many positions combined. Even if it is not that busy; working that many frequencies aircraft are stepping on each other and then I'm having to repeat myself multiple times. There were too many aircraft; too many frequencies; too many positions and I had to read clearances and issue EDCT times to aircraft off PAE. Second; since we have started commercial operations in and out of PAE; we haven't trained any kind of procedures; haven't changed the airspace to accommodate the increase of traffic; haven't even had a briefing on anything; we've just had to figure it out. Every day we just wing it; every controller works the PAE arrivals differently and you never know what to expect. It has been 6 months; and every week at our briefing I bring up concerns and nothing ever gets done.Third; PAE Tower has to extend their hours. They open at XAam; but there's always 3 or 4 first thing in the morning and they call right during the morning push. During this event; all positions were combined and it was too busy. Same thing at night; PAE Tower closes at XKpm and there's always 3 or 4 aircraft that come in after they close. Then it's one in one out. If they come in close together; we have to delay vector the second and third and sometimes forth aircraft until we get the first cancellation. Sometimes they forget to cancel in which case we have to put the other aircraft in holding. There have been many ideas on how to fix our procedures; some good; some not so good. Management refuses to step up and get anything done. It's almost like they are waiting for something really bad to happen before they will take action.




Synopsis: S46 TRACON Controller reported failure to notice an aircraft's incorrect altitude readback; resulting in a loss of separation.