Date: 201705
Local time of day: 0601-1200
Location: BOI.TRACON, ID
Light: Daylight
Aircraft: Small Aircraft; Low Wing; 1 Eng; Fixed Gear
Operating under: Part 91
Flight plan: IFR
Mission: Personal
Flight phase: Cruise
Airspace: Class E BOI
ATC / advisory: TRACON BOI
Second aircraft: Light Transport; Low Wing; 2 Turboprop Eng
Reporter organization: Government
Reporter function: Approach; Departure
Reporter qualification: Air Traffic Control Fully Certified
Human factors: Situational Awareness; Time Pressure; Workload; Human-Machine Interface; Distraction; Troubleshooting
Anomaly: ATC Issue All Types; Conflict Airborne Conflict; Deviation / Discrepancy - Procedural Published Material / Policy
Detector: Person Air Traffic Control
When detected: In-flight
Result: Air Traffic Control Separated Traffic
Contributing factors: Staffing
Primary problem: Staffing

Narrative: One runway (28L) operation in MVFR low ceiling conditions set the stage for a strung out final. The controller on north radar was working the airspace combined. I was working Bozeman; having worked local; taken a short break and direct to BZN for bi-annual over-the-shoulders from my Supervisor on those positions. I heard north radar asking for a split so I went to the phone and called the supervisor and told him north needed the radar split. I noticed 4 people were on break; only one was a CPC; and he was on break 4 minutes. I went back to Bozeman and the situation at Boise deteriorated to the point north controller could not answer land line calls. I began taking his coordination calls and fixing his data blocks; while ignoring my own sector (nothing was happening at BZN). After about 10 minutes a supervisor came in and took Bozeman from me so I could slide to south. I got there; called to split printers; configured my scope; brought up the frequencies and told the tower we were about to split the radar. I was ready for the brief but north controller was too busy to even give a brief. Finally; as he was missing more and more traffic calls; clearances; check ins and land line calls I buzzed in his ear and said pre-brief complete; I've got the SIA (Systems Information Area); give me the traffic. Once I'd assumed the sector; I went about trying to get everyone on my 's' tag and correcting data blocks that did not show runway and approach assignments. The SR (South Radar) airspace was a mess of planes with the added complication of a parachute drop zone 10 nm southeast at and below 7100; 4 miles in diameter. The orchard range was hot to FL220 and had to be missed. The area in which to vector aircraft to the Runway 28L final was very tight and all altitudes between 7000 and 13000 were being used. Aircraft Y was stuck high something like 10000 and chipping for lower. His data block said 'can' still for arrival from CANEK so I didn't know what approach he'd been issued; if any. I determined it was the RNAV-Y 28L he wanted (makes sense as the right was closed) so I turned him towards the IAF and descended him. Shortly thereafter; as north radar caught his wits and his breath; he said; 'watch Aircraft X is going to get together with Aircraft Y.' I looked and Aircraft X was on a 100 heading encroaching on Aircraft Y's final; opposite courses; both at 7000. I immediately turned Aircraft X to 180 and when he acknowledged and I saw the target begin to turn I did a 'splat-t' and saw 2.98. I was tunneled in on a flight of military fighters twice the speed of their traffic to follow to the airport and broke that traffic out to the south as well as fixing data tags; so I didn't see the development of this pending loss of separation.After re-establishing separation with 2 flights of military fighters as well as Aircraft X and Aircraft Y; shipping aircraft to ZLC and Tower I got Aircraft X back towards the base towards NESLE for the RNAV-Y 28L approach. Controller on north radar stated; after the dust settled; this was outside his ability; it should have been split sooner and he doesn't work enough Boise radar to handle this level of traffic. The supervisor that came in and relieved me from BZN to slide to south radar; had no breaks all morning. He was giving me over-the-shoulders and the associated paperwork. On top of that; the busy north radar controller had a [aircraft] report a NMAC with a drone so the supervisor was very busy with that report and phone calls; yet he stepped up to get on position and me to slide over and help the north radar controller; while the controller that was directed to have made the split long before enjoyed a lunch break.Controller that was supposed to come back and split south radar 30 minutes prior to the event disregarded the assignment to come work radar and elected to take their meal break without telling anyone. Once the CIC tracked him down the controller stated he was on his lunch break; should he come back now and take a missed meal break or stay on break. He was left on break; so I get his deal. I recommend [controller] gets talked to about milking a 45 minute ground session debrief; followed by a full; un-interrupted; minimum 30 meal break while his crew mates work short. This is a routine occurrence with that controller. I routinely take short breaks or even go straight back to work after training my trainees daily. I really took one for the team on this one. Not cool.




Synopsis: BOI TRACON Controller reported an unsafe situation where it was too busy to split the position.