Date: 201509
Local time of day: 1801-2400
Location: ZOA.ARTCC, CA
Light: Night
Aircraft: B737 Undifferentiated or Other Model
Operator: Air Carrier
Operating under: Part 121
Flight plan: IFR
Mission: Passenger
Flight phase: Descent
Airspace: Class A ZOA
ATC / advisory: Center ZOA
Second aircraft: Any Unknown or Unlisted Aircraft Manufacturer
Reporter organization: Government
Reporter function: Enroute
Reporter qualification: Air Traffic Control Fully Certified
Human factors: Situational Awareness; Training / Qualification; Communication Breakdown
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 Issued New Clearance
Contributing factors: Procedure; Airspace Structure; Chart Or Publication
Primary problem: Procedure

Narrative: I was conducting training on the Radar Position when Aircraft X was issued clearance to descend via the SILCN2. Norcal Approach (NCT) who works the sector for the arrivals; called us on the shout line; but we were unable to pick up due to coordination with another sector at the time. ZOA Sector picks up the line for us; as NCT advised that they were going to stop Aircraft X at 20000 feet due to traffic. However; we still had communications with Aircraft X; but didn't know that NCT wanted to stop the aircraft at 20000 feet for their traffic climbing to 19000 feet. I didn't see the traffic for Aircraft X until conflict alert went off as soon as the aircraft descended below 20000 feet and lost separation with the aircraft climbing to 19000 feet. A lot of miscommunication led to this event since we initially didn't pick up the line with NCT. We failed to communicate effectively with ZOA Sector regarding NCT's intentions with Aircraft X; who descended on the SILCN2 with no restrictions. Again; there has been multiple complaints on the metroplex procedures because of potential traffic events like this. If we still implemented our old procedures and stopped SFO and SJC arrivals at 20000 feet; then these aircraft would never be a factor with NCT's aircrafts climbing to 19000 feet. Although this event is primarily caused by miscommunication; the new metroplex procedures are still putting aircraft at risk every single day by allowing us to descend them into NCT's airspace without knowing what traffic they have. Coordination like this takes time; and sometimes we just don't have enough time to spend on the line with another sector/facility if we ourselves are inundated with heavy traffic in our sector. I feel like we're compromising safety for 'efficiency' with these metroplex procedures every single day; which is something we should never do if we want to maintain airspace integrity in the NAS.




Synopsis: Aircraft was descending on the SILCN2 STAR to SJC. NCT TRACON had departing traffic climbing. TRACON attempted to verbally coordinate with ZOA ARTCC to stop the descent of the inbound at 20000 feet. An adjacent ARTCC Sector took the call from the TRACON to help the ARTCC sector working the arrival but the coordination did not get forwarded to the Controller working the arrival.