more info about SUNCOMM
"Our Dispatchers are highly-skilled multi-taskers. Our Dispatchers are responsible for dispatching both Fire and Police agencies while keeping citizen and responder safety at the forefront of all their actions. They dispatch for two different Law Enforcement agencies, the City of Yakima Police and the City of Union Gap Police. They also dispatch all Fire Departments in the Upper Valley; City of Yakima, East Valley, Selah, Training Center, Gleed, Naches, Naches Heights, Nile, Highland and West Valley."
from
About | Suncomm - 911 Communications
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Perhaps that means that Yakima County Sheriff dispatches the law enforcement units that serve Upper Valley, East Valley, Selah, Training Center, Gleed, Naches, Naches Heights, Nile, Highland, and West Valley
(possibly - Upper Valley, East Valley, Training Center, Highland, and West Valley are not cities)
(SUNCOMM is the primary PSAP for all of Yakima County - apparently they forward some calls to Yakima County Sheriff Dispatch Center and Yakima County Fire District 5 Dispatch Center)
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Overall - the 911 / dispatch scheme seems to be -
all 911 calls go to Suncomm - Suncomm dispatches all calls in the Yakima area - other calls are forwarded to Sheriff or FD 5 - FD 5 dispatches fire and EMS units in the Lower Valley area (SE Yakima County) - Sheriff Dispatch Center apparently dispatches everyone else