Directly to the SW, there's a small camping area where a yao guai might spawn. There will be three bodies here that you can loot, a duffle bag, and ammo box.
The building itself has several radioactive barrels. To reach the sub-level, you have to access the Supervisor Terminal to the south and select the option to unlock the security gate below.
Inside the secured area, you can find a generator with fusion core inside. In front of that generator, there's a trapdoor between a loading ramp and a push cart, behind some radioactive barrels. Enter it to reach the sub-level.
There are only a handful of lootable items here so just find the circuit breaker and trigger it to stop the broadcast. Some ferals may also appear in the loading area so be prepared.