I have previously shut down the HVAC over the whole site, increasing the inspiral range (Link, Link). The PEM injection report (Link) indicates that coupling in the 5-80 Hz HVAC band is largest at the corner station so I tried shutting down just the corner station. Figure 1 shows that a shutdown of the corner station HVAC reduces the DARM floor above 80 Hz. Figure 2 shows that SF1,2,3 and 4 contribute little, but SF5, 6 and the chiller pump (actually the turbulence in the system), are the worst contributors.   

Nov 15 UTC

AHU 1-4 and chiller pump off 16:40:00 - 16:42:25; Back on 16:50:00-16:51:30

AHU 1-4 and chilled water pump off 17:00:00-17:01:30; Back on 17:10:00 - 17:11:30

AHU 1-4 and chilled water pump off 17:20:00-17:21:45; Back on at 17:30:00-17:31:30

AHU4 off 20:15:00 -20:15:30; Back on 20:30:00 - 20:30:30

AHU3 (SF5 and 6) off 20:45:00-20:45:30; Back on 20:55:00-20:55:30

AHU1,2 SF1,2,3,4 off 21:02:00-21:07:00; Back on 21:17:00- 21:17:30

SF1,2,3,4,5,6 off 21:30:00 - 21:30:30; Back on 21:41:00 - 21:42:00

Chiller pump off 22:13:00-22:13:30; Back on 22:33:00-22:33:30

SF5,6 off at 22:40:00-22:40:30; Back on 22:51:00 to 22:52:00

SF1,2,3,4 off 23:00:00-23:00:30; Back on 23:10:00-23:10:30

AHU4office off 23:17:00 to 23:17:30; Back on 23:27:00