VHF Trunking in Northern Virginia?

I just spotted a post over on Radio Reference that someone is hearing "P25 control channels" on multiple VHF federal frequencies. No system ID, site ID, WACN or NAC information accompanied the frequencies that were posted.

Here are the frequencies that were posted:
168.8250
170.8625
170.9125
171.5375
171.6250
171.9875
172.6375
173.9000

I'd love to get some additional information from someone else that hears these so we can try to determine what they are. Many of these frequencies are being used in the federal Integrated Wireless Network (IWN) VHF trunked system in operation in Oregon and Washington. This possibly could be an expansion of the IWN sites in the DC area, but more information is needed.

Gifford-Pinchot National Forest

I recently spent some time near the Gifford-Pinchot NF Headquarters in Vancouver, WA. Us locals have been trying to piece together some of the new P-25 frequencies that have been heard recently. While I was there I searched for VHF or UHF frequencies coming from the tower there. Here is what I found active during my time near the tower:

406.3875 MHz, 136.5 PL
406.5750 MHz
408.5750 MHz
408.9875 MHz, N788
415.3875 MHz, 114.8 PL
415.4250 MHz, 162.2 PL
415.5250 MHz, N4F9
415.5750 MHz, N4CE
415.5750 MHz, N459
417.9875 MHz, N68F
418.1875 MHz, N47C
419.7875 MHz, N4F9

During the afternoon weather forecast broadcast, multiple channels were all transmitting at the same time. I did not find any active VHF transmissions from the tower while I was there. The frequency 415.5750 MHz showed two different NAC's, probably depending on something like what site they were controlling. Others have noted that the analog link frequencies sometimes have different CTCSS tones also.

We are still trying to figure out what VHF repeaters are associated with what UHF links. The work continues...