Noble,
I know which pits you are refering to. Long time ago, SWAMP used to have a trail that went to that area. It is only visited by old time SWAMP members that know about it now. I was taken there two times now and enjoyed each time. There is a crazy hill that is as big as the Big Drop at Boyette. Once you hit the bottom of it, you can still ride down even more by hitting the little creek/pit. But you have to do a U-turn to get out of it.
That old trail has long been closed and SWAMP no longer encourages anyone to go there. I am sure Garry or Kevan may know more about it. It still very easy to get to them just West of FR3 and south of FR4. I don't recommand you ride this area since if it is not visited by anyone, it is not visited for a reason. Besides, if you were to have an accident there, chances are you won't be seen by anyone for many days or not at all.
As with other public parks, to keep our trails open for everyone to enjoy, it is best if we stay on approved MTB trails. Be safe and try not to ride alone out there. If you do, let someone know where you are going and when you should be back.
BTW, SWAMP has an official ride this July 4th at Croom with a picnic afterwards. YOu are welcome to ride with us if you like. Even if you have a BMX bike. Just bring your helmet and your water. See you there.