UUS really doesn't connect any trails in Rifle (currently) nor is it a destination trail. It's just a fun trail to add a few more miles to your ride. Supposedly, it's one of the oldest MTB trails in the Hubbard area.
To access UUS, from the BLM lot, head southwest down the gravel road about a quarter mile. Look straight south at a moto play area and climb the gas pipeline road that heads straight up the hill veering slightly southwest. It's a short and pleasant climb. When you gain the top, you bike through a dispersed campsite and that it is where UUS begins. The trail entrance is obvious.
It's very easy to stay on the trail from here. Follow it as it flows along above Upper Sidewinder
and begins it's descent back towards Paul's Trail
. Enjoy some fast corners and cruisin' through the junipers. There is one section of note: just as you're flying along, having a good ol' time, the trail switches back steeply to the right. I've only been able to clean this punchy little climb once - it's steep and filled with loose dirt. After the short climb, enjoy the descent back towards Paul's Trail
where you have many options of where you'd like to continue.