The trail is pretty easy to follow. However, a few miles in to it, you will pop up at an old road intersection in a clearing with lots of road choices. The first road to your left will take you back to Foothill Rd. The second trail (large hump at the bottom) is a steep, straight climb, eventually going to Southside Trail. The third trail should have a small sign for "Headwaters". This is the one you'll want to take as it switchbacks up the hillside for another ½ mile (see image). The other two options are going straight on the road (which eventually just peters out) or a road to the right that's blocked with logs. The trail to the right is on property whose owner does not allow biking/hiking. Please respect their request and privacy.<br />
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In another 1/2 mile, you will cross another trail (beginning of Southside trail). Head directly across this trail. You'll then enjoy a few downhill switchbacks, followed by eight challenging back-to-back uphill switchbacks. Once you at the top of the switchbacks, the rest of the trail is largely downhill-with just an occasional uphill burst. You'll be on this section for ~2 miles. The trail drops onto Foothill Rd again when you're finished with that section.<br />
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Turn right and head slightly uphill across the road just a few feet (directly southwest from where you exited) for more singletrack (a Headwaters' sign and a Boy Scout sign are posted at the start of this trail). This section of the trail was built as part of an Eagle Scout project and has been nicknamed Boy Scout Trail. This section is shorter and then you'll be dumped on the main road directly across from where you first started the trail (near Pond 9). Turn right (downhill) to get back to your car.<br />
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Alternate Route: Ride the loop clockwise (starting to the left) if you want a tougher workout. It is somewhat easier to ride counter-clockwise.
Ride ¼ mile further up Foothill Rd. You'll come to a junction of many roads. Stay in the middle road (look for the big blue gate), walk around or under the gate and keep going on that road. Ride another ¼ mile past the gate to the entrance located on the right side and marked with a white "Headwaters" sign (about 100' past Pond 9). If you do the full Headwaters loop, you'll exit the trail right about the same place except on the left side of the Foothill Rd.
http://www.singletracks.com/item.php?c=1&i=8084