Call after it rains to ensure the trails are open.
Starting from the front parking/restroom area, you can access this trail via the Spillway Trail. Alternatively, you can park at the next smaller parking area a few hundred feet up the road and head down the trail to the creek shelf and go left. When you come out onto the creek shelf stay on your side of the creek. The trail picks up to the left just up from the creek crossing area. The trail "Y's" shortly after you enter the trees; go left to add a 1/4 mile. You'll wind back around and then head down a fairly steep drop into the spillway's creek. Continue back up the other side until you come out onto a flat landing with a nice spot to view the spillway.
The trail cuts back into the trees at this spot, but continue up the hill and take the next left you see, and run back into the trees. From this point, just follow the trail through the tight twisting, mostly dirt, singletrack with some rocks and roots for variety. After around 1 1/2 miles you'll pop out at a "T" intersection onto a doubletrack road. Go back to your right and follow the trail as it heads slightly back up and takes you to the earthen dam. Return across back to the spillway where you had just come from.