Turn left off the dirt road to start the Sleepy Lion Trail. A sign will indicate where it begins.
The trail immediately starts climbing through pines. This area is called Deadman Gulch. Continue until reaching a really nice meadow, where you'll have views of RMNP. From there, keep on the trail as it continues gaining elevation. The trail will get a little bit rockier and then begin descending. You'll then see a sign for the Hall Ranch Open Space.
Instead, continue to the right to stay on the trail. You'll soon see the reservoir to your right in the distance. Stay on the trail as it ascends some more and then begins descending. This section of the trail has some pavement on it. Soon you'll reach the base of the Ralph Price Reservoir and Button Rock Dam. A huge amount of water was being released from the dam when we were there and was spraying into the river. You can get up very close to the spray.
Head back the way you came or head northeast on the Button Rock Dam Access
and Longmont Dam Road
for a nice loop.