The Jefferson County Sheriff's Office and the West Metro Drug Task Force seized more than 5,100 marijuana plants weighing nearly 2,000 pounds from land near Sugarloaf Mountain on July 9.
The plants have an estimated street value of $2.5 million.
The large grow area had a sophisticated irrigation system using water from a nearby stream, according to sheriff's spokeswoman Jacki Kelley.
"This looked like a very sophisticated operation," Kelley said.
Sugarloaf Mountain is in the Pike National Forest near Cheesman Reservoir.