RS 3.5M Trailhead Rock Springs Parking Map: Marin Municipal Water District Trails Start on Cataract Trail. Right on Simmonds Trail. Left on Mickey O'Brien Trail. Left on Cataract to finish. Route Total distance: 2.85 miTotal climbing: 584 ft Disclaimer Share this:Click to share on Twitter (Opens in new window)Click to share on Facebook (Opens in new window)Click to share on Google+ (Opens in new window) Posted in Rock Springs, Trailhead and tagged 3M, 4M, Cataract, MMWD.