From Steve Schweitzer's A Fly Fishing Guide To Rocky Mountain National Park, flyfishingrmnp.com:
Sandbeach Lake Trail
For an energetic day hike and rewarding fishing opportunity, access Sandbeach Creek via the southern end of Sandbeach Lake, then fish the creek down to Wild Basin Trail just before Copeland Falls. The stream is small, boulder ...
From CO-7, take Wild Basin Rd (Co Hwy 115) which ends at the Wild Basin trailhead. Wild Basin Trail takes the hiking fishing to several small streams for an easy day hike to all. just minutes into the hike, the trail crosses Sandbeach Creek and then follows the North St. Vrain closely for about 1.4 miles. Wild Basin Trail takes a sharp turn to the south about 1.5 miles from teh trailhead, at the junction of the Campsite Shortcut Trail. It then turns northwesterly, following Ouzel Creek for a short time. The trail is wide and well-maintained for the first mile, then becomes thinned and more rock-strewn as it gains altitude modestly and steadily throughout, While it follows the North St. Vrain, it is flanked by tall pines and aspen, making a beautiful stroll in the autumn as the aspens leaves turn yellow.