The Flume Trail is enjoyable mostly flat singletrack twisting along a steep mountain side dropping only 40' per mile. If you're afraid of heights, this ride might not be for you, but it's an intermediate trail otherwise, and an incredible one at that. The views are spectacular and the riding is flowy and fun.
There is one very short rock slide area that you'll walk over that has a sign warning you.
Access to the Flume Trail is via the North Canyon Road
at Spooner Lake State Park or the Tahoe Rim Trail through Tahoe Meadows.
The first section is very technical, and many riders walk this section. It is very short, and once you clear it, the ride gets much easier. From here, the singletrack swings out on the side hill and gives you a great view of Lake Tahoe. Follow the singletrack north for 4.2 miles (10.5 miles) where you'll intersect Tunnel Creek Road.
From here you could go right and intersect the Tahoe Rim Trail, or intersect with the Red House Flume trail, or just turn around and retrace your path back to Spooner Lake State Park.