Elevation is about 7700 ft. In "Mammal Tracks & Sign: A Guide to North American Species" By Mark Elbroch:
"Voles also create eskers, although they have smaller diameters. I've often found small, short sections of dirt deposited by meadow voles during the winter months, but I've yet to find them leaving long sections, beyond several feet, as is common of pocket gophers' eskers." Length of pictured esker is over 10 ft.