http://ipm.ucanr.edu/PMG/PESTNOTES/pn7433.html
A Pocket Gopher’s tunnel system can cover an area anywhere between 200 and 2,000 square feet, with burrows around 2 1/2 to 3 1/2 inches in diameter, feeding burrows around 6 to 12 inches below ground, and the nest and food storage chamber as deep as 6 feet.
Gophers are constantly burrowing and sealing any openings to their tunnel system with earthen plugs. Short, sloping lateral tunnels connect the main burrow system to the surface. They will push dirt to the surface, creating a horseshoe-shaped mound that is visible from above ground.
