Of course, as far south as CM is, and as it is't over 9000 feet, any freezing would be either temporary or not very deep. Naturally, if surface mining were to be done, it could be performed year-round.
The ground does freeze in northern California and they do get snow in Lone Pine. But CM is in mid/central California and I doubt freezing would be a problem although at higher elevations it could be. CM is at 7,644 ft. and would get snow.