A Skagway truck driver this week said his plan to dig two, 500-foot-long trenches for mineral exploration on state land near Mount Riley amounts to a rock-hunting outing that would last about two weeks and have the impact of a residential driveway.

Eric Hosford has sought a state permit for the work that would dig, then backfill exploratory trenches up to 12 feet wide and 10 feet deep, one parallel to Mud Bay Road and…