43 CFR § 3832.42 - How do I locate a tunnel site?
You may locate a tunnel site by:
(a) Erecting a substantial post, board, or monument at the face of the tunnel, which is the point where the tunnel enters cover;
(b) Placing a location notice or certificate on the post, board, or monument that includes:
(1) The names of the claimants;
(2) The actual or proposed course or direction of the tunnel;
(3) The height and width of the tunnel; and
(4) The course and distance from the face or starting point to some permanent well-known natural objects or permanent monuments, in the same manner as required to describe a lode claim (see § 3832.12(a) and (b)); and
(c) Placing stakes or monuments on the surface along the boundary lines of the tunnel at proper intervals as required under state law from the face of the tunnel for 3,000 feet or to the end of the tunnel, whichever is shorter.