A tunnel site is a subsurface right-of-way under Federal land open to mineral entry. It is used for access to lode mining claims or to explore for blind or undiscovered veins, lodes, or ledges not currently claimed or known to exist on the surface.

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.

You may use the tunnel site for subsurface access to a lode claim or to explore for and acquire previously unknown lodes, veins, or ledges within the confines of the tunnel site.

(a) If you located your tunnel site in good faith, you may acquire the right to any blind veins, ledges, or lodes cut, discovered, or intersected by your tunnel, by locating a lode claim, if they—

(1) Are located within a radius of 1,500 feet from the tunnel axis; and

(2) Were not previously known to exist on the surface and within the limits of your tunnel.

(b) Your site is protected from other parties making locations of lodes within the sidelines of the tunnel and within the 3,000-foot length of the tunnel, unless such lodes appear upon the surface or were previously known to exist.

(c) You must diligently work on the tunnel site. If you cease working on it for more than 6 consecutive months, you will lose your right to possess all unknown, undiscovered veins, lodes, or ledges that your tunnel may intersect.

(a) Even if you have located the tunnel site, you must separately locate a lode claim to acquire the possessory right to a blind vein, lode, or ledge you have discovered within the boundaries of the tunnel site sidelines.

(b) The date of location of your lode claim is retroactive to the date of location of your tunnel site.