Prospecting and exploration for and the development and utilization of mineral resources authorized in this chapter shall be entered into or continued at the financial risk of the individual party or parties undertaking such work: Provided, That the United States, its permittees and licensees shall not be responsible or held liable or incur any liability for the damage, destruction, or loss of any mining claim, mill site, facility installed or erected, income, or other property or investments resulting from the actual use of such lands or portions thereof for power development at any time where such power development is made by or under the authority of the United States, except where such damage, destruction, or loss results from the negligence of the United States, its permittees and licensees.

The owner of any unpatented mining claim located on land described in section 621 of this title shall file for record in the United States district land office of the land district in which the claim is situated (1) within one year after August 11, 1955, as to any or all locations heretofore made, or within sixty days of location as to locations hereafter made, a copy of the notice of location of the claim; (2) within sixty days after the expiration of any annual assessment year, a statement as to the assessment work done or improvements made during the previous assessment year.

Nothing in this chapter contained shall be construed to limit or restrict the rights of the owner or owners of any valid mining claim located prior to the date of withdrawal or reservation: Provided, That nothing in this chapter shall be construed to limit or restrict the rights of the owner or owners of any mining claim who are diligently working to make a discovery of valuable minerals at the time any future withdrawal or reservation for power development is made.

Notwithstanding any other provisions of this chapter, all mining claims and mill sites or mineral rights located under the terms of this chapter or otherwise contained on the public lands as described in section 621 of this title shall be used only for the purposes specified in section 621 of this title and no facility or activity shall be erected or conducted thereon for other purposes.