So much land of the State, not exceeding one hundred and fifty acres, as may be needed for the permanent construction of the shore end of the jetties in Charleston Harbor lying on and next adjacent to Morris’ Island and the creeks and marshes contiguous thereto has been granted to the United States for the purpose of the erection and construction of the shore end of such jetties. But nothing contained in such grant shall be construed to impair or affect the rights of any owner or of any private individuals claiming such lands or any part thereof.