California Code, Public Resources Code - PRC § 8623

The trustee shall make all reasonable attempts to acquire the mineral and other subsurface rights in any acquisition pursuant to this division.  In the event the trustee is unable to acquire the mineral and other subsurface rights, the trustee may purchase the parcel subject to the reserved subsurface rights upon the trustee expressly finding that:  (1) a reasonable attempt has been made to acquire the subsurface rights without success, (2) it is unlikely that the subsurface rights can be acquired within the provisions of this division, (3) the outstanding subsurface rights are not likely to unreasonably damage or interfere with the contemplated public trust uses for the parcel, and (4) the public benefits to be derived from acquisition are so substantial that acquisition of the parcel without the subsurface rights is in the best interests of the state for the public purposes set forth in this division.