|(a) The commissioner may grant easements or leases for commercial and non-commercial improvements constructed on, across, through or under non-tidally influenced state-owned riverbeds and beds of navigable streams in the public domain, for bridges and those structures and purposes specifically enumerated in Texas Natural Resources Code §51.291 and §51.292. (b) The fees for such instruments shall be determined in accordance with §13.17 of this title (relating to Fees for Right-of-Way Easement) and §13.18 of this title (relating to Fees for Surface Leases for Certain Facilities). (c) Certain private, non-commercial improvements and structures which were constructed prior to September 1, 1993, and which are located upon state-owned riverbeds or beds of navigable streams, such as dams, low water crossings, docks, piers, groins, bulkheads, guy and tie-down cables, boat houses or similar structures, are considered properly permitted in accordance with the provisions of Texas Natural Resources Code §51.302(a) without further action on the part of the owner or payment of fee set forth in this chapter. (d) Any modification of the improvements contemplated in subsection (c) of this section made after September 1, 1993 which results in an expansion of the footprint occupied by those improvements upon state land shall automatically void the permit granted by that subsection, requiring the owner or possessor of such facility or structure to obtain from the commissioner an easement, lease, permit or other instrument in accordance with Texas Natural Resources Code Chapters 33 or 51, and may subject the facility or structure to the provisions of Texas Natural Resources Code §51.302 and §51.3021, related to penalties for and the removal of unauthorized structures on state lands. (e) In an action under Texas Natural Resources Code §51.302 or §51.3021, the person who constructs or maintains the structure or facility has the burden of demonstrating that it was constructed prior to September 1, 1993. (f) Nothing contained in this section shall be construed so as to limit the authority of the commissioner contained in Texas Natural Resources Code Chapters 33 or 51.