Section 13. The department may license any person to construct and maintain booms in or across the Connecticut river, for periods of not more than five years, in such locations and upon such terms as it prescribes, or to build and extend a wharf, pier or shore wall below high water mark in said river, or to build or extend a wharf, pier, dam, wall, road, bridge or other structure, or to drive piles, fill land or excavate in or over the waters of any great pond below natural high water mark, or at or upon any outlet thereof, upon such terms as the department prescribes; but such license shall not validate acts beyond the line of riparian ownership or affecting the level of the waters in such pond, unless approved by the governor and council.