Section 14. The department may license and prescribe the terms for the construction or extension of a wharf, pier, dam, sea wall, road, bridge or other structure, or for the filling of land or flats, or the driving of piles in or over tide water below high water mark, but not, except as to a structure authorized by law, beyond any established harbor line, nor, unless with the approval of the governor and council, beyond the line of riparian ownership. A license shall not be granted for the construction of a bridge across a river, cove or inlet, except in a location above a bridge, dam or similar structure authorized by law over such tide water, in which no draw actually exists or is required by law, and not then, if objection is made by the aldermen or selectmen of the town where the bridge is to be built.

The said department may license and prescribe the terms for the construction or extension of a pipe line, conduit or cable under tide water beyond any established harbor line; provided, that such pipe line or conduit is entirely imbedded in the soil and does not in any part occupy, or project into such tide water, and provided also that said department may at any time require any pipe line, conduit or cable to be moved or relocated if channel changes or alterations demand the same.

Except as provided in section eighteen, no structures or fill may be licensed on private tidelands or commonwealth tidelands unless such structures or fill are necessary to accommodate a water dependent use; provided that for commonwealth tidelands said structures or fill shall also serve a proper public purpose and that said purpose shall provide a greater public benefit than public detriment to the rights of the public in said lands.