Section 1. In this chapter, unless the context otherwise requires, the following words shall have the following meanings:

''Boston harbor'', that part of Boston harbor lying westerly and inside of a line drawn between Point Allerton on the south and the southerly end of Point Shirley on the north.

''Department'', the department of environmental protection; provided, however, that in sections two, two A, three, four, five, six, seven, eight, nine, nine A, ten, eleven, eighteen A, twenty-five, twenty-seven, twenty-nine, twenty-nine A, thirty-one, thirty-two, thirty-three, thirty-six, thirty-seven, thirty-eight, thirty-nine, forty, forty-one, forty-two, forty-three, 43A, 43B, 43C, forty-five, forty-six, forty-seven, forty-eight, forty-nine, forty-nine A and fifty, the word ''Department'' shall mean the department of conservation and recreation.

''Landlocked tidelands'', filled tidelands, which on January 1, 1984 were entirely separated by a public way or interconnected public ways from any flowed tidelands, except for any portion of such filled tidelands that are presently located: (a) within 250 feet of the high water mark of flowed tidelands; or (b) within any designated port area under the Massachusetts coastal zone management program. For the purposes of this definition, a public way may also be a landlocked tideland, except for any portion thereof which is presently within 250 feet of the high water mark of flowed tidelands.

''Structure'' or ''structures'', as used in sections ten, twelve to twenty-two, inclusive, twenty-eight and thirty-four, shall include pipe lines, wires and cables, and all words used in connection with ''structure'' or ''structures'' shall mean and include their appropriate equivalent as applied to pipe lines, wires and cables.

''Tidelands'', present and former submerged lands and tidal flats lying below the mean high water mark.

''Commonwealth tidelands'', tidelands held by the commonwealth in trust for the benefit of the public or held by another party by license or grant of the commonwealth subject to an express or implied condition subsequent that it be used for a public purpose.

''Private tidelands'', tidelands held by a private party subject to an easement of the public for the purposes of navigation and free fishing and fowling and of passing freely over and through the water.

''Secretary,'' the secretary of the executive office of energy and environmental affairs.

''Substantial change in use'', a use for a continuous period of at least one year of ten per cent or more of the surface area of the authorized or licensed premises or structures for a purpose unrelated to the authorized or licensed use or activity.

''Substantial structural alteration'', a change in the dimensions of a principal building or structure which increases by more than ten per cent the height or ground coverage of the building or structure specified in the authorization or license, or an increase by more than ten per cent of the surface area of the fill specified in the authorization or license.

''Water-dependent uses'', those uses and facilities which require direct access to, or location in, marine or tidal waters and which therefore cannot be located inland, including but not limited to: marinas, recreational uses, navigational and commercial fishing and boating facilities, water-based recreational uses, navigation aids, basins, and channels, industrial uses dependent upon waterborne transportation or requiring large volumes of cooling or process water which cannot reasonably be located or operated at an inland site.