Section 7. All piers and other similar structures in Boston harbor built by the department or its predecessors shall be equipped, either by the department or by the lessees thereof, with fireproof sheds, railway tracks, cranes and other machinery and accommodations for the convenient, economical and speedy loading and discharge of freight; and the department may acquire, hold and operate such lighters and other vessels as it deems convenient and needed therefor. The department shall make such reasonable rules and regulations and charge such reasonable rates for the use of such structures and equipment as it may from time to time deem wise.