(35) Essential Services: The erection, construction, alteration or maintenance by a public utility, or municipal department or commission of underground surface or overhead gas, electrical, steam or water transmission or distribution systems, collection, communication, supply or disposal systems, including mains, drains, sewers, pipes, conduits, wires, cables, fire alarm boxes, traffic signals, hydrants, towers, poles, and other similar equipment and accessories reasonably in connection therewith, for the furnishing of adequate services by such public utility or municipal department or commission or for the public health or general welfare, but not including buildings other than such buildings as are primarily enclosures or shelters of the above essential service equipment.