An underground utility enclosure assembly adapted for making remote fiber optic cable splices, the utility enclosure assembly comprising: a grade level box, a removable cover plate on the box, a section of the cover plate including a plug opening adapted to receive a removable plug for forming a section of a traction surface atop the box, and a sealed fiber distribution enclosure unit removably mounted in the plug opening and extending in an upright position above the cover plate, the sealed fiber distribution enclosure unit including: a base frame assembly having; a lower base frame section thereof which has bendable clips (46, 48) and is adapted to be removably disposed in the plug opening by snap-locking said bendable clips therein, and including a cable opening therein providing a passageway from the grade level box, an above-ground lower base structure (54, 62) rigidly affixed to the lower base frame section and including a lower base ring and a base plate, the base plate affixed to an upper portion of the lower base ring and spaced above the cable opening, the base plate separating the interior of the unit sealed fiber enclosure unit from the interior of the ground level box and having sealed holes for passing cables through, the sealed fiber distribution enclosure unit further including a fiber distribution enclosure assembly mounted to the lower base structure, the lower base structure providing sealed passage of fiber optic utility cables passing from the grade level box through the cable opening into the fiber distribution enclosure assembly via the sealed holes, wherein the fiber distribution assembly includes a moulded plastic socket affixed to the base plate which supports an upright rigid support bar, a back plate affixed to the support bar and a plurality of fiber splice trays mounted to the back plate; the sealed fiber distribution enclosure unit removable as a unit from the plug opening, with active cables undisturbed, to facilitate transporting the fiber distribution enclosure assembly thereof to a remote work site for use in making fiber splice connections to fiber optic cables passing from the grade level box through the lower base structure into the fiber distribution enclosure assembly, the sealed fiber distribution enclosure unit adapted to be transported away from the work site as a unit, with active cables undisturbed, and the lower base frame section thereof removably secured in the plug opening. a grade level box, a removable cover plate on the box, a section of the cover plate including a plug opening adapted to receive a removable plug for forming a section of a traction surface atop the box, and a sealed fiber distribution enclosure unit removably mounted in the plug opening and extending in an upright position above the cover plate, the sealed fiber distribution enclosure unit including: a base frame assembly having; a lower base frame section thereof which has bendable clips (46, 48) and is adapted to be removably disposed in the plug opening by snap-locking said bendable clips therein, and including a cable opening therein providing a passageway from the grade level box, an above-ground lower base structure (54, 62) rigidly affixed to the lower base frame section and including a lower base ring and a base plate, the base plate affixed to an upper portion of the lower base ring and spaced above the cable opening, the base plate separating the interior of the unit sealed fiber enclosure unit from the interior of the ground level box and having sealed holes for passing cables through, the sealed fiber distribution enclosure unit further including a fiber distribution enclosure assembly mounted to the lower base structure, the lower base structure providing sealed passage of fiber optic utility cables passing from the grade level box through the cable opening into the fiber distribution enclosure assembly via the sealed holes, wherein the fiber distribution assembly includes a moulded plastic socket affixed to the base plate which supports an upright rigid support bar, a back plate affixed to the support bar and a plurality of fiber splice trays mounted to the back plate; the sealed fiber distribution enclosure unit removable as a unit from the plug opening, with active cables undisturbed, to facilitate transporting the fiber distribution enclosure assembly thereof to a remote work site for use in making fiber splice connections to fiber optic cables passing from the grade level box through the lower base structure into the fiber distribution enclosure assembly, the sealed fiber distribution enclosure unit adapted to be transported away from the work site as a unit, with active cables undisturbed, and the lower base frame section thereof removably secured in the plug opening.