The "sump" reported in Northern Caves Vol. 1, p. 29 is merely a shallow silt-floored pool with no way on underwater.
The sump was inspected with a face mask; a squeeze leading down to a short stretch of horizontal passage was all that could be seen. With the aid of a hand-held 15 cu. ft. bottle the squeeze was passed, but finding nowhere to put his feet and the visibility dropping to zero, the diver assumed he had reached the end. From the feel of it, it closes.