Regarding the concreting and sealing of the second entrance, here is a jolly account of the fun that was had by those involved (OUCC Depth Through Thought 9.14 16/6/99):
Chelsea Flower Show
On Sunday morning a select handful of landscape gardening enthusiasts assembled on the slopes of Pwll Du to seal the second entrance of Ogof Draenen. The Ground Force crew comprised Ali, Ben, a new MCC recruit, Ian W-J, and muggins here. The main problem was that the entire slope was becoming eroded. Most of the day was spent building a series of grassed terraces, graced with a ring of small hawthorn trees. In a few years, and providing it is undisturbed, it should make a fine shrubbery. One side of the shaft was also collapsing, and this was filled with some rolled up wire fencing and capped with rocks and turf. Making the entire shaft safe would have been quite an undertaking, which we were too undermanned to attempt.
The sealing of the man hole cover, which had been agreed at the last PDCMG meeting, did not take long. A layer of grease on the cover was removed, a new lock was placed, and the recess containing the door was filled with cement, leaving a hole for bats. The entire area was then turfed over.
Of course this work will be very easy to vandalise. The unstable nature of the slope means that anyone with a little determination could break into this entrance again. I hope no-one does.
Chris 'tropical fruit all round' Densham
In reply to Mel's last post:
There is indeed a locked gate as well, it is beneath the concrete and the turf. It is claimed that, in the event of a serious rescue, this entrance could be easily opened up to extract a casualty. Ali Garmin emphasised this at the latest PDCMG meeting, using it as yet another reason why Drws Cefn should not remain accessible to cavers.
Footnote:
For those who might be unaware of the past sequence of events, it could be worth pointing out that the second entrance was opened up by members of CSS, hence the title of the OUCC report.