The Binnian Tunnel was constructed to divert the waters from the Annalong Valley to the Silent Valley reservoir. It was completed in the early 1950’s and the story of this achievement of blasting and digging a tunnel two and a half miles long, under Slieve Binnian, can be found here. The tunnel was started from both ends, the two teams meeting in the middle with inch accuracy, using candles to establish the line of the bore.
The coordinates shown are those of a suitable parking spot at the entrance gates to Dunnywater. There is normally ample parking here unless the local ramblers have chosen this as their portal to the Mournes for that day, in which case you will have to abandon your car some distance away and walk back. During July and August a Mourne Rambler bus circles the Mournes every hour, with the last bus leaving Newcastle at 5.00pm. Its route passes this point. If you buy a day ticket (for about £4) you can jump on and off all day picking up other caches scattered around the Mournes.
The pedestrian’s gate is four feet wide with a four inch step, which I hope is navigable by wheelchair users. Any feedback on this would be welcomed. From there you are on a paved road all the way for a 3.2 miles round trip, with only moderate inclines. There is another gate a short distance along the road with a sign purporting to deny public access. It is indeed within the powers of the water service to deny access from this direction but this right is seldom, if ever, exercised.
There used to be three parts to this cache, all of which lie along this service road for the tunnel. Unfortunately a recent storm (2022) has removed the first of these waypoints by bringing down the tree containing the micro cache. In order to preserve the rest of the experience I have supplied, below, the information that would have been found at Waypoint 1
Waypoint 1 N54 08.421 W005 56.223
This is a micro cache. Collect the coordinate slip from here. The forking tree no longer stands. The coordinate slip stated
W005 56.750
You will need this information for the final part of the cache.
Waypoint 2 N54 08.974 W005 56.862
Look for the foot high numbers close by. ABCD
Waypoint 3 ?
Add together the numbers from (2) A+B+C+D . Add this number to the coordinate from (1) to give you the position of the final cache. Unfortunately my GPSr was on the blink that day 
and only gave out westings for the final position so you won’t be able to follow your arrow to the cache site.
The cache is a lock-tab box wrapped in a black cover sheet. Please hide it back carefully from prying eyes!
In his youth my brother, Bill, had walked the tunnel. More recently, after an abortive attempt on the Mourne Wall which failed on Slieve Binnian, he sent me this poem –
Binian
I’ve been over and under this Mountain,
Back in my warm summered youth,
But now one thing is certain –
It’s harder (to tell you the truth).
Here in the rain
It’s hard to explain.
But today I can’t crack it.
The poor legs won’t hack it.
I’m going back for a Gin & Vermouth.
Any similar contributions will be welcomed!
There are several spellings for Binnian. Also Binian, Bignian and, on one local school, Bingian.