There is a commemorative plaque in the Portal next to the road, and a video can be found at..
http://www.bbc.co.uk/news/uk-22554314
The cache is located near to the parking area where you can get a good photographic view of the dam.
As with everything relating to the RAF, you need to spuce up your act for best results.
Congratulations to Bilkobaggins on his epic cycle ride up the Snake Pass from Glossop, to be the FTF these two caches.