it's the quality of the time you spend with your dog that counts, not the quantity.
Not as far as your dog is concerned - all time you spend with, near, or around a dog is quality time as far as the dog is concerned.
It bothers me when people use the behaviour of others to justify how they treat animals - as if the treatment of animals in Ireland is somehow 'the norm' - Ireland has in general an appalling attitude to animal welfare, on a par with many third world cultures.
most people leave their dogs at home during the day. We leave ours from 8am till 6pm - with a quick call at lunch time - and I know I'm not cruel. Some people mistake dogs as little people and they're not I'm afraid - as much as we think they are sometimes! They are more than capable of being left on their own for short periods.
Sorry, but how exactly did anyone infer that I was accusing anyone of being cruel? I simply suggested, as others have, that it sounds as if your dog is bored - collies in particular are intelligent, active dogs, requiring a lot of mental and physical stimulation, on a constant, ongoing basis.
Believe me, I am not mistaking dogs for little people - nor however, am I mistaking them for inanimate 'lifestyle' accessories, which is what you seem to be doing. A period of 9-5 being left alone, with a couple of hours interaction, then being left outside alone all night, is not sufficient for a young dog, no matter what you think 'most people' deem acceptable.
If you follow others' advice here and contact a dog trainer/behaviourist, or any animal welfare organisation, they will tell you as much.
If digging is to relieve boredom then he is no longer bored when he digs.
Digging is likely a manifestation of his boredom, not a bloody cure for it. Dogs and in fact most other pets can manifest boredom in many ways, including far more destructive ways than digging i.e. self mutilation through biting, excessive, obsessive grooming, feather pulling etc. When animals do these things, it is not a cure for boredom!
I don't mean to get at you, and am certainly not attacking you - I simply suggested that it could be boredom, and suggested one way to help both you and your dog. Others have suggested other ways, so check them all out.