The last time I went to the Glow Worm tunnel was pre 1975 on a trail bike and although the road was rough, you could drive a vehicle to within 200 metres of the Glow Worm tunnel mouth but it was easy to ride my trail bike into the tunnel and through to the Wolgan end where I remember seeing what could only be described as a 'I aint crossing THAT' timber structure over a gully.
I wanted to go thru but as I was on my own I wasnt leaving the bike there while I ventured on so I turned back.
I think it wasnt too long after that the big storm washed away the road and near closing the tunnel to even foot access.
If you could call what I saw a bridge, it no doubt disappeared by either age, flood or fire but I regret not crossing it as I believe had I gone on, I would have been able to see out over the Wolgan Valley from the old line.
That picture beginning the thread looks like it was intended to carry pipes across and as suggested, from the works to the big tanks that were not far from the Newnes Junction station on the main line.
Being a pipe line it could follow a more direct route than the railway had to and made a much smaller 'footprint' than the line needed.