Leaky tunnel argument

Further to Councillor William Walker's article (12 November), I wish to add to the responding letters (14 November) by pointing out further inaccuracies.

The cost of adding a heavy rail crossing to the bridge option "could possibly double its cost" was the initial thoughts of the Transport Scotland reports, not increase it "by at least two times", as his article states.

It is interesting to note that he doesn't speculate on the likely increased cost of making the tunnel multi-modal. This would double the excavation process in the river and on land and would increase the riskiest parts of the whole project.

The exposure to ground risk and environmental risks would double with his proposal, making the delivery of the crossing in time even more unlikely. This is far more costly to our economy than any increase in concrete or steel quantities.

I dispute his assertion that there is a groundswell of public opinion for an immersed tube tunnel (ITT). There may be support in some areas but this is fed by partial information from interested parties. There has been a huge swell of opinion in favour of a bridge based on our efforts and common sense.

He talks about the oldest ITT approaching 100 years old. In fact it opened in 1928, which would make it approaching 80 years. It closed in 2000 for strengthening works and remained partially closed for three years, and it is only about 300 metres long. It also flooded due to a burst water main on the same day Cllr Walker's article was published; it closed for a day and will remain partially closed for five more - proof perhaps that a higher power is supportive of a bridge?

ALASDAIR MacKERRON, STAYonFORTH, Brucehaven Crescent, Limekilns, Fife