Is it Feasible?
Since I wrote the stuff below, RBC have prepared a report for Councillors, to inform their decision-making.
It makes clear that the tunnel at Pooley Green is entirely feasible, and that it could be built if funds were available. It would “necessitate the removal of one residential property” and affect access to some others.

Our reply to a Resident who wonders if what we are asking for is possible
I am a resident in Egham and have been forwarded your internet link to object to the proposal.

I have read your example letters and whilst, without doubt I support the reasons for objecting this, I need to understand the logistics of suggesting a tunnel/bridge before suggesting this in any letter I write.

Is a bridge/tunnel really possible? I cannot see how it can be either on Pooley Green road or certainly next to Egham station. My concern is that any objections could be weakened if the suggestions within them are not considered a prudent alternative.

Can you provide me with any further info

Answer:
The answer is that Egham Chamber of Commerce does not know if a tunnel or bridge are feasible, or can be built for a reasonable cost. We are concerned that if we don’t get either, this town will die. The time it will take to get across the line, the high probability of being stuck for 20 or 30 minutes in a queue, and then being stuck again going home, will deter people who have the choice from heading towards the town centre, Those who don’t have the choice will sit in queues which will feed back through all the local roads, reducing the entire town centre to permanent gridlock and deter people who don’t need to cross the line from using the town.
People in Egham Hythe will have no choice: a look at the map on page 33 of Airtrack’s own environmental statement will show how limited the options are for residents of Egham Hythe: there are only two routes in or out that don’t use level crossings and one of those is acknowledged to be unsuitable for heavy traffic. In Airtrack’s words, Egham Hythe is an island, and it is an island with a population of 6,000 who did not elect to live cut off from the world.

Alternatives
So alternatives to the level crossings are necessary. It has been accepted for many years that the level crossings are a problem, and that Airtrack would make it worse. We have been asking about the practicality of a bridge or tunnel at Pooley Green, at various meetings with senior officers at the Borough Council, since about 2004.

Runnymede Borough Council
Despite this, no one at Runnymede Borough Council, (who have no highways responsibility but are responsible for the residents of Egham Town and Egham Hythe), no one at Surrey County Council (who are the Highways authority), no one at Network Rail, no one at the Department for Transport, no one at Airtrack, or BAA, had done any work at all on finding out whether a bridge or tunnel would be feasible. It was merely assumed to be so technically difficult that it was not worth investigating.

October consultation
As far as we can ascertain, the statement in Airtrack’s October consultation document, the bridges or tunnels were not feasible, does not appear to have any actual measurements or calculations to substantiate it. There were, apparently, some back-of-an-envelope calculations and that was it.

Responsibility of our local authorities
The Chamber does not feel that is is our responsibility to carry out a technical assessments, and more to the point, since we did look into it, we don’t have £50,000 (or £100,000) to pay for one. That is the responsibility of our local authorities, Network Rail, and of those private sector organisations who wish to profit from the extra services on these lines.
What we are clear about is that nothing is impossible, it will merely be difficult and probably expensive, and without a great head of public pressure, there is no chance of us getting this disaster averted. So I do hope you will add your voice to the pressure, and if you feel that another solution is viable, that you will nonetheless write and make clear that doing nothing about Egham is not an option.” And I quite forgot to add, actually, now that the technical people have started looking at it, it does seem that there is quite a lot to look at: they have definitely got past “impossible”.