Holdfast Training Services Trial Blog

I tried to post this before my holiday, but it seems that WordPress and I don’t get on that well so here I go again 4th time lucky!!

Well this is my 3rd attempt at a blog as first my computer turned itself off then the site crashed whilst trying to save my work.  I am off on holiday in 1 hour so I will be quick!

For the last 6 weeks I having been waiting to be able to write a great blog about pipe-jacking under Battersea Park Road with pictures of the launch shaft or some pipes going in.  But alas no, we are now going back to looking at different methods because it is too expensive.  To cut a long story short the client’s representatives (T&T) and client (BPSDC) nearly had a fit when the £75k provisional sum wouldn’t even cover the launch shaft.  Due to the soil type (Terrace Gravels) and water table above the pipe-level, the costs have escalated to £960k!  Cue lots of panic and many meetings questioning how on earth it had become so expensive.  Here’s why:

Due to the likelihood of hitting an obstruction under Battersea Park Road Bridge the open-face pipe-jacking technique was decided using a 1.2m diameter ID pipe allow miners to excavate inside.  Due to the groundwater, this would require de-watering along the full length.  As the bridge covered half of the 75m the de-watering regime would not be able to achieve such a large radius of influence without potentially affecting the railway lines 10m from the pipe.  Therefore resin grouting would be required for the last 35m.  So what was once around £250k for the pipe-jacking alone ballooned to nearly £1m once you looked into the detail design.

Despite my best efforts to explain this with the sub-contractor T&T looked at alternative solutions such as micro-boring and a representative from Barhale came along with his sales pitch.  He tried to say that pipe-jacking with miners over 25m went against HSE guidelines (our H&S person then dispelled this as it is allowed with safe systems of work in place).  He then said that micro-boring would save lots of money as de-watering and resin grouting would not be required.  T&T thought that this was the golden chalice and they put a halt on all pipe-jacking work and made us investigate this more.  Since we had already done this exercise back in March less the pricing side of things it wasn’t too difficult to highlight the constraints for the micro-boring.  The big ones being: if it hits a boulder over 1/3 the size of the pipe, or timber or steel, it gets stuck-a cost of £350-500k and still no pipe under the bridge with no back-up plan.  If that wasn’t enough to put you off then the installation of the reception shaft would need to be in a public cul-de-sac over the trunk main.  Diverting services and digging up the street is also not a cheap option.  A representative from Terra another tunnelling company also came in to explain this and suddenly T&T’s golden chalice turned into a poisoned one (and I refrained from shouting “told you so!!”).   Now we will not get the job done by our deadline of the end of the year when the Northern Line Extension starts at the south of the site in Jan.

So it looks like we will be back to pipe-jacking when they make their mind up this week and I have left the 200 pages of Risk Assessment and Method Statements and temporary works designs with Network Rail for approval.  Now I am off to Turkey kite-surfing for a week so next week should be quite interesting!