Holdfast Training Services Trial Blog

I have been rather quiet as I realised that all I seemed to be writing about was what size cast iron pipe we unexpectedly uncovered on our drainage run and what was going on with the latest in the HV cable installation saga.  Well nothing has changed there we are on big old cast iron pipe number 6 in the last 10m of drainage, the client are getting excited about us damaging the HV cables and we are now extended the HV sub station slab because they put the wrong size GRP housing on top of it.

At the end of last week we had a team meeting to discuss roles and responsibilities as the Project Director has realised that they may have scrimped too much on construction management staff.  We have no resident temporary works engineer or quality assurance person and these are the areas that the project are crashing and burning.  At the start of the week I was looking at a promotion to being the resident engineer of the block G construction-think Ex COFFERDAM but 40m wide and 100m long with 2 stages of propping!  In the initial meeting I pointed out that they might want to consider the detail of the connection of the waler to the sheet piling as they were suggesting a 1m gap to allow the construction of columns.  They said not to worry about it as they would use wedges, until I pointed out that wedges spanning 1m taking vertical components of the forces probably wouldn’t work!  So they went back to the drawing board and asked to move the columns in a bit!

OIC Power and Drains again!  But this is taking an interesting step as we are planning our pipe jacking exercise to tunnel under Battersea Park Road.  In a nutshell the masterplan is to build a cofferdam to launch the pipe jacking machinery to cut a 70m tunnel approx 5m BGL to meet with an existing sewer on the other side of Battersea Park Road. watering scheme.

Pipe jacking launch shaft in top left corner tunnelling 68m with the final 30m under a raised section of the Battersea Park Road bridge: and a typical pipe jacking launch shaft:

General works:

The main issue is one of John’s favourites: GROUNDWATER!  In the foul drainage run we have had to sump pump a considerable amount of water flowing through the Terrace Gravels, which is also slightly tidal as we are about 300m away from the river.

The plan is to control the groundwater with a de-watering system:

Likely issues:

-Proximity and state of dilapidation of the Battersea Park Road Bridge.

-Proximity of Network Rail lines.

-Risk of settlement of bridge foundations.

-Risk of encountering unknown services or obstructions.

-BOUNDARIES/PROPERTIES-although we can’t be tunnelling through much worse than the gravels which will be pouring water in!  Unless we hit an old brick pile or more of the old gas works infrastructure.

-GROUNDWATER-we are pretty much in the worst case scenario.

-CONTAMINATION-So far we have been OK with de-watering around the site so fingers crossed it can just go down the foul sewer.

Without looking at my notes they were the main points I remember from John banging his hand against the wall!  No doubt I will have more to write on this over the next few weeks.

On a plus point I held a Colossal Cake Sale for Help for Heroes in the canteen and we made £220.  I mentioned to our Environment/Schools/PR person that I could come in uniform and she held me to that offer.  The problem was mine was all in the attic in Poole.  So after a quick cycle to a friend’s house 5 miles away I squeezed myself into an ex-Army Air Corps Adjutant’s tailored(!) green kit to sell our cakes for an hour.  I was overwhelmed by the generosity of some of the guys on site and the support from both the managerial staff and groundworkers.  Not a bad outcome for a couple of hours work.