One Nine Elms
Hi All, It’s a long one with few pictures, but interesting……. I think.
A recent series of events on One Nine Elms has left me wondering why project managers get paid ‘the big bucks’.
A new project manager has recently started in the project team, he previously worked on the project for McGees before joining Multiplex about 2 years ago. As such he has a good understanding of the project with exception of the sewer complications. Anyway he has arrived to impress the two project directors, with his current mantra being progress at all costs, which has potentially had some significant cost implications for Multiplex.
The diaphragm wall has been constructed under a design and build contract by Balfour Beatty Ground Engineer (BBGE), who Is contracted directly to the client. The first main contractor, CI- ONE, had a traditional bottom up sequence with props below or above the permanent basement slabs. This is what the wall was originally designed and partly constructed for. Balfour Beatty then became the main contractor (on a PCSA), and they changed the methodology to top down. This different sequence was re-checked against the as built wall, with BBGE confirming the design was sufficient. When Balfour Beatty and the client were unable to agree on cost and programme, Multiplex won the subsequent re-tender on a semi-top methodology which I have mentioned in a previous blog. Crucially as MPX did not signed the head contract until July and potentially not doing an in depth review of the project risks, they recommended to the client that the new sequence be checked again, instead of spending the c£40k themselves. As a result this check only started about 6 weeks ago despite Multiplex starting on site in January.
In the meantime, Multiplex have tendered, appointed and started on site the basement box subcontractor. As a result there is significant pressure to justify the subcontractors preliminaries and see some progress, i.e. Excavation to B1 formation. Armed with the fact that AKT (structural designers) had conducted a study confirming the D Wall could cantilever from B1, the new project manager actively encouraged the basement package manager to commence excavation. At this point both the project engineer and I advised that this was unwise, BBGE had not yet ‘approved’ the new sequence and there was no deflection monitoring in place. The Project and Package Manager came back with AKT have approved the sequence and an interim monitoring package has been signed with ITM. When I said that BBGE will not give warranty on their work (c£35M) if excavation commences without the approval of the sequence, I was told not to worry about the contractual stuff.
The week before the excavation started, BBGE returned the calculations for section of Wall where excavation was planned to start. The calculations showed the wall was acceptable under ULS but not SLS. The retained soil has high sulphate content, therefore the concrete exposure class is XC3, which has a. crack width limit of 0.3mm. The new sequence SLS moments cause cracks which exceeded this (theoretically), therefore the new sequence is not acceptable to BBGE. This was known before excavation and a number of things are currently being looked at to get this cracking issue to be acceptable. Interestingly during the first sequence change, BBGE could not get the deflections within limits in their WALLAP calculations. As a result AKT modelled the basement in 3D FE and have taken responsibility for deflections, slightly worryingly BBGE deflections are an order of magnitude higher.
Despite this excavation commenced, with active encouragement from the project manager and construction director. With this in mind, the last thing you would want is a poor monitoring package. By chance I was asked to chair ITMs (monitoring company) pre-start meeting on behalf of the package manager, who had effectively tendered the package. It quickly became apparent that the inclinometers are not fit for purpose. They only went to B2 formation level where there would still be significant movement. This means the head of the inclinometer would need surveying manually in order to provide a reference point to baseline the inclinometer, not good for an automatic system to rely on the manual input of data to work. Furthermore it would appear that this manual reading had only been bought to be conducted once a week.
So, Multiplex have basically started excavation without approval from the designer and without any deflection monitoring in place. Low and behold, the client receives a letter from BBGE, informing them that they cannot offer warranties on their works because Multiplex have excavated not to the approved sequence and with no monitoring. The project manager and construction direction then hit the roof and basically blame the package manager, conveniently forgetting their encouragement to start excavation.
The result of this is not yet known. The two individuals had been given sound advice which they chose to ignore, they then tried to blame everyone but themselves. Poor management, decision making and leadership from individuals paid a lot to do this well.
Fellow Multiplexers don’t show this to anyone in the company.
Holdfast Training Services Trial Blog 
Hmm. Looks like even more fun to come then. They’ll pay the price for jumping the gun and now throw away the time gained, which they’ll have to pay for anyway, whilst trying to negotiate a way forward. Not sure I fully understand the diagram; figures in green boxes don’t seem to relate to dimensions on the section, is this the AKT BBGE comparison? Presumably the floating datum at B2 is tied back in by total station measurement on the wall face. Possible a good thing if this gives at least one guaranteed fixed point. I’d be loath to accept a deeper inclinometer as a reference given the variation in predictions of movement you have.
Hi Rich, my placement so far has been ‘fun’ this example is typical. The green boxes are horizontal movement of the inclinometer with the section of the perm structure. We have manual monitoring as a back up, but the required frequency and duration results in a more expensive monitoring package. The different colour lines at AKT estimations at different stages of the excavation.
Good post mate. Something similar happened here where concrete was ‘horsed in’ despite a dewatering problem. The proposed remedial works are still at the option stage 5 months later! ‘Progress at all costs’ seems to be a constant lure rather than appreciating the engineering required.