Holdfast Training Services Trial Blog

Site Two Fifty One – Environmental Problems

During the removal of spoil from Two Fifty One to enable the installation the Groundforce props some of the lorries of muck were rejected from the tip because they smelt of diesel. I had no record of a diesel spillage on site so it all seemed strange. The loads had to be returned to site because the tip was refusing to take them and the carrier (Erith) were not able to dispose of them. Typically as the excavation progresses it becomes harder to separate/segregate anything. Therefore having excavated material returned to site is somewhat of a problem.

Contaminated material being stored left of the ramp access into site.

On further inspection of the area the muck was being excavated from it was identified that some of the sand and gravels had turned grey. I.e. it contains diesel.

The photos show the grey streak in the sand and gravel showing the diesel contaminated ground.

Aside from the fact that the majority of the area had been excavated and loaded onto tippers (albeit to then be returned to site) it was clear where some of the more affected areas were which should help reduce the spread of contamination.

So what? 

The extent of the problem is just getting started (no environmental agency involvement yet) and as it has happened and now stopped, typical actions – such as using a spill kit/isolating the source are redundant. Therefore I have highlighted some of the post incident considerations we are currently going through.

1. Stop sending muck away from the site (significant impact on programme as the key task is to remove muck at this stage).
2. Identify what the contamination is. Initially, this will be done by using a Photo Ionization Device – this gives a rough and ready level of volatile organic compounds in the sample. Below 50 parts per million is apparently acceptable. You don’t need much diesel to make things smell of diesel so I am hoping that is the case…
3. Record/report the incident, brief the site team on the importance of reporting spillages.
4. Once we know the extent and type of the contamination the loads can be removed. Worst case the muck will be removed as hazardous waste at £1700 per load which comes with permits to move hazardous material. We are paying about £200 at present so that would have significant commercial implications!
5. Attempt to keep to schedule with a mini-mount Everest forming in the corner of the site!

More widely here is a brief update on drainage and reinforcement installation.

Drainage.

We have just started to install below ground drainage in the Basement Level 2 raft slab. We are using the Saint Gobain timesaver inspection chambers and Ensign pipes. For future reference, Ensign is a significantly lighter product, more easily moved/handled and costs much less (we have made a circa £30K saving by requesting to use the lighter system).

The drainage is being installed within the area between the bottom and top mats of reinforcement.

What I wish I’d known:

1. Testing methods – something about bungs, and air bags. More to follow when I understand what that is.
2. That a foul gully run cannot rapidly change gradient in a run because the solids will separate out.

Basement Raft.

The 2.1m deep raft foundation is currently being constructed. It is quite an impressive site seeing 40mm, 12m long bars being positioned by hand.

Raft bottom mat reinforcement being installed.

The original aim was to use Pecafil formwork (permanent sheeting) for the concrete pour. Due to the number of piles this is proving a little more complex. As the ground is excavated, pile reinforcement acts a bit like dragons teeth preventing easy access to return to backfill around the raft. The plan is continuing with the idea to use a small dumper to move material back into position, rather than switching to the use of shuttering. Again, more to follow on the success of this plan!

A final thought:

There is a slab (450mm) which will be poured across the site, including on top of the raft making a total of a 2.1m deep foundation.

There is a bottom mat to fix in the raft and a top mat to fix in the slab.

Would you, a) fix the bottom mat, pour the concrete raft then fix the top mat and pour the slab? Or, b) fix bottom and top mat, then pour raft, then pour slab (i.e. do pours with all steel fixed)?

Raft foundation comprised of 450mm slab and 1650mm raft.

In should come as no shock to anybody that water in is pretty expensive in South Australia, costing in the region of $3.32 per kl. The   project received its first bill this month (don’t ask me why it has taken this long to get here) that covered the start of the project Dec – Apr which was quickly followed by a second covering May – Jul, with the total over $350,000. The cost arose from the fact that water was required almost 24hrs during the summer months for dust suppression during the bulk earth works. Surprisingly this cost was not captured in the budget for the project and was excluded from contract with the subcontractor responsible for the earth works, so it will eat in to the profit for the job.

From this episode the project team were tasked with carrying out a review of the budget to identify any other holes and quite a few were identified. The main one sticks with the water theme as it became apparent that the cost of filling the various systems on the site (in the region of 30Ml) with demineralised water had not been accounted for. The options for supplying this were limited, using the reverse osmosis plant at the local power station or getting in portable reverse osmosis plant to site to produce our own. The power station was discounted because in order to fill the tanks on site we would need to fill the 5km worth of pipe to get it here and find a method of pumping it. The current plan is to use a subcontractor to bring in temporary plant to produce it on site. This is producing a number of issues in itself, the main one is trying to find a subcontractor with the capability to do this, we are currently looking at GE supplying the equipment and another subcontractor to install and operate. Further issues we will need to work out on site include finding space for the plant, power and water to operate the plant and a method of discharging the brine, all of which the project will have in the future but not necessarily in time.

No one is sure what this is going to cost but best estimates coming from our procurement team at the moment are around $500,000, plus the cost of the feedwater approximately $100,000. This is likely to fall to John Holland, as the head contractor we are ultimately responsible for commissioning the plant (although no doubt we will try and push some of the cost back to the client).

Looking for causes as to how this could have been missed I think it’s quite simple, in the rush to get shovels into the ground after signing the contract a draft program was produced, with no product or work breakdown conducted to back it up. As the project progressed no one has had the time revisit the program so it has just been updated where necessary, which is fine for sequencing works, but doesn’t identify items that are missing altogether. In their defence I know at the time the project team was pretty limited and they were under immense pressure to get the project started.

The picture below is just to attract some attention to this blog, it shows the planned lifting strategy for the 115m high tower, hopefully before I leave site in November.