The Keys to Sustainable Development
Last week Ground & Water Director, Fran Williams took part in a panel discussion at the 2022 London Build Expo entitled ‘Future Proofing Buildings Through Sustainable Design’.
Fran says… The panel was interesting as it involved everyone from ground engineers (us) structural engineers, to transport planners, ecologists and architects.
One of the main points I made was that we [Ground Engineers] can do so much more now, to deliver better results to enable builders to get out the ground. All of which can reduce waste, reduce concrete usage and potentially reduced the use of reinforcement… All of which are sustainable principles.
Doing better with what we already have
Better site investigation and early planning can get you, more out of the ground we stand on. After all, a lot of what you spend on developments is about getting out the ground.
Apparently, we spend around 0.04% of a contract budget on ground investigation. Research suggests that in order to maximise what we get out the ground, we need to be spending more like 1.1%.
Stories sell, so here’s very quick one
Two sites in Hackney, with Made Ground over Hackney Gravels and then London Clay from around 10m bgl to 21m bgl. A paper looked at design lines based on a site which had good quality Undrained Triaxial and SPT data and the other which had a ‘sparsity’ of such data. The costing exercise involved applying the design lines for the good and sparse data to one hundred 450mm diameter piles, looking for a 700kN working load. The depth of pile required to achieve this was 15.8m for one site (good data) and 19.8m for the sparse data. The saving was £18,000 on piling. The uplift in SI costs being nowhere near this.
You must ensure that your ground engineers have the ability to use better data to its full advantage; and thankfully Ground & Water’s engineers can do that.
We can also do better with risk management and design by collaboration
A client wanted to add a third story to an existing two-storey dwelling. Investigation indicated that the load coming down the walls was basically similar to what the load bearing capacity of the soils were, based on a factor of safety of three.
Ground & Water provided analysis that indicated that any increase in load would create a slightly lower factor of safety on the foundations and we also provided our engineering judgement on what the additional settlement would be.
It was then necessary to manage this risk with the structural engineers and client.
We can also get more out the ground, by looking at more sustainable strategies earlier in the design process
A few examples are:
1. Not planning plots directly where an oak tree is on London Clay.
Anticipating the ground conditions and planning a development to utilise the ground’s positives and minimising the negatives must take place. This will future proof developments and make getting out the ground easier.
2. Planning the re-use of foundations – we have re-used piles in London over the last year.
3. Thinking about material management early.
Instead of assuming the material excavated from the ground will be waste, assessing it more as a commodity, through schemes such as the Definition of Waste Code of Practice (DoWCoP) has real benefits.
Do you have sites which need subsoil/general fill and a site which has lots of cut? It just needs some thought and pre-planning. The situation that must be avoided is… Once dug, what do I do with it?
It’s win win
The term ‘sustainable’ in relation to building design can be defined as one that is constantly evolving and has minimal impact on the environment. A closer look suggests a sustainable building is one where the structure and processes are environmentally responsible and resource-efficient throughout the lifecycle of the building.
The key phrase here is resource-efficient. Why…? Because in the long run you will get more out the ground for less cost and for a lower impact on the environment.
A win, win outcome and one that Ground & Water can work with you to achieve. Give us a call and start your journey to more sustainable and profitable developments today.