Select a page

Ground investigations gather key data for efficient project designs. It’s all about cutting costs without cutting corners, says Giannis Kallika.

Major real estate investments are today subject to considerably stricter financial scrutiny than ever. Project stakeholders, in some cases independently from other project partners, increasingly focus on analyses and studies that assess value and risk, as much as potential financial returns. And with the banking system demanding readily-liquid collateral for loans, and in some cases bankable cost-overrun guarantees, the financing of real estate development is becoming increasingly demanding.
In this challenging environment, investors have little option but to look for ways to cut costs to drive improved returns. With pre-construction costs being of particular consideration, as they are typically financed from equity rather than debt finance, minimising the extent of any ground investigation (GI) is something that typically comes under pressure. Developers considering such an approach should, however, think again.

From the top

As opposed to structural engineers, who identify the layout of buildings and the type of materials used to provide the overall structural integrity of a building, geotechnical engineers determine the condition of natural rather than fabricated structures, and their influence on the overall structural integrity of a building.
GI involves gathering data such as geotechnical parameters and groundwater levels, enabling engineers to make more efficient, effective design decisions for aspects such as slope stability, foundations, retaining walls and excavations. It is crucial in providing the right data to deliver reliable, efficient designs.

Multifaceted role

A well-considered GI can be cost-effective in the early stages of a development. Some developers are often wary of the number of boreholes required when designing projects. Used to collect samples that shed light on the chemical composition of the soil, they are crucial; sulphates and acids from the soil and groundwater can attack and damage concrete and have serious effects on structures. However, they are also costly. A good geotechnical engineer delivering a quality GI can keep these instances to a minimum.
A detailed GI also provides the necessary data that enables geotechnical engineers to develop an optimum design, which can reduce programme, drive better financial returns and allow risk to be managed more proactively. Recent developments now allow importing GI data into 3D models, reaping the benefits of Building Information Modelling for complex multi-phased projects by allowing the development of a single model containing all available data — from soil data to the lightning rod.
Another area where GI can play a pivotal role is at the optioneering stage of the development. This technique assesses alternative design options, analysing their long-term capital and operational costs to identify those with the lowest price tag over a project’s lifecycle. For example, in retaining wall design, an engineer can choose from a simple and cheap solution such as a sheet pile or gabion wall, to an expensive and complex solution such as gravity wall. The right data enables an engineer to deliver the optimum solution, considering all key factors.
A detailed GI can also protect clients and contractors in cases where anticipated soil conditions vary from the actual site conditions. For example, during the excavation for the construction of deep basements, the contractor can raise a claim for more money stating that the ground conditions were not those anticipated. The results of the GI can work in favour of the defendant since they can prove that a skilled contractor should have had expected those conditions. This is a great example of the benefit of having a comprehensive GI when dealing with claims on unexpected ground conditions.

Put into numbers

Having sufficient data from the GI enables geotechnical engineers to select the most appropriate parameters, such as an average value for soil strength rather than a conservative one (see Figure A and B). With more data comes higher confidence in the selected value, but engineering knowledge and experience remains essential.
A report commissioned by the UK’s Institute of Civil Engineering claims that the average cost of a site investigation is approximately 0.21 per cent of project cost. For larger schemes, the final cost of construction was on average 17 per cent greater than the tendered sum due to inadequate ground investigation or the poor interpretation of results. Though achieving best value remains at the heart of successful property investment, the thoughtless minimising of cost seldom reaps long-term rewards.

An absolute necessity

GI plays a vital role during the design and construction of commercial projects, and the need to invest well and early is paramount. Cutting corners limits the amount of data available to geotechnical engineers, a strategy that seldom drives best-in-class solutions, or improves long-term investment returns.
And while the aim of scaling back on GI may be to cut initial costs, in the long term it can end up costing much more — both contractually and commercially. A thorough GI typically repays on any investment many times over, manages risk and delivers better projects. Rather than a choice, performing a thorough GI is an absolute necessity.