Introduction

At Roberts Environmental, much of our day-to-day focus is delivering quality risk assessment and management of in-ground hazards. Most often, the focus of REL’s risk management are hazards arising from chemical contamination of soils and groundwater from legacy industrial processes and historical development. This often results in unlocking land for our valued clients, enabling development and satisfying the relevant regulatory and statutory bodies.

Whilst contaminated land hazards often represent the most onerous issues posing as obstacles to development, geo-hazards and the associated Geotechnical implications are often misinterpreted, or not identified at all.

This can be due to a number of issues, sometimes involving a perceived priority around discharging planning conditions, tailoring an investigation to fit a required budget, or a combination of both. Often the geotechnical, built-environment scope items are the first to receive scope cut-backs on a project because of this focus.

On some projects however, geo-hazards are the main source of both risk to human health and the built-environment and is often not suitably investigated when considering ground investigation budgets and appetite for risk reduction. Sometimes, geo-hazards may not be identified sufficiently at desk study stage, leading to a misinformed risk assessment from the outset.

Failing to identify geo-hazards can lead to unforeseen expenditure during the construction phase due to inadequate planning at the design stage. More often that not, spending more on a ground investigation will outweigh the potential financial expenditure of not sufficiently reducing risks.

What are Geo-Hazards?

Geo-hazards relate to a potential source of harm that may originate from the natural world, specifically the ground beneath our feet. Construction related activities are heavily involved with manipulating the ground and can exacerbate existing hazards, or even create new secondary hazards. Examples of geo-hazards that are commonly encountered are:

• Compressible ground conditions;
• Shallow groundwater table;
• Aggressive ground geo-chemistry;
• Subsidence and Heave;
• Slope instability and failure;
• Soil liquefaction;
• Ground instability from under-mining; and
• Dissolution features.

The list is not exhaustive and is often bespoke to a particular parcel of land and the underlying geology. Geo-hazards can determine many project variables, with some examples including the suitability of earthworks, the cost of stabilising a site, the feasible (or unfeasible) foundation solutions, and associated liabilities moving forward.‍

Staged Approach to Mitigating Geo-Hazards & Reducing Risk

Similarly to a staged risk management approach for contaminated land, a similar approach would apply for initially identifying, then quantifying geo-hazards to inform suitable mitigation measures:

1.     Detailed Geo-Environmental Desk Study –Construct and build a geological ground model

A suitably detailed Geo-Environmental Desk Study (or bespoke Geotechnical Desk Study), should go some way to identifying geo-hazards and geotechnical risk associated with a parcel of land, offering extremely good value for money to inform key decisions.

This initial stage is useful in both a due-diligence context to make informed decisions about an investment or divestment, or to better inform future construction phase considerations.

2.     Undertake Preliminary Ground Investigation to confirm or revise the anticipated geological ground model.

Once geo-hazards have been identified during an initial desk study, future ground investigation works should seek to gather further geotechnical information on the specific hazards and as a minimum provide an initial assessment on the level of subsequent risk that a geo-hazard may pose.

This may be sufficient to either discount expected geo-hazards, confirm additional geo-hazards that may not have been expected, and determine the need for further investigation.

3.     Undertake Supplementary Ground Investigation to further target remaining geo-hazards to allow suitable mitigation measures to be considered and designed.

This may, for example, be a more bespoke package of works such as ground movement assessment for compressible ground, or a slope stability assessment.

Supplementary works can then be determined if unacceptable risk still remains and a designed solution is required.

The extent that the above approach will be implemented is dependent on the acceptable level of perceived risk that the client is willing to accept either at construction phase, or as part of a transaction.

Whilst Roberts Environmental would encourage maximising risk reduction by costing and allowing for sufficiently detailed ground investigation, it is recognised that it is not always feasible or practical to consistently achieve optimal risk reduction across all scales of projects.

Implications of a Changing Climate

Roberts Environmental recognise that a changing climate doesn’t just provide meteorological, above ground challenges, but also poses significant risk to the existing or proposed built environment, infrastructure assets and more. As the climate changes, so does the behaviour of the ground beneath our feet.

The ground investigation industry will become increasingly important in years to come, not only providing initial ground risk management advise, but also providing the ongoing monitoring of ground movement to ensure that critical assets and structures are protected for the longer term.

Rising sea levels and river catchments may result in rising groundwater tables, inundating foundations, potentially causing settlement reactivation and instability of footings.

Another example relating to groundwater rises maybe the hydration of cohesive soils, causing excessive heave. Alternatively, extreme temperature may drive down groundwater catchments resulting in excessive subsidence of foundations, pavements, roads and hardstanding.

Conclusions

Whilst there is a clear focus upon investigating and unlocking brownfield land for sustainable re-use, it is clear that this approach needs to be balanced with ensuring geo-hazards are suitably assessed and mitigated. Sustainable assessment and management of geo-hazards should be considered as important as ensuring sites are remediated and made safe for future end-users as a requirement of planning.

At a time where cost-benefit, value and a positive planning outcome sit at the forefront of pre-construction assessment, Roberts Environmental would urge our existing, and prospective clients to consider the impact of climate change upon their developments and consider how geotechnical ground risk may impact the feasibility of their developments in the longer term.

Whilst this is already becoming paramount in the public sector for national transport infrastructure assets such as road and rail, a similar approach and mindset needs to be adopted by private sector developers.