Excavated Soil and Rocks: Potential, Complexity, and New Challenges

Excavated Soil and Rocks (ESR) are produced during earthmoving and operations for the construction of foundations, trenches, consolidation works, drilling, earthworks leveling, boring, and tunnels in infrastructure projects.

These materials are extremely variable in terms of volume, physical, geological and geotechnical, chemical, and mechanical characteristics, and the regulatory framework under which they must be managed.

In terms of volumes, they range from so-called micro-sites, with volumes below 600 m3, up to large infrastructure project sites capable of producing over 2 Million m3 of excavated soil and rocks for a single project. Just considering the volume of ESR expected from the construction of major railway infrastructure in the coming years—only a portion of what will be generated in Italy in the next 3 or 4 years—we easily exceed 120 Million m3 (Italferr data, RemTech 2024). With this volume of soil, you could fill over 50,000 Olympic swimming pools and nearly 800 times the Colosseum. Think about the volumes at stake in Europe or, even more so, globally!

Regarding the characteristics of ESR, the range of possibilities is extremely wide, ranging from backfill soils, resulting from shallow excavations, often of poor quality, to rocks resulting from deeper excavations or borings with excellent mechanical characteristics. They range from soils characterized by strong interactions with anthropogenic activities and potential contamination to soils originating from several hundred meters deep, free of any contamination, up to soils and rocks naturally containing potentially hazardous substances such as, for example, asbestos.

All ESR are characterized by some common elements, such as:

• Their management is a significant element of a project from an economic, logistical, and environmental point of view;

• Their management on-site during the construction phase can have significant impacts on the operability and the time schedule of activities;

• Their management involves an extremely wide number of stakeholders. Just to mention a few: the Project Proponent, designers, local regulatory bodies, the contractor and any sub-contractors, the company in charge of managing transport, the managers of temporary storage and final disposal sites—and the list could continue when considering laboratories tasked with sampling and analysis, earth movement, and so on…

A Different Perspective: ESR as a Resource

It is important to add the following considerations, which help to view Excavated Soil and Rocks from a slightly different perspective.

ESR are, in fact, natural, non-renewable materials available in large quantities, which, within a circular economyframework, could be seen as a valuable resource to be exploited intelligently rather than a waste product to be disposed of.

ESR are also materials that humans have been using profitably for centuries for many purposes, including, for example:

• The implementation of morphological reshaping interventions, coastal nourishment, or other coastal defense works, the restoration of abandoned quarries (over 15,000 in Italy);

• The construction of road, motorway, and railway embankments or earth dikes and dams;

• Use as aggregate for mortars and concretes;

• The manufacture of artifacts, bricks, and everyday objects.

Naturally, in making these considerations, the many implications necessary for such exploitation are not overlooked, which, unfortunately, sometimes still represent a brake on the implementation of virtuous reuse processes. To mention a few, one need only think of:

• The complexity of authorization procedures, the interpretation of constantly evolving legislation (the promulgation of the new regulation, which will repeal DPR 120/2017, is expected shortly), the disuniformity of implementing regulations and interpretations provided by the diverse and numerous subjects involved in the complex process;

• The complex administrative, logistical, and organizational (if not judicial) situation in which several sites that could constitute a natural terminal for the deposit of large volumes of excavated soil and rocks currently find themselves, such as abandoned and/or disused quarries or areas exploited for industrial activities not adequately restored;

• The complexity of predicting and the disuniformity of the geological/geotechnical and environmental characteristics of excavated soil and rocks and the consequent difficulty of predicting management methods during the design phase;

• The complexity of predicting the effects on excavated soil and rocks generated by different types of excavation processes and the associated environmental implications;

• The relevance in the process of activities related to earth movement and road transport.

For years, the scientific community has been asking how to make a concrete contribution to facilitating the adoption of virtuous circular economy models by overcoming the mentioned criticalities. With this objective, various studies have been developed, and we at GEEG have also provided our contribution regarding:

• Studies on the characterization of excavated soil and rocks, both geotechnical and environmental (chemical and ecotoxicological), and analysis of the potential interferences produced by excavation activities, such as interaction or residual presence of traces of materials or products, variation in water content, or grain size variation;

• Studies on the effects of normal industrial practice activities, such as grain size separation, spreading on the ground to promote drying processes;

• Studies on the effects of specific treatments, such as those with lime and cement, useful for facilitating their reuse and expanding their methods of use;

• Studies to analyze the feasibility and implications of specific reuse methods.

–> Do you have ideas for innovative and sustainable use of large volumes of excavated soil and rocks? Have you carried out or are you carrying out ESR reuse projects? Tell us about them by writing to comunicazione@geeg.it

–> Do you need support in developing a project for the use of excavated soil and rocks? Let’s talk about it, we might be helpful!

–> Do you want to know more about excavated soil and rocks? Consult our publications and discover the sections “Environmental Impact” and “Circular Economy.”

Would you like me to translate this back into Italian or look up information about the Italian regulation (DPR 120/2017) regarding excavated soil and rocks?