Several Autonomous Communities publish technical guides to establish the guidelines to be considered in the preparation of this type of studies, in order to guarantee the reliability of the results obtained.
In soil investigation and remediation, Quantitative Risk Analysis (QRA) is an essential decision-making tool for assessing the adverse effects that a given contamination of a site may have on human health and ecosystems. This methodology also provides a notion of the urgency with which it would be necessary to adopt actions to minimize these effects. Its correct execution is essential to carry out an unbiased evaluation of the assessed impact.
Although Quantitative Risk Analyses cannot be standardized, since each one is different, adapted to each specific case and its characteristics (types of contaminants, activity, environment, etc.), it is advisable to establish certain guidelines to ensure the reliability of the results.
Royal Decree 9/2005 establishes the criteria for the declaration of contaminated soils, as well as the elements that the assessment of the risks associated with contaminated soils must contain, but beyond these general guidelines, several autonomous communities have decided to publish technical guides on the preparation of Risk Analyses. The Basque Country, Andalusia and Madrid have technical guides and instructions that provide guidance on the processes of selection, treatment and calculation of data and other important aspects of the RCA to ensure its rigor. The last autonomous community to draw up and publish a document of this type was Catalonia, through the technical circulars of the Waste Agency of Catalonia (Agència de Residus de Catalunya). This document, recently published, establishes guidelines to be followed, from the relationship between the different phases of subsoil characterization and risk analysis to the definition of the source of contamination, the scenarios and receptors to be considered, as well as the presentation of the results, as detailed in the following points:

When to carry out an RCA?
One of the key aspects that define the circulars of the Agència de Residus de Catalunya is in which cases it is convenient to carry out the development of a Quantitative Risk Analysis, as well as its relationship with respect to the different phases of subsoil characterization.
The first step in a soil investigation project is to collect and interpret site-specific data to develop the conceptual model, which is the basis for the RCA. The conceptual model defines the interrelationship between the source of contamination, its movement through soil, water or air, and the routes of human exposure to it. In this first phase, it is important that the data be as careful and representative as possible, reliable to the reality of the site, as this will provide reliability to the conceptual model and to the subsequent assessment of the potential risk.
The Quantitative Risk Analysis is to be carried out after the detailed subsurface evaluation phase, although, under certain circumstances, it is acceptable to perform a QRA in the preliminary evaluation phase of an investigation.
What contaminants are to be assessed in the RCA?
It is essential to define which contaminants of interest are to be considered in the different matrices to be evaluated (soils and groundwater). This new publication suggests including all those compounds with concentrations that exceed the reference criteria established in the current regulations (taking into account the expanded uncertainty of the analysis), contaminants that do not have a reference level and related contaminants, even if they do not exceed the established thresholds. In addition, it is indicated that in the RCA the maximum concentrations detected for each pollutant and each medium must be assessed, although there is the possibility of a statistical treatment of the concentrations, which will have to be duly justified.
It also establishes the criteria and methodology for the selection of toxicological data to be applied and lists the preferred sources of information and their hierarchy for updating toxicological data.

What scenarios are to be considered?
The definition of exposure scenarios is the part of the conceptual model that determines the basic parameters that relate contamination to potential human exposure. Therefore, these new circulars state that in the RCA, reasonable exposure scenarios must be defined according to the current and future use of the site (on-site) and its surroundings (off-site).
It is also suggested that for each scenario proposed, the receptors, media and exposure pathways that may occur at the site evaluated should be characterized.
The transport of the pollutant from the source to the point of exposure of the receptor can be simulated by means of so-called transport models. The new technical circulars point out that the parameters to be applied in these models must be as specific as possible for the case being evaluated, since they are data relating to the environments where the contamination is located and migrates. These technical documents detail the aspects to be taken into account in the definition of the affected area and in the selection of the type of soil.
How are the RCA results presented?
The structured and detailed presentation of the results of the Quantitative Risk Analysis is vital for its understanding. That is why the Agència de Residus de Catalunya establishes the optimal way to organize the data, offering table and chart formats as elements to help in the realization and presentation of the risk analysis reports.
Litoclean’s Risk Analysis department knows all the regulations and technical instructions of the national territory and works applying the requirements and guidelines of each region in its studies, which are based on high quality criteria as well as being in line with international standards and methodologies. The company has been a pioneer in Spain in the use of simulations for risk calculation and one of the first consulting firms in the country to obtain ENAC accreditation in this area, which is why it maintains its requirements in the preparation of RCAs.