ISDI thresholds: The complete guide to compliance for your inert waste

Here's the heart of the matter: the values ​​that must not be exceeded. The table below, summarized from regulatory data provided by organizations such as UNIFER , presents the thresholds for the eluate obtained after the leaching test.

(1) Exceptions exist if the waste complies with either the chloride and sulfate values, or the soluble fraction values.
(²) A higher value may be admitted under strict conditions (percolation test).
(³) If the threshold is not met, a controlled pH test (7.5-8.0) can be carried out.

These figures may seem abstract. The graph below allows us to visualize the differences in scale between the thresholds for certain heavy metals, illustrating the severity of the limits for elements such as mercury or cadmium.

In addition to the analysis of the eluate, regulations require that the concentration of several families of organic pollutants be checked directly in the waste. These substances are closely monitored due to their toxicity and persistence in the environment.

(⁴) For soils, a higher value may be allowed if the TOC threshold on eluate (500 mg/kg) is respected.

The following graph puts the thresholds for these organic compounds into perspective. The extremely low limit for PCBs (1 mg/kg), reflecting their high toxicity, is immediately noticeable, compared to that of TOC, which is a more general indicator of organic matter.

Knowing the thresholds is one thing, ensuring that your waste complies with them is another. Regulations have established a strict procedure to guarantee traceability and compliance: the Prior Acceptance Request (PAR).

As explained by the ECT group, a major player in the sector , the DAP (Declaration of Pre-Avoided Waste) is a mandatory step in the soil traceability chain. Before any delivery, the waste producer must submit a dossier to the ISDI (Industrial Landfill Site) operator. This dossier contains:

• The origin of the waste: precise location of the construction site.
• Identifying the actors: producer, transporter.
• Waste characterization: this is where the analysis reports (the "ISDI pack") are provided, proving compliance with the thresholds.
• The estimated quantities.

The ISDI operator reviews the preliminary acceptance report (DAP). If the analyses are compliant and the soil origin shows no signs of pollution (for example, by consulting databases such as BASOL on contaminated sites), they issue a Prior Acceptance Certificate (CAP). This document, often valid for one year for a given site, authorizes the transporter to deliver the waste to the site.

Visual checks are also carried out upon the arrival of trucks at the ISDI site to verify the absence of unauthorized waste (plastics, wood, plaster, etc.). Any non-compliant load is refused, and the incident is recorded.

What happens if the analysis results reveal that one or more ISDI thresholds are exceeded? The waste is not necessarily condemned. It is simply reclassified and must be directed to a treatment stream appropriate to its level of pollution. It is strictly forbidden to dilute or mix waste to artificially meet acceptance criteria.

Here are the main alternatives:

• ISDI+: Some facilities benefit from a prefectural decree authorizing them to accept waste with slightly higher thresholds for certain parameters (for example, sulfates or fluorides). This is an intermediate disposal pathway for low-level inert pollution.
• Non-Hazardous Waste Storage Facility (ISDND): If waste is no longer considered inert but remains non-hazardous, it must be sent to a non-hazardous waste storage facility. These facilities are designed with more complex sealing and leachate treatment systems to manage more biologically or chemically active waste. Logically, the acceptance thresholds are higher at these facilities.
• Hazardous Waste Storage Facility (ISDD): For waste with pollutant concentrations that classify it as "hazardous" (for example, high levels of PAHs, heavy metals, or asbestos), the only solution is an ISDD. These high-security sites are designed to contain highly toxic substances.
• Treatment and Recovery: Before considering storage, the question of recovery must always be addressed. Techniques such as biological treatment, soil washing, or physicochemical stabilization can sometimes "decontaminate" a material and allow it to be reused or accepted into a less restrictive recycling stream.

Far from being a mere administrative constraint, ISDI thresholds are the cornerstone of responsible construction and demolition waste management. They embody the balance between the need to build and the imperative to protect our natural resources. By setting clear and scientifically sound limits, the regulations ensure that the storage of inert waste will not become an environmental burden for future generations.

For professionals in the sector, mastering these thresholds and the associated procedures has become an essential skill. It is not only a legal obligation, but also a sign of professionalism and a commitment to a more virtuous circular economy, where each material is directed to the most appropriate channel, safely and transparently.

Solutions for individuals, farmers, communities and businesses

Each soil analysis kit is specialized and pursues a specific purpose:

• AGROKIT for agronomic soil analysis.
• POLLUKIT for pollutants.
• PESTIKIT for pesticide detection.
• PFASKIT for PFAS.
• METKIT for soil metals.
• SOLKIT for the complete health status of the soil (agronomic analysis, detection of pollutants and metals).
• ISDIKIT is aimed at construction professionals.