Testing hierarchies and simplified procedures

3.8.1

Basic purpose of testing hierarchies

Different systems aimed at reducing the amount of testing necessary and avoid redundant testing have been developed. The systems most relevant to the assessment of compliance with future EoW criteria for aggregates are probably those developed by CEN/TC 292: Characterisation of waste and CEN/TC 351: Construction products – Assessment of the release of dangerous substances. They are both based on the principle of performing one thorough characterisation of the environmental properties of a given waste material or product which then only have to be repeated if the material changes. Simpler test methods which can be related to the initial characterisation and to compliance with criteria are then applied routinely at certain intervals. The principle of this tiered approach is illustrated in Figure 3.6.

Figure 3.6

Tiered approach in testing – detailed when needed, simple when possible.

The two systems from CEN/TC 292 and CEN/TC 351 which are both embedded in or associated with EU Directives, are described in more detail below.

3.8.2

CEN/TC 292: Characterisation of waste

To avoid unnecessary or redundant testing, CEN/TC 292 has developed a test hierarchy, consisting of basic characterisation, compliance testing and on-site verification. The hierarchy, which is included in all standards and technical specifications issued by CEN/TC 292, may be described as follows: Basic characterisation tests are used to obtain information on the short and long term leaching behaviour and characteristic properties of waste materials. Liquid/solid (L/S) ratios, leachant composition, factors controlling leachability such as pH, redox potential, complexing capacity and physical parameters are addressed in these tests.

Compliance (or conformity) tests are used to determine whether the material complies with specific reference values. The tests focus on key variables and leaching behaviour identified by basic characterisation tests.

On-site verification is a rapid check to confirm that the material received at the site of application is the same as that which has been subjected to the characterisation and compliance test(s).

Basic characterisation may be quite comprehensive and will generally consist of more than one leaching test. Apart from producing information on the leaching behaviour under various conditions, it should also produce information on the variation of the leaching properties of a material. In addition to the leaching characteristics, basic characterisation should also include information on the origin of the material, the process and the raw materials from which it is generated, its composition, its functional/geotechnical properties, etc. A given material of a given origin will only have to be subjected

Level of detail Frequency of testing “compliance”testing “characterization”testing “compliance”testing “characterization”testing Factory production control /compliance

Initial type testing/ characterisation

to basic characterisation once; when the information obtained by basic characterisation is available, the performance of compliance testing, which generally consists of fewer (often just one) and simpler leaching tests, will be sufficient. If major changes occur in the processes that produces the material or if material of another origin is introduced, a new basic characterisation will be required. The test(s) chosen for compliance testing must be included in the basic characterisation programme. The results of the basic characterisation will determine the frequency of the compliance testing. On-site verification will generally not require actual testing, but rather consist of visual checks and verification of the accompanying certificates and papers. It could include collection and storage of samples. The hierarchy developed by CEN/TC 292 has been adapted and incorporated into the EU Landfill Directive (1999/31/EC) and forms the basic structure of the accompanying Council Decision on criteria and procedures for acceptance of waste at landfills (2003/33/EC).

3.8.3

CEN/TC 351: Construction products – Release of dangerous substances

As part of the fulfilment of the obligation of producers of construction products, including aggregates, to provide information on the release of regulated substances to soil, groundwater and surface water (and indoor air), CEN/TC 351 and the Product TCs regulated by the CPR are adopting and developing a system aimed at minimising the level of testing and avoid unnecessary testing while still ensuring that sufficient information is available. This is done in cooperation with DG Enterprise from the EU commission.

A procedure is described in the Technical Report CEN/TR 15858: “Construction Products – Assessment of the release of regulated dangerous substances from construction products based on the WT/WFT/FT procedures”. It describes how Regulated Dangerous Substance classes (RDS classes) for each mandated Regulated Dangerous Substance (RDS) are developed and how sets of these RDS classes may be grouped for user convenience. It introduces the idea of an Initial Type Assessment (ITA) as the first step in the technical process. Where the ITA identifies that the construction product satisfies the criteria set out in the product standard with either no, a limited amount or in specific cases more extensive testing using European test methods, the construction product may be deemed-to-conform to one or more RDS classes. Where all relevant RDS classes are satisfied by these procedures, the construction product may be deemed-to-conform to a set of RDS classes. The technical procedure(s) for establishing a deemed-to-conform approach (based on assessment of conformity with relevant criteria), and its informational requirements, is described in CEN/TR 15858.

In the technical procedure, there is a hierarchy of testing using reference test methods for the determination of release/emission, alternative test methods and screening tests. These may be used in the Initial Type Testing (ITT) and in the further testing (factory production control and evaluation of conformity) to assess the constituents or materials and approve the construction product. The overall objective of the system is to set out a framework for an effective, appropriate and cost effective system for providing, when required, information on the release/emission of RDSs from construction products. It should be noted that the WT (without testing) procedure is likely to disappear since it creates the misunderstanding that a product can be approved without consideration of any test results. During the ITA, existing data may be sufficient for an evaluation of a material and if not, such data must be produced. Both will be entered into an ITA dossier together with other information. Regardless of the source of information, the evaluation of the dossier will result in further procedures of WFT (without further testing) if there is strong evidence of compliance with criteria, and in FT (further testing) if it is found that non-compliance with criteria may sometimes occur. The further testing procedure consists of (often simpler) routine tests carried out at production level, often referred to as Factory Production Control (FPC).

The form of the ITA dossiers is currently being developed by CEN/TC 351, and a draft example of such a dossier is shown in Annex 3.

It is suggested to adopt the dossier approach (and the FPC approach as well) to the assessment of compliance of various waste-derived aggregates with possible future EoW criteria on leaching and (for organic substances) content. It is, however, too early to develop the details of the dossier, since the methodology and criteria for achievement of EoW status have not yet been determined.

3.8.4

Practical application of the waste hierarchy

The testing hierarchy for a given material can be seen as consisting of the following decision steps: The release behaviour of any (granular) material type needs to be characterised properly using pH dependence (see section 3.7) and percolation test (see section 3.7) to ensure that the full spectrum of possible exposure scenarios for the material can be addressed (Landfill, EoW declaration, Beneficial use, recycling and coming full circle End of Life aspects). By requiring the same type of tests to be performed for any of the regulations related to the mentioned scenarios, double testing of a material possibly falling under different regulations or specification will be avoided. For more specific requirements, see chapter 7.

There needs to be a sufficient understanding of the bandwidth of cumulative release and leaching concentrations under the range of conditions of relevance in exposure scenarios (see statistical data for a range of material types Separate Appendix Part 2). This characterisation data set will allow identification of the relevant substances for compliance testing (defined by the chance of exceeding the regulatory or class limit) as well as the frequency of testing, when the regulatory criteria or class limits for a given use are identified (see section 3.9).

Once adequate characterisation data is available and assessable for a given material type, simplified testing by analysing specific eluate fractions from the characterisation tests or performing a simpler, suitable batch leaching test will suffice to demonstrate compliance with limit values or class limits. The simplified test data then need to be placed in conjunction with such more extended data to adequately substantiate this. From this description it is clear the reference tests in case of dispute will be the full characterisation tests and simplified tests (like a batch procedure) are allowed for compliance conformity testing. When a compliance test shows significant deviation from the available bandwidth of test data, then additional checks are needed to verify that the deviation is not caused by the analysis itself (dilution factor, inadequate calibration, interference, unit conversion mistake). If that check does not lead to conformity/compliance, then a full characterisation is called for to identify what has caused the deviation (e.g. other source materials, changes in processing, handling), which may lead to the identification of a new subcategory.

The hierarchy in testing as laid out here satisfies the needs from a regulatory perspective to ensure compliance with health and environmental quality targets, but at the same time provides an efficient means of complying with requirements by industry without carrying out more tests and analysing more substances than strictly necessary. For several major material streams substantial data sets are available to be used as a reference base for compliance verification purposes. In the Separate Appendices 1 and 2, both raw test data as well as aggregated data for specific material types are given. The latter would be most relevant for comparison of single test data from a dedicated compliance/conformity test. Such a comparison is illustrated in Figure 3.7 for leaching data on Cr and Zn from MSWI bottom ash.

Figure 3.7

Compliance test data for Cr and Zn in comparison with bandwidth data form MSWI bottom ash and associated domain for regulatory or class judgment. Black line – average leaching of log transformed data; red dotted line – median leaching of log transformed data; broken blue lines – 90 % confidence interval of log transformed data.