Sampling and pre-treatment

Reliable mine waste characterization data are needed for choosing treatment and disposal options for waste and planning the closure of a waste facility. When available data on waste characteristics is insufficient for decisions and actions, sampling is required and a plan for sampling and testing needs to be developed. The base for a sampling activity is collection of existing background information (see also Overall guidance document CEN/TR 16376). A field visit will normally be part of developing a sampling plan with special focus on accessibility to the location (e.g. safety restrictions).

Many different aspects need to be taken into account when planning a sampling campaign. The key issue in sampling is the objective of the sampling (screening, comprehensive characterization or confirmation of a specific property). The sampling approach depends on the required reliability in sampling and also previous information about the variability in waste properties (waste heterogeneity) and previous information of potential critical properties linked to planned actions. The amount of samples to be taken depends on the heterogeneity of the waste to be sampled together with the objectives for the sampling (how reliable information is needed). Sample size depends both on the heterogeneity and requirements for testing. Sampling techniques depends beside the sample objective also on the waste property to be determined (e.g. for many geotechnical analyses special sampling equipment is necessary). During sampling and also pretreatment of samples (e.g. subsampling) it is important to have appropriate knowledge of sample requirements and the critical factors influencing the waste properties of interest in order to take measures to minimise changes in samples. Changes in sample properties may occur due to various environmental factors, e.g. oxidation, carbonation or due to sampling approach (e.g. loss of sample integrity in taking the sample).

In some cases sampling campaigns are conducted in two steps. The first sampling campaign is a screening of waste properties and the second sampling campaign more targeted to a specific area or property based on the results from the first sampling round.

A specific sampling guideline for the characterization of waste from extractive industries has been developed (CEN/TR 16365). The guideline builds upon EN 14899, “Sampling of Waste Materials – Framework for the preparation and application of a Sampling Plan” and its supporting technical reports (see Table 1). The sampling guideline is focusing on the development of sampling plans but does also discuss some practical aspects such as sampling equipment, storage and transport. According to the sampling guideline a plan for characterization of extractive waste should normally cover the aspects listed in Table 2. Furthermore, ISO 10381-2 gives information on appropriate sampling techniques and equipment for different soil sampling situations and EN ISO 22475-1 on sampling methods particularly for geotechnical testing.

Taken into account the great variety of waste types, sampling situations and objectives, it is not possible to develop definitive instructions that cover all scenarios. Therefore the standards and guideline documents (see Table 1) discuss the basic considerations to be followed, and provides guidance on selection of sampling approaches that might be relevant to the three principle phases of a mine from exploration, operation to closure.

Focus	Standard number and name	Applicability	Comment
Characteristics of mine waste sampling	CEN/TR 16365:2012: Characterization of waste – Sampling of waste from extractive industries	The guidance is applicable for sampling during exploration phase, operation phase and closure. The report focuses mainly on sampling for geochemical rather than geotechnical requirements. Note! Sampling at closed sites, including abandoned historic mine-sites, may in some cases require specific approaches e.g. due to accessibility and limited background information.	Complementary information to EN14899 and its supporting technical reports (CEN/TR 15310 package)
Sampling plan	EN 14899: Characterization of waste – Sampling of waste materials – Framework for preparation of a sampling plan preparation	General information	The objective of the sampling plan is translated sampling steps into specific and concrete technical instructions.
Sampling principles	CEN/TR 15310-1: Sampling of waste materials: Information on selection and application of criteria for sampling under various conditions	General information	Discussion on statistical principles in sampling and description of statistical tools for design of testing programmes
Sampling techniques	CEN/TR 15310-2: Sampling of waste materials. Information on sampling techniques	General information	General description of sampling techniques for various wastes found in a variety of location
Sub-sampling	CEN/TR 15310-3: Sampling of waste materials: Information on procedures for sub-sampling in the field	General information	Description of procedures for reducing size of the waste materials in field to aid practical transportation of a sample to the laboratory
Sample preparation and storage	CEN/TR 15310-4: Sampling of waste materials: Information on procedures for sample package, storage, preservation, transport and delivery	General information	Description of procedures for packaging, preservation, short-term storage and transport
Sampling plans	CEN/TR 15310-5: Sampling of waste materials. Guidance on the process of defining the sampling plan	Note! Limited applicability of the practical examples. Examples are given in CEN/TR 16	Guidance in important steps in sampling including illustrative examples on how to define technical goals
Geotechnical testing	EN ISO 22475-1:2006, Geotechnical investigation and testing. Sampling methods and groundwater measurements.  Part 1: Technical principles for execution (ISO 22475-1:2006)	Applicable for geotechnical investigations
Soil sampling	ISO 10381-2:2002, Soil quality. Sampling. Part 2: Guidance on sampling techniques	General information
Pre-treatment	EN 15002: Characterization of waste – Preparation of test portions from the laboratory sample	Applicable
Pre-treatment	ISO 11464: Soil quality – Pretreatment of samples for physico-chemical analysis	Partly applicable, see comment	Method is limited to particle size < 2 mm while > 2 mm material is not treated because for soil analysis only material < 2 mm is relevant. If this method should be applied to wastes the fraction > 2 mm has to be crushed and included in the sample.
Pre-treatment	ISO 16720: Soil quality – Pretreatment of samples by freeze-drying for subsequent analysis	See comment	Method has limitations as water may not be fully removed, better applicable to very moist samples

Technical Committee CEN/TC 292 2012. Characterization of waste – Overall guidance document for characterization of wastes from extractive industries. CEN/TR 16376:2012.