Use of sludge and treated biowaste can lead to release of contaminants towards the groundwater. European Directives in the fields of Sludge, Soil and Biowaste require European (CEN) standards to prevent unacceptable release of contaminants, impairment of soil function or unacceptable exposure to pathogens. Standards are required, the Directives can refer to them to ensure proper enforcement of the regulations. In view of the development of transparent guidelines for all parties concerned, confusion resulting from different standards for the same parameter or property in closely related fields like soil, sludge and bio-waste shall be avoided.

The history of project HORIZONTAL goes back to the workshop on harmonisation of sampling and analytical methods for heavy metals, organic pollutants and pathogens in soil and sludge in Stresa in February 2001, with participants from a wide range of CEN Technical Committees (TC). The main conclusion of the workshop was that horizontal standardisation is very much needed to avoid unnecessary duplication of work. In a follow-up meeting in Ispra, initiatives were taken to apply for funding through DG Research. This route was not succesful due to administrative reasons