1.1 ,This standard establishes a classification of the comprehensive hierarchical list of elements for life-cycle environmental work. The classification is based on the Interagency Environmental Cost Element Structure (ECES).2 Elements, as defined here, are major components common to environmental projects.3 The elements represent the life-cycle activities for environmental projects regardless of the project design specification, construction method, technology type, or materials used. The classification serves as a consistent reference for cost estimating, analysis, and monitoring during the various phases of the project life cycle. Using ECES ensures consistency, over time and from project to project, in the cost management and performance measurement of environmental projects. It also enhances reporting at all phases of a project, from assessment and studies through design, construction, operations and maintenance (O&,M), and surveillance and long-term monitoring (SLTM).