Synopsis: Environmental practitioners are often constrained by rigorous time and monetary constraints, which can lead to the collection of limited data sets and decisions made based on an inadequate understanding of site conditions. To facilitate effective site assessments in British Columbia, the BC Ministry of Environment recently released a new guidance document, 'Technical Guidance #8', for the investigation and characterization of groundwater at sites that are or may be contaminated. A fundamental tenet of the new draft guidance is the recognition that virtually sites should be examined within the context of a conceptual site model (CSM) to found the planning process and to guide the investigation in achieving the goals of defining the presence and extent of groundwater contamination. The guidance is designed in an easy-to-read format that is based on a series questions and answers including: When is groundwater investigation necessary? How should a field program be designed? What methods and approaches are acceptable? What level of investigation is necessary for Preliminary Site Investigations and for Detailed Site Investigations? What types of Information should be reported? The guidance recognizes the importance of acquiring detailed spatial and temporal data using conventional and innovative approaches, and the potential implications of decision-making in the absence of this information. Other key items addressed by the guidance include measures to limit the length of monitoring well completion intervals to avoid dilution and potential cross contamination, and recommended spacing intervals between wells when designing field programs.