The Geostatistics for Remediation Optimization (GRO) team was established to develop guidance to help practitioners better apply geospatial analyses in environmental projects. The Geospatial Analysis for Optimization at Environmental Sites (GRO-1) guidance will help state regulators and other practitioners to understand, evaluate, and make informed decisions about optimization activities at environmental sites using geospatial analyses. Geospatial analyses are tools that can evaluate optimization opportunities for the total project life cycle, providing enhanced data evaluation, interpretation, and communication for data that are related in time or space. In some cases, the geospatial analysis methods include statistical analyses involving spatial or spatial and temporal interpretations of environmental data, as well as uncertainty evaluations of those data. When such statistical assumptions and metrics are involved, those geospatial analysis methods are often referred to as geostatistical methods. Geospatial analyses can help get the most information from sampling locations and results to avoid sampling redundancy and to adjust remediation efforts through appropriate performance evaluation. Geospatial analyses can be used at environmental sites in all project life cycle stages (release detection, site characterization, remediation, monitoring, and closure), for all environmental media (soil, groundwater, vapor, or sediment), and for different sizes and types of sites (for example, Brownfields, UST, RCRA).