[en] The goal of this sampling plan is to identify and develop specific plans for those investigative actions necessary to: (1) characterize the hydrologic regime; (2) define the extent and impact of contamination; and (3) predict future contaminant migration for the Weldon Spring Site (WSS) and vicinity. The plan is part of the Weldon Spring Site Remedial Action Project (WSSRAP) sponsored by the US Department of Energy (DOE) and has been developed in accordance with US EPA Remedial Investigation (RI) and Data Quality Objective (DQO) guidelines. The plan consists of a sequence of activities including the evaluation of data, development of a conceptual model, identification of data uses and needs, and the design and implementation of a data collection program. Data will be obtained to: (1) confirm the presence or absence of contaminants; (2) define contaminant sources and modes of transport; (3) delineate extent of contaminant migration and predict future migration; and (4) provide information to support the evaluation and selection of remedial actions. 81 refs., 62 figs., 26 tabs