This Small Business Innovation Research Phase I project is Object-Oriented Groundwater Data Repository Technology. Subsurface groundwater systems require large-scale models. Credible groundwater modeling needs the assemblage of all available information. Currently, the interpreted groundwater data and calibrated parameters are stored as input files of a code. All new modeling efforts are generally attempted from scratch. This object-oriented data repository will systematically store basin data, and will be independent of any groundwater code. It will have integrated tools to import, edit, view, and export information. It will have capabilities to convert any model data into a selected repository format. Integrated tools will provide options to screen water level and chemical data for generating good quality datasets for inverse parameter estimators. Groundwater is the primary water source for millions of people, agriculture, and industries. Groundwater modeling is a key requirement for (1) groundwater management; (2) permit applications; and (3) each waste site EA, RI/FS, risk assessment, and record of decisions (ROD) negotiations. Anyone using these data will potentially benefit from the use of this data repository.