A ground-water test site on the Brazos River floodplain has been instrumented and characterized for research, education and the assessment of ground-water technology. This 8.5 ha (21 ac) site, known as the Brazos River Site, is located near College Station, Texas, on the Texas A&M University Research Farm and is intended to function as a test facility for the development of new and innovative technologies. The site is overlain by a surface clay layer that extends to an average depth of 7.6 m (24.9 ft). Below the clay is an alluvial, heterogeneous unconfined aquifer that is approximately 13.4 m (44.0 ft) thick. The aquifer, which is in direct hydraulic connection with the Brazos River, is comprised of a fluvial deposited upward fining sequence of gravel, sand, silt and clay. At an average depth of 21 m (69 ft), the site is underlain by an impermeable shale formation. The Brazos River Site has nine well nests, arranged in a 3 × 3 grid, oriented parallel and perpendicular to the river. Each well nest consists of four monitoring wells that are screened at different intervals throughout the aquifer that are instrumented to monitor water levels. The site has a large diameter pumping well and an injection well for forced gradient tracer studies. Other site instrumentation includes weather stations, surface runoff collection systems to quantify and sample runoff, and experimental 3-D ground-water velocity meters.