The United States Department of Energy Savannah River Site (SRS) is a unique facility for geology, geophysics, and environmental geosciences. Construction began in 1950, and nuclear materials production started in 1952. Beginning with early regional characterization by the United States Army Corp of Engineers, the geology of the SRS has been extensively studied. Presently, the site geologic database has more than 12,000 borings, wells and cone penetrometer soundings, more than 300 km (200 mi) of reflection seismic data, many kilometers of refraction seismic and ground-penetrating radar data, large areas of time domain and very low-frequency geophysics, regional soil gas geochemical surveys, plus hundreds of smaller scale geological and geophysical studies. The hydrogeology and stratigraphy of the SRS is, perhaps, the best known in the eastern United States.