Several hazards are being studied, as follows. Detailed geologic mapping will identify flood plains. Large earthen dams have been constructed west of Las Vegas by the Corps of Engineers but these provide protection only from storms in the Spring Mountains. Most of the flooding occurs from local storms within the urban area. These kinds of soils are being mapped to aid future construction.
Landslides are abundant in the Spring Mountains but most are far from populated areas.
For example, the Little Skull Mountain earthquake of magnitude 5.8 took place in June 1992 on the northern side of the active Rock Valley fault zone, which is in the southern part of the Test Site. Lakes Mead and Mohave are the sites of numerous small quakes but these reflect the movement of rocks under the reservoirs due to the weight of the water, and thus they are not tectonic and not likely to be life-threatening. Environment For about 40 years, almost 900 underground nuclear tests, including 200 sited below or near the water table, have been detonated on the Nevada Test Site. Water Resources Divisions has shown that ground water beneath the south half of Nevada flows southward from high-rainfall source areas in central Nevada, and that flow rates are fast enough so that some ground water contaminated by radionuclides may have migrated to public and private lands south and southwest of the Test Site. In the last five years, work on the Nevada Test Site by the USGS has been funded by the Department of Energy, under their Environmental Restoration program.