Many factors are considered. When drilling is required after a test location is chosen by the sponsoring national laboratory, a drilling program outlining the requirements of the specific hole is completed. The event site is surveyed, staked, and checked for cultural and biological resources. When all environmental clearances are completed, the site is graded and leveled, and a drilling-fluid sump is constructed to contain drilling fluid and cuttings. A drill rig, usually with its own power and utilities, is moved onto the site.
Water is brought in by truck, or piped in, and mixed with drilling compounds to fill the sump.
The hole is then drilled using standard NTS big-hole drilling techniques. After drilling is complete,geophysical logs are run into the hole to evaluate the condition of the hole and gain a more thorough understanding of the geology. The drill site is then secured by filling the sump and installing specially designed covers over the hole. Event-Site Engineering and Construction. When a hole is selected as a location for a nuclear test, the area around the hole is surveyed and staked according to the criteria set forth by the sponsoring national laboratory.