Underground detonations may produce observable effects in surrounding aquifers and wells. The nature and the duration of the effect at any observation point seem to depend on several factors such as the amount of energy released by the detonation, the geologic environment, the position of the buried explosive device in relation to the saturated zone, aquifer characteristics, and the distance from point of detonation. Precise measurement of these effects in wells presented numerous technical problems and resulted in the development of specialized techniques. Initially, these effects were observed by measuring the fluctuation of the free water surface in wells. The current technique employs high‐resolution pressure transducers deep in the water column. Pneumatic packers may be used to restrict the movement of water into the well. Data are recorded on high‐speed oscillographs.
The hydrological effects of the underground nuclear explosion, CANNIKIN, were monitored by a network of streamflow stations and ground-water boreholes located on Amchitka Island. Continuous records were obtained from six surface-water stations that range from 1.50 to 14.07 km from surface ground zero (SGZ). Confined fluid pressures in boreholes were recorded at five stations with slant distances ranging from 2.14 to 14.11 km from ground zero (GZ). Fluctuations of water level were measured in one open hole 6.42 km from GZ. The stream system draining the CANNIKIN site lost 96 per cent of its flow within hours after the explosion. Lakes formed near SGZ remain low in stage and appear to be providing infill water for the rubble chimney. Measurements in boreholes also showed that the ground-water gradient was toward the explosion site. The response of confined fluid pressures was recorded in a number of boreholdes, and a relationship between maximum fluid pressure, P, and slant range, Rs, has been established as P = 920 Rs−2.10.
Six exploratory wells were drilled into the cap rock underlying Salt Valley, Utah, for geologic, geophysical, and hydrologic data to augment information obtained from three previous test wells. Drilling of three other test holes was abandoned due to caving and loss of drilling tools, Before reaching the zone of saturation; the upper 100 meters of cap rock is unsaturated. Within the saturated part of the cap rock, hydraulic heads generally decrease with depth and to the northwest in this part of the valley.Hydraulic conductivity of the cap rock, as determined from pumping tests, ranged from 9.3 X 10 to 2.06 X 10 * meters per day; as a result, groundwater flow rates in the cap rock are low. Water ranges from a calcium bicarbonate sulfate type on the western edge of the valley to a calcium magnesium sodium bicarbonate, sulfate, chloride type near the center of the valley. Carbon-14 specific activity for cap-rock water yielded an uncorrected age of about 17,000 to 26,000 years before present near the western edge of the valley and about 41,000 years before present near the center of the valley.
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