Analysis of thermal data from drill holes UE25a-3 and UE25a-1, Calico Hills and Yucca Mountain, Nevada Test Site

Thermal data from two sites about 20 km apart in the Nevada Test Site indicate that heat flow both within and below the upper 800 meters is affected significantly by hydrothermal convection. For hole UE25a-1, Yucca Mountain, the apparent heat flow above the water table ({similar_to}470 m) is 54 mWm{sup -2} ({similar_to}1.3 HFU). Below the water table, the temperature profile indicates both upward and downward water movement within the hole and possibly within the formation. Hole UE25a-3, Calico Mountain, is characterized by conductive heat flux averaging 135 mWm{sup -2} ({similar_to}3.2 HFU) to a depth of about 700 meters below which water appears to be moving downward at the rate of nearly 1 ft y{sup -1} (255 mm y{sup -1}). Between 735 and 750 meters, the hole intersected a nearly vertical fault along which water seems to be moving vertically downward. The nearly threefold variation in conductive heat flow over a lateral distance of only 20 km suggests the presence of a more deeply seated hydrothremal convective system with a net upward flow beneath Calico Hills and a net downward flow beneath Yucca Mountain