The nuclear test Dalhart, U4u, was executed at a depth of 2100 ft on October 13, 1988. This test has multiple radioactive isotopes or fission products associated with it and knowledge of the distribution of these isotopes is desirable for the Nuclear Test Program. A slant post shot hole was drilled in late August 1990 to sample the geologic material from the collapsed zone or chimney above Dalhart. This 9 7/8 inch borehole was drilled at approximately 19 degrees from the vertical toward the Dalhart executive depth. This borehole started at approximately 734 ft due south of the Dalhart event. Drilling circulation was lost at a slant depth of 1030 ft (980 ft True Vertical Depth, TVD). Drilling was completed to 2280 ft (2156 ft TVD). The water level was encountered at a depth of 1063 ft (1513 ft TVD). A Halliburton 1 11/16 in diameter TracerScan gamma-ray-spectroscopy log was run inside the drill string at a speed of 10 ft/min. Spectra were obtained from TD to the surface. Radioactive material produced by the test was present from TD to 1850 ft (1746 ft TVD). Spectra were acquired at .025 ft depth intervals and averages recorded digitally every ten ft and thirty ft were displayed on the blue line log together with the total observed gamma ray and casing collar locater signal. Also a DOE high intensity gamma log was run by Atlas Wireline Services from TD to the surface. This log did not detect any radioactive activity in the hole. The gamma-ray photo peaks on the spectroscopy log were used to determine the depths for sampling with the Hunt sidewall sampling tool. Eleven samples were acquired from the depth interval 2212 ft to 1823 ft (2089 to 1721 ft TVD). None of these samples contained enough activity to be measured with normal drillback survey instruments. 7 refs., 8 figs., 3 tabs
